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TPS65381-Q1: Max Output Capacitance

Needhu Gunasegaran
Intellectual 2890 points
Part Number: TPS65381-Q1

Hello,

One of my customer came with the following questions,

There is a maximum output capacitance requirement for the linear regulators. (5 uF Max)

For 3.3V I have a separate DCDC converter. In the meanwhile the load of this separate converter changed to only one remaining IC, which has a small isolated power transfer inside. This IC recommends 10uF at input and at the output.
Charging the 10uF at the output may cause quite some peak load so that I think that I will need the 10uF on the input. (I did not get a recommendation back from the IC supplier if it is OK to reduce that to 1uF)

So when I move that load to the TPS65381, I would have to increase the capacitive loading to about 14uF. Can you give me a recommendation, if 15uF instead of 5uFmax is a problem on the TPS 3.3V LDO output?

There is some physical distance on the PCB, so there will be some milliohms of trace resistance at least.

Thanks in advance,

- Needhu

  • 0
    TI__Genius 9380 points

    Needhu,

      The max capacitance requirement for the TPS65381-Q1 is based on tight coupling of the output capacitance. Placing no more than 5uf directly at the pin of the regulator. Once a trace has been routed to the load more capacitance can be added at the load. The trace will decouple the capacitance.

      It is up to the customer to verify proper startup and operation of the regulator when adding more capacitance, but you should be able to go up to 40uf with trace decoupling between the LDO and the load. Please test and verify the startup process and operation, when adding more capacitance to this rail.