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Original question:

PMP23340UCD: DAC Ramp Model——softstart

PMP23340UCD: How to calculate the value of IOUT

Martin
Prodigy 170 points
Part Number: PMP23340UCD
Other Parts Discussed in Thread: UCD3138A

Tool/software:

Hi，

Thank u for ur time.

I have some doubts about PMP23340UCD.

Hardware：PMP23340UCD(UCD3138A) （48v-12v）
Firmware：TI supplied routines——UCDIBCFirmware

Problem Description:

I use electronic loads to measure the characteristics of power supplies.

When I adjust the load current in the range of 0.1A to 1.5A, the IOUT in the GUI does not change as shown.

At this point the input current and power are varying with the current of the electronic load.

Questions:

  1. IOUT, is that  output current?
  2. How is it calculated and how are "iout_offset" and "constant_0_01733" determined in the program?
  3. How to make the GUI display normal IOUT values?

Regards，

Martin.

  • 0
    TI__Genius 14570 points

    Actually, the current sensing is not good, very coarse. Just used for OCP, not for monitoring.

    Regards,

  • 0 in reply to Sean Xu
    Prodigy 170 points

    Hi, Sean

    Thanks for you reply.

    1. When the load current changes, according to power conservation, the inductor current will also change, but because VOUT is 12V and VIN is 48V, the magnitude of the inductor current change is much smaller, so when I adjust the load current in small increments, the inductor current change is barely noticeable, can it be understood in this way?
    2. Vsw1 and Vsw2 in the ADC sampling circuit are actually the voltages across a series of parallel capacitors as shown in the diagram below, correct?The current is then calculated.Is constant_0_01733 the coefficient calculated by this way?So how is the iout_offset calculated, I measured the ADC reading of 33 when 48V is not powered up and the iout_offset is 65, how do I calculate that?
    3. But is the amount of current in the circuit really what the GUI shows, being able to reach 20A or even more, I'm confused about that.
    4. How are ADC12_IOUT_SCALER_MANTISSA and ADC12_IOUT_SCALER_EXPONENT determined?

    Regards,

    Martin.