AD9546SLASHPCBZ datasheet(193/205 Pages) AD

193 / 205 page

Data Sheet

AD9546

Rev. 0 | Page 193 of 205

CLOCK PROPAGATION DELAY MEASUREMENT

Consider an application comprising a clock source (in) driving

additional components that introduce propagation delay (tP) to

the final output (out) signal (see Figure 129). The additional

components can be, for example, a combination of physical

interconnects (cables and PCB traces), clock buffers or other

elements that introduce propagation delay.

In applications requiring quantification of the propagation

delay between two clock signals, the TDCs in the AD9546

provide a means to measure the delay and make the result

available in digital form via serial port registers. Figure 129

shows a simplified propagation delay measurement setup using

the AD9546.

To measure propagation delay, the user connects the in and out

signals to any two of the eight independent reference clock

inputs of the AD9546. The reference clock inputs comprise the

REFx pins or one of the Mx control pins configured as an input

to one of the four auxiliary references (auxiliary REFx). Then,

using the skew measurement processor (see the Timing Skew

Measurements Using Two TDCs section), the user can read the

measurement results via the serial port, which indicates the

value of tP with approximately 1 ps resolution.

The measured value of tP can then be used by the controller to

adjust the timing of the clock source to compensate for the

delay through the clock components. By periodically measuring

tP and compensating accordingly, the user can correct for time

dependent changes in tP that may arise from temperature

variations.

DELAY

COMPONENTS

OUT

REFx/Mx

SKEW

MEASUREMENT

PROCESSOR

SERIAL

PORT

CONTROLLER

AD9546

SPI/I2C

TDC

CLOCK

SOURCE

DELAY ADJUST

REFx/Mx

Figure 129. Propagation Delay Measurement Application

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