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Original question:

BQ34Z100-R2: Surge Protection for BQ34Z100-R2

BQ34Z100-R2: I want to design the fuel gauge BQ34Z100PWR-R2 for 5S2P battery

Murali C
Prodigy 230 points
Part Number: BQ34Z100-R2
Other Parts Discussed in Thread: BQ25756, BQ34Z100

Tool/software:

Hi

I'm using 5S2P dump pack and standalone charger IC BQ25756 with BQ34Z100PWR-R2. 

I have checked the datasheet, EVM schematics for reference. Still i have few doubts mentioned as below:

  • Based on EVM BQ34Z100, do I need to provide the alert configuration? or can it be left unconnected? if it is not given, TS pin simply can be connected as with NTC 10K and powered with REG25.
  • How to connect the BAT pin, since my battery is 5S2P? I don't want LED display. just need this fuel gauge for battery SOC monitoring.
  • Since i don't use SW1, VEN cannot give input to Q4 fet, so Q5 won't turn on whole translated network won't happen right? So can i keep BAT pin with 16.5K pulled with GND and 3300pF tied to GND. no other mosfet required right? or explain me how it will work?
  • REGIN pin input schematics ?

  • 0
    TI__Mastermind 26845 points

    Hello,

    This question has been assigned within the team and will be followed up with a response when possible.

    Thank you,
    Alan

  • 0 in reply to Alan Frias
    TI__Mastermind 26545 points

    Hi,

    Murali C said:
    Based on EVM BQ34Z100, do I need to provide the alert configuration? or can it be left unconnected? if it is not given, TS pin simply can be connected as with NTC 10K and powered with REG25.

    Not if you will not be using the ALERT feature, the HDQ pin can be GND. 

    correct

    Murali C said:
    How to connect the BAT pin, since my battery is 5S2P? I don't want LED display. just need this fuel gauge for battery SOC monitoring.

    You will connect the top of the battery stack to BAT+ and the bottom to BAT-.

    Murali C said:
    Since i don't use SW1, VEN cannot give input to Q4 fet, so Q5 won't turn on whole translated network won't happen right? So can i keep BAT pin with 16.5K pulled with GND and 3300pF tied to GND. no other mosfet required right? or explain me how it will work?

    VEN will turn on Q4, i am confused on this question, can you clarify?

    Murali C said:
    REGIN pin input schematics ?

    Regin needs a stable power supply, the small circuit connected to the Regin pin functions as an LDO.

    Regards,

    Diego

  • 0 in reply to Diego
    Prodigy 230 points

    Hi Diego,

    Thanks for the feedback.

    could you check the schematics and let me know if i need to add anything else:

    LDO section, VBAT+ is 21 to 15V (5S battery).

    Check, VEN, TS, BAT pins. REGIN is 3.3V. Note: I have added 4.7k pull up on MCU side.

    Looking forward for your review comments!

    Thanks

  • 0 in reply to Murali C
    TI__Mastermind 26545 points

    Hi,

    Here are my concerns about the schematic.

    1) the TS pin connection is wrong, the pin does not need to be tied to gnd, and the thermistor should be connected to TS and reg 25. See EVM

    2) you need pull ups on i2c lines, they could be off the schematic

    3) on the VEN pin, that is the purpose of the pullup to reg25 and the 1M resistor? These are not necessary to drive the VEN pin.

    EVM schematic below for reference. 

    bq34z100EVM Wide Range Impedance Track Enabled Battery Fuel Gauge (Rev. B)

    Regards,

    Diego

  • 0 in reply to Diego
    TI__Mastermind 26545 points

    sorry missed your note about the pull ups at the bottom

  • 0 in reply to Diego
    Prodigy 230 points

    Hi Diego,

    Thanks for your detailed review. 

    As you mentioned, TS pin is connected with 10k NTC to REG25 right? No need of 10k resistor with ground? Then I'll DNP it. No need of any additional circuits to be added since i'm not using alert configuration.

    VEN pin is output drive type, it can give high when REGIN is supplied and it can change low when REGIN is not present. no need of pull up and optional 1M pull down? 

    Then I'll DNP the Pull up to REG25, Pull down to VEN pin, Pull down to 10K resistor in TS pin. It will solve the connection issues right?

    Need your response accordingly!

  • 0 in reply to Murali C
    TI__Mastermind 26545 points

    Hi,

    Murali C said:
    As you mentioned, TS pin is connected with 10k NTC to REG25 right? No need of 10k resistor with ground? Then I'll DNP it. No need of any additional circuits to be added since i'm not using alert configuration.

    correct, looks good on the schematic

    Murali C said:
    VEN pin is output drive type, it can give high when REGIN is supplied and it can change low when REGIN is not present. no need of pull up and optional 1M pull down? 

    correct

    Murali C said:
    It will solve the connection issues right?

    sorry, what is the connection issue? I thought we were just reviewing the schematic for errors.

    Regards,

    Diego