Yellow is Voltage out of L1
Blue is high gate voltage Q4
We are getting very low currents out from the BQ24753 design, and they are dependent on the voltage difference between V+Raw and VPack. This is to be expected if the charge pump is not working, which seems to be the case. When the 753 tries to go into Synchronous mode, the voltage out from L1 goes down instead of up. After some time later it goes back into Async and stays there briefly, just to repeat again a few hundred microseconds later.
The charge caps have been replaced so they aren't opens. The inductor has been replaced and so has the 753 itself. So also have both high and low Mosfets. Something is keeping the currents from building up in the coil and accumulating in the tantalum caps before and after the current sampling resistor (.2ohms). The currents we should see are 160ma. The currents we get are 50ma and dependent on charge of the cells. The highside gate voltage appears good and there is switching go on (or so it seems.) But the chip can't stay in Synchronous without voltage out from the inductor sagging.
What can be causing this?
