BQ77PL900: Becomming hot during normal operation

Hi John,
Without host operation. There are 2 expected causes of the chip heating, 1 being regulator load, the other being damage.
You will likely know your load on the regulators and/or have a way to confirm the expectation. You might measure the voltage across the BAT pin resistor if the diode is not used. If the diode is used you might raise the voltage of PACK+ (with FETs off) so that it provides power for the IC, then measure across its filter resistor.
Measure the voltage across the input resistors for the VCn pins. If there is an unexpected value you have likely found the cause. A positive voltage on one and a negative voltage on the next indicates a short or damage from a differential voltage between the pins, positive voltage on one or several indicates a short or shorts to GND.
Unfortunately the bq77PL900 is not very tolerant to transients beyond abs max and users have reported it is easily damaged. With power removed you may be able to measure resistance of shorts with a (low voltage) DMM. It sounds like you are observing this on several parts, be sure the parts have been handled properly. Inspect the assembly and test process to be sure the devices are not exposed to an unexpected voltage in test or assembly. Check the schematic for conditions which could stress the part during cell assembly. For example single ended input capacitors will hold one input voltage at GND while the next is connected possibly stressing the differential voltage limit.

That is the recommendations I know at this point and will mark "thinks resolved", please reply though when you have had a chance to inspect boards and let the community know what you find.

Hi,

Thanks for helping point me in the right direction.
The regulators are not currently being used to power any other circuitry, so this shouldn't be an issue. I did some measurements on the Batt and Pack pin voltages (after the diode), as well as the individual cell voltages with the following findings.

Battery voltage = 23.7 V
Vbatt (pin) = 22.93 V
Vpack (pin) = 22.94 V

VC1 = 23.69 V
VC2 = 19.77 V
VC3 = 15.8 V
VC4 = 11.87 V
VC5 = 7.9 V
VC6 = 3.94 V

All of the VCn voltages match the LiPo balance plug voltages EXACT. From what I can tell from prior testing with the EVM - these measurements seem fine.
After looking through the assembly/test process for both of these boards, I came across a mistake in the layout where the CP4 pin (pin 3) became un-grounded. This mistake was found after the battery power had been applied and the appropriate rework was done to connect this pin to ground.
This raises the question: Could applying battery power to the chip with the charge pump not grounded properly permanently damage the chip?
If so, my next test would be to replace the IC, make the proper connections and then see if heat is still being generated internally with an IR camera.