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BQ76920: bq76920

MONOJIT GOSWAMI
Prodigy 30 points
Part Number: BQ76920

Dear Sir/Madam

I have used bq76920 just to monitor cell voltage of 4 cell connected in series. But while interfacing with arduino nano using i2c communication only two cell voltage I have able to read. other cell voltage is coming as '0'. I was unable to find the root cause for this. Also I have checked by replacing the IC with  other IC.I have done the connection diagram according to Data sheet. The following pins are only used 3,4,5,9,10,12,13,14,15,16 and 17. Please suggest if i have missed any pin just to monitor cell voltage.

  • 0
    TI__Guru 54715 points
    Hi Monojit,
    If you can read one cell voltage you should be able to read all cell voltages since it is the same register interface. Be sure the response is from the bq76920 and not some other device on the bus. Regarding other pins:
    Pin 6, TS1 must have a pull down and a rising edge applied to start (boot) the part.
    Pin 7, CAP1 must have a capacitor to stabilize the internal voltage for proper operation.
    Pin 8, REGOUT must have a cap to stabilize the voltage for the interface circuits. This might be used for the I2C pull ups if they are not pulled up externally.
    The part must be booted to operate. Without the capacitors above it may be that the supply is lost after the 2 voltages are read.
    Pins 18 and 19, SRP and SRN are inputs and should be pulled down to VSS if not used, this may affect power or reported faults but I would not expect this to affect the register access.
    Please see the data sheet figure 8-1 for a simple diagram or the EVM user guide for an example schematic of connection.
  • 0 in reply to WM5295
    Prodigy 30 points

    HI

    I have done the connection as per the suggestion. But VC5 HI coming as '0'. Please help.

    Rc=100 ohm, Cc=1 micro F used in my case.

    What may be the cause where other register value are correct only VC5 HI is Zero.

  • 0 in reply to WM5295
    Prodigy 30 points
    HI
    Now I have connected all the 5 cell.
    I have done the connection as per the suggestion. But VC5 HI coming as '0'. Please help.

    Rc=100 ohm, Cc=1 micro F used in my case.

    What may be the cause where other register value are correct only VC5 HI is Zero.
  • 0 in reply to MONOJIT GOSWAMI
    TI__Guru 54715 points
    Hi Monojit,
    Check the voltage at the pins. If the voltage is too low the upper register value will be 00. If the pin voltage is correct, and the addressing is correct on the bus, and the part has the ADC enabled then the part must be damaged.