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AD9375 CLGC Relative Threshold

I am trying to correct configure CLGC on my custom board but there is something I don't get about Relative Threshold, from UG992:

"Value given by 100 × (Relative Gain Threshold in dB). Enforce this
threshold by setting tx1RelThresholdEn/tx2RelThresholdEn to 1 in
mykonosClgcConfig_t. When the CLGC is tracking at a given
gain level in steady state, this threshold represents the maximum
dB change allowed in currentGain from one CLGC iteration to
the next. ERR_16 is thrown if the relative threshold is violated.
Note that the steady state condition implies that the currentGain
and desiredGain values are fairly close because the relative
threshold test condition checks the currentGain against a bound
of desiredGain ± tx1RelThreshold/tx2RelThreshold limit.
Default value is 600 (6 dB)."

So what I don't get:
1) What is it's purpose if the check is done  between two different iterations?
2) Is it something that only rise a flag? Since i get error 16 if I shrink it too much but the clgc is still active
3) why should I want to use it? 
4) What should I monitor currentGain for?
5) And I didn't got the bound with desired gain, so this threshold does limit both current and power gain?




Parents Reply
  • We discussed desired gain earlier.

    When CLGC tracking is run it calculated the loop gain in real time and that is given as current gain. The difference between desired gain and current gain will give the amount of correction applied by CLGC on Tx gain/attenuation.

    The relative threshold defines how much gain adjustment the CLGC can make in one iteration while tracking.

    1. The CLGC tracking cal calculates current gain and adust Tx attenuation to maintain gain over time, In normal scenario the gain change due to temperature will be gradual and we don't expect sudden Jump . So relative threshold can be used to avoid sudden change in gain due to some false alarm. You can disable this if not used.

    2. Yes . It generates error and do not make any gain update. CLGC will continue checking for next iterations and update if the threshold is not crossed.

    3. This prevents PA from getting damaged if there is any sudden decrease in ORx power due to hardware issue or false alarm.

    4., 5 . Explained above.