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BQ27546-G1: Programming questions

Anadi MARTEL
Prodigy 10 points
Part Number: BQ27546-G1
Other Parts Discussed in Thread: BQSTUDIO

We made a new design with bq27546 because bq27421 (our preferred option) is out of stock, and you had > 1M bq27546 in stock. Now we see that bq27546 itself is out of stock! Anyway we are using it in our current production run and we have the following programming questions:

1) We will program the required registers (Design Capacity, Terminate Voltage...) at first initialization with our firmware. But since we don't need great precision on the SOC, for simplicity we'd rather use the default Chemistry 0100 (our cell is a regular 1200mAh, 3.7V, 4.2V charging Li-Ion, similar to 18650). Is the bq27546-G1 delivered with this default Chemistry already programmed and ready to use?

2  The only registers values that are not clear to us are the CC Gain and CC Delta (104,0 and 104,4). We use a 20mOhm sense resistor. We don't have an EVM to connect bqStudio to our own PCB. How can we calculate approximate CC values without bqStudio connection? BTW bqStudio reports at start that bq27546 is not supported?

3) In the bq27546 Technical Reference Manual (Literature Number: SLUUB74, May 2015) section 5.11.3.4 (Pack Configuration D) there seems to be an error in the description of bits :

SE_POL = Pullup enable for SE pin. True when set (push pull).
SE_PU = Polarity bit for SE pin. SE is active high when set (makes SE high when gauge is ready for shutdown).
Shouldn't SE_PU be Pullup enable and SE_POL be Polarity? Please confirm which bit has which function.

 Thanks for your support

  • +1
    TI__Guru 57697 points

    Hello Anadi,

    Note that since bq27546 is a flash based gauge the data memory parameters need to be written only once. Repeated writes may cause wear of data flash.

    1. The bq27546-G1 is preprogrammed with the default chemistry of 100

    2. CC Gain and CC Delta are derived from the calibration procedure. bqStudio makes it easier to calibrate but you can refer the TRM and perform calibration external to bqStudio. Refer this document for the procedure https://www.ti.com/lit/pdf/slua640. Please use latest version of bqStudio if bq27546 is not detected.

    3. Yes the descriptions are incorrect. Please exchange the bit descriptions. All other places where these bits are mentioned are correct in the TRM.