Part Number: TPS65986
Dear Experts,
System consists of TPS65986, bq25892 charger and host MCU. All three are connected to same I2C-bus and MCU is a master. TPS65986 receives power from external USB-charger and feeds it through to bq25892 which charges the battery.
Problem occurs during dead-battery situation, meaning that TPS65986 is powered from VBUS. MCU is accessing to bq25892's registers during start-up routines. I2C address of bq25892 is 0x6B and the register which is accessed is 0x03. When MCU sends 6B03, TPS65986 removes pull-downs from C_CC1 and C_CC2. Due to this external charger cuts off VBUS and device shuts down because there is no power.
If MCU is accessing to different register, there is no issue. This happens only if 6B03 is sent. For example, 6B04 is not causing any issues.
Any ideas what could cause such odd behavior?
Rgds,
Juha