Datasheet LMH6715MA, LMH6715MAX Datasheet (NSC)

Page 1

LMH6715 Dual Wideband Video Op Amp

General Description

The LMH6715 combines National’s VIP10™high speed complementary bipolar process with National’s current feedback topology to produce a very high speed dual op amp. The LMH6715 provides 400MHz small signal bandwidth at a gain of +2V/V and 1300V/µs slew rate while consuming only

5.8mA per amplifier from

5V supplies.

The LMH6715 offers exceptional video performance with its

0.02% and 0.02˚ differential gain and phase errors for NTSC and PAL video signals while driving up to four back terminated 75Ω loads. The LMH6715 also offers a flat gain response of 0.1dB to 100MHz and very low channel-tochannel crosstalk of −70dB at 10MHz. Additionally, each amplifier can deliver 70mA of output current. This level of performance makes the LMH6715 an ideal dual op amp for high density, broadcast quality video systems.

The LMH6715’s two very well matched amplifiers support a number of applications such as differential line drivers and receivers. In addition, the LMH6715 is well suited for Sallen Key active filters in applications such as anti-aliasing filters for high speed A/D converters. Its small 8-pin SOIC package, low power requirement, low noise and distortion allow the LMH6715 to serve portable RF applications such as IQ channels.

Features

TA= 25˚C, RL= 100Ω, typical values unless specified.

n Very low diff. gain, phase: 0.02%, 0.02˚ n Wide bandwidth: 480MHz (A

= +1V/V); 400MHz (AV=

+2V/V)

n 0.1dB gain flatness to 100MHz n Low power: 5.8mA/channel n −70dB channel-to-channel crosstalk (10MHz) n Fast slew rate: 1300V/µs n Unity gain stable n Improved replacement for CLC412

Applications

n HDTV, NTSC & PAL video systems n Video switching and distribution n IQ amplifiers n Wideband active filters n Cable drivers n DC coupled single-to-differential conversions

Differential Gain & Phase with Multiple Video Loads

20042908

Frequency Response vs. V

OUT

20042916

January 2003

LMH6715 Dual Wideband Video Op Amp

Page 2

Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.

ESD Tolerance (Note 4)

Human Body Model 2000V

Machine Model 150V

6.75V

OUT

(Note 3)

Common-Mode Input Voltage

Differential Input Voltage 2.2V

Maximum Junction Temperature +150˚C

Storage Temperature Range −65˚C to +150˚C

Lead Temperature (Soldering 10 sec)

+300˚C

Operating Ratings

Thermal Resistance

Package (θ

)(θJA)

SOIC 65˚C/W 145˚C/W

Operating Temperature Range −40˚C to +85˚C

Nominal Operating Voltage

5V to±6V

Electrical Characteristics

AV= +2, RF= 500Ω,VCC=±5V,RL= 100Ω; unless otherwise specified. Boldface limits apply at the temperature extremes.

