BQ25120 SYSout voltage return to default value after a few sec of configuration via I2c.
Observation: The SYSout voltage won't drop if we constantly read the system register(0x06) valuevia I2c
Here is our register configuration.
#define BQ25120_SLAVE_ADDR 0x6A
#define BQ25120_BTTN_REG 0x08
#define BQ25120_SYS_REG 0x06
#define BQ25120_LDO_REG 0x07
#define BQ25120_FAST_CHRG_REG 0x03
#define BQ25120_PRECHRG_REG 0x04
#define BQ25120_BATTV_CTRL_REG 0x05
#define BQ25120_ILIM_CTRL_REG 0x09
/* configure BQ25120 register */
/*Push-button Control Register, 1st wake up event at 600ms, 2nd wakeup event at 1.5s*/
err_code = nrf_drv_twi_tx(&m_twi1, BQ25120_SLAVE_ADDR, bttn_config, sizeof(bttn_config), false);
APP_ERROR_CHECK(err_code);
/*SYS VOUT control Register, Range 1.8V~3.3V, SYS output at 3V*/
err_code = nrf_drv_twi_tx(&m_twi1, BQ25120_SLAVE_ADDR, sysv_config, sizeof(sysv_config), false);
APP_ERROR_CHECK(err_code);
/*Load Switch and LDO control Register, Range 1.8V~3.3V, SYS output at 3V*/
err_code = nrf_drv_twi_tx(&m_twi1, BQ25120_SLAVE_ADDR, ldo_config1, sizeof(ldo_config1), false);
APP_ERROR_CHECK(err_code);
/*Load Switch and LDO control Register, Range 1.8V~3.3V, SYS output at 3V*/
err_code = nrf_drv_twi_tx(&m_twi1, BQ25120_SLAVE_ADDR, ldo_config2, sizeof(ldo_config2), false);
APP_ERROR_CHECK(err_code);
/*Fast Charging current control Register, Iset pin connects to 2.49kohm resistor for 80mA charging current*/
err_code = nrf_drv_twi_tx(&m_twi1, BQ25120_SLAVE_ADDR, fast_chrg_config, sizeof(fast_chrg_config), false);
APP_ERROR_CHECK(err_code);
/*Pre-charge current control Register, 10% pre-charge/termination current (8mA)*/
err_code = nrf_drv_twi_tx(&m_twi1, BQ25120_SLAVE_ADDR, prechrg_config, sizeof(prechrg_config), false);
APP_ERROR_CHECK(err_code);
/*Battery Voltage Control Register, Charging voltage 4.2V (default)*/
err_code = nrf_drv_twi_tx(&m_twi1, BQ25120_SLAVE_ADDR, batt_vol_config, sizeof(batt_vol_config), false);
APP_ERROR_CHECK(err_code);
/*Input current and voltage protection control Register, Input current 200mA, UVLO 3.0V*/
err_code = nrf_drv_twi_tx(&m_twi1, BQ25120_SLAVE_ADDR, ilim_config, sizeof(ilim_config), false);
APP_ERROR_CHECK(err_code);
}
