LMR33620: 12V to 3.8V application

Patrick Chen(TPE System & Application)

Part Number: LMR33620
Other Parts Discussed in Thread: TPS22916

Hi Sir,

My customer would like to know if they apply a 4.2V on the output of LMR33620, will there any risk?

Below is the detail.

My customer are using LMR33620 on their platform for 12V to 3.8V application for their system and 12V is the main input source.

And on their system there is a li-battery will be charged by a boost circuit from the 3.8V.

When 12V is removed, the Li-battery will be switch to the output of LMR33620 to as a power source of the system.

Therefore, there will be a short time that 12V still on LMR33620 input while the Li-battery already supply to LMR33620 output.

Thanks,

Patrick

0 Frank De Stasi over 7 years ago

This is not a good idea for any buck regulator. The body diode of the HS MOSFET will conduct

when the 12V is removed with 4.2V on the output. This can cause uncontrolled current through this

diode and may damage the device. You will need some kind of power switch or diode OR gate.

0 Patrick Chen(TPE System & Application) over 7 years ago in reply to Frank De Stasi

Hi Sir,

Customer put a TPS22916 between LM33620 output and 4.2V.

And the TPS22916 have a reverse current protect, but it wont active unless it see a 500mA reverse current.

So a follow up question is, if there is a 500mA or less reverse current to the LMR33620 output.

Will this ok?

Thanks,

Patrick

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