Symbol Parameter Conditions Min Typ Max Units

Frequency Domain Response

SSBW -3dB Bandwidth V

OUT

0.5VPP,RF= 300Ω 280 400 MHz

LSBW -3dB Bandwidth V

OUT

4.0VPP,RF= 300Ω 170 MHz

Gain Flatness V

OUT

0.5V

GFP Peaking DC to 100MHz, RF= 300Ω 0.1 dB

GFR Rolloff DC to 100MHz, R

= 300Ω 0.1 dB

LPD Linear Phase Deviation DC to 100MHz, R

= 300Ω 0.25 deg

DG Differential Gain R

= 150Ω, 4.43MHz 0.02 %

DP Differential Phase R

= 150Ω, 4.43MHz 0.02 deg

Time Domain Response

Tr Rise and Fall Time 0.5V Step 1.4 ns

4V Step 3 ns

Ts Settling Time to 0.05% 2V Step 12 ns

OS Overshoot 0.5V Step 1 %

SR Slew Rate 2V Step 1300 V/µs

Distortion And Noise Response

HD2 2nd Harmonic Distortion 2V

, 20MHz −60 dBc

HD3 3rd Harmonic Distortion 2V

, 20MHz −75 dBc

Equivalent Input Noise

Non-Inverting Voltage

1MHz 3.4 nV/

Inverting Current

1MHz 10.0 pA/

Non-Inverting Current

1MHz 1.4 pA/

SNF Noise Floor

1MHz −153 dB

1Hz

XTLKA Crosstalk Input Referred 10MHz −70 dB

Static, DC Performance

Input Offset Voltage

Average Drift

30 µV/˚C

Input Bias Current Non-Inverting

µA

Average Drift

30 nA/˚C

Input Bias Current Inverting

µA

Average Drift

20 nA/˚C

PSRR Power Supply Rejection Ratio DC 46

60 dB

LMH6715

www.national.com 2

Page 3

Electrical Characteristics (Continued)

AV= +2, RF= 500Ω,VCC=±5V,RL= 100Ω; unless otherwise specified. Boldface limits apply at the temperature extremes.

Symbol Parameter Conditions Min Typ Max Units

CMRR Common Mode Rejection Ratio DC 50

56 dB

Supply Current per Amplifier RL=

∞

4.7

4.1

5.8 7.6

8.1

Miscellaneous Performance

Input Resistance Non-Inverting 1000 kΩ

Input Capacitance Non-Inverting 1.0 pF

OUT

Output Resistance Closed Loop .06 Ω

Output Voltage Range RL=

∞

4.0 V

RL= 100Ω

3.5

3.4

3.9 V

CMIR Input Voltage Range Common Mode

2.2 V

Output Current 70 mA

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but specific performance is not guaranteed. For guaranteed specifications, see the Electrical Characteristics tables.

Note 2: Electrical Table values apply only for factory testing conditions at the temperature indicated. Factory testing conditions result in very limited self-heating of the device such that T

J=TA

. No guarantee of parametric performance is indicated in the electrical tables under conditions of internal self heating where T

TA. See Applications Section for information on temperature de-rating of this device." Min/Max ratings are based on product characterization and simulation. Individual parameters are tested as noted.

Note 3: The maximum output current (I

OUT

) is determined by device power dissipation limitations. See the Power Dissipation section of the Application Division for

more details.

Note 4: Human body model, 1.5kΩ in series with 100pF. Machine model, 0Ω In series with 200pF.

Connection Diagram

8-Pin SOIC

20042904

Top View

Ordering Information

Package Part Number Package Marking Transport Media NSC Drawing

8-pin SOIC

LMH6715MA

Rails

M08A

LMH6715MAX 2.5k Units Tape and Reel

LMH6715

www.national.com3

Page 4

Typical Performance Characteristics (T

= 25˚C, VCC=±5V, AV=±2V/V, RF= 500Ω,RL=

100Ω, unless otherwise specified).

Non-Inverting Frequency Response Inverting Frequency Response

20042913

20042912

Non-Inverting Frequency Response vs. V

OUT

Small Signal Channel Matching

20042916 20042901

Frequency Response vs. Load Resistance Non-Inverting Frequency Response vs. R

20042915

20042914

LMH6715

www.national.com 4

Page 5

Typical Performance Characteristics (T

= 25˚C, VCC=±5V, AV=±2V/V, RF= 500Ω,RL= 100Ω,

unless otherwise specified). (Continued)

Small Signal Pulse Response Large Signal Pulse Response

20042918 20042919

Input-Referred Crosstalk Settling Time vs. Accuracy

20042907

20042924

−3dB Bandwidth vs. V

OUT

DC Errors vs. Temperature

20042925

20042926

LMH6715

www.national.com5

Page 6

Typical Performance Characteristics (T

= 25˚C, VCC=±5V, AV=±2V/V, RF= 500Ω,RL= 100Ω,

unless otherwise specified). (Continued)

