Tektronix P7313SMA Reference manual

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P7313SMA 13 GHz Differential Probe Technical Reference

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071-1968-00

P7313SMA 13 GHz Differential Probe Technical Reference

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071-1968-00

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Table of Contents

General Safety Summary ... . .. . .. . .. . ... ... ... . .. . .. . .. . .. . .. . ... ... . .. . .. . .. . .. . .. . ... ... ... ... . .. . .. . .. . .. . .. . ... ... ... . .. . .. . .. . .. iii

Preface................................................................................................................................. v

Operating Basics ...................................................................................................................... 1

Differential Measurements for Serial Data Compliance Testing................................................................ 1

Probe Block Dia

Termination Voltage Control ..................................................................................................... 8

Overdrive Error..................................................................................................................10

Differential a

Extending the Input Connections .. . .. . .. . .. . .. . .. . ... ... ... . .. . .. . .. . .. . ... ... . .. . .. . .. . .. . ... ... ... . .. . .. . .. . .. . ... ... ... . .. . . 17

Checking Cable Skew........................................................................................................... 18

Adjusting Cabl

Deskewing Probes . ... . .. . .. . .. . ... ... . .. . .. . .. . ... ... ... . .. . .. . .. . ... . .. . .. . .. . ... ... ... . .. . .. . .. . ... ... ... . .. . .. . .. . ... . .. . .. . 20

Reference ............................................................................................................................. 23

Serial Bus Stan

InﬁniBand . .. . .. . ... ... ... ... . .. . .. . .. . .. . .. . .. . ... ... . .. . .. . .. . .. . .. . ... ... ... ... . .. . .. . .. . .. . .. . .. . ... ... ... ... . .. . .. . .. . .. . .. . . 24

Speciﬁcations .........................................................................................................................25

Warranted Chara

Typical Characteristics ..........................................................................................................26

Nominal Characteristics......................................................................................................... 30

Mechanical Char

Performance Veriﬁcation ............................................................................................................. 32

Equipment Required . .. . .. . .. . .. . ... ... ... . .. . .. . .. . .. . ... ... . .. . .. . .. . .. . ... ... ... . .. . .. . .. . .. . .. . ... ... ... . .. . .. . .. . .. . ... ... . 32

Special Adapter

Equipment Setup................................................................................................................ 34

Input Resistance . ... . .. . .. . .. . .. . ... ... ... ... . .. . .. . .. . .. . ... ... . .. . .. . .. . .. . ... ... ... ... . .. . .. . .. . .. . ... ... ... ... . .. . .. . .. . .. . . 35

Termination Vol

Output Offset Zero .............................................................................................................. 39

DC GainAccuracy .............................................................................................................. 40

Rise Time........................................................................................................................42

Optional Accessories .. ... ... . .. . .. . .. . .. . .. . .. . .. . ... ... ... ... . .. . .. . .. . .. . .. . .. . .. . ... ... ... . .. . .. . .. . .. . .. . .. . .. . ... ... ... ... . ..... 48

Options................................................................................................................................ 49

Maintenance .......................................................................................................................... 50

Inspection and Cleaning . .. . ... ... . .. . .. . .. . .. . .. . ... ... ... ... . .. . .. . .. . .. . .. . ... ... ... . .. . .. . .. . .. . .. . ... ... . .. . .. . .. . .. . .. . ... 50

Replacement Parts.............................................................................................................. 50

Preparation for S

gram (Simpliﬁed) ............................................................................................... 3

nd Single-Ended Signal Measurement . . .. . ... ... . .. . .. . .. . ... ... ... . .. . .. . .. . .. . ... ... . .. . .. . .. . .. . ... . .. . .. . .. . 11

e Skew........................................................................................................... 19

dards ........................................................................................................... 23

cteristics ...................................................................................................... 25

acteristics ..................................................................................................... 31

s Required .. . .. . .. . .. . .. . .. . ... ... ... . .. . .. . .. . .. . ... ... . .. . .. . .. . .. . .. . ... ... ... . .. . .. . .. . .. . .. . ... ... ... . .. . . 33

tage Accuracy .................................................................................................. 36

hipment ....................................................................................................... 50

Table of Content

P7313SMA Technical Reference i

Table of Content

ii P7313SMA Technical Reference

General Safety S

ummary

General Safet

Review the following safety precautions to avoid injury and prevent damage to this product or any products connected to it.

To avoid potential hazards, use this product only as speciﬁed.

Only qualiﬁed personnel should perform service procedures.

While using this product, you may need to access other parts of a larger system. Read the safety sections of the other component manuals for warnings and cautions related to operating the system.

To Avoid Fire or Personal Injury

Connect and Disconnect Properly. Connect the probe output to the measurement instrument before connecting the

probe to the c input. Disconnect the probe input and the probe reference lead from the circuit under test before disconnecting the probe from the measurement instrument.

Observe All Terminal Ratings. To avoid ﬁre or shock hazard, observe all ratings and markings on the product. Consult

the product m

Do Not Operat

qualiﬁed service personnel.

Avoid Exposed Circuitry. Do not touch exposed connections and components when power is present.

ircuit under test. Connect the probe reference lead to the circuit under test before connecting the probe

anual for further ratings information before making connections to the product.

e Without Covers.

e With Suspected Failures.

y Summary

Do not operate this product with covers or panels removed.

If you suspect that there is damage to this product, have it inspected by

Do Not Operate in Wet/Damp Conditions.

Do Not Operate in an Explosive Atmosphere.

Keep Product Surfaces Clean and Dry.

P7313SMA Technical Reference iii

General Safety S

TermsinthisManual

These terms may appear in this manual:

WARNING. Warning statements identify conditions or practices that could result in injury or loss o f life.

CAUTION. Caution statements identify c onditions or practices that could result in damage to this product or other property.

Symbols and Terms on the Product

These terms may appear on the product:

DANGER indicates an injury hazard immediately accessible as you read the marking.

WARNING indicates an injury hazard not immediately accessible as you r ead the marking.

CAUTION indicates a hazard to property including the product.

The following symbols may appear on the product:

ummary

iv P7313SMA Technical Reference

Preface

This is the technical reference manual for the P7313SMA differential probe. This manual provides operating theory, speciﬁcations, and performance veriﬁcation procedures for the probe.

Preface

P7313SMA Technical Reference v

Preface

vi P7313SMA Technical Reference

Operating Basic

Operating Bas

This section discusses differential measurements using an SMA input probe for Serial Data compliance testing. It also provides information on the probe architecture and operational details to aid in its proper application.

ics

Differential Measurements for Serial Data Compliance Testing

Differential

Gigabit serial data signals are commonly transmitted using differential signaling techniques because of improved signal ﬁdelity and noise immunity. Although the physical layer speciﬁcations differ somewhat between the different gigabit serial data communication standards, they have some common elements. Most gigabit serial data signals are transmitted over 50 Ω transmission lines, which are terminated at both ends of a point-to-point differential interconnect. The signal transmitter provides a 50 Ω source impedance from each of its two differential outputs and the s ignal receiver provides an effective 50 Ω input impedance on each of its two differential inputs.

The two complementary single-ended signals that make up the differential signal are generally offset from ground at a common-mode voltage level, which allows the use of unipolar transmitters and receivers that are powered from a s ingle power supply v oltage. The transmitted signals are usually encoded using a DC-balanced encoding technique that allows the signals to be either AC or DC coupled in the transmission path. If DC coupled, the receiver termination must generally be terminated to the same DC common-mode voltage as the transmitter, to reduce DC loading on the transmitter output. An example of the single-ended signals transmitted by an InﬁniBand standard driver and the resultant differential signal that would be measured by a differential measurement system is shown in Inﬁniband. (See Figure 14 on page 24.)

Signaling

Although the differential response is generally the primary measurement of interest for a differential signal, full characterization of the signal also requires measurement of the single-ended response of the two complementary signals including the DC common-mode voltage.

Pseudo-Differential Measurements

A common differential measurement technique uses two single-ended probes or direct connection to two oscilloscope channels for the differential signal capture. By calculating the difference between the two input signals using waveform math, the effec

This meas limitations when compared to the use of a differential probe like the P7313SMA. In addition to the obvious overhead of two oscilloscope channels for the measurement instead of the single channel needed by a differential probe, there are a number o

Unlike t measurement uses two oscilloscope channels, which are physically separated and generally not matched as well. Although it is possible to deskew the timing differences between two high performance oscilloscope channels to improve the accuracy of a pseu oscilloscope parameter, such as vertical gain, is changed.

The gain match between two different oscilloscope channels is also a potential problem, particularly at higher frequencies where channel gain mismatch can contribute to signiﬁcantly reduced CMRR performance. The CMRR performance of a differ full probe bandwidth.

tive differential signal seen by a differential receiver can be displayed for analysis.

urement technique, which is commonly refered to as pseudo-differential measurement, has a number of

f additional problems.

he differential probe, which has been carefully designed with short, matched-input signal paths, a pseudo-differential

do-differential measurement, deskewing is a relatively involved procedure that may need to be repeated if any

ential probe, on the other hand, is generally much better controlled, with fully characterized speciﬁcations over the

P7313SMA Technical Reference 1

Operating Basic

The requirement of generating a math waveform for d isplay of the differential signal in a pseudo-differential measurement can also introduce may not be fully supported with math waveforms. The use of a differential SMA-input probe like the P7313SMA also provides additional features like adjustable termination voltage that may be very useful in fully characterizing the performance of differential voltage, since the oscilloscope termination resistor is connected directly to signal ground.

