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BQ25120A: I2C register [SYS_VOUT, BUVLO] questions

agusta mir
Intellectual 480 points
Part Number: BQ25120A
Other Parts Discussed in Thread: BQSTUDIO

Hi -

1) For SYS_VOUT register, can you clarify what is the mV step size when SYS_SEL = 00 or 10. Table 18 says 00 has 1.1V and 1.2V selection, although in table 19 with SYS_SEL=0, SYS_VOUT goes upto 2.33V. 

2) ILIM and BUVLO register has BUVLO = 2.2V for both 110 and 111. Is that correct?

  • 0
    TI__Genius 12485 points

    Hi Agusta,

    1. What step are you looking for? the table SYS_SEL Codes highlights all the possible combinations of the VSYS settings. If you have BQStudio, you can also easily decipher what bits to write for a given voltage. 

    2. Correct. Both those settings lower the BUVLO setting to the lowest value which is 2.2V. 

    Let us know if you have any questions. 

    regards,

    gautham

  • 0 in reply to Gautham
    Intellectual 480 points

    Hi gautham - 

    1) Ok got it. There is step size(mV) mentioned only for SYS_SEL 10 and 11, not for SYS_SEL = 00 or 10 (Table 18). For the purpose of setting a fixed voltage, its probably fine. I thought there is a generic formula to compute VOUT based on the values of SYS_SEL, like :

    SYS_SEL = 01, then SYS = 1.30 V + SYS_VOUTCODE x 100 mV

  • 0 in reply to agusta mir
    TI__Mastermind 21590 points

    Agusta,

    Please take a look at table 19 in the datasheet which shows the SYS_SEL and SYS_VOUT combinations. Only SYS_SEL = 01 and SYS_SEL = 11 have equations which are in table 18.