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Timer D to trig ADC10_A, ADC10_A to trig DMA

Keld
Prodigy 140 points


Hi: I have to make a new design, a PFC bucket converter.

In the new design ther is needed for ultra low power consumption, so I'll try if I can use a MSP430F51X2 and its high-resolution timer D.

But now I have some question as:

Can I set timer D0 or timer D1, to trigger ADC10_A, to start the an auto scan, in the Sequence-of-Channels mode.

Can I sette ADC10_A to trigger the DMA control, to move the result from ADC10_A, to a buffer i memory.

 Keld

  • 0
    Guru 23000 points

    It’s well possible to use a MSP430 to control a Buck or SEPIC converter. Even without a High-Resolution timer you can get 375KHz Buck-PWM at 24MHz clock speed with a resolution of 6-bit. With the High-Resolution timer you can create higher Buck-PWM speed or increase resolution, all depending on your need.

    The ADC is too slow to do a full conversion cycle each PWM cycle, so quick changes in load can give a problem. Starting the ADC with a timer is dangerous, if the triggers comes too fast the ADC gives-up (on overflow). Better to let the ADC continuous in Sequence-of-Channels mode running and synchronize the conversion, at the moment Ibuck should be measured, to the Buck-PWM.

    Using DMA is also dangerous, the DMA is edge-triggered and if it misses a trigger (due to another interrupt) the DMA stops. Otherwise use of DMA has no sense, after each ADC channel conversion you have to calculate the Buck-PWM and to do some other work, after this you start manually the next channel conversion.

  • 0 in reply to Leo Bosch
    Prodigy 140 points

    Hi.

    When my bucket converter should operate in DCM mode, the adjustment from 0 to 100%, of the output power, gives 0-20% of PWM output, which  the lead to, at 24MHz clock frequency and 375kHz PWM. I only gets 3-4 bit resolution, with the nomale timer.

    With the High-Resolution timer this is not a problem.

    I think I'll make an external sample and hold circuit to eliminate the time-critical part from the ADC.

     

    Keld

     

    discontinuous conduc tion mode (DCM),

  • 0 in reply to Keld
    Guru 46710 points

    Keld said:
    When my bucket converter should operate in DCM mode, the adjustment from 0 to 100%, of the output power, gives 0-20% of PWM output, which  the lead to, at 24MHz clock frequency and 375kHz PWM. I only gets 3-4 bit resolution, with the nomale timer.

    You shall consider C5000 microcontroller  instead which I find more useable for such a quite high performance DSP and PWM task.

  • 0 in reply to Keld
    Guru 23000 points

    C5000 are 16-bit Digital Signal Processors and not right suitable for digital power, therefore the 32-bit C2000 with CLA is a very good solution. But I understood it should be ultra low power then: MSP, but depends on SMPS parameters.

    The PWM resolution doesn’t define your output resolution, but if too low it may become a little bit nervous, and can lead to over-current of your switch (and inductor). Output resolution is defined by ADC, digital-filter and PWM frequency.

    The only time-critical ADC part is measuring of the switch current, this should start at the right moment.

  • 0 in reply to Leo Bosch
    Guru 46710 points

    Leo Bosch said:
    C5000 are 16-bit Digital Signal Processors and not right suitable for digital power, therefore the 32-bit C2000 with CLA is a very good solution.

    Yups, my fault :) I meant C28x Piccolo, not C5000. Indeed you are right.

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