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Original question:

[FAQ] UCC5880-Q1: Getting Started with UCC5880-Q1 Without SPI

UCC5870-Q1: ADC sampling Frequency

MOHD ISMAIL
Prodigy 45 points
Part Number: UCC5870-Q1
Other Parts Discussed in Thread: UCC5880-Q1

Tool/software:

Hi, 

I am going through Datasheet of UCC5870 gate driver and i see that Time to complete ADC conversion is 5.1 uS and still is is saying that "the maximum INP frequency supported in order to get at least one full ADC conversion per PWM cycle is 30kHz". Can you please explain whether i can complete ADC sampling at 50 kHz pwm frequency or not because 50 Khz is 20us Time period in which sampling could be done(according to my understanding).

  • 0
    TI__Expert 7473 points

    Hi Ismail,

    Thanks for reaching out.

    There are two main factor which limit the max PWM input frequency:
    a. It's primarily due to ADC sampling. 
    b. Power dissipation.

    If you switch too fast - higher than 30kHz, you could run into scenarios where the ADC FIFO buffer fills up and starts skipping samples. Thus, triggering ADC_FAULT. It's generally not an issue to switch higher frequency if you don't care about missing samples. Operation to at higher frequencies possible with ADC deactivated, though power dissipation must be considered.

    Have you considered the latest gen gate driver UCC5880-Q1 with higher CMTI rating and more configurability? You can complete ADC conversion with this device up to 50kHz switching frequency.

    Hope this answers your question. If this answered your question, could you please press the green button? If not feel, free to ask more questions.

    Best,

    Pratik

  • 0 in reply to Pratik Adibatla
    Prodigy 45 points

    thanks for the prompt reply Mr. Adibatla,

    So if at greater than 30Khz adc is missing samples, is it possible to use ADC at 30Khz while keeping PWM frequency at >30khz.

    Also, about UCC5880, i really want to use that IC but i'm not getting detailed datasheet of that IC which tell the adresses of SPI communication and i did file a request on the website but it keeps getting denied for some reason, so would you please help me get that detailed datasheet of UCC5880 as well.

    Thanks.

  • 0 in reply to MOHD ISMAIL
    TI__Expert 7473 points

    Hi Ismail,

    Thanks for the follow-up question.

    Input PWM frequency should be 30kHz when ADC is enabled for not missing samples but with ADC disabled PWM frequency can go up to 50kHz.

    You need to have a Standard NDA executed with us in order to have the full datasheet version of UCC5880-Q1. We're currently not executing NDA with Universities at the moment.

    Best,

    Pratik

  • 0 in reply to Pratik Adibatla
    Prodigy 45 points

    Thank You for the information Pratik,

    Also i would like to ask whether this 5.1us for adc conversion time is for all 6 adc channel conversion or only 1 adc conversion. I'm guessing its for all of them otherwise 30Khz wouldn't be enough.

  • 0 in reply to MOHD ISMAIL
    TI__Expert 7473 points

    Hi Ismail,

    The ADC sampling duration differs for different modes please refer to section 7.3.3.2 ADC Setup and Sampling Modes for see the waveforms and timing diagrams. That 5.1 us ADC conversion is for sampling the ADC channels selected to sample during the ON time when IN+ goes from LO to HI and for all the ADC channels selected to sample during OFF time when IN+ goes from HI to LO.

    Hope this answers your question. If this answered your question, could you please press the green button? If not feel, free to ask more questions.

    Best,

    Pratik