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Help in selecting MCU for low frequency application

ibbidy2
Prodigy 60 points

Hi all,

    I have used the parametric search tool but am not having any luck finding what I'm looking for.  Rather than moving on I decided to ask here if someone might have a suggestion.

   I have a need for a low power microcontroller with an 8-10bit ADC (one channel is enough) that runs at a clock rate of 9kHz or less (no clock on the chip can be higher than this).

    The rest of the parameters I can sort through if someone can point me in the right direction, but here are a few

VDD 3V

Iquiescent < 2mA

at least 15 I/O

Thanks,

sne

  • 0
    TI__Genius 10860 points
    Hi,

    thanks for taking a chance on this forum, the information you're looking for is really hard to find, even outside the parametric search.
    I understood you're looking for a device running from a 9 kHz clock, not just the ADC running at that frequency, correct?

    Let me share some consideration with you before focusing on your question:
    I understood that you are looking for a low power microcontroller and thus you're looking for an MCU running at a low clock rate. Using a slow clock frequency can definitely decrease the peak currents so if that's your goal your probably on the right track. To decrease the average current though it's a bit more tricky. Depending on the application profile, the more important can be how much time the CPU is active versus in a low-power mode. Reducing the clock could, in some cases, actually result in a higher average current, so we advice our customers to check this. It might be more beneficial to use a higher clock frequency and reduce the active time - if the application allows.

    Some of our devices have the capability to connect the external LFXT or HFXT to the CPU, in that way you can control the frequency. You'll find this information in the Family User's Guide, in the Clock Module Section. You could check the different Families and crosscheck with devices which have the set of parameters you need. Please check the ADC performance at low clock frequency. Decreasing the Frequency could at very low frequencies allow time for the capacitors to discharge before the conversion which might result in inaccurate conversion results.

    Hope this helps,

    Britta
  • 0
    Guru 302950 points

    All MSP430s start up with an internal clock of about 1 MHz, and all other microcontrollers I've heard of do something similar.

    As far as I can see, it is not possible to avoid CISPR with any microcontroller.

  • 0 in reply to Clemens Ladisch
    Prodigy 60 points

    Clemens Ladisch said:

    All MSP430s start up with an internal clock of about 1 MHz, and all other microcontrollers I've heard of do something similar.

    As far as I can see, it is not possible to avoid CISPR with any microcontroller.

    Thank you for the reply.  I believe there are several microcontrollers that can basically have their clocks stop.  Perhaps this is only after startup - I'll look into that.

    You are correct, avoiding CISPR would be quite attractive.

  • 0 in reply to ibbidy2
    TI__Genius 10860 points
    Hi,

    are you fine with the answers you've gotten or do you need further assistance here? Please verify a given answer in case it solved your issue, or otherwise let me know how we can further help you.

    Thanks and best regards,
    Britta

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