Differential Probe Measurements

A differential probe is designed to provide a differential input interface for a single-ended oscilloscope channel. It includes a carefully matched differential signal input path and a differential buffer ampliﬁer.

A conventional differential probe input generally has a high DC input resistance and as small an input loading capacitance as possible. The light input loading of a c onventional differential probe is designed to perturb the circuit being measured as little as possible when the probe is attached.

An SMA-input probe like the P7313SMA has a v ery different input structure. It has a dual, matched 50 Ω input that is designed to terminate the measured signal transmission path with minimum reﬂections. It is designed speciﬁcally for serial compliance testing. Its SMA input connectors provide a reliable, repeatable interconnect for making accurate eye pattern measurements that are used to characterize the quality of a serial data transmission channel.

The P7313SMA probe has also been carefully designed for ﬂat amplitude response and very small pulse response aberrations. This helps to ensure accurate eye pattern measurements over a wide data rate range.

some subtle problems with waveform analysis, since some features such as COMM triggering or mask testing

data transmitters. High performance oscilloscope channels are almost always limited to zero volt termination

The differential ampliﬁer is at the heart of any device or system designed to make differential measurements. (See Figure 1.) Ideally, the differential ampliﬁer rejects any voltage that is common to the inputs and ampliﬁes any difference between the inputs. Voltage that is common to both inputs is often referred to as the Common-Mode Voltage (V voltage as the Differential-Mode Voltage (V

) and difference

The simpliﬁed input signal voltage source model driving the differential ampliﬁer shows a complementary differential signal without source or termination impedance. In a real-world measurement, the signal source and measurement termination impedance must be known and included in the measurement analysis.

The model also shows that the output from the differential ampliﬁer has twice the peak-to-peak amplitude of each complementary input signal.

Figure 1

:Simpliﬁed model of a differential ampliﬁer

2 P7313SMA Technical Reference

Operating Basic

Common-Mode Rejection Ratio

Differential ampliﬁers cannot reject all of the common-mode signal. The ability of a differential ampliﬁer to reject the common-mode signal is expressed as the Common-Mode Rejection Ratio (CMRR). The CMRR is the differential-mode gain (A

) divided by the common-mode gain (ACM). It is expressed either as a ratio or in dB.

CMRR = A

DM÷ACM

CMRR(dB) = 20 log (ADM÷ACM)

CMRR generally is highest (best) at DC and degrades with increasing frequency.

The typical CMRR response of the P7313SMA differential probe over frequency is shown in S peciﬁ cations . (See Figure 15 on page 27.) High CMRR in a differential probe requires c areful matching of the two input paths. Poorly matched signal source impedances can signiﬁcantly degrade the C MRR of a measurement. Mismatches between the two differential signal input paths result in an effective conversion of V

Probe Block Diagram (Simpliﬁed)

The SMA inputs and probe termination network provide a high frequency, 50 Ω signal path to the internal probe ampliﬁer. The use of SMA-female connectors provides a reliable, repeatable attachment method for input signals. The s ymmetry of the input ter

Asimpliﬁed s

mination network is designed to reduce skew and maximize CMRR.

chematic of the P7313SMA input termination network is shown. (See Figure 2.)

to VDM, which reduces the CMRR.

Figure 2:

Input termination network

P7313SMA Technical Reference 3

Operating Basic

Matched-Delay Cables

The standard delay-matched cables for the P7313SMA differential probe have been carefully designed to provide guaranteed probe performance at the SMA connector interface on the end of the cable. The delay between the two matched cables in the standard cable assembly is adjusted to provide an initial skew of less than 1 ps. Cable skew this small can be degraded by cable ﬂexure and through other environmental factors. Care should be taken to minimize physical mishandling of this quality cable assembly to preserve probe performance.

The cable used in the standard cable assembly has also been selected for its low-loss characteristics, and the cable length was selected to match the cable loss compensation designed into the probe differential ampliﬁer. If an alternative cable assembly is used in measurements with the P7313SMA differential probe ampliﬁer, this loss compensation characteristic must be considered. The following approximate equation for cable loss compensation can be used as a guideline in custom cable designs and is valid o ver a frequency range of about 1 GHz to 8 GHz:

Loss = –[0.5 dB + 0.15 dB * (F ⁄1.25)], where F is frequency in GHz.

Custom cable pairs must also be designed with very low skew or the skew must be minimized using a pair of adjustable phase trimmer adapters like those listed in the Optional Accessories. (See page 48, Optional Accessories.)

Input Termination Network

The input termination network in the P7313S MA differential probe includes a pair of attenuation resistor networks laser trimmed to 5 The common-mode termination voltage node, V input common-mode signals. The probe termination voltage can be adjusted using several different modes that will be describ

0 Ω terminations, connected together at a common-mode voltage node, labeled V

, is designed to provide a broadband, low impedance termination for

ed later.

. (See Figure 2 on page 3.)

The termina

tion voltage range is +3.6 V/–2.5 V. For DC-coupled serial data signals, the termination voltage, V generally be set to equal the input signal common-mode voltage, V voltage, V

, should generally be set to 0 V.

; for AC-coupled serial data signals, the termination

, should

The adjustability of the termination voltage also provides measurement ﬂexibility for characterizing or stressing serial data signal dri

vers. Because of the low impedance of the input termination and attenuator network, the signal termination c urrents can become quite large. The following table can be used to calculate the DC common-mode voltages and currents at the probe inputs and termination voltage driver under several common source impedance conditions. (See Table 1.)

Table 1: Common-mode voltage and current formulas

. Source impedance

Common-mode term 0 Ω 50 Ω

When inputs are AC coupled: VI=VT,II=0,IT= 16.67 mA x V

40.00 mA x VT- 40.00 mA x V

40.00 mA x

- 23.33 mA x V

0.5 x (VT+VCM)

20.00 mA x VT- 20.00 mA x V

28.33 mA x

- 11.67 mA x V

4 P7313SMA Technical Reference

Operating Basic

The probe block diagram shows that the input termination network is followed by an attenuator and VCMcompensation circuit. The attenuator

is used to increase the effective input dynamic range of the probe differential ampliﬁer.

The P7313SMA probe has two attenuation settings, 2.5X and 12.5X, that allow dynamic range to be traded off against signal noise. The 12.5X attenuator setting has the largest dynamic range; the 2.5X attenuator setting has the lowest noise.

The V

compensation c ircuit automatically minimizes the DC common-mode voltage at the probe differential ampliﬁer inputs

even with varying termination voltage and input signal DC common-mode voltage. This maximizes the differential mode signal input dynamic range. The V

compensation circuit allows the DC common-mode input voltage range to be the same

for both attenuator settings. (See Figure 4 on page 7.)

Internal Probe Ampliﬁer

The P7313SMA differential probe is designed to measure high frequency, low-voltage circuits. Before connecting the probe to your circuit, take into account the limits for maximum input voltage, the common-mode signal range, and the differential-mode signal range. For speciﬁc limits of these parameters, see the Speciﬁcations section. (See page 25, Speciﬁcations.)

Maximum Input Voltage. The maximum input voltage is the maximum voltage to ground that the inputs can withstand

without damaging the probe input circuitry.

CAUTION. To avoid damaging the inputs of the P7313SMA differential probe, do not apply more than ±5 V (DC + peak AC)

between each input and ground. In addition, to avoid probe damage, the maximum termination resistor power must not be exceeded.

Maximum Termination Resistor Power. The internal termination resistors can safely dissipate 0.2 W of power

continuously, which is the case for normal probe operation without termination driver current overload. However, the probe will be damaged if you apply more than 0.5 W of power through the termination resistors for more than 5 minutes.

If you suspect your measurement application will approach these limits, use the formulas that follow to calculate the power dissipated by the termination resistors.

The power calculation formulas are based on the simpliﬁed model, which represents the signal at the probe inputs. (S ee Figure 3 on page 6.) If a signal source with 50 Ω source impedances is used, the signal levels used should match the zero-ohm source impedance model shown in the ﬁgure.

The signal source model de ﬁned for these equations is as follows:

P7313SMA Technical Reference 5

Operating Basic

This results in the terms to be used in the preceding power equations:

NOTE. With a balanced DC signal, in the preceding equations, VDMis half of the value of a conventional differential signal.

Figure 3: Probe maximum input limits

6 P7313SMA Technical Reference

Operating Basic

Common-Mode Signal Range. The common-mode signal range is the maximum voltage that you can apply to each

input, with res exceeds the common-mode signal range may produce an erroneous output waveform even when the differential-mode speciﬁcation is met.

pect to earth ground, without saturating the input circuitry of the probe. A common-mode voltage that

Differential-Mode Signal Range. The differential-mode signal range is the maximum voltage difference between the

plus and minus inputs that the probe can accept without distorting the signal. The distortion from a voltage that is too large can result i n a clipped or otherwise distorted and inaccurate measurement. The differential mode signal range is dependent on the probe attenuator setting as shown. (See Figure 4.)

