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PMP23340UCD: DPWM Automatic Mode--What dpwm mode does the open-loop system operate in

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

Hi，

Thank u for ur time.

I have some doubts about PMP23340UCD.

      Hardware：PMP23340UCD(UCD3138A) 
      Firmware：TI supplied routines——UCDIBCFirmware 

Issues：

  1. The PMP23340UCD is referred to as open loop in the documentation, does this mean that the FE, Filter are not involved in the operation?(both EAP0 and EAP1 have inputs on the schematic)
  2. If it is open loop，what does the YN depend on ？
  3. What does PID_PERIOD_FACTOR mean?
  4. With the same VIN and load, adjusting the frequency, the VOUT change is not significant because the Gain change is small?（The dpwm output waveform is consistent with the adjusted frequency）.
  5. Is Automatic Mode working in open loop and what mode is the PWM in at that time? Does changing the frequency_switch change the PWM mode?

Best Regards.

  • +1
    TI__Genius 14580 points

    Hi,

    1. It is called open loop because the frequency is not changed at different load and input voltage. But the PID works like closed loop. The loop is saturated and clamped at max value;

    2. YN is saturated at max value (for example, 0x197B70)

    3. PID_PERIOD_FACTOR  is used for switching period scaled.

    4. Right, small gain can't change the output;

    5. At the start up, it works at normal mode; then in resonant mode after start up.

    Regards,
    Sean