I'm using a BQ28400 in a new design to replace the 2 separate ICs previously used for protection & gas-gauging and I'm having some trouble with it. I have implemented the example application schematic from the datasheet almost exactly.
I connect up my pair of Li-Ion cells, then connect up my charger circuit, and I see the BQ wake up from sleep (2.7V is present on the REG27 pin).
I have PRES tied to ground through a 100R resistor.
I am able to communicate with the BQ and it seems to be returning valid data, but it stubbornly refuses to enable any of the charge or discharge FETs - all of the DSG, CHG & ZVCHG pins just remain floating high.
When I issue a Manufacturer Access command (0x00) and ask for the Manufacturer Status word (0x0006) it returns a value of 0x010a which I interpret to mean that its saying that the FETs are on and that its in Normal Discharge mode - but the gate drive out of the BQ to my FETs remains floating high.
I have tried issuing a Reset (Mfg Access 0x00, Reset 0x0041) but this had no effect.
Is there something I need to do to get the BQ to enable the FETs ?
Any help or insight would be very much appreciated.