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Original question:

BQ24193: Is the safety timer stopped when charging completes?

BQ24192: Charging safety timer

Janhavi Rane
Prodigy 170 points
Part Number: BQ24192
Other Parts Discussed in Thread: BQ27531-G1, , BQSTUDIO

Hello,

We are using BQ27531-G1 along with bq24192 charger and we would like to test charging safety timer. In our case, gauge is controling the charger(GG_CHRGRCTL_ENABLE).

Charger register setting in bqStudio:

Reg0

  • EN_HIZ=0
  • VinDPM[6:3]=0110
  • IINLIM[2:0]=111=3A

Reg1

  • REG_RESET=0
  • WDT_RESET=0
  • CHG_CONFIG[5:4]=10=Enable OTG
  • SYS_MIN[3:1]=101
  • BOOST_LIM=0=500mA

Reg2

  • ICHRG[7:2]=011000=2048mA

Reg3

  • IPRECHG[7:4]=0000=128mA
  • ITERM[3:0]=0000

Reg4

  • VREG[7:2]=100101=4.096V (read by gauge)
  • BATLOWV=0=2.8V
  • VRECHG=1=300mV

Reg5

  • EN_TERM=0
  • TERM_STAT=0
  • WATCHDOG[5:4]=01=40 seconds
  • EN_TIMER=1=Enable Timer
  • CHG_TIMER[2:1]=00=5hrs
  • JEITA_ISET=0=not used with bq27531-G1

Reg6

  • BAT_COMP[7:5]=000
  • VCLAMP[4:2]=111
  • TREG[1:0]=11

Reg7

  • DPDM_EN=0
  • TMR2X_EN=0
  • BATFET_DIS=0
  • JEITA_VSET=0
  • INT_MASK[1:0]=11=INT enable

Reg8

  • VBUS_STAT[7:6]=10
  • CHRG_STAT[1:0]=10=Fast charging
  • DPM_STAT=1
  • PG_STAT=1
  • THERM_STAT=0
  • VSYS_STAT=0

Reg9

  • WATCHDOG_FAULT=0
  • OTG_FAULT=0
  • CHRG_FAULT[5:4]=00
  • BAT_FAULT=0
  • NTC_FAULT[2:0]=00

RegA

  • PN[5:3]=101=bq24192
  • TS_PROFILE=0
  • REV[1:0]=11

We have used a battery with constant capacity (e.g 10% SOC) for 6 hours but after 6 hours of charging,  the fault register REG09[5:4] =CHRG_FAULT[1] CHRG_FAULT[0]  not set high.

How to test charging safety timer is working or not?

Regards,

Janhavi Rane

  • 0
    TI__Mastermind 19195 points

    Hi Janhavi,

    I will review the registers and get back to by this thursday. Can you also share the schematic your using.

    Thanks,
    Nick

  • 0 in reply to Nick Brylski
    Prodigy 170 points

    Hello,

    Thank you for your reply. Please find the attachment of our schematic.

    Regards,

    Janhavi Rane

  • 0 in reply to Nick Brylski
    Prodigy 170 points

    Hello,

    Today we have tested charging safety timer using bq24192 charger EVM board and safety timer expiration is working. CHRG_FAULT[5:4] set =1 after 5 hours of charging.

    Test results using bq24192 EVM board.

    After performing this test, we observed that charging safety timer function work alone with the charger but not together with the bq27531-G1 gas gauge(as gauge controls the charger GG_CHRGRCTL_ENABLE). Is it so?

    Why it is not working together with gas gauge?

    Regards,

    Janhavi Rane

  • 0 in reply to Janhavi Rane
    TI__Mastermind 19195 points

    Hi Janhavi,

    How are you isolating the charger from gauge during the charger only test? Is it possible that any of the following are occurring when the gauge is added in? 

    • A new charging cycle begins (see 9.3.3.1 of d/s)
    • Toggle CE pin HIGH to LOW to HIGH (charge enable) 
    • REG01[5:4] toggles: 01 ->00 ->01 (charge enable) 
    • REG05[3]  toggles: 1 -> 0 -> 1 (safety timer enable)

    The safety timer will count at half normal rate during input voltage/current regulation or thermal regulation, or when FORCE_20PCT (REG02[0]) bit is set. You may try running the test for at least 2x the normal time to see if this is the case.

    Would be good to see a log of the gauge registers during the test from bqstudio. You can also log the charger registers with BQ2419x GUI (file-> I2C log on).

    Thanks,

    Nick

  • 0 in reply to Nick Brylski
    Prodigy 170 points

    Hello Nick,

    I have not isolated the charger from the gas gauge from our pcb board. I have just used  bq24192 charger evaluation board separately to test the charging safety timer function.

    As you have mentioned above that run the test for at least 2x the normal time, but I have set TMR2X_EN=0 = Disable 2x extended safety timer.Then why should I test for 2 x normal time?

    Kindly find an attachment of log file.

    BQ27531G1_Safety_Timer_Test_02.log

    P.S. During the test with bq27531-G1 and bq24192, gas gauge sense change in voltage and update SOC as we are using constant voltage and SOC for charging using a battery simulator. Change in SOC is a problem that safety timer expiration is not occuring?

    Regards,

    Janhavi Rane

  • 0 in reply to Janhavi Rane
    TI__Mastermind 19195 points

    Hi Janhavi,

    I am reviewing the log, I will get back to you by this Wednesday.

    Thanks,

    Nick

  • 0 in reply to Nick Brylski
    Prodigy 170 points

    Hello Nick,

    Thank you. Waiting for your reply.

    Regards,

    Janhavi Rane

  • 0 in reply to Janhavi Rane
    TI__Mastermind 19195 points

    Hi Janhavi,

    Charger termination is disabled whenever EN_TERM = 0. You may want to log the charger registers to see when this bit is toggling. Does it happen after your host MCU performs a write operation?

    From the BQ27531 TRM section 3.1.7 (https://www.ti.com/lit/ug/sluua96a/sluua96a.pdf), the gauge has read only access to this bit. Also in that section you can read ". . . the gauge disables the charger termination function." -- So it seems like the gauge can disable the charger termination. If you do the test with a battery that has completed a learning cycle you may have better results. I will be checking with the fuel gauge team to see if they have any input here

    Thanks,

    Nick

  • 0 in reply to Nick Brylski
    Prodigy 170 points

    Hello Nick,

    In our case, gauge reads EN_TERM = 0 when we enable GG_CHRGRCTL_ENABLE command. We are doing this test using battery simulator where we have placed our battery model with constant SOC. Is it the correct method right? 

    As you have explained above that to do the test with a battery that has completed a learning cycle.means what? I didn't understand this.

     

    Regards,

    Janhavi Rane

  • 0 in reply to Janhavi Rane
    TI__Mastermind 19195 points

    Hello Janhavi,

    With GG_CHRGRCTL_ENABLE the gauge disables the chargers own termination methods (if the right conditions are not met). Kindly refer to the gauge TRM section 6.10.1.2.2.  From the log you are keeping Vbat < Charging Voltage – Taper Voltage  (4.1V typically).  

    For performing the test in question you may try setting BYPASS = 1 in gauge data memory (TRM  6.10.7.3.1 )

    Best regards,

    Nick