TPS3808: Discharge resistor for RESETn pin with capacitor

Gary Chang

Part Number: TPS3808

Tool/software:

Hello TI team,

The customer is using TPS3808G33DBVR and has added a capacitor to the RESETn pin for decoupling noise, a current limit resistor has been reserved (R253).

Could you give me any suggestions for the value of the current limit resistor?

Thanks

8 months ago

0 Jesse Villanueva 8 months ago

TI__Mastermind 20280 points

Hi Gary,

One quick comment, would it be possible to move the R253 to right side of R252 instead of the current position. This is because at its current location, when RESET pull LOW, R252 and R253 becomes a voltage divider preventing FM_CPLD1_RESET2 pull-down all they way down to 0V.

If the schematic is finalized and a current limiting resistor is still needed, the maximum value of the R253 resistor is V(input LOW of FM_CPLD1_RESET2) = V2 and V2 = (P3v3_STBY) x R253/(R252 + R253).

If the location can be changed, R253 can go up to 100kohm, depending on the amount of current that need to be limited.

Jesse

0 Gary Chang 8 months ago in reply to Jesse Villanueva

Intellectual 500 points

Hello Jesse,

Thank you for your reply

I have modified the schematic as follows. Please help review it

Thanks

0 Jesse Villanueva 8 months ago in reply to Gary Chang

TI__Mastermind 20280 points

Hi Gary,

The schematic looks good to me.

Jesse

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TPS3808: Discharge resistor for RESETn pin with capacitor