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LM2755 charge pump open loop/closed loop mode

Hi team,

Could you help to explain what is the meaning of open loop/closed loop mode?

I know the output voltage are different, but i do not understand what is the reason causes these different voltage.

What condition should use open loop and what condition should use closed loop?

please help.

Thanks

  • Closed loop operation occurs when the charge pump is able to regulate the output to 4.6V under load.  This device has a 3/2 charge pump so regulation occurs when VIN * 1.5 is greater than 4.6V.  When VIN drops or the load increases to a point where the charge pump can no long regulate the output to 4.6V, it is then considered to be in open loop mode.  In this region, the output will drop as VIN drops and IOUT increases.