For a more detailed description of the differential mode dynamic range, see Differential Measurement Topology.

Figure 4: Differential and Common-Mode operating ranges

Common-Mode Rejection. The common-mode rejection ratio (CMRR) is the ability of a probe to reject signals that are

common to both inputs. More precisely, CMRR is the ratio of the differential-mode gain to the common-mode gain. The higher the ratio, the greater the ability to reject common-mode signals.

Probe Ampliﬁer Outputs. The P7313SMA probe has a differential signal output. The positive polarity output is

ed to the oscilloscope through the TekConnect probe interface. The inverted polarity output is connected to the Aux

connect Output SMA connector on the top of the probe.

The positive polarity main output is automatically scaled b y the intelligent TekConnect probe interface to compensate for probe attenuation and display the differential signal voltage at the probe inputs. The inverted Aux Output is an attenuated

n of the differential signal input, which must be manually accounted for in signal measurements or processing.

versio

P7313SMA Technical Reference 7

Operating Basic

Termination Voltage Control

The P7313SMA probe termination voltage can be controlled either internally or externally, as selected by three different modes. A block diagram of the probe termination network is shown. (See Figure 5.) A discussion of the circuitry follows.

Figure 5:

Termination voltage network drive

8 P7313SMA Technical Reference

Operating Basic

The P7313SMA probe is designed for compliance testing of high-speed, serial data standards such as PCI Express, InﬁniBand, Ser deﬁne a common-mode voltage less than the +3.6 V/–2.5 V termination range of the P7313SMA probe.

The probe termination voltage can be set to the desired input signal common-mode voltage using one of three control modes: Auto (the default mode at power-on), Internal, and External. The operation of these modes are described below.

ialATA, XAUI, Gigabit Ethernet, Fibre Channel, and others. All of these high-speed, differential data standards

Auto Mode

When the probe is ﬁrst connected to the oscilloscope, a self test runs, and the default termination voltage control mode is set to Auto. When the probe is in Auto mode, the c omm on-mode voltage of the input signal is monitored, and the DC termination voltage is set to match the common-mode i nput voltage. Auto mode provides the minimum DC loading on the input signal source.

With open inputs or a high DC source impedance, such as an AC-coupled input signal, the Auto mode select LED ﬂashes, indicating that the termination voltage has been set to zero volts.

This is the mode that you will likely use for most compliance testing of current serial data standards.

Internal (Int) Mode

The internal mode allows you to set the termination voltage with user controls that are available on some TekConnect-interface oscilloscopes. You can adjust the DC termination voltage within the +3.6 V/–2.5 V range. See your oscilloscope manual for details on u

sing this mode.

External (Ext) Mode

When the probe is in external mode, it allows control of the DC termination voltage with an external power supply. You can adjust the DC termination voltage within the +3.6 V/–2.5 V termination voltage range of the probe.

The external DC termination voltage control input is buffered by an internal ampliﬁer with 100 K Ω input impedance.

WARNING. Do not exceed the ±15 V maximum external mode voltage for the probe. Excess voltage will damage the probe.

P7313SMA Technical Reference 9

Operating Basic

In Ext m ode, the external DC voltage is connected to the red (+) and black (-) terminals on the end of the probe head, which accept standar connections from these connectors to external power sources. The black terminal is ground and is connected to the outer case of the shielded module that holds the SMA input terminals. When you are not using these terminals, they can b e left open and uncon

d 80 mm plugs. A pair of 0.080 in-to-banana plug adapter cables are included with the probe for making

nected. When the Ext mode input terminals are left open, the Ext mode termination voltage defaults to 0.0 V.

The terminati

on voltage supplied to the input termination network by the Vterm driver can be monitored with a DMM on a pair of 0.040 inch pin jacks on the top of the probe. This allows you to verify the termination voltage setting, and when you are using Auto mode, allows you to measure the common-mode input voltage.

You can use a pair of 0.040 inch-to-0.080 inch pin jack adapters with the 0.080 inch-to-banana plug cables (both are standard accessories

included with your probe), to make a more permanent connection to the monitoring DMM.

Overdrive Error

The P7313SMA differential probe can measure signals that have a common-mode voltage range of ±2.5 V. Although the termination voltage range is speciﬁed to be +3.6 V/–2.5 V, limitations on the linear current range of the termination voltage driver restrict the voltage difference between V

Generally, you must keep the termination voltage within about 2 volts of the common-mode voltage (when using a s upply with 0 Ω source impedance), or 3 volts of the common-mode voltage (with a 50 Ω source impedance), or the Overdrive Error LED will glow solid, indicating an over-current situation, which may lead to a measurement error.

The speciﬁc voltage difference between V values. You can use the input termination network table to determine allowable conditions, wit h the Overdrive Error current threshold for I

The Overdrive Error LED will also ﬂash red when the termination voltage exceeds the allowable +3.6 V/–2.5 volt range. This can occur in Auto mode when V the same threshold. If this occurs, remove all signal sources from the probe to clear this LED.

The Overdrive Error LED provides an active status monitor of error conditions; it does not latch and store the occurrence of an error condition.

and VT.

and VTis dependent on both the source impedance and the VCMand V

set at about ±80 mA. (See Table 1 on page 4.)

exceeds a threshold of about ±2.8 V, or in Ext mode when the VTinput voltage exceeds

Figure 6:

Overdrive Error indicator

10 P7313SMA Technical Reference

Differential and Single-Ended Signal Measurement

Although designed for differential signal measurement, the P7313SMA probe can be used to make single-ended measurements when properly conﬁgured. The analysis that follows describes some differential and single-ended measurements of typical high-speed serial data signals.

Differential Measurement Topology

A typical differential measurement topology using the P7313SMA probe is shown. (See Figure 7.) The termination network for the probe in this ﬁgure includes a termination capacitor. This is intended to show that the termination network provides a broadband AC

ground for common-mode signals.

Operating Basic

Figure 7: Differential measurement topology

Although an ideal differential signal is theoretically terminated at the V

node due to symmetry, the low impedance VTnode

terminates any non-ideal, AC common-mode signal components. The input signal source model includes a common-mode component, V

, and complementary differential mode components, ±VDM.

The differential mode signal source models have double the signal amplitude of the measured signal at each input because of the 50 Ω voltage divider between the source and termination resistance. The common-mode signal source model does not have double the signal source amplitude because most serial data transmitters are designed to drive a load resistance terminated with the DC common-mode voltage, not signal ground.

With V

set equal to VCMin this model topology, the DC common-mode voltage at each probe input should equal VCM.

The resulting differential signals at the probe inputs are:

The attenuator and VCMcompensation network that follows the termination network nulls out the VCMsignal and attenuates the V

signals. The resulting differential signals at the probe ampliﬁer input

s for a 2.5X attenuation setting are:

The resulting output signal from the probe output is:

P7313SMA Technical Reference 11

Operating Basic

The inverted polarity of the probe ampliﬁer output can be veriﬁed by examining the probe Aux Output signal. The main probe output si differential amplitude at the probe input connectors.

Differential Dynamic Range

The VCMcompensation c ircuit in the probe attenuator is designed to maximize the dynamic range of the AC component of the input signal. For most high-speed serial data signals, the AC component of the signal is of most interest for compliance testing where an eye pattern display of the differential signal is checked for timing jitter and voltage amplitude and ﬁdelity.

The DC common-mode component of the input signal is present primarily to bias the signal into the operating range of the receiver and may even be removed in the transmission path with AC coupling. The V P7313SMA probe is designed to null out the DC common-mode component of the input signal, V differential mode component of the input signal is passed through to the probe ampliﬁer inputs.

gnal is routed through the TekConnect interface connector and is automatically scaled to show the correct

compensation circuit in the

, so that only the

The V

compensation circuit allows the dynamic range of the probe to be speciﬁed as a differential peak-to-peak voltage

with a separate DC common-mode range. The differential peak-to-peak voltage speciﬁcation is different for the two probe attenuation settings, but the DC common-mode range is the same for both attenuation settings.

The DC common-mode range of the probe is actually describing the performance of the V

compensation circuit, rather than

the dynamic range of the probe ampliﬁer. The dynamic range of the probe has been speciﬁed as a differential peak-to-peak voltage because that best represents the way in which the signal is typically displayed and speciﬁed for compliance testing.

