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USB-PD-CHG-EVM-01: TPS25750 overwrites BQ25792 PROG Pin

Part Number: USB-PD-CHG-EVM-01
Other Parts Discussed in Thread: BQ25792, TPS25750, USB2ANY


I just connected a 4S cell pack to the BAT pin of BQ25792 and wanted to charge it directly using USB-PD. Before I connected the battery pack, I switched the Jumper from JP2 (3s) to JP3 (4s) to select the right resistance to the PROG Pin. Then I connected an USB-C power supply to the USB-PD-CHG-EVM-01. But the STAT Pin (D1) starts to blink as described in the datasheet of BQ25792: "Charge suspend (A fault condition which disable charging)".

So I checked what TPS25750 sends to BQ25792 over I2C for initialization using the pin header J7. In the first phase, TPS25750 reads from EEPROM (I2C address 0x50). In the second phase then it writes to the BQ25792 (I2C address 0x6B).

It configures the BQ25792 to set

  • the Charge Voltage Limit Register (reg. address 0x01) to 0x04 0xEC = 1260 * 10mV = 12’600mV = 12.6 V => 3s cellpack
  • the Charger Control 1 (reg. address 0x10) to 0x80 => disables the Watchdog

So the PROG Pin doesn't have an effect because the TPS25750 oversteers it afterwards.

That's why the STAT Pin blinks: Overvoltage of the battery (current battery voltage is 14.2V).

How can I configure USB-PD-CHG-EVM-01 using a host microcontroller (Tiva or different ARM based microcontroller) so that it uses a 4s cellpack?

I checked documents like the following, but only found something using a GUI to produce a binary file and USB2ANY or Aardwark devices to flash the file.