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LM25056: Incorrect VREF and VDD voltages

Sohail Akram
Prodigy 10 points
Part Number: LM25056

Hi All,

 

We have designed a 175W (5V 35A) DC power supply and have used LM25056 for voltage/current/power monitoring. 

 

We are able to communicate with the LM25056 through I2C bus, however, the computed voltage and current values, based on the registers read from device, doesn't make sense. 

We found that the VREF and VDD pins show 3.37V and 4.22V respectively, which is 0.5V above what the correct values should have been according to the datasheet. We have tried with and without load, but the voltage on VREF and VDD remains the same. Why are VREF and VDD 0.5V above their actual value? Can an improper connection of thermal GND pad cause this kind of problem?

 

Please advise how to fix this problem.

 

Thanks,

Sohail

  • 0
    TI__Expert 4915 points

    Hi Sohail,

    The pin description on the datasheet indicates this pin is not internally connected (it is recommended to ground it to reduce noise and thermal considerations).

    What debugging has been performed other than reading of the reference voltages?

    Have you tried to replace the LM25056 to make sure it didn't got damaged somehow?

    Were the reference pins measured with the device removed from the board to ensure there are no parasitic connections or shorts on the PCB?