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ONET4211LD: Questions when disabling the APC loop

high speed guy
Expert 3505 points
Part Number: ONET4211LD

Hi,

I intend to disable the APC loop, when I do I need to know the following:    

1. If the diode at PD is removed, the current there should be zero. Is it safe to remove the MONP resistor in this mode?

2. If the APC loop is disabled, does there need to be a 100nF capacitor connected to CAPC?

Thank you,

HSG 

  • 0
    TI__Guru* 93670 points

    Greetings HSG:

    In your #1 question, are you referring to MONB or MONP since APC is disabled?

    For stability purpose, even though APC is disabled - it is recommended to provide this 100nF CAP.

    Regards,,nasser

  • 0 in reply to Nasser Mohammadi
    TI__Expert 3505 points

    Hi Nasser,

    Yes we are referring to MONB and MONP.


    Thank you,

    HSG

  • 0 in reply to high speed guy
    TI__Guru* 93670 points

    Greetings,

    In order to disable the APC loop a 100k Ohm resistor needs to be connected from APCSET to VCC and PD left open. In fact, it's preferred to ground PD. In this case, CAPC could be omitted.

     

    If you remove the MONP resistor, I think a fault would be triggered. Depending on the selected fault mode, either bias and mod current would be shut-down (hard fault mode) or SDOWN would be set w/o affecting bias and mod current (soft fault mode). However, in the latter case any other fault mechanism would be masked by the MONP fault. If you want to remove the MONP resistor and maintain fault detection, MONP could be connected to GND.

    Regards,,nasser