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Original question:

BQ27531-G1: Gauging accuracy at low temperature

BQ27531-G1: BAT and REGIN

Shunsuke Nagata
Genius 13070 points
Part Number: BQ27531-G1

Hi,

Could you please let me know the relation between BAT pin and REGIN pin?

Are these pin connected internally? As battery is attached to PACK+(BAT pin), the voltage would be shown at REGIN. I believe both pin are used for Vin for internal LDO, then they are shorted each other. Is it correct?

Regards,
Nagata.

  • 0
    TI__Guru 52115 points

    Your question has been assigned to one engineer and we will get back to you next week.

    Andy

  • 0 in reply to Andy Liu (BMS)
    TI__Genius 13070 points

    Hi, Andy,

    I have additional question for Vce. Is there input voltage range requirement for Vce? I found Vce <= VREGIN condition in datasheet. Is there others? 

    I have two option for setting of Vce and VREGIN as below:

    - Vce = VREGIN = 3.3V which is provided from external circuit  

    - Vce = VREGIN = SYS ( same as Typical Application in datasheet)

    Can I use both case?

    Regards,
    Nagata.

  • 0
    TI__Mastermind 34775 points

    Hello Nagata,

    Shunsuke Nagata said:
    Could you please let me know the relation between BAT pin and REGIN pin?

    REGIN is supply voltage input for the internal regulator that powers the internal digital and analog circuits. BAT is the cell voltage input to the ADC that measures voltage.

    Please refer to the pin function table on page 3 of datasheet: 

    Shunsuke Nagata said:
    Are these pin connected internally?

    No they are not

    Shunsuke Nagata said:
    I believe both pin are used for Vin for internal LDO, then they are shorted each other. Is it correct?

    You can if they are connected directly to PACK+ in your application.  

  • 0 in reply to Shunsuke Nagata
    TI__Mastermind 34775 points

    Hello Nagata,

    Shunsuke Nagata said:
    I have additional question for Vce. Is there input voltage range requirement for Vce? I found Vce <= VREGIN condition in datasheet. Is there others?

    Yes, VIH(CE) and VIL(CE) on page 5 of datasheet 7.6 Digital Input and Output DC Characteristics


    Shunsuke Nagata said:

    I have two option for setting of Vce and VREGIN as below:

    - Vce = VREGIN = 3.3V which is provided from external circuit  

    - Vce = VREGIN = SYS ( same as Typical Application in datasheet)

    Can I use both case?

    You can simply connect CE pin to REGIN pin via 10k or greater resistor and REGIN is connected to PACK+. Did I miss something? Is the gauge always going to be enabled or do you want to have the capability to disable the gauge?

  • 0 in reply to Damian Lewis
    TI__Genius 13070 points

    Hi, Lewis,

    For your reply :

    > You can simply connect CE pin to REGIN pin via 10k or greater resistor and REGIN is connected to PACK+. Did I miss something? Is the gauge always going to be enabled or do you want to have the capability to disable the gauge?

    Typical application in datasheet shows CE pin connect SYS which from output of charger. Is there a issue if user connect CE to SYS? 

     

    Regards,
    Nagata.

  • 0 in reply to Shunsuke Nagata
    TI__Mastermind 34775 points

    Hello Nagata,

    Both CE and REGIN are connected to SYS, which is inline with my comment to connect CE to REGIN. I would recommend adding a >10k resistor between CE to REGIN connection for current limiting.

  • 0 in reply to Damian Lewis
    TI__Genius 13070 points

    Hi, Lewis,

    Could you please give me your support for additional question?

    1. Will bq27531-g1 work with Power supply from BAT which mean is VREGIN = OPEN (or 0V) and VBAT = 3.0 ~ 4.2V?

    2. How much time host mcu wait to send command to bq27531-g1 after POR?  I guess host mcu should wait about 300ms due to Initial OCV. is it correct?

    Regards,
    Nagata.

  • 0 in reply to Shunsuke Nagata
    TI__Genius 13070 points

    Hi, team,

    Could you please support this post?

    Regards,
    Nagata.

  • 0 in reply to Shunsuke Nagata
    TI__Mastermind 34775 points

    Hello Nagata,

    Shunsuke Nagata said:
    1. Will bq27531-g1 work with Power supply from BAT which mean is VREGIN = OPEN (or 0V) and VBAT = 3.0 ~ 4.2V?

    BAT is not the power supply for the gauge REGIN is. Without REGIN the gauge has no power. BAT pin is a high impedance voltage sense node for voltage ADC measurement.

    Shunsuke Nagata said:
    2. How much time host mcu wait to send command to bq27531-g1 after POR?  I guess host mcu should wait about 300ms due to Initial OCV. is it correct?

    Host should wait >2s before communicating with gauge after POR for data reported to be valid. I would recommend host poll Flags() [BAT_DET] bit to know when the data is valid.