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TPS3851: Why the actual value of MR is about 1.2V, and not the same with VDD?

Part Number: TPS3851

Dears:

From datasheet the pin of MR is pulled up to VDD, however, the actual value we tested is about 1.2V. 

VDD is about 3.1V, and the MR is not pulled up by other resister.

The schematic is follows:

Btw, when we test the value of MR, R255, R536 and R253 all do not been welded.

Pls. give some advice about the issue.

Thanks a lot!

Best regards

Luck Wu

  • Luck Wu,

    Please remove all components and all connections from /MR pin including resistors, capacitors, and any other component that could cause leakage and re-measure. Typically, the /MR pin is shorted to GND via an external button or pulled low with an MCU GPIO but high impedance when not pulled low. I think the reason you aren't seeing VDD on /MR is because of the other connections on that pin.

    -Michael