BQ25155: VBAT ADC readout value is not correct while Active Battey Mode

PS. BTW, the LP is always High while test w/ battery only

Hello Peter,

It appears that everything in your register configuration process is correct. The ADC read voltage for VBAT should not be affected by the presence of VIN. Can you share your schematic for this device?

Additionally, do you have a waveform of VBAT? This is just to discard any possible oscillations or glitches that might affect the ADC reading.

Best Regards,

Juan Ospina

Dear Juan,

I use BQ25155EVM for test and also use oscilloscope to monitor VBAT while testing, no 1V glitches on VBAT observed

BR

Peter

HI Peter,

I'll attempt to recreate the behavior you are seeing on my end. Please let me know if any modifications have been made to the EVM.

Best Regards,

Juan Ospina

Dear Juan,

there is no HW modification of EVM, the following is my init flow~

void bq25155_init(){
printf("%s\r\n", __func__);

//1) wake bq25155 - #LP pin(PB0) set low
HAL_GPIO_WritePin(CHG_LP_GPIO_Port, CHG_LP_Pin, GPIO_PIN_RESET);

//2) init registers
BQ25155_RegWrite(BQ25155_MASK0, 0x5C);//PG, THERM_MITIGATION, CHG_DONE
BQ25155_RegWrite(BQ25155_MASK1, 0xB0);//TS
BQ25155_RegWrite(BQ25155_MASK2, 0x31);//ADC_READY, COMP1
BQ25155_RegWrite(BQ25155_MASK3, 0x70);//MR_WAKE
BQ25155_RegWrite(BQ25155_VBAT_CTRL, 0x3C);
BQ25155_RegWrite(BQ25155_ICHG_CTRL, 0x11);//0x11
BQ25155_RegWrite(BQ25155_PCHRGCTRL, 0x01);
BQ25155_RegWrite(BQ25155_TERMCTRL, 0x0A);
BQ25155_RegWrite(BQ25155_BUVLO, 0x00);
BQ25155_RegWrite(BQ25155_CHARGERCTRL0, 0x90);//disable WD
BQ25155_RegWrite(BQ25155_CHARGERCTRL1, 0x00);
BQ25155_RegWrite(BQ25155_ILIMCTRL, 0x06);
BQ25155_RegWrite(BQ25155_LDOCTRL, 0xEC);//enable 3.3V LDO
BQ25155_RegWrite(BQ25155_MRCTRL, 0x68);//wake1-0.5s, wake2-2s, reset-4s, warn-1s
BQ25155_RegWrite(BQ25155_ICCTRL0, 0x10);//disable ship mode
BQ25155_RegWrite(BQ25155_ICCTRL1, 0xC0);
BQ25155_RegWrite(BQ25155_ICCTRL2, 0x20);
BQ25155_RegWrite(BQ25155_ADCCTRL0, 0x00);//disable ADC first
BQ25155_RegWrite(BQ25155_ADCCTRL1, 0x00);
BQ25155_RegWrite(BQ25155_ADCALARM_COMP1_M, 0x91);//set ADC COMP1 to VBAT low threshold MSB
BQ25155_RegWrite(BQ25155_ADCALARM_COMP1_L, 0x10);//set ADC COMP1 to VBAT low threshold, below 3.4V
BQ25155_RegWrite(BQ25155_ADCALARM_COMP2_M, 0x00);
BQ25155_RegWrite(BQ25155_ADCALARM_COMP2_L, 0x00);
BQ25155_RegWrite(BQ25155_ADCALARM_COMP3_M, 0x00);
BQ25155_RegWrite(BQ25155_ADCALARM_COMP3_L, 0x00);
BQ25155_RegWrite(BQ25155_ADC_READ_EN, 0x08);//enable VBAT ADC read
BQ25155_RegWrite(BQ25155_TS_FASTCHGCTRL, 0x34);
BQ25155_RegWrite(BQ25155_TS_COLD, 0x6F);
BQ25155_RegWrite(BQ25155_TS_COOL, 0x61);
BQ25155_RegWrite(BQ25155_TS_WARM, 0x39);
BQ25155_RegWrite(BQ25155_TS_HOT, 0x38);

//4) boot completed - LED slow blink x 1
//led_control(LED_SLOW_BLINK, 1);
BQ25155_RegWrite(BQ25155_ADCCTRL0, 0xC3);//enable ADC measurement period 1min

//5) toggle CHG IRQ
CHG_INT+=1;
HAL_GPIO_WritePin(CHG_LP_GPIO_Port, CHG_LP_Pin, GPIO_PIN_SET);
}

BR

Peter

Thank you for this additional context peter. I will attempt to recreate your scenario and find any potential causes for the behavior you are seeing.

Best Regards,

Juan Ospina

Hi Peter,

I've been working to recreate your scenario but I'm not able to see any issues in accuracy with the register set up provided. On an EVM the battery ADC voltage reading will drop slightly when VIN is removed, but this is likely due to charge stopping. Can you provide the schematic to confirm there isn't any components that may have an effect? Additionally, is this test being performed with a battery or a battery simulator?

Best Regards,

Juan Ospina