I have built 5 BMS boards using the device (3 12s-boards and 2 7s-boards), and they have been working fairly well. But recently one of them broke; the device will not supply REG1 (3.3V) although REG18 slhows 1.8V. And then I noticed checking othre boards that some of them (one 12s and another 7s) keep 1,8V at REG18 after shutdown (other functions like REG1 seem to stop). The other two boards shutdown also REG18 to 0 V.
My mechanism for shutting down is to use RESET-SHUT pin set permanently by a micro-processor, but the power for the upc is supplied by REG1 of BQ76952 and hence shutdown of the device causes the upc to stop functioning also. As for the wakeup of the device, LD pin is utilized; transient pulse (~200msec) is applied. I took photos showing awaking and shutting down, which have no anomalies.
My questions are 1) Are these device with 1.8V at REG18 alter shutdown possibly damaged already? If that is the case, any hint of possible causes is appreciated .
or Is there the possiblity that the device is shut down partially? (they work normally when re-switched on.) If so how can I shut them down completely?
Best regards,
Junkichi
RED: LD pin, BLUE: RESET-SHUT. Left shutdown pulse (longer than 1 second), Right: wakeup pulse.
