Hi there,
We followed the reference design except for the VP power connection, where we used a regulator controlled externally by a microprocessor regulated from the top of the stack.
Attached schematic snippet of the power section of BQ chip here.
We are not stacking the board, so there's just one of the bq76 chip in question here.
The issue is, we are not able to get any voltages from the cell measurements Vsense (batteries 9-16 is tied short). All cells measure basically couple mV of noise. We connected the chip to a USB converter, so its not the microcontrollers firmware, we see cells 1-9 being almost zero on the GUI. One hint that shows the Analog Front End has an issue is the analog die temperature is invalid -268C, I also do not get anything for REF2 AFE voltage. Everything else in the chip works, digital side and AUX ADC, also EQ lines (balancers) are working fine as well.
Measurement on the Vsense lines from meter are as expected, from bottom of the stack, 3.5V, 7.0V, 10.5V etc... from Vsense1 to Vsense9 (above 9 is tied together). The BQ chip itself also has being changed out once to make sure its not a faulty hardware.
Register 14, NPNB controller is disabled on boot. The cells are plugged in, then the 3V3M is enabled, in that sequence. Is there a power sequence requirement here? Or some other requirement for the VP line? Any other possibilities for cells with no data?
Thanks for any help!