Single-Ended Measurement Topology

Although the P7313SMA differential probe can be used to make single-ended measurements, it is important to understand the impactoft

Because of common-mode component of the signal, must be carefully checked for possible overdrive problems. The single-ended measurement topology can also affect the performance of Auto mode, which will only function properly with a matched source imp

Three poss the (-) input of the probe when the single-ended signal is connected to the (+) input.

he termination network on the measured response, particularly on the DC common-mode component of the signal.

the limited dynamic range of the probe ampliﬁer, single-ended measurements, which also display the DC

edance conﬁguration.

ible single-ended measurement topologies will be examined in this section. They differ in the termination used on

12 P7313SMA Technical Reference

Operating Basic

50 Ohm Termination on (-) Input. A single-ended measurement topology with a 50 Ω termination on the probe (-) input

is shown. (See F DC loading on the signal source.

igure 8.) The general equations that describe the response of that topology are also shown, including

Figure 8: 50 ohm termination on (-) input

The equations for this topology show that varying the termination voltage, V

, affects the DC loading on the signal

source, but does not affect the measured DC voltage. The measured, single-ended DC voltage also represents only half the c

ommon-mode input voltage, V

, because of the voltage divider network formed by the four 50 Ω resistors and

the differential amp liﬁer response.

Although the 50 Ω termination resistors have been laser trimmed for guaranteed performance, it should be noted that the precision of the signal measurement in this topology is affected by the signal source impedance and the impedance o f the 50 Ω termi

nation resistor inside the probe positive input connector. This matched source impedance topology is the only

single-ended topology that can be correctly used with Auto mode.

P7313SMA Technical Reference 13

Operating Basic

Shorting Termination on (-) Input. An alternative single-ended measurement topology with a shorting termination on

the (-) input is shown. The equations for this topology show identical loading of the signal source when compared to the 50 Ω termination topology. This is because the termination voltage, V the probe nega

shown. (See Figure 9.) The general equations describing the response and loading of this topology are also

, effectively isolates input signal loading from the termination on

tive input.

Figure 9: Shorting termination on (-) input

The measured single-ended signal response for this topology differs from the 50 Ω termination topology. The measured AC voltage, V common-m

In the spe

, is the same for both single-ended topologies, but the m easured DC voltage is affected by both the

ode input voltage, V

, and the termination voltage, VT.

cial case where the termination voltage is set equal to the common-mode input voltage, the input signal DC loading is minimized and the measured DC output voltage equals the full common-mode input voltage, scaled by the probe attenuation. The intelligent TekConnect probe interface automatically accounts for the probe attenuation setting and a TekConn

Althoug

ect oscilloscope will display the full single-ended input signal when V

h this topology displays the correct DC common-mode voltage, it also has a greater risk of exceeding the probe

equals V

CM.

dynamic range and overdriving the probe ampliﬁer.

14 P7313SMA Technical Reference

Operating Basic

Open (-) Input. Another alternative single-ended measurement topology is shown. (See Figure 10.) In this case, the (-)

input is left op

en, effectively keeping it at the V

of this topology are also shown.

voltage level. The general equations describing the response and loading

Figure 10

:Open(-)input

The measured single-ended response for this topology has the same AC voltage, V common-mode voltage term that is propor tional to the difference between V but common case, where V

, only the AC component is displayed, somewhat like an AC-coupled condition.

T=VCM

and the termination voltage, VT. In the special

, as the other topologies, but has a

P7313SMA Technical Reference 15

Operating Basic

Single-Ended Measurement Procedure

The description of characteristics of the three alternative single- ended measurement topologies suggests the following procedure for making single-ended measurements on serial data signals that require light DC loading, (for example, when V =VCM):

First, determine the common-mode input voltage, V

, of the single-ended signal by making a measurement with the 50 Ω

termination topology shown. (See Figure 8 on page 13.) With this topology and the Termination Voltage Select set to Auto mode, the common-mode input voltage can be measured with a DMM on the Termination Voltage Monitor output pins.

Note that measuring the common-mode input voltage on the single-ended signal using this topology is more accurate than using a differential measurement topology, where the measured common-mode voltage is the average between the two single-ended signals that comprise the differential signal. The common-mode voltage for each of the single-ended inputs that comprise the differential signal should be measured independent ly and recorded for use in the second step of this procedure.

Next, since the 50 Ω termination topology only displays half the common-mode input voltage, it is now necessary to switch to the shorting termination topology shown. (See Figure 9 on page 14.) This can be done simply by changing the termination attached to the (-) input from a 50 Ω SMA termination to an SMA shorting termination.

Since Auto mode only works with matched-source impedances on both probe inputs, it is also necessary to switch the Termination Voltage Select to either Int or Ext mode. The termination voltage should be set to the voltage measured in the ﬁrst step. This can be done easily in Int mode, but requires a TekConnect oscilloscope that has support for probe termination voltage select.

Setting the termination voltage in Ext m ode requires the use of an external power supply and the accessory cables supplied with the probe. Once the termination voltage has been set to match the DC common-mode input voltage, the complete input signal is displayed with the shorting termination topology. This shorting termination topology, however, has the highest risk of exceeding the probe dynamic range. Dynamic range calculations for single-ended measurements will now be described.

Single-Ended Dynamic Range

The dynamic range of the probe has been speciﬁed for differential measurements, as described in the differential measureme longer nulled out, but becomes a differential mode DC signal that must be within the input dynamic range of the probe to be measured accurately.

nt topology section. When single-ended measurements are made, the input common-mode voltage is no

The speciﬁed dynamic range for differential signals, which is expressed as a differential peak-to-peak voltage, can be converte

d to a more conventional voltage range for single-ended signal measurements as shown. (See Table 2.)

Table 2: Differential to single-ended conversion table

nded measurement

Attenuation

Differen

tial measurement

dynamic range

Single-e dynamic range

2.5X 800 mVp-p ±0.400 V

12.5X 3.6 Vp-p ±1.8 V

Because

the common-mode DC voltage of many serial data signals is larger than the s ignal differential mode voltage, the relatively small single-ended dynamic range in the 2.5X attenuation setting may not be adequate. As a result, single-ended measurements will generally be made using the 12.5X attenuation setting.

16 P7313SMA Technical Reference

Operating Basic

In the case where single-ended measurements are made on signals w ith a large common-mode DC voltage, it should be noted that the u taken into account as an offset to the displayed signal, it allows single-ended signals with a relatively large DC common-mode voltage to be measured.

If only the AC component of the single-ended signal needs to be measured, then the open input topology provides the greatest d

se of the 50 Ω termination topology effectively attenuates the DC common-mode voltage by half. If this is

ynamic range.

Although it is should be taken to account for the signal loading and the impact on the termination voltage of the probe.

If an external attenuator is used, its attenuation accuracy must be taken into account when factoring the impact on measurement accuracy. The increase in attenuation also brings an increase in noise.

Extending th

At times it may be necessary to extend the probe inputs with cables that are longer than the standard 38 inch cables. The 38 inch cables are precision-matched to minimize time-delay differences (skew).

If you substitute cables, you should use low-loss, ﬂexible cables and keep the lengths matched and as short as possible to minimize skew and optimize common-mode rejection. C heck the skew between the cables, and if necessary, use a pair of phase adjusters to minimize the skew.

Extending the input leads will also increase the skin loss and dielectric loss, which may result in distorted high-frequency pulse edges. You must take into account any effects caused by the extended leads when you take a measurement.

possible to attenuate an input signal with external attenuators to increase the effective dynamic range, care

e Input Connections

P7313SMA Technical Reference 17

Operating Basic

Checking Cable Skew

The time-delay difference (skew) between the ends of the matched-delay SMA cable pair supplied with the probe is typically less than 1 ps. If you use a pair of matched, high-quality, low-loss cables other than those supplied with the probe, you can bring the skew to within 1 ps by using a pair of phase adjusters. (See page 48, O ptional Accessories.)

You can measure the skew of a pair of matched cables by connecting the cables to a Tektronix 80E08 or 80E10 Sampling Head, conﬁgured for a TDR output. (See Figure 11.)

1. Turn on the equipment and let it warm up for 20 minutes. Do not connect the cables to the sampling head yet.

2. Do a system compensation for the TDR module, and then verify the skew of the two outputs with the TDR outputs

open, using a common-mode TDR drive.

Skew between the two outputs can be compensated with the TDR module deskew control. Refer to your sampling head or oscilloscope manual for instructions.

3. Connect the matched cable pair to the TDR outputs.

Figure 11: Checking skew between inputs

4. The measured skew of the matched cable pair that are supplied with the probe should be less than 1 ps. User-supplied

cables may not be nearly as accurate, and may require some trial-and-error testing to select an optimally-matched pair. Adjust the horizontal scale to locate the pulse (to account for the cable delay; it is approximately 4.5 ns for the cable set supplied with the probe). If you use the system cursors, be aware that the displayed time is the round-trip time (step and reﬂection). You need to divide the displayed time difference by 2 to derive the actual skew.

If you need to minimize the skew of a pair of cables not supplied with the probe, continue with Adjusting Cable Skew. (See page 19, Adjusting Cable Skew.)

18 P7313SMA Technical Reference

Adjusting Cable Skew

If you want to minimize the skew introduced by cable pairs other than those supplied with the probe, you can use a pair of phase adjusters to bring the skew to within 1 ps. (See page 48, Optional Accessories.) The phase adjusters have male and female SMA connectors to simplify connections to your measurement system.

You must add a phase adjuster on each cable to balance the delay and insertion loss introduced by the phase adjuster. You only adjust (add delay to) the phase adjuster on the cable with the shorter delay.

