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BQ40Z50-R1: BQ40Z50-R1

Mario Moraes
Prodigy 90 points
Part Number: BQ40Z50-R1

We designed a custom board with the bq40z50-r1 for two cells only. 

Start testing the prototypes boards and can not start the gauge.

The same procedure with the EVM works fine but we originally had to connect three cells battery in order to change the configuration to two cells.

In our custom design we did not included the option to change to three cells.

1. Is it mandatory to change to three cells configuration in order to start the gauge?

2. Can you please provide guidance how can we start the gauge with two cells connected?

3. Also in our custom design the present pin is permanently connected thru 1.2K resistance to pack-, same as in the EVM. Is this configuration OK?

Thank you,

Regards,

Mario

T

  • 0
    TI__Mastermind 34775 points

    Hi Mario,

    If you can share your PCB schematic that would be helpful. You should be able to apply a voltage > 2.45V  across pack+ and pack- to wake up the gauge and change the number of series cells to 2 cells  (b'01). Did you connect VC2, VC3 and VC4 together? Also BAT should be connected to VC2 through a schottky diode.

  • 0 in reply to Damian Lewis
    Prodigy 90 points
    Hi Damian,

    I think all your recommendations above are included in the circuits. I can send you the gauge schematics. Do you have an email to send?

    We had the same problem with the EVM and was able to fix it only when changed the configuration to 3 cells connected a 2 cells bat and changed to 2 cells.

    We did not included the option to configure as 3 cells in the design. We may change for production version and include this option.

    We have few prototype boards and are afraid to force writing to the gauge and damage it.

    Thank you,
    Regards,
  • 0 in reply to Mario Moraes
    TI__Mastermind 34775 points

    Hello Mario,

    I reviewed your schematic and it looks very similar to the EVM. It doesn't seem like your using pin 16 on bq40z50-R1, so it would be best to connect it directly to VSS or leave it floating (NC), but you will have to set NR bit to 1 in the DA Configurations register. Pin 17 /DISP should be floating, since you're not using the LED display feature.

    Can you communicate with the gauge when the 2S cells are connected? What do you mean you're afraid to force writing and damage it? If you can communicate with the gauge with the 2S cells connected it's ok to write the new configurations and change the DA configuration register from 3S to 2S then send a reset command. This should NOT cause any damage to the gauge.

    What is the battery voltage with your 2S cells? It's strange that you had to configure 3S to change the configuration to 2S and can't start with just 2S cells. Can you also provide an SREC?

  • 0 in reply to Damian Lewis
    TI__Mastermind 34775 points

    Issue was with I2C mux on custom PCB. No 3S connection needed before switching to from 3S to 2S.