BQ25120A: We encountered the following questions when using "BQ25120A", please help analyze and answer!

Hello,

1) /PG is open drain output so it will be pulled low when VIn > VBAT + 65mV. When you say charging voltage is not within specified range do you mean VBAT? What is your VBAT outside the specified range? If VIN is below that threshold, /PG will be high impedance. 

2) If VIN is absent, you need to set /CD high to place the device in Active BAT mode to enable I2C communication.

3) /INT only send interrupts to the MCU and is not intended to wake up the device. If the device is in shipmode, you need to use /MR or VIN to exit shipmode. Faults dont prevent I2C communication. Most likely the cause of the fault is preventing charging and not the fact that the fault has not been cleared due to I2C read.

4) You can ignore RESET if you dont intend to use it. You need /MR if you intend to use the shipmode function unless you intent to exit shipmode only by VIN plugin.

5) That is correct. You should be able to communicate with the charger during charging.

Hello Raheem,

Thanks for your support; Let me input more detail about our product requirement;

There is a charger case supply VIN power supply to the product if product in case;And the charger case is powered by battery,so we need make sure the power consunption is very low during charger connect;

The product uses BQ25120A  as a charger and supply 1.8V to the other chips; And there is a host controller connected to BQ25120A,they can communicate by I2C and GPIOs;

The host controller need to enter power down to cust low power during VIN connected(in case);And power on (wake up)  to work normal after VIN disconnect(out of case);

The host only provides one GPIO which can wake the host controller,so we intend to use /PG connecting to host which will wake up host if charger disconnect, and notify host to power down when charger connect;

During power down,the functions of host almost shut down,I2C will not work, host can only be wake up by the only one wake up pin, can not be notified(interrupt) by the other normal GPIO;

1) /PG is open drain output so it will be pulled low when VIn > VBAT + 65mV. When you say charging voltage is not within specified range do you mean VBAT? What is your VBAT outside the specified range? If VIN is below that threshold, /PG will be high impedance. 

-->Seems /PG could notify the host controller when VIN plugin,and wake up the host controller when VIN disconncet;  We are worry about when VIN is abnormal and not within the specified limits(in datasheets),the /PG will be pulled high by external pull up resistor, and this will wake up the host controller to power on; It means that the power consumption may high during VIN inserted in abnormal situation;

2) If VIN is absent, you need to set /CD high to place the device in Active BAT mode to enable I2C communication.

-->Yes,Seems /PG could notify the host controller when VIN plugin,and wake up the host controller  when VIN disconncet; The host will set /CD high after wake up to have communication with BQ;

3) /INT only send interrupts to the MCU and is not intended to wake up the device. If the device is in shipmode, you need to use /MR or VIN to exit shipmode. Faults dont prevent I2C communication. Most likely the cause of the fault is preventing charging and not the fact that the fault has not been cleared due to I2C read.

-->Based on 1) and 2),the host controller can only wake up by /PG;so the host can not clear the faults during VIN in and host power down,since /INT just connected to the normal GPIO which can not wake up the host and I2C function of the hsot can not work during power down;Do you mean that charging will recover if the fault cause is gone so the host controller can ignore the fault during VIN connceted? Is there a need to clear the faults when I2C recovered after VIN disconnected?

4) You can ignore RESET if you dont intend to use it. You need /MR if you intend to use the shipmode function unless you intent to exit shipmode only by VIN plugin.

-->Yes ,the product only exit shipmode by charger connected;

5) That is correct. You should be able to communicate with the charger during charging.

-->OK.