Open Loop Transimpedance, Z(s) Equivalent Input Noise vs. Frequency

20042920 20042923

Differential Gain & Phase vs. Load Differential Gain vs. Frequency

20042908

20042909

Differential Phase vs. Frequency Gain Flatness & Linear Phase Deviation

20042910

20042911

LMH6715

www.national.com 6

Page 7

Typical Performance Characteristics (T

= 25˚C, VCC=±5V, AV=±2V/V, RF= 500Ω,RL= 100Ω,

unless otherwise specified). (Continued)

2nd Harmonic Distortion vs. Output Voltage 3rd Harmonic Distortion vs. Output Voltage

20042902 20042905

Closed Loop Output Resistance PSRR & CMRR

20042906 20042917

Suggested RSvs. C

20042927

LMH6715

www.national.com7

Page 8

Application Section

Application Introduction

Offered in an 8-pin package for reduced space and cost, the wideband LMH6715 dual current-feedback op amp provides closely matched DC and AC electrical performance characteristics making the part an ideal choice for wideband signal processing. Applications such as broadcast quality video systems, IQ amplifiers, filter blocks, high speed peak detectors, integrators and transimedance amplifiers will all find superior performance in the LMH6715 dual op amp.

FEEDBACK RESISTOR SELECTION

One of the key benefits of a current feedback operational amplifier is the ability to maintain optimum frequency response independent of gain by using appropriate values for the feedback resistor (R

). The Electrical Characteristics and

Typical Performance plots specify an R

of 500Ω, a gain of

+2V/V and

5V power supplies (unless otherwise specified).

Generally, lowering R

from it’s recommended value will peak the frequency response and extend the bandwidth while increasing the value of R

will cause the frequency

response to roll off faster. Reducing the value of R

too far below it’s recommended value will cause overshoot, ringing and, eventually, oscillation.

Frequency Response vs. R

20042914

The plot labeled “Frequency Response vs. RF” shows the LMH6715’s frequency response as R

is varied (RL= 100Ω,

= +2). This plot shows that an RFof 200Ω results in

peaking and marginal stability. An R

of 300Ω gives near maximal bandwidth and gain flatness with good stability, but with very light loads (R

300Ω) the device may show some

peaking. An R

of 500Ω gives excellent stability with good bandwidth and is the recommended value for most applications. Since all applications are slightly different it is worth some experimentation to find the optimal R

for a given circuit. For more information see Application Note OA-13 which describes the relationship between R

and closedloop frequency response for current feedback operational amplifiers.

When configuring the LMH6715 for gains other than +2V/V, it is usually necessary to adjust the value of the feedback resistor. The two plots labeled “R

vs. Non-inverting Gain”

and “R

vs. Inverting Gain” provide recommended feedback

resistor values for a number of gain selections.

20042935

FIGURE 1. Non-Inverting Configuration with Power

Supply Bypassing

20042937

FIGURE 2. Inverting Configuration with Power Supply

Bypassing

LMH6715

www.national.com 8

Page 9

Application Introduction (Continued)

vs. Non-Inverting Gain

20042921

Both plots show the value of RFapproaching a minimum value (dashed line) at high gains. Reducing the feedback resistor below this value will result in instability and possibly oscillation. The recommended value of R

is depicted by the solid line, which begins to increase at higher gains. The reason that a higher R

is required at higher gains is the

need to keep R

from decreasing too far below the output impedance of the input buffer. For the LMH6715 the output resistance of the input buffer is approximately 160Ω and 50Ω is a practical lower limit for R

. Due to the limitations on R

the LMH6715 begins to operate in a gain bandwidth limited fashion for gains of

5V/V or greater.

vs. Inverting Gain

20042922

When using the LMH6715 as a replacement for the CLC412, identical bandwidth can be obtained by using an appropriate value of R

. The chart “Frequency Response vs. RF” shows

that an R

of approximately 700Ω will provide bandwidth very close to that of the CLC412. At other gains a similar increase in R

can be used to match the new and old parts.

