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TPS65218: DC34_SEL Correct Resistor Value

Don Schelle
Expert 4150 points
Part Number: TPS65218

Folks,

I'm trying to program DCDC3 to 1.5V output and am unsure of the resistor value to select for the DC34_SEL pin.

According to the datasheet it should be 20kOhm (with a maximum of 22kOhm):

According to the AM437x GP EVM it's 22kOhm

A couple of questions:

1. Wouldn't a 22kOhm resistor violate the recommended values given resistor tolerances?

2. If not, would a 22.1kOhm (1%) resistor function fine in this case?

3. I notice that there's a grey area between default values.    Are there additional default values that can be programmed in between these area?    For example, suppose we use 26.45 kOhm, what would be programmed defaults?

Don

  • +1
    TI__Genius 12735 points

    Hi Don,

    1. It is possible to violate the recommended value given resistor tolerances if a 22kohm resistor is used, although I would expect this violation to have little to no impact if you used a 1% or 0.1% resistor. The processor team put together this EVM so I cannot comment why they did this but I would recommend using a 20kohm resistor on your design given that is the value in the datasheet.

    2. I would recommend staying in the datasheet specified values. We cannot guarantee function above 22kohm and while you may find the device operates without any issues there are potential corner cases where you may find the device does not properly detect the resistor value and may output a different voltage than is expected.

    3. Unfortunately there are not any additional values between the resistor values shown above. We provide these margins to ensure the device is clearly able to detect the proper resistor value based on differences in manufacturing. 

    Best regards,

    Layne J