I have a strange issue with the battery Management chip. It doesn't switch on the BAT-MOSFET after inserting the batteries.
Normally it is supposed to switch on the BAT-MOSFET after POR and checks then if there is a connected supply.
If the SRN voltage is greater than VCC, indicating that the battery is the power source, the BQ24616 is supposed to enables BATFET, and enters
SLEEP mode to minimize current drain from the battery.
My schematic is except of the MOSFET the same as the evaluation board. At the EVB it works, at my design it starts to Switch on the MOSFET
but switchs it off (very fast) after 200us. I checked nearly everything but I cannot find the error.
Conditions:
- no powersupply is connected
- VFB is calculated for 2 Li-Ion Accus (and the same on the EVB)
- Design is the same as on the Evaluation board (EVB) also the 1k in series to the gate
- SRN voltage is approximately 1V higher as VCC
- no shorts
- treshold voltage of the MOSFET is nearly the same
Description of the attached Pictures:
Pic1:
yellow VCC
blue SRN (Vbat)
Pic2:
yellow: /BATDRV of my board
White: /BATDRV of EVB