The adjustment range of the phase adjusters on the Optional Accessories list is 25 ps, so if you use cable pairs other than those supplied with the probe, the initial delay mismatch should be less than 25 ps.

1. Connect the phase adjusters to the cables.

2. On the cable w ith the longer delay, loosen the phase adjuster locking nuts, set the phase adjuster to minimum delay

(shortest length), and secure the locking nuts. (See Figure 12.)

Operating Basic

Figure 12: Using the phase adjuster

3. Loosen the locking nuts on the adjuster that is connected to the other cable (with the shorter delay).

4. While observing the oscilloscope display, turn the collar on the phase adjuster counterclockwise to increase the delay.

5. When the displayed skew on screen is less than 1 ps, tighten the locking nuts.

6. Conﬁrm that the skew is acceptable after you tighten the locking nuts, as the adjustment may change slightly during

ing.

tighten

7. Disconn

P7313SMA Technical Reference 19

ect the cables from the sampling head, and connect them to the P7313S MA probe head.

Operating Basic

Deskewing Probes

You can measure the skew between two P7313SMA probes by using a Tektronix 80E10 Sampling Head conﬁgured for a TDR output. Because the skew of the P7313SMA probe inputs is less than 1 ps, two P7313SMA probes can be deskewed using single-ended drive signals from a dual-channel TDR source. The TDR output provides a pair of time-aligned pulses that you can use to compare probe response times, and if necessary, adjust them to match (deskew).

A setup is shown for checking and deskewing two probes. (See Figure 13.) Deskewing aligns the time delay of the signal

ough the oscilloscope channel and probe connected to that channel, to the time delay of other channel/probe

path thr pairs of the oscilloscope.

If you need to deskew more than two probes, keep one deskewed probe connected to the sampling head as a reference (after deskewing two probes), and deskew additional probes to that probe. In this procedure, Channel 1 i s used as the reference channel.

1. Set up the equipment and let it warm up for 20 minutes, but don’t make any connections to the TDR outputs yet.

2. Do a system compensation for the TDR module, and then verify the skew of the two outputs with the TDR outputs

open, using a common-mode TDR drive.

Skew between the two outputs can be compensated with the deskew control. Refer to your sampling head or oscilloscope manual for instructions.

3. Attach the probes to the TDR outputs. (See Figure 13.)

Figure 13: Deskewing two P7313SMA probes

4. Display the channel(s) that you want to deskew.

5. Push the AUTOSET button on the instrument front panel.

20 P7313SMA Technical Reference

Operating Basic

6. Turn averaging on to stabilize the display.

7. Adjust vertical SCALE, and POSITION (with active probes, adjusting offset may be required) for each channel so that

the signals ove

rlap and are centered on-screen.

8. Adjust horizon

9. Adjust horizon

10. Adjust horizon

want to, you can use the measurement cursors to display the channel-channel skew, and enter this value in step 14.

11. To u ch the VERT button or use the Vertical menu to display the vertical control window.

12. Touch the Probe Deskew button to display the channel-deskew control window.

13. In the Channel box, select the channel that you want to deskew to Channel 1.

NOTE. If possible, do the next step at a signal amplitude within the same attenuator range (vertical scale) as your planned

signal measur can generally hear attenuator settings change) and, therefore, a slightly different signal path. This different path may cause up to a 200 ps variation in timing accuracy between channels.

14. Adjust the de can do this several ways:

Click the Deskew ﬁeld and input the time value you m easured with the cursors in step 10.

Use the front-panel controls to position the signal.

Use the on-screen controls to position the signal.

tal POSITION so that a triggered rising edge is at center screen.

tal SCALE so that the differences in the channel delays are clearly visible.

tal POSITION again so that the rising edge of the Channel 1 signal is exactly at center screen. Now, if you

ements. Any change to the vertical scale after deskew is complete may introduce a new attenuation level (you

skew time for the signal that you want to deskew s o that the signal aligns with the Channel 1 signal. You

15. Repeat steps 3 through 14 for each additional channel that you want to deskew.

P7313SMA Technical Reference 21

Operating Basic

22 P7313SMA Technical Reference

Reference

This section contains reference information about communi cation standards and related differential measurements.

Serial Bus Standards

Some popular high-speed data communication standards that can be measured with the P7313SMA differential probe are listed below. (See Table 3.)

Table 3: Serial bus standards with dynamic range requirements

Standard Data Rate Vdm_max Vdm_min Vcm_max Vcm_min

HDMI

1.65 Gb/s

InﬁniBand TX

2.5 Gb/s

InﬁniBand RX

2.5 Gb/s

PCI Express TX

2.5 Gb/s

PCI Express RX

2.5 Gb/s

Serial ATA

1.5 Gb/s

Serial ATA RX

1.5 Gb/s

XAUI TX

3.125 Gb/s

XAUI RX

3.125 Gb/s

OIF-SxI-5 TX

3.125 Gb/

OIF-SxI-

3.125 Gb/s

LV PECL (stdECL) >12GHz

LV PECL (RSECL) >12GHz

5RX

800 mV 150 mV 3.3 V 2.8 V

1.6 V 1.0 V 1.0 V 0.5 V

1.6 V 0.175 V 1.0 V 0.5 V

1.2 V 0.8 V

1.2 V 0.175 V

0.6 V 0.4 V 0.3 V 0.2 V

0.6 V 0.325 V 0.3 V 0.2 V

0.4 V

0.1 V

1.0 V 0.5 V 1.23 V 0.72 V

1.0 V 0.175 V 1.30 V 1.10 V

1.66 V (typ)

1.05 V 0.70 V

1.48 V

AC AC

1.3 V (vt) 0.5 V (vt)

Reference

P7313SMA Technical Reference 23

Reference

InﬁniBand

A number of high-speed serial data communication standards have been introduced to address the need for next generation I/O connectivity. One of these interface standards, InﬁniBand, is brieﬂy discussed here. (See Figure 14.)

An InﬁniBand communication lane includes two independent differential signaling paths, one for transmit and one for receive, both operating at a 2.5 Gb/s rate. As shown in the example below, the differential output parameter is speciﬁed as a peak-to-peak voltage difference, and thus the signal swing on each pin of the driver is half that value.

The V

signal shown in (b) is measured with a differential probe connected between the two signals in (a). The V

diff

signal represents the result of the receiver processing the two complementary input signals from the driver shown in (a), and cannot be measured directly as a single-ended signal.

Figure 14: InﬁniBand signals

24 P7313SMA Technical Reference

Speciﬁcations

Speciﬁcation

The speciﬁcations in the following tables apply to a P7313SMA probe installed on a TDS6804 oscilloscope. The probe must have a warm-up period of at least 20 minutes and be in an environment that does not exceed the limits described. (See Table 4.) Speciﬁcations for the P7313SMA differential probe fall into three categories: warranted, typical, and nominal characteristics.

Warranted Characteristics

Warranted characteristics describe guaranteed performance within tolerance limits or certain type-tested requirements. (See Table 4.) Warranted characteristics that have checks in the Performance Veriﬁcation section a re m arked wi th the

Table 4: Warranted electrical characteristics

Characteristic

Differential rise time, 10-90% (probe only) (Main output)

Differential signal range 0.800 Vp-p (2.5X attenuation)

DC gain (Main output)

Termination voltage range

Termination voltage accuracy

(EXT mode)

(INT mode)

(AUTO mode)

Linearity

Output offset voltage (Main output) VCM=0V,VDM=

0V,V

=0V

Differential-mode input resistance

Maximum nondestructive input voltage VT= 0 V, applied <5 minutes

Maximum nondestructive external termination input voltage

Temperature

Humidity

symbol.

Description ≤40 ps, +20 °C to +30 °C (+68 °F to +86 °F),

100 mV diffe 500 mV differential step in 12.5X attenuation

3.6 Vp-p (12.5X attenuation)

0.40 ±2.0% (corresponds to 2.5 X attenuation)

0.08 ±2.0%

+3.6 V /-2.

±(0.2% x V

±(0.3% x V

±(2.5% x V

±1% or less of dynamic range

±2.5 mV +20 °C to +30 °C (+68 °F to +86 °F)

100 Ω ±2%

±5 V (DC + peak AC) on either SMA input

±15 VDC

Operating: 0 to +40 °C (+32 to +104 °F)

Nonoperating: -55 to +75 °C (-131 to +167 °F)

Operating: 0-90% RH, tested at +30 to +40 °C (+68 to +104 °F)

Nonoperating: 0-90% RH, tested at +30 to +60 °C (+68 to +140 °F)

rential step in 2.5X attenuation

(corresponds to 12.5 X attenuation)

+2 mV) over a +3.6 V/–2.5 volt VTrange

+ 2 mV) over a +3.6 V/–2.5 volt VTrange

+ 20 mV) over a +3.6 V/–2.5 volt VCMrange

P7313SMA Technical Reference 25

Speciﬁcations

Typical Characteristics

Typical characteristics describe typical but not guaranteed performance. (See Table 5.)

