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TPS65218D0: LDO1 loading issue

Nitish Kumar
Prodigy 110 points
Part Number: TPS65218D0
Other Parts Discussed in Thread: AM3352,

Hi,

We have used TPS65218DO PMIC to processor AM3352 and we are in the process of bringing-up the board. The following behaviour is observed

  • Power Good does not come when LDO1 (1.8V) is connected to load circuit
  • Once LDO1 o/p is removed from load, then PG comes up

We have not used RTC features of processor so disabled DCDC5 & DCDC6 regulator o/p and connected processor IOs as per recommendation.

Please let us know the cause.

Regards,

Nitish

  • 0
    TI__Mastermind 30310 points

    Nitish,

    What is connected to LDO1 output of the TPS65218D0 device? If this load is >400mA, then the LDO1 will not be able to supply the current due to overcurrent protection. This would prevent PG from going high.

    If you measure LDO1 voltage during power-up sequence, it should be very easy to see if this is causing the problem. I cannot comment on the issue without seeing oscilloscope measurement of LDO1 during power-on.

    If any IC other than AM335x is connected to LDO1 which is adding to the load, then this could be the reason, but I cannot comment on this without reviewing the schematic. For example, one time someone connected a 1.8V rail of an FPGA to LDO1, and it was large enough load to cause LDO1 to go into over-current protection.

    DCDC5 and DCDC6 do not impact PGOOD. DCDC5/6 only have an impact on PGOOD_BU.