Question on Battery Charger

[FreshmanNewbie]

I'm having issues with status pin on the MCP73831. I have this pin connected to a GPIO pin on a microcontroller (Nordic Semiconductor nRF52832-QFAB-R) with a 10K pullup resistor to 3V. I find when the battery is charging this pin is measured low and when the battery is not charging (but battery is connected) the status pin measures high. This correlates with what we expect to see in the datasheet.

However, when the battery is not connected the pin should go high impedance and I would expect to measure a high voltage (3V) on the GPIO due to the external 10K pullup resistor but I see a low voltage (0V). I measured the resistance of the pin and can see that it has gone high impedance. I've tried cutting the PCB trace to the microcontroller to confirm that it is not interfering with the circuit, with the trace cut I still see a low voltage signal. This means we see battery disconnected and battery charging as the same signal.

 

[KlausST]

Hi,

What is VDD in this case?

If VDD is not supplied, then the internal protection diodes of the pin will pull the signal LOW.

--> Datasheet: 1.0 Absolute maximum ratings: All outputs: "VDD+0.3V"



Klaus

 

[danadakk]

Sure sounds like UP Pin driving pin low.....No chance its a multi purpose
read modify write pin ? When you cut trace, with it in HiZ, you are just
reading leakage driven state left behind due to drive low then hi Z ?

Regards, Dana.

 

[FreshmanNewbie]

Hi,

What is VDD in this case?

If VDD is not supplied, then the internal protection diodes of the pin will pull the signal LOW.

--> Datasheet: 1.0 Absolute maximum ratings: All outputs: "VDD+0.3V"



Klaus

Vdd is 5V

 

[KlausST]

Hi,

To be clear: VDD is 5V when Battery is disconnected?
And still the STAT1 output is LOW?

If so, then show your complete schematic.

Klaus