help required in right selecting MCU

Discussion in 'Embedded Systems and Microcontrollers' started by embedded.world, May 29, 2014.

  1. embedded.world

    Thread Starter Member

    Feb 27, 2014
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    1. I need to select a small form factor MCU with below features:

    1. Debug/program on chip
    2. 6 I/o
    3. Uart
    4. One channel 16 or 24 bit adc.
    5. IDAC (optional, if not I will use external)

    I had searched on internet but I am not getting any MCU with small form factor.
    Like for Silabs , the mcu matching thses specs is in TQFP-32 , but I need SSOP-20 or smaller.
    TI's does not have mcu in small form factor also

    QFN package I am avoiding as they are hard to solder by hand.
     
    Last edited: May 29, 2014
  2. John P

    AAC Fanatic!

    Oct