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TPS7A83A: short current protection

Intellectual 2530 points

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Part Number: TPS7A83A

Hi , 

Here is a question on TPS7A83A Vout short protection. 

In customer side, there is a DCDC as input of the TPS7A83A. Then when Vout of TPS7A83A is short, then Vout of DCDC also drops. 

Current Cout of TPS7A83A is 2x22uf. Then they decrease the Cout to 1x10uf and do Vout short test again, then Vout of DCDC drops less then before. 

So just want to check with you on the reason. Is it due to fold-back current limit that smaller Cout has slow discharging? Thanks. 

BRs

Given

  • Hi Given, 

    As you observed, with less Cout, during the output short event, the DC-DC dropped less. This is because when the short happens on the output, the output capacitors will first be quickly discharged and this will cause the LDO immediately tries to charge the output capacitor again. Due to the higher in-rush current for the bigger output capacitor, the current flowing from the DC-DC is also higher which causes the DCDC to drop more. But this higher drop is also temporary, as current limit loop will kick in to limit the current. 

    You may find this app note helpful and it shows higher output capacitor will have higher in-rush current. 

    http://www.ti.com/lit/an/slva670a/slva670a.pdf

    Regards, 
    Jason Song

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