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BQ24610: Issue with GAIN of internal differential amplifier for ACSET (IDPM)

Jakub Johanek
Prodigy 20 points
Part Number: BQ24610

Hello, 

I was trying to set DPM current, but I think that equation (3) in datasheet is incorrect:

I set voltage Vacset to 430 mV and this should equal to current limit up to 2,15A, but real limit was only 1,7A.

or 

I set voltage Vacset to 580 mV and this should equal to current limit up to 2,9A, but real limit was only 2,3A.

I think that gain of internal differential amplifier is not 20 but is 25? It is correct?

Thank you

BR

Jakub

  • 0
    TI__Mastermind 18810 points

    Hello Jakub,

    The equation from the data sheet is correct.

    Did you confim the Rac value is correct, 10mohms and not 12.6mohms?

    Best regards,

    Christian.

  • 0 in reply to Christian Moyer
    Prodigy 20 points

    Hello Christian, 

    yes, I am sure that Rac has 10mOhms.

    see this schematic:

    Do you have any other idea?

    Thank you

    BR

    Jakub

  • +1 in reply to Jakub Johanek
    TI__Mastermind 18810 points

    Hello Jakub,

    If you have measured and confirmed that the Rac is 10mOhms, and Vacset to 580 mV.

    The layout of the design could also be affecting the accuracy of the internal differential amplifier. The Input-current sensing resistor should be placed as close to the IC as possible. Route the sense leads connected across the sensing resistor back to the IC in same layer, close to each other (minimize loop area) and do not route the sense leads through a high-current path (see Figure 27 for Kelvin connection for best current accuracy). 

    Best Regards,

    Christian.