Table 5: Typical electrical characteristics

Characteristic Description

Differential bandwidth (probe only)

Main output

Aux output

Differential rise time, 20-80% (probe only, Main and Aux output)

Single-ended rise time, 10-90%, (probe only, Main and Aux output)

Differential signal input skew <1 ps (with matched SMA cable pair)

Differential input return loss >35 dB @500 MHz (VSWR <1.06:1)

Termination voltage driver current

Common-mode DC input signal range +3.6 V/–2.5 V

Common-mode input return loss >35 dB @500 MHz (VSWR <1.06:1)

Common-mode rejection ratio (Main output) (See Figure 15 on page 27.)

Common-mode rejection ratio (Aux output) >45 dB @1 GHz

Delay time (includes standard cables) 5.15 ns ±100 ps, relative to a TCA-SMA adapter

Noise, referred to input

DC gain (Aux output) 0.40 ±2.5% (corresponds to 2.5 X attenuation)

Output offset voltage (Aux output) ±15 mV, +20 °C to +30 °C (+68 °F to +86 °F)

Output offset voltage (Main output) V

=0V,VT=±2.0V

=±2.5V,VT=0V

DC to 13 GHz (-3 dB)

DC to 13 GHz (-6 dB) ≤25 ps, +20 °C to +30 °C (+68 °F to +86 °F),

100 mV differential step in 2.5X attenuation 500 mV differential step in 12.5X attenuation

≤40 ps, +20 °C to +30 °C (+68 °F to +86 °F), 250 mV step

>20 dB @6.5 GHz (VSWR <1.22:1) >15 dB @10 GHz (VSWR <1.43:1) >12 dB @13 GHz (VSWR <1.67:1)

±(82.5 mA ±8 mA) overload

>20 dB @6.5 GHz (VSWR <1.22:1) >15 dB @10 GHz (VSWR <1.43:1) >12 dB @13 GHz (VSWR <1.67:1)

>45dB@1GHz >40 dB @2.5 GHz >30dB@5GHz >20 d B @10 GHz >15 dB @13 GHz

>40 dB @2.5 GHz >30dB@5GHz >20 d B @10 GHz >15 dB @13 GHz

13 nV/ √Hz (2.5 X attenuation) 40 nV/ √Hz (12.5 X attenuation)

0.08 ±2.5% (corresponds to 12.5 X attenuation)

<±5mV,+20°Cto+30°C(+68°Fto+86°F)

26 P7313SMA Technical Reference

Table 5: Typical electrical characteristics (cont.)

Characteristic Description

DC offset drift -50 mV/°C or less at output of probe

(results in -0.125 mV/°C or less (2.5 X), or

-0.625 mV/°C or less (12.5 X) displayed on screen)

DC voltage measurement accuracy (referred to input) ±(2% of input + 8.00 mV + 8.00 mV) (2.5 X)

±(2% of input + 36.00 mV + 36.0 mV) (12.5 X)

gain error = ±2% of input voltage

output zero offset (referred to input) = ±8.00 mV (2.5 X) ±36.00 mV (12.5 X)

linearity error = ±1.0% of: 800 mV dynamic range = 8.00 mV (2.5 X)

3.6 V dynamic range = 36.0 mV (12.5 X)

Typical differential CMRR plot for the probe. (See Figure 15.)

Speciﬁcations

Figure 15: Typical CMRR plot

P7313SMA Technical Reference 27

Speciﬁcations

Typical differential input return loss plot for the probe. (See Figure 16.)

Figure 16: Typical differential input return loss

Typical differential-mode bandwidth plot for the probe. (See Figure 17.)

17: Typical differential-mode bandwidth

Figure

28 P7313SMA Technical Reference

Typical eye pattern as measured with the probe. (See Figure 18.)

Speciﬁcations

Figure 18:

Typical eye pattern

Typical step response as measured with the probe. (See Figure 19.)

Figure 19: Typical differential step response

P7313SMA Technical Reference 29

Speciﬁcations

Nominal Characteristics

Nominal characteristics describe guaranteed traits, but the traits do not have tolerance limits. (See Table 6.)

Table 6: Nominal electrical characteristics

Signal input conﬁguration Differential (two SMA inputs, + and - )

Input coupling

Attenuation 2.5 X and 12.5 X Common-mode input resistance 50 Ω ±1% (internally per side)

Termination voltage input conﬁguration DC (two 0.080 in jacks, + and - ) Termination voltage buffer input resistance 100 KΩ

Termination voltage output monitor

Termination voltage output monitor resistance Output coupling and termination DC, terminate output into 50 Ω

Auxiliary signal output

All TekConnect host instruments recognize this gain setting and adjust the Volts/Div setting to correspond to a normal 1-2-5 sequence of gains.

DC (two 0.040 in jacks, + and - ) 1KΩ

SMA output

30 P7313SMA Technical Reference

Mechanical Characteristics

The mechanical characteristics of the probe are listed below. (See Table 7.) The mechanical dimensions are shown. (See Figure 20.)

Table 7: Typical mechanical characteristics

Speciﬁcations

Dimensions

Unit weight

Shipping weight (includes shipping materials) 1.38 kg (3.1 lb)

Standard cable assembly length 0.96 m (38 in)

Figure 20: Probe dimensions

48.0 mm × 31.8 mm ×129.5 mm (1.9 in × 1.3 in × 5.1 in)

230 g (0.51 lb)

P7313SMA Technical Reference 31

Performance Ver

iﬁcation

Performance V

Use the following procedures to verify speciﬁcations of the probe. The recommended calibration interval is one year.

These procedures test the following speciﬁcations:

Differential mode input resistance

Termination voltage accuracy

Output offset zero

DC gain accuracy

Differential mode rise time

eriﬁcation

Equipment Required

A list of the equipment required to verify the performance of your probe is shown. (See Table 8.)

Table 8: Equipment required for performance veriﬁcation

Item description Performance requirement Recommended example

Oscilloscope TekConnect interface Tektronix TDS6804 or TDS7704

Sampling Oscilloscope Windows 2000 OS, with oscilloscope

Sampling Module 30 GHz bandwidth

Sampling Module 20 GHz bandwidth

TekConnect Probe Interface Module with semi-rigid cable

DMM (2), with leads 0.1 mV and 0.01 Ω resolution

Dual Power Supply 5.0 VDC at 200 mA

Feedthrough Termination Attenuators (2) SMA, 50 Ω, 5X attenuation

Coaxial cable Male-to-Male SMA

Coaxial cable

Coaxial cable Male-to-Male BNC, 50 Ω

Test leads (2)

Test leads 0.080 in pin-to-Banana plug ends, one

Adapter Adapters (3) SMA 50 Ω termination

Adapter

Adapters (2)

Tektronix TDS8000

FW ≥V2.5 (for compatibility with Tektronix 80E08/10 modules)

Tektronix 80E08

Tektronix 80E04

Firmware version V2.2 or above Tektronix 80A03, with 174-4857-xx

cable

Fluke 187 or equivalent

B+K Precision 1760A or equivalent

BNC, 50 Ω ±0.05 Ω

Dual, matched-delay Male-to-Male SMA

Banana plug ends, red 012-0031-00

Banana plug ends, black 012-0039-00

each color

(See Figure 21 on page 33.) Tektronix TCA-SMA

SMA Male-to-SMA Male

0.040 in-to-0.080 in pin jack 012-1676-xx

011-0129-00

015-1002-01

012-0649-00

174-4944-00

012-0057-01

012-1674-00 (red) 012-1675-00 (black)

015-1022-00

015-1011-00

32 P7313SMA Technical Reference

Table 8: Equipment required for performance veriﬁcation (cont.)

Item description Performance requirement Recommended exam ple

Adapter

Adapters (2) BNC Male-to-SMA Female

Adapters (3) BNC Female-to-Dual Banana

Adapter

SMA torque wrench 5/16-in, 7 in-lb.

Nine-digit

Standard accessory included with the probe.

One adapter is included with the probe.

part numbers (xxx-xxxx-xx) are Tektronix part numbers.

Special Adapters Required

Some of the adapters listed in the previous table are available only from Tektronix. These adapters are described on the following pages.

SMA Male-to-BNC Female

BNC T

BNC Female-to-BNC Female

015-1018-00

015-0572-00

103-0090-00

103-0030-00

103-0028-00

Performance Ver

iﬁcation

TekConnect-to-SMA Adapter

The TekConn connected to a TekConnect input. (See Figure 21.) Connect and disconnect the adapter the same way as you do the probe.

This adapter is an oscilloscope accessory that may be used for measurement applications, as well as these performance veriﬁcation procedures.

Figure 21: TekConnect-to-SMA Adapter

ect-to-SMA Adapter, Tektronix part number TCA -SMA, allows signals from an SMA cable or probe to be

P7313SMA Technical Reference 33

Performance Ver

iﬁcation

Equipment Setup

The following tests use two oscilloscopes; use this procedure to set up and warm the equipment to test the probe. Wear the antistatic wriststrap when performing these procedures.

1. Connect the 80A03 TekConnect probe interface to channels 3 and 4 of the TDS8000 oscilloscope. (See Figure 22.)

2. Connect the 80E04 module to the 80A03 TekConnect probe interface.

3. Connect the 80E08 module to channels 7 and 8 of the TDS8000 oscilloscope.

4. Connect a 50 Ω termination to the Aux Output connector on the probe, and connect the probe to one of the 80A03

channels.

