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SM72445: SM72445 Programming Questions

Richard Elmquist
Mastermind 45250 points
Part Number: SM72445

I have a customer who is asking questions about programming the device. Can you please look at the questions and send me a response?

1. According to the datasheet, A0, A2, A4, A6 are analog pins used to configure the maximum output voltage, and output current, etc… is it possible for me to configure it through I2C software only without any hardware interacting to those pins? I saw the register bits are writable in the datasheet so I think it is possible.

2. For the A0, A2, A4, A6, can they be used as normal ADCs? For example, I connect the output of solar irradiance to A0 and I read the register for output through I2C. Will this alters my software configured maximum output voltage?

3. Is it possible for me to read the ADC values for AVIN, AVOUT, AIIN, AIOUT through the I2C registers?

4. Will this chip be turned off if the output voltage exceeded the configured maximum output voltage? Since it is sensing through ADC, does this means the range for maximum output voltage is restricted in a way it cannot have a maximum output voltage of higher than 5V?

5. What is the MPPT algorithm using for this chip?

6. Are there any minimum VOUT that might cause this chip to turn off? Under “startup” section, it stated “A counter will start once the minimum output current threshold is met (set by ADC input channel 4, pin A4).” However, A4 is stated to set the maximum output current. Can you explain this in a more detailed way? How low can this threshold current be?

9. What is the panel mode? From the datasheet, I know that it is controlling a mosfet that can bypass the MPPT, but it stated it is outputting a square wave signal. What does this actually doing? 

For your information, I am going to use this chip as the MPPT controller for a buck boost DC-DC converter to charge a 60V super capacitor bank so I want to know the flexibility and capability of this MPPT chip. I hope my questions are not too much and thank you very much for your time!

Thanks for your help with this!

Richard Elmquist

  • 0
    TI__Guru* 78100 points
    Hi Richard,
    Give me a call at 480-629-2487. Here let me answer what I can now. Pardon me for not repeating your questions.

    1. Yes it can as the designer told me many years ago, but I don't have the info about how to.
    2. Not sure.
    3. Not sure.
    4. The controller is buck boost with sync FET, and it may stop switching but allow the voltage to recover from over voltage. You are right that it cannot have voltage >VDDA.
    5. The algorithm is the simple perturbation and observation algorithm. It change the duty cycle and check if the power is increase of decrease. If it increases, the duty cycle will be increased again, until the power calculation shows decreasing, then the duty cycle will stop growing but reducing by one step, and it continues such mode.
    6. Need to recall.
    9. The square wave feeds to a driver that can turn on the back-to-back bypass FETs so the power does not pass through the buck-boost stage. This is to increase efficiency: saving the power loss in current sense resistors, inductor, and the switching FETs.

    Thanks,
    Youhao
  • 0 in reply to Youhao Xi
    TI__Mastermind 45250 points

    Youhao,

    I will call you tomorrow as I am out of the office today.

    Are you on the west coast? What time do you get to the office?

    Thanks for your help with this!

    Richard Elmquist

  • 0 in reply to Richard Elmquist
    TI__Guru* 78100 points
    Richard,
    Can we move this discussion to off line? Anyway, please call me on Thursday. Current I am on a biz trip.

    Thanks,
    Youhao