MMPF0100 behavior when VIN is lower than Vout setting.

[satoshishimoda]

Hi community,

I have a question about MMPF0100.

I want to know the behavior when VIN is under voltage of switching regulators or linear regulators output setting.

(e.g. VIN=3.0V, SW2=3.3V, VGEN3=3.3V)

I understand MMPF0100 goes into coincell mode when VIN < UVDET(2.65V), then how about when UVDET < VIN < Vout?

Vout = VIN in this case? or Vout is stopped?

Best Regards,

Satoshi Shimoda

[igorpadykov · Accepted solution]

Hi Satoshi

when VIN < output setting then regulation transistor will be fully turned on.

So output voltage will follow the input, for example one can refer to

http://cache.freescale.com/files/analog/doc/data_sheet/MMPF0100.pdf

SW2 footnotes 46,47 on p.57 and Figure 18. SW2 Block Diagram:

(VIN - VSW2) = ISW2* (DCR of Inductor +RONSW2P + PCB trace resistance).

The same is for LDO, one can refer Figure 30. General LDO Block Diagram:

(VIN - VLDO) = ILDO* (RONLDOtransistor + PCB trace resistance).

Best regards

igor

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