5. Turn on both oscilloscopes and allow 20 minutes for the equipment to warm up.

6. Photocopy the test record to record the performance test results. (See Table 9 on page 47.)

Figure 22: Preliminary test setup

34 P7313SMA Technical Reference

Input Resistance

This test checks the differential mode input resistance (the resistance between each SMA input). The test is performed with the probe disconnected from the oscilloscope.

1. Disconnect the probe from the oscilloscope.

2. Zero the DMM with its measurement leads connected together on the lowest scale that can measure 100 Ω.

3. Remove the SMA terminations from the two probe inputs and gently probe the center contacts of the input connectors.

Be careful not to touch the outer edge (ground) of the connector. (See Figure 23.)

4. Measure the resistance and write down the value.

5. Reverse the DMM connections and repeat the measurement. Write down the value.

6. Add the two measurements from steps 4 and 5, and divide the total by two. Record the result in the test record.

7. Connect the probe to the oscilloscope channel that you will use in the next test so that the probe warms up to operating

temperature.

Performance Ver

iﬁcation

Figure 23: Checking differential mode input resistance

P7313SMA Technical Reference 35

Performance Ver

iﬁcation

Termination Voltage Accuracy

These tests compare the termination control voltage that you apply (using the adjustment control for that termination voltage mode), to the termination voltage output at the Vterm monitor jacks.

NOTE. The Auto mode LED will ﬂash when the probe inputs are open-circuit, or below a 50 mV threshold. If the LED

continues to ﬂash after you connect the inputs, cycle the mode SELECT button.

External (Ext) Mode

The Ext mode test setup is shown. (See Figure 24.)

1. Plug the probe directly into an oscilloscope channel and set the Vterm Source Select to EX T on the probe.

Figure 2

2. Connect the 50 Ω terminations on the three probe SMA connectors. This s ets the common mode input voltage to 0.0 V.

3. The probe attenuation can be set to either 2.5X or 12.5X.

4. Using the 0.080 in pin-to-Banana plug cables, connect the power supply to the external DC input jacks on the front

5. Set the power supply as close as practical to 0.000 volts, and use the DMM to measure this input voltage at the terminals

36 P7313SMA Technical Reference

4: Termination Voltage Accuracy, E xt mode setup

of the probe.

on the front of the probe. Record this voltage as Vin on the test record.

Performance Ver

6. Use the second DMM to measure the output voltage at the termination voltage monitor jacks on the top of the probe. Record this vol columns. For example, within ±2 mV of the actual Vin voltage that you measured in the previous step.

7. Repeat steps 5 and 6 for the +2.500 volt and -2.500 volt input values listed in the test record.

tage as Vout on the test record, and verify that the Vout voltage is within the speciﬁed limits in the min/max

iﬁcation

Internal (Int) Mode

If your oscilloscope supports internal mode, use this test to check the accuracy of the internally-generated termination voltages. In Int mode, you use a graphical user interface in the oscilloscope to set the test values to the 0.000, +2.500 and

-2.500 volt levels, instead of using external power supplies. You do not need to measure these values in Int mode, as

they are digitally set.

See your oscilloscope manual for details on using the interface.

1. Disconnect the power supply from the probe.

2. Set the Vterm Source Select to INT on the probe.

3. Use the graphical user interface in the oscilloscope to set the termination voltage to 0.000 V.

4. Use the DMM to verify that the termination voltage output at the Vterm monitor jacks on the top of the probe is within the

limits on the test record. Record this value as Vout on the test record.

5. Repeat steps 3 and 4 for the +2.500 volt and -2.500 volt input values listed in the test record.

P7313SMA Technical Reference 37

Performance Ver

Auto Mode

In Auto m ode, the probe measures the input signal DC common mode voltage and automatically sets the termination voltage to equal that voltage. In this test, the two signal inputs are connected together and driven by an external power supply to set the common mode voltage to the 0.0, +2.500 and -2.500 volt test values.

1. Connect the test setup as shown. (See Figure 25.)

iﬁcation

Figure 25: Termination Voltage Accuracy, Auto mode setup

2. Set the Vterm Source Select to Auto on the probe.

3. Set the power supply as close as practical to 0.000 volts, and use the DMM to measure this input voltage at the terminals

on the power supply. Record this voltage as Vin on the test record.

4. Use the second DMM to measure the output voltage at the termination voltage monitor jacks on the top of the probe. Record this voltage as Vout on the test record, and verify that the Vout voltage is within the speciﬁed limits in the min/max columns.

5. Repeat steps 3 and 4 for the +2.500 volt and -2.500 volt input values listed in the test record.

38 P7313SMA Technical Reference

Output Offset Zero

By terminating the two probe SMA inputs with 50 Ω, this procedure tests the zero output voltage of the probe. The probe output is measured at the SMA connector on the front of the 80A03 interface.

1. Connect the equipment as shown. (See Figure 26.)

2. Connect two 50 Ω terminations to the two probe SMA inputs on the probe, and plug the probe into the 80A03 module.

3. Connect the cable from the DMM to the SMA connector that is located below the 80A03 channel that you plugged

the probe into.

Performance Ver

iﬁcation

Figure 26

4. Set the Vterm source to Ext on the probe. Leave the external termination control v oltage inputs open. This sets the

5. Set the multimeter to read DC volts.

6. Verify that the output voltage is 0 V, ±2.5 mV for both the 2.5X and 12.5X attenuation settings.

7. Record the results on the test record.

: Setup for the output offset zero test

termination voltage to zero.

P7313SMA Technical Reference 39

Performance Ver

iﬁcation

DC Gain Accuracy

This test checks the DC gain accuracy of the probe at the two attenuation settings, 2.5X and 12.5X.

Gain Check at 2.5X A ttenuation

1. Set the attenuation on the probe to 2.5X, and the termination select to Auto.

2. Connect the probe to the power supplies as shown. (See Figure 27.) Make sure the ground tabs on the BNC-to-dual

banana plug ad one of the DMMs.

apters are connected to the ground connections on the power supplies. Monitor the source voltage with

Figure 27: DC Gain Accuracy setup

3. Set the voltage on each power supply to approximately +0.160 V (+0.32 V differential total). This represents 80% of the

probe dynamic range in this attenuation se tting. Record this source voltage as V

4. Record the output voltage (on the second DMM) as V

out

5. Disconnect the BNC-to-dual banana plug adapters from the power supplies. Leave the DMM leads connected to

pters.

the ada

6. Connec

t the BNC-to-dual banana plug adapters into the opposite power supplies to reverse the v oltage polarity to the

probe inputs. (See Figure 28 on page 41.)

7. Record the actual source voltage (now a negative value), as V

40 P7313SMA Technical Reference

Figure 28: Reverse the power supply polarity on the probe inputs

Performance Ver

iﬁcation

8. Record the output voltage (on the second DMM) as V

1-V

9. Calculate the gain as follows: ( V

out

2) ÷ (Vin1-Vin2).

out

10. Verify that the gain is 0.4, ±2.0%.

11. Record the calculated gain for the 2.5X setting on the test record.

Gain Check at 12.5X Attenuation

12. Set the attenuation on the probe to 12.5X.

13. Repeat steps 2 through 9, but in step 3, set each power supply to +0.7 V (+1.4 V differential total).

14. Verify that the gain is 0.08, ±2.0%.

15. R ecord the calculated gain on the test record.

P7313SMA Technical Reference 41

Performance Ver

Rise Time

This procedure veriﬁes that the probe meets the differential rise time speciﬁcation. Two rise times are measured; the test system alone, and the test system with the probe included. The probe rise time is calculated using the two measurements.

Note: This test uses the TDR function of the 80E08 or 80E10 sampling head as a fast rise time signal source. A second 80E0X sampling head is used to take the measurements, using an 80A03 TekConnect probe interface. Although the following procedure assigns the TDR and measurement functions to speciﬁc o scilloscope channels, any valid channel combination can be used. However, the TDR rise times required of the sampling heads in this test are only available on 80E08 and 80E10 sampling heads.

This test checks both of the probe attenuation settings, but due to the differential TDR output amplitude and common mode voltage, inline 5X attenuators must be used when checking the 2.5X attenuation setting on the probe.

Rise Time Check at 12.5X Attenuation

1. Connect the test equipment as shown. (See Figure 29.)

CAUTION. To prevent mechanical strain on the connectors, use care when working with SMA connectors: support

equipment a

iﬁcation

nd use a torque wrench to tighten connections to 7 in-lbs.

Figure 29: Test system rise time setup

NOTE. The ﬁrmware of the 80A03 TekConnect Probe Interface used to power the probe must be version V2.2 or above.

42 P7313SMA Technical Reference

Performance Ver

2. Turn on Channel 4 and set the vertical scale to 50 mV/div.

3. Set the Channel 7/8 sampling head to TDR mode: Press the SETUP DIALOGS button and select the TDR tab. (See

Figure 30.)

iﬁcation

Figure 30: Setting the TDR parameters

4. Set the Channel 7 (C7) Polarity to negative (falling).

5. Set the Channel 8 (C8) Polarity to positive (rising).

6. Set the Preset of Channel 7 and 8 on.

TDR Preset sets Internal Clock in the Trigger menu, turns on the TDR Step in the TDR Setups menu, turns on the channel and selects the acquisition Units i n the TDR Setups menu, and sets the horizontal scale, position, and reference. The sampling module will turn on a red light next to the SELECT channel button, indicating that TDR is activated for that channel.

