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BQ24171: Current regulation at precharge term of BQ24171

takahiko yokota
Mastermind 7135 points
Part Number: BQ24171

Hi

I have a question about BQ24171.
There are the value of current regulation at precharge in  Electrical Characteristics.
If I use higher Rsense, does that's value change?  
If it changes, are there those data?  

Best regards,
  • 0
    TI__Guru**** 166996 points

    Hi Yokota-san,

    The current regulation for precharge and fast charge is a function of the voltage drop across the sense resistor, RSENSE.  The electrical characteristics table shows current regulation accuracy as a function of V(SRN-SRP) = I(PRECHARGE)*RSENSE.  Larger RSENSE results in larger V(SRN-SRP) which results in better accuracy.  

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Mastermind 7135 points

    Hi Jeff-san

    Thank you for the information.
    Please let me ask you further question.
    Are there the equation to calculate current regulation accuracy on usinging higher Rsense?

    Best regards,
    Yokota
  • 0 in reply to takahiko yokota
    TI__Guru**** 166996 points

    Yokota-san,

    There is no equation to determine regulation accuracy.  The accuracy in the datasheet was determined empirically.  The tightest accuracy is 4% assuming V(SRP-SRN) = ICRG*RSNS=40mV. Increasing RSNS will likely not improve accuracy much as 4% is the in range of the internal reference and errors from amplifier offsets.

    Regards,

    Jeff  

  • 0 in reply to Jeff F
    Mastermind 7135 points

    Hi Jeff-san

    Thank you for the information.
    Please let me ask you further one question.
    Current regulation at precharge term is defined at Tj=-40~125℃.
    If Tj is 25℃, does the accuracy become better than Tj=-40~125℃? 

    Best regards,
    Yokota
  • 0 in reply to takahiko yokota
    TI__Guru**** 166996 points

    Yi Yokota-san,

    The regulation specifications are at -40 to 125 C, although practically if using TS function you cannot charge outside of 0-60C.

    At Tj=25C, the regulation will likely be tighter on most but I cannot warranty outside of the datasheet spec.

    Regards,

    Jeff