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TPS65218: PMIC - coin cell battery to PMIC IC series resistor selection

prem kumar1
Prodigy 50 points
Part Number: TPS65218
Other Parts Discussed in Thread: TMDSEVM437X

HI ,

could you please suggest how to choose the series resistor RTC coin cell battery.

In PMIC IC "TPS65218"  series resistor mentioned 10ohms . But EVM AM437x board 1.4K resistor used.

PMIC - TPS65218 IC datasheet image

EVM-AM437x- board image

Regards,

prem

  • 0
    TI__Mastermind 30280 points

    3.3V/10Ohms = 330mA  (max current from coin cell into PMIC).

    3.3V/1.4kOhms = 2.36mA (max current from coin cell into PMIC).

    It is a current-limiting resistor. Personally, I think 1.4kOhms sounds a little high (not enough current will be allowed through) and 10Ohms sounds a little low.

    I would use a value between 100Ohms and 330 Ohms.

  • 0
    TI__Mastermind 30280 points

    Prem,

    I apologize, but I did not see the images you tried to share, so I did not see the 1.4k resistor you were talking about in the AM437x EVM (TMDSEVM437X).

    On the EVM schematic, above R61, do you see header J25? When you install a jumper across these 2 pins, R61 is shorted out.

    In my opinion, R61 should be marked as DNI or swapped out for a 10-Ohm current-limiting resistor. It is likely that R61 was used for testing but was not intended to be in the final design.

    I answered a similar question here:

    Maybe you and M Amarnath are working on the same design :-)