I have a custom board designed using the bq24620 to charge a pair of Li ion batteries.
The bq24620 does not seem to be charging the batteries. I took the following list of conditions from the datasheet. The schematic is basically the same as the reference design in section 9.2 of the datasheet.
8.3.6 Enable and Disable Charging
The following conditions must be valid before charge is enabled:
- CE is HIGH.
: Tied to Vref. Is 3.3V
- The device is not in VCCLOWV mode.
: VCCLOWV mode is not defined; however, the VCC pin is at 11.8V
- The device is not in SLEEP mode (that is, VCC > SRN) .
: SRN is 6.96V which is less than VCC so the device should not be in SLEEP mode.
- The VCC voltage is lower than the ac overvoltage threshold (VCC < VACOV).
: VCC is much less than VACOV which is 31V
- 30-ms delay is complete after initial power up.
: Charging doesn't start no matter how long the system sits.
- The REGN LDO and VREF LDO voltages are at the correct levels.
: REGN is 6.1V
: VREF is 3.3V
- Thermal shutdown (TSHUT) is not valid.
: Device does not appear hot. Top of case is 26C
- TS fault is not detected.
: TS pin is 1.6V
: Vts is not defined in terms of Voltage but working design example backwards yields
Tcold is 2.43V
Thot is 1.33V
The STAT and nPG pins are both 3.3V (connected to 3.3V pullups).
The Iset voltage is 0.2V
The battery is 6.95V
The voltage across the 10 mOhm sense resistor is zero (battery neither charging nor discharging)
The voltage at Vfb is 1.51V
The gate and source of the upper MOSFET are 6.95V
Why isn't the bq24620 trying to charge the battery?
