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BQ76920: Can't Establish I2C communication BQ76920

Kangdi Liu1
Prodigy 30 points
Part Number: BQ76920

Hello, I am trying to design a 5s BMS using BQ7692006 IC for an engineering project, but now I am unable to establish I2C communication with the chip. I connected the boot (TS1) to 3.3V using a jumper, Then I tried to send the I2C signal; the device is not responsive when I sent this at 100Khz: 

Data = 0x00; 
ReturnVal = HAL_I2C_Mem_Write(&hi2c1, BQWriteCmd, SYS_STAT, 1, &Data, 1, 1000);
if( ReturnVal != HAL_OK ) { SerialPrint("Transmit unsucessful1\n"); } 

Where these address are defined:

#define BQWriteCmd 0x30  //0x18 with 0 at end

#define BQReadCmd 0x31  //0x18 with 1 at end

#define SYS_STAT 0x00

I spend 2 days and can't find the issue, tried everything I can think of. Attached below is my Schematic and I2C signals from the scope. I am relatively new to PCB design and Programming, so any help would be greatly appreciated!

   I2C signal, 0x30, no acknowledgment by BQ

Schematic_Powerbank BMS 5 Cell 10A_2021-01-03.pdf

  • 0
    TI__Guru 54715 points

    Hi Kangdi,

    The waveform looks good casually, there can be many details with the edges which prevent successful communication with I2C.  However before exploring that, REGSRC and REGOUT are required for the part but are not shown as connected on the schematic.  REGSRC powers the current detection and output buffers, a capacitor is required on REGOUT to stabilize the regulator which is also used for internal operation.

    Boot requires a rising edge.  Be sure the boot signal goes from low to high to wake the part, then be sure REGOUT and CAP1 are high (3.3V).  

    If you have other inventory, be sure it is the right version so that the I2C address is correct.

    ALERT is shown as open on the schematic, a pull down resistor is recommended in the data sheet to help pull the pin low.  It should not affect communiction.