I’m using the MP2672A in a microcontroller circuit as a battery management IC. The basic circuit is below:
The ACOK and STAT lines are connected to microcontroller (STM32F413RGT6) pins that are setup as inputs with a pull up resistor. The datasheet says the pullup is 30K min, 50K max.
The microcontroller is powered by 3.3V.
When the battery is not charging (U_PWR is not connected) I’m seeing 3.3V on the ACOK line (as expected), but only 1.5V on the STAT line (I’m expecting 3.3V).
Is there a minimum pullup I need to use on the STAT and ACOK lines? Seems like 50K should be sufficient.
When I connect U_PWR, both ACOK and STAT go to ground as expected and the battery is charging.
Just a quick update. I disabled the internal uC pullup and put a pullup of 3.75K to microcontroller VDD (3.3V). I’m now getting about 2.7V on the STAT pin when not charging. The system is working, but there is leakage current into the STAT pin of 160uA ((3.3-2.7)/3.75K), which is way above the MP2672A datasheet leakage : 1uA max. The ACOK pin is behaving correctly with 1uA leakage as expected. What am I missing on the STAT line?
I checked the resistance between the STAT line and ground when the circuit is not powered and I’m getting between 3 and 4 Meg, so there is no short.
The STAT line connection is clean. I tried two different boards with exactly the same results.
Does it make a difference that the STAT line is pulled up to external VDD and not the MP2672A VCC line? It should not since this is what open drain is for.
