GS3590 datasheet(52/118 Pages) SEMTECH

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GS3590

Final Data Sheet Rev.4



PDS-061414 September 2017

52 of 118

Semtech

Proprietary & Confidential

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4.8.5.1.1 Fine Optimization Procedure

The procedure requires access to the signal at the downstream device input, or

non-re-timed device output. If there are multiple stages between the initial downstream

device input and final measurement point, it is still possible to perform optimization;

however link settings within the other stages must be fairly optimized. The

pre-emphasis amplitude (PPA) and pre-emphasis width (PPW) settings can be

optimized by sweeping the PPA and PPW settings in increments of 'a' and 'w' and

selecting the setting which results in the lowest jitter. For Trace Driver optimization, 'a'

and 'w' increments of 5 should be sufficient.

The procedure has three steps.

1. Pre-emphasis Amplitude (PPA) Optimization: Set the PPA and PPW to the values

obtained from the graph selected out of Figure 4-12 to Figure 4-19, and then

measure the downstream jitter. While keeping PPW constant, increment the PPA by

'a'. If the jitter is lower after the first increment, continue to increment by 'a' until the

jitter begins increasing or a setting of 50 is reached. If there was a setting which

resulted in a lower jitter measurement than the initial setting, that is the Optimized

Pre-emphasis Amplitude setting: PPAOptimal, and the PPA optimization procedure is

complete.



However, if the jitter increased after the first increment, decrement the setting by 'a'

below the initial value. If the jitter is lower after the first decrement, continue to

decrement by 'a' until the jitter begins increasing or a setting of 0 is reached. If there

was a setting which resulted in a lower jitter measurement than the initial setting,

that is the Optimized Pre-emphasis Amplitude: PPAOptimal.



If incrementing the PPA or decrementing the PPA did not result in a setting with

lower jitter, then the initial setting obtained from the graph selected out of

Figure 4-12 to Figure 4-19 is the PPA optimized Pre-emphasis Amplitude setting:

PPAOptimal.

2. The second step is to set the PPA to the optimized setting PPAOptimal determined in

step 1 and PPW to the values obtained from the graph selected out of Figure 4-12

to Figure 4-19, then measure the downstream jitter. While keeping PPA constant,

increment the PPW by 'w'. If the jitter is lower after the first increment, continue to

increment by 'w' until the jitter begins increasing or a setting of 15 is reached. If

there was a setting which resulted in a lower jitter measurement than the initial

setting, that is the Optimized Pre-emphasis Width setting: PPWOptimal, and the

optimization procedure is complete.



However, if the jitter increased after the first increment, decrement the setting by

'w' below the initial value. If the jitter is lower after the first decrement, continue to

decrement by 1 until the jitter begins increasing or a value of 0 is reached. If there

was a setting which resulted in a lower jitter measurement than the initial setting,

that is the Optimized Pre-emphasis Width setting: PPWOptimal, and the optimization

procedure is complete.



If incrementing the PPW or decrementing the PPW did not result in a setting with

lower jitter, then the initial setting value obtained from the graph selected out of

Figure 4-12 to Figure 4-19 is the optimized Pre-emphasis Width setting: PPWOptimal.

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