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TPS5401 design-in with very low output load

Francois Audeon
Prodigy 10 points
Other Parts Discussed in Thread: TPS5401

Hello

I'm designing a dc/dc conversion function with following characteristics:

- 3.6 to 24 V input

- 3.3 V ouput at max 0.300 mA

I was thinking of using TPS5401 but the datasheet is not 100% clear to me with respect to the behaviour at very low outoup loads.

In some conditions the output load of the system I have to power may fall to a few micro-ampers, but still I need to maintain

the 3.3 supply (typically to power a micro controller in sleep mode). Generally the load has the be as low as possible to power consumption reasons.

The figures at page 14 suggest that the TPS5401 would stop regulating the 3.3V at such a load.

Any suggestion how to maintain the 3.3V during these conditions (eventually using another part) ?

Thanks -

  • 0
    TI__Guru**** 191445 points

    When the TPS5401 is used under BOTH light load and low input voltage conditions, there exist the possibility that there will be high ripple of approximately 2.1 V on the output, and the DC value will be low as well.  You can use the charge pump circuit of SLVA444 http://focus.ti.com/general/docs/litabsmultiplefilelist.tsp?literatureNumber=slva444 to prevent that.  If you really only need 0.3 mA (300 uA) you could consider using an LDO such as TPS71501 as you will only be dissipating 6.21 mW max.