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TPS53667: READ_IIN measurement method

K. Sasaki14
Guru 10200 points
Part Number: TPS53667

TPS53667 has "READ_IIN" register.

How does the TPS53667 measure input current value?
When TPS53667 is used with CSD95490, current information is communicated from CSD95490.

Output current is measured from LS FET voltage difference. However I don't know the input current measurement method.

Best Regards,
Kohei Sasaki 

  • 0
    TI__Expert 4060 points
    Hi Kohei,

    Unlike some of the newer controllers, the TPS53667 doesn't directly measure IIN through a shunt resistor or input inductor. Instead it uses other measurements to indirectly calculate input current.

    The controller is sensing VIN and VOUT directly while also setting the constant on time for the phases. These three parameters combined with the output current readings from the power stages allow the controller to make a good estimation of what IIN likely is. This method isn't as accurate as a direct measurement but it gets close enough for all but the most demanding applications.

    Cheers,

    Carmen
  • 0 in reply to Carmen Parisi
    Guru 10200 points

    Carmen-san,

    Thank you for your answer.
    Could you tell me the equation for calculating of IIN?

    Best Regards,
    Kohei Sasaki

  • 0 in reply to K. Sasaki14
    TI__Expert 4060 points

    Hi Kohei,

    The basic equation from the sensed parameters is

    IIN = (IOUT * D) / Efficiency

    IOUT and D are known from the power stages, VIN, and VOUT. Efficiency is just assumed to be 90% (0.9) for simplicity which is why this method is less accurate than a direct measurement. Actual efficiency could be higher or lower depending on the exact operating conditions.

    Thanks,

    Carmen