CIRCUIT LAYOUT

With all high frequency devices, board layouts with stray capacitances have a strong influence over AC performance. The LMH6715 is no exception and its input and output pins are particularly sensitive to the coupling of parasitic capaci-

tances (to AC ground) arising from traces or pads placed too closely (

0.1”) to power or ground planes. In some cases, due to the frequency response peaking caused by these parasitics, a small adjustment of the feedback resistor value will serve to compensate the frequency response. Also, it is very important to keep the parasitic capacitance across the feedback resistor to an absolute minimum.

The performance plots in the data sheet can be reproduced using the evaluation boards available from National. The CLC730036 board uses all SMT parts for the evaluation of the LMH6715. The board can serve as an example layout for the final production printed circuit board.

Care must also be taken with the LMH6715’s layout in order to achieve the best circuit performance, particularly channelto-channel isolation. The decoupling capacitors (both tantalum and ceramic) must be chosen with good high frequency characteristics to decouple the power supplies and the physical placement of the LMH6715’s external components is critical. Grouping each amplifier’s external components with their own ground connection and separating them from the external components of the opposing channel with the maximum possible distance is recommended. The input (R

) and gain setting resistors (RF) are the most critical. It is also recommended that the ceramic decoupling capacitor (0.1µF chip or radial-leaded with low ESR) should be placed as closely to the power pins as possible.

POWER DISSIPATION

Follow these steps to determine the Maximum power dissipation for the LMH6715:

1. Calculate the quiescent (no-load) power: P

AMP=ICC(VCC

-VEE)

2. Calculate the RMS power at the output stage: P

=(V

-V

LOAD

)(I

LOAD

), where V

LOAD

and I

LOAD

are the voltage and

current across the external load.

3. Calculate the total RMS power: Pt = P

AMP+PO

The maximum power that the LMH6715, package can dissipate at a given temperature can be derived with the following equation:

Pmax = (150

- Tamb)/ θJA, where Tamb = Ambient tempera-

ture (˚C) and θ

= Thermal resistance, from junction to

ambient, for a given package (˚C/W). For the SOIC package

is 145˚C/W.

MATCHING PERFORMANCE

With proper board layout, the AC performance match between the two LMH6715’s amplifiers can be tightly controlled as shown in Typical Performance plot labeled “Small-Signal Channel Matching”.

The measurements were performed with SMT components using a feedback resistor of 300Ω at a gain of +2V/V.

The LMH6715’s amplifiers, built on the same die, provide the advantage of having tightly matched DC characteristics.

SLEW RATE AND SETTLING TIME

One of the advantages of current-feedback topology is an inherently high slew rate which produces a wider full power bandwidth. The LMH6715 has a typical slew rate of 1300V/ µs. The required slew rate for a design can be calculated by the following equation: SR = 2πfV

Careful attention to parasitic capacitances is critical to achieving the best settling time performance. The LMH6715

LMH6715

www.national.com9

Page 10

Application Introduction (Continued)

has a typical short term settling time to 0.05% of 12ns for a 2V step. Also, the amplifier is virtually free of any long term thermal tail effects at low gains.

When measuring settling time, a solid ground plane should be used in order to reduce ground inductance which can cause common-ground-impedance coupling. Power supply and ground trace parasitic capacitances and the load capacitance will also affect settling time.

Placing a series resistor (R

) at the output pin is recommended for optimal settling time performance when driving a capacitive load. The Typical Performance plot labeled “R

and Settling Time vs. Capacitive Load” provides a means for selecting a value of R

for a given capacitive load.

DC & NOISE PERFORMANCE

A current-feedback amplifier’s input stage does not have equal nor correlated bias currents, therefore they cannot be canceled and each contributes to the total DC offset voltage at the output by the following equation:

The input resistance is the resistance looking from the noninverting input back toward the source. For inverting DCoffset calculations, the source resistance seen by the input resistor R

must be included in the output offset calculation as a part of the non-inverting gain equation. Application note OA-7 gives several circuits for DC offset correction. The noise currents for the inverting and non-inverting inputs are graphed in the Typical Performance plot labeled “Equivalent Input Noise”. A more complete discussion of amplifier inputreferred noise and external resistor noise contribution can be found in OA-12.

