On the relationship between oscillator circuit with the external crystal and Battery switch-over function for PCF8523

[kazuhiroozuchi]

I'd like to knwo on the relationship between oscillator circuit with the external crystal and Battery switch-over function for PCF8523.

I had set PM[2:0] to 101 (battery switch-over function is enabled in direct switching mode; battery low detection function is disabled).

It is the case that VDD is turned off and electric charge of the electric double layer capacitor was discharged until the oscillation stops.

If VBAT is larger than VDD due to a malfunction of the electric double layer capacitor, does PCF8523 select VBAT for power of oscillator circuit after turning on the power supply?

I am studying the reason why the oscillation stops due to a defect of the electric double layer capacitor.

[reyes]

Hi,

Correct, with this configuration, if VBAT is larger than VDD, the internal logic of the PCF8523 will select VBAT as the main power supply of the circuit until the battery discharge to a voltage level lower than VDD, only then VDD will be supplying your circuit.

Have a great day,
Jose

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