Tektronix P77DESKEW Instructions Manual

P77DESKEW Fixture Instructions

The P77DESKEW probe deskew fixture provides an edge source to time-align
(deskew) signals at the inputs of P7700 Series probes. The fixture provides a
means to desk
powered by one of the USB ports of the oscilloscope; a USB cable (Tektronix part
number, 174-6919-xx) is included with the fixture.

For performing the deskew procedure, Tektronix recommends using a
DPO/MSO70000C/70000DX series oscilloscope.

Connectors on the fixture accept solder tips that are available for the P7700 Series
probes. The fixture can also be used to deskew probes with browser accessories.

CAUTION. The probes used with the deskew fixture are ESD sensitive. To avoid

ing the probes, perform these procedures at an antistatic workstation, with

damag
an anti-static wrist strap while observing proper ESD practices. Refer to your
probe user manual for the anti-static information.

ew two probes at the same time. The probe and the fixture are

eck the calibration

Ch

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status

For best performance, you should check the calibration status of the oscilloscope
before performing the deskew procedure. If the oscilloscope requires calibration
or the probe requires compensation, perform these steps before deskewing the
probes. Refer to your oscilloscope manual for instructions on performing the
oscilloscope calibration procedures.

To check the calibration status of the probe, perform the following steps:

1. Select Probe Cal... from the Vertical menu.

2. Select the channel to which the probe is attached and then check the Probe

Status readout. There are three possible values for the status:

Initialized. The probe has not been calibrated on the selected channel;
perform the DC probe calibration procedure.

Compensated. The probe has been calibrated on the selected channel.

Fail. The probe has not been calibrated; repeat the procedure.

If the test continues to fail, troubleshoot the problem; do not continue with the
deskew procedure.

*P077126300*

077-1263-00

P77DESKEW Fixture Instructions

Deskew procedure

The deskew func

tion compensates for signal delays that occur between probes
due to different tips or cable lengths. The oscilloscope deskew feature applies
deskew values after it completes each acquisition. The deskew values do not
affect logic triggering.

Refer to the following illustration while connecting the probes and cables to the
deskew fixture.

Figure 1: Connection diagram

1. Connect the deskew fixture to a USB power source, such as the front panel

USB connector on the oscilloscope. The LEDs on the fixture will turn on.

2. Connect the probes to oscilloscope channels where they will be used.

3. Connect the TekFlex tips to the ends of the main probe cables.

4. For single-ended inputs, connect an SMA cable from a single source, such as

the FAST EDGE output connector on the oscilloscope to the A input of the
fixture.

5. If using a signal generator with differential inputs, connect the + output of

the signal generator to the A input of the fixture using an SMA cable. Then
connect the - output of the signal generator to the B input of the fixture using
an SMA-style cable with equal electrical length as the first SMA cable.

NOTE. If you are deskewing probes with solder tips, try to use the same solder

tips with the deskew fixture that you will use to take measurements. If that is not
possible, try to use a solder tip of similar length to the one you have soldered to
your device.

2 P77DESKEW Fixture Instructions

P77DESKEW Fixture Instructions

6. For P77STFLXA o
follows:

a. Locate the Por

spring-loaded clamp. Insert one of the probe tips in the direction shown in
the following figure, and release the clamp so that the tip locks in place.

r P77STCABL tips, connect the tips to the fixture as

t1 plastic clamp on the fixture and press down on the

Figure 2: Connecting the probe tip to the deskew fixture

A green LED lights up under the probe tip clamp when the tip is properly
inserted.

b. Repeat the above step for inserting the second probe tip into the Port2

plastic clamp.

c. Verify that the green LEDs under both probe tips are on. If not,

double-check your connections.

7. For P77BRWSR browser accessory, there are several pads on the deskew
fixture that can be contacted by the browser tips. Using these pads, two probes

th browser accessories or one probe with a solder tip and one probe with a

wi
browser can be deskewed relative to one another.

he pads on the fixture provide access to the same signals routed t o the

T
clamps used to connect the solder tips. There are also ground pads located in
the same area for use when deskewing using a single-ended signal.

NOTE. The s ignals routed to the pads are delayed by 30 ps relative to the signal

output at the solder tip clamps. There is a 5.7 ps time difference between the
first row of pads and the second row.

P77DESKEW Fixture Instructions 3