DIFFERENTIAL GAIN & PHASE

The LMH6715 can drive multiple video loads with very low differential gain and phase errors. The Typical Performance plots labeled “Differential Gain vs. Frequency” and “Differential Phase vs. Frequency” show performance for loads from 1 to 4. The Electrical Characteristics table also specifies performance for one 150Ω load at 4.43MHz. For NTSC video, the performance specifications also apply. Application note OA-24 “Measuring and Improving Differential Gain & Differential Phase for Video”, describes in detail the techniques used to measure differential gain and phase.

I/O VOLTAGE & OUTPUT CURRENT

The usable common-mode input voltage range (CMIR) of the LMH6715 specified in the Electrical Characteristics table of the data sheet shows a range of

2.2 volts. Exceeding this range will cause the input stage to saturate and clip the output signal.

The output voltage range is determined by the load resistor and the choice of power supplies. With

5 volts the class A/B

output driver will typically drive

3.9V into a load resistance of 100Ω. Increasing the supply voltages will change the common-mode input and output voltage swings while at the same time increase the internal junction temperature.

Applications Circuits

SINGLE-TO-DIFFERENTIAL LINE DRIVER

The LMH6715’s well matched AC channel-response allows a single-ended input to be transformed to highly matched push-pull driver. From a 1V single-ended input the circuit of Figure 3 produces 1V differential signal between the two outputs. For larger signals the input voltage divider (R

) is necessary to limit the input voltage on channel 2.

DIFFERENTIAL LINE RECEIVER

Figure 4 and Figure 5 show two different implementations of an instrumentation amplifier which convert differential signals to single-ended. Figure 5 allows CMRR adjustment through R

20042945

FIGURE 3. Single-to-Differential Line Driver

20042946

FIGURE 4. Differential Line Receiver

LMH6715

www.national.com 10

Page 11

Applications Circuits (Continued)

NON-INVERTING CURRENT-FEEDBACK INTEGRATOR

The circuit of Figure 6 achieves its high speed integration by placing one of the LMH6715’s amplifiers in the feedback loop of the second amplifier configured as shown.

LOW NOISE WIDE-BANDWIDTH TRANSIMPEDANCE AMPLIFIER

Figure 7 implements a low noise transimpedance amplifier using both channels of the LMH6715. This circuit takes advantage of the lower input bias current noise of the noninverting input and achieves negative feedback through the second LMH6715 channel. The output voltage is set by the value of R

while frequency compensation is achieved

through the adjustment of R

20042947

FIGURE 5. Differential Line Receiver with CMRR

Adjustment

20042949

FIGURE 6. Current Feedback Integrator

20042950

FIGURE 7. Low-Noise, Wide Bandwidth,

Transimpedance Amp.

LMH6715

www.national.com11

Page 12

Physical Dimensions inches (millimeters)

unless otherwise noted

8-Pin SOIC

NS Package Number M08A

LIFE SUPPORT POLICY

NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:

1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user.

2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness.

National Semiconductor Americas Customer Support Center

Email: new.feedback@nsc.com Tel: 1-800-272-9959

National Semiconductor Europe Customer Support Center

Fax: +49 (0) 180-530 85 86

Email: europe.support@nsc.com Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +44 (0) 870 24 0 2171 Français Tel: +33 (0) 1 41 91 8790

National Semiconductor Asia Pacific Customer Support Center

Fax: 65-6250 4466 Email: ap.support@nsc.com Tel: 65-6254 4466

National Semiconductor Japan Customer Support Center

Fax: 81-3-5639-7507 Email: nsj.crc@jksmtp.nsc.com Tel: 81-3-5639-7560

www.national.com

LMH6715 Dual Wideband Video Op Amp

National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.