P7313SMA Technical Reference 43

Performance Ver

Deskew Channel 7 and 8 by doing the following:

7. Check that Ch 7 is set to negative s lope and Ch 8 is set to positive slope.

8. Verify/clear all deskew values for Ch 7 and Ch 8 in both the TDR menu and the vertical menu.

9. Turn off the display for Ch 7 and Ch 8 so that only Ch 4 is shown on screen.

10. Set the horizontal scale to 10 ps/div, and the vertical scale to 50 mV/div.

11. Adjust Ch 4 to position the step at 0 V, and then enter –125 mV offset to position the step as shown. (See Figure 31.)

Save this wavef

iﬁcation

orm to a reference.

Figure 31: Deskew the TDR steps

12. Remove Ch 7 from the Ch 4 input and connect Ch 8 to the Ch 4 input.

13. Press the Ch 4 button to display Channel 4.

14. Enter 125 mV offset to position the step as shown. (See Figure 31.)

15. From the TDR menu, adjust the deskew on Ch 8 to align the edges with the reference value from step 11.

16. Use the oscilloscope measurement capability to display rise time. Increase the stability of the pulse edge measurement

by using averaging, if available. Rise time is measured from the 10% and 90% amplitude points on the waveform. Recordtherisetimeast

44 P7313SMA Technical Reference

Performance Ver

The following steps instruct you to assemble the test setup that includes the probe. (See Figure 32.) The system and probe rise time (t

)thatyoumeasureinstep24isusedtocalculatetheproberisetime(tp)instep25.

s+p

iﬁcation

Figure 32: Test system rise time setup with probe

17. Remove the TekConnect-to-SMA adapter from the test setup.

18. Connect the probe to the 80A03 TekConnect probe interface.

19. Connect the matched SMA cables to the probe SMA inputs and the 80E08 sampling head (Channels 7 and 8).

20. Set the attenuation on the probe to 12.5X.

The test setup should now be connected as shown. (See Figure 32.)

21. Expand the horizontal scale to help locate the step edge, and then adjust horizontal range to 50 ps/div while maintaining

the edge view. For a more stable measurement display, turn averaging on.

22. Adjust the vertical scale to 100 mV/div, averaging on.

23. Adjust the vertical and horizontal positioning to place the rising edge of the signal on the second vertical and center

horizontal graticule lines.

24. Use the oscilloscope measurement capability to display rise time. Rise time is determined from the 10% and 90%

amplitude points on the waveform. Record the rise time as t

s+p.

25. Calculate the probe rise time using the following formula:

26. Record the calculated probe rise time on the test record.

P7313SMA Technical Reference 45

Performance Ver

Rise Time Check at 2.5X Attenuation

The TDR output levels of the 80E08 module must be attenuated when checking the 2.5X attenuation setting on the probe. The attenuators add some delay and a small bandwidth reduction to the test system, so a new system time, t be measured to accurately calculate the probe rise time.

1. Disconnect the matched SMA cables from the TDR outputs.

2. Install inline 5X attenuators on the TDR outputs. (You will need to set the step offset to 25 mV and vertical scale

to 10 mV/div. in the procedure).

3. Measure a new system time by repeating steps 1 through 16 of the 12.5X attenuation check.

4. Remove the TekConnect-to-SMA adapter from the test setup.

5. Connect the probe to the 80A03 TekConnect probe interface.

6. Connect the matched SMA cables to the probe SMA inputs and the inline 5X attenuators on the TDR outputs.

7. Set the attenuation on the probe to 2.5X and set the vertical scale to 20 m V/div, averaging on.

8. Repeat steps 21 through 25 for the 2.5X attenuation setting.

9. Record the calculated probe rise time on the test record.

iﬁcation

,must

46 P7313SMA Technical Reference

Performance Ver

Table 9: Test Record

Probe Model:

Serial Number:

Certiﬁcate Number:

Temperature:

RH %:

Date of Calibration:

Technician:

Performance test Minimum Measured Maximum

Differential mode input resistance 98 Ω 102 Ω

Termination voltage accuracy

Ext Mode

Int Mode

Auto Mode

Output offset zero

DC gain accuracy

Differentia

l rise time

Vin @ 0.000 V

Vin @ +2.500 V

Vin @ -2.500 V

Vin @ 0.000 V

Vin @ +2.500 V

Vin @ -2.500 V

Vin @ 0.000 V

Vin @ +2.500 V

Vin @ -2.500 V

2.5X -2.5 mV +2.5 mV

12.5X -2.5 mV +2.5 mV

2.5X 0.392 0.408

12.5X 0.0784 0.0816

2.5X NA 40 ps

12.5X NA 40 ps

Vin - 2 mV Vin______Vout

Vin - 7 mV Vin______Vout

-0.002 V Vout +0.002 V

+2.4905 V Vout +2.5095 V

-2.4905 V Vout -2.5095 V

Vin - 20 mV Vin______Vou

Vin - 82 mV Vin______Vou

Vin - 82 mV Vin______Vo

______

t______

ut______

Vin+2mV

Vin+7mV

Vin + 20 mV

Vin + 82 mV

iﬁcation

P7313SMA Technical Reference 47

Optional Access

ories

Optional Acce

The optional accessories that you can order for the P7313SMA differential probe are listed below. (See Table 10.)

Table 10: Optional accessories

Description Accessory

Phase adjuster. Use two phase adjusters if you need to

bring the skew between inputs to 1 ps or less because of skew in the device under test differential signal path. (See page 19, Adjusting Cable Skew.)The phase adjuster has a 25 ps adjustment range.

The matched-delay SMA cables that come with your probe have a ≤1 ps skew at the cable ends.

Tektronix part number: 015-0708-XX (package of 1)

80A03. The 80A03 TekConnect Probe Interface Module is an adapter that allows you to use TekConnect probes with CSA8000 and TDS8000 Series sampling oscilloscopes and 80E0X sampling modules.

The interface contains an enclosure that houses a compartment for one 80E0X electrical sampling module and two TekConnect probe inputs. The interface routes the probe signal outputs through SMA connectors on the front panel. Semi-rigid SMA cables link the probe outputs to the 80E0X module inputs.

The 80A03 Interface Module is required to complete a performance veriﬁcation of the probe.

ssories

48 P7313SMA Technical Reference

Options

These options are available when ordering the P7313SMA probe:

Option D1-Calibration Data Report

Option CA1-A single calibration event or coverage for the designated calibration interval, whichever comes ﬁrst.

Option D3-Calibration Data Report, 3 years (with Option C3)

Option C3-Calibration Service 3 years

Option D5-Calibration Data Report, 5 years (with Option C5)

Option C5-Calibration Service 5 years

Option R3-Repair Service 3 years

Option R5-Repair Service 5 years

Options

P7313SMA Technical Reference 49

Maintenance

This section contains maintenance information for the P7313SMA differential probe.

Inspection and Cleaning

Protect the probe from adverse weather conditions. The probe is not waterproof.

CAUTION. To p r

agents; they may damage the probe. Avoid using chemicals that contain benzine, benzene, toluene, xylene, acetone, or similar solvents.

Clean the exterior surfaces of the probe with a dry, lint-free cloth or a soft-bristle brush. If dirt remains, use a soft cloth or swab dampened with a 75% isopropyl alcohol solution. A swab is useful for cleaning narrow spaces on the probe. Do not use abra

CAUTION. To prevent damage to the probe, avoid getting moisture inside the probe during exterior cleaning, and use only

enough solution to dampen the swab or cloth. Use a 75% isopropyl alcohol solution as a cleanser, and rinse with deionized water.

event damage to the probe, do not expose it to sprays, liquids, or solvents. Do not use chemical cleaning

sive compounds on any part of the probe.

Replacement Parts

Due to the sophisticated design of the P7313SMA differential probe, there are no user replaceable parts within the probe. Refer to the Quick Start User Manual for a list of replaceable accessories for y our probe.

If your probe does not meet the speciﬁcations tested in the Performance Veriﬁcation, you can send the probe to Tektronix for repair. Follow the procedure below to prevent damage to the probe during shipping.

Preparation for Shipment

ginal packaging is unﬁt for use or not available, use the following packaging guidelines:

If the ori

1. Use a corr dimensions. The box should have a carton test strength of at least 200 pounds.

2. Put the probe into an antistatic bag or wrap to protect it from dampness.

3. Place the probe into the box and stabilize it with light packing material.

4. Seal the carton with shipping tape.

5. Refer to Contacting Tektronix on the copyright page for the shipping address.

50 P7313SMA Technical Reference

ugated cardboard shipping carton having inside dimensions at least one inch greater than the probe

Tektronix P7313SMA Reference manual

Specifications and Main Features

Frequently Asked Questions

User Manual