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Original question:

ADS7951-Q1: ADS7951 resetting when used in high power inverter switching application

TPS763-Q1: Need recommendation on maximum output capacitor allowed at source end and load end

Abhijith V P
Prodigy 160 points
Part Number: TPS763-Q1
Other Parts Discussed in Thread: REF5025, AMC1311, ADS7951-Q1,

Hello,

We are using this device to power ADS7951-Q1 and 2.5V Generator REF5025 devices. Additionally, it is loading 2 opamps, 4channel digital isolator and output section of AMC1311 device.

Load current expected typically is around 60mA

As the devices are placed in a high power switching application, we need to keep decoupling capacitors at the load side near to each power supply pin.

Could you suggest maximum capacitor we can keep near the source end and cumulative capacitance which can be kept near the loads?

Regards

Abhijith V P

  • 0
    TI__Mastermind 23361 points

    Hi Abhijith, 

    The TPS763-Q1 does not have a specification on the maximum output capacitor it can drive, but it needs to meet the following listed conditions:

    Please note when the LDO is driving large capacitance, the LDO may enter into the current limit or thermal shutdown during the startup. However, the detailed performance will vary depending on how much capacitance you have connected at the output pin of the LDO. 

    Regards, 

    Jason Song

  • 0 in reply to Jason Song
    Prodigy 160 points

    Hello Jason, 

    ESR mentioned in datasheet is effective ESR (parallel combination) of all the capacitors connected at the output , correct?

    For experiment, we had connected around 100uF in total (all MLCC) at all loads and source and when we powered ON. Immediately, LDO failed.

    Could it be overcurrent during power ON?

    Regards

    Abhijith V P

  • 0 in reply to Abhijith V P
    TI__Mastermind 23361 points

    Hi Abhijith, 

    Yes, if you have multiple output capacitors, the ESR requirement is the combined effective ESR. 

    We would need more details to tell what is causing the failure. Will you please provide scope shoot that clearly shows the Vin, Vout, Input current during startup and potentially to capture how the LDO fails? 

    Regards,
    Jason

  • 0 in reply to Jason Song
    Prodigy 160 points

    Hi Jason,

    We didn't face the issue with design intended values of capacitance. 

    Currently we are resolving other issues. I will update with the scope measurements later.

    Regards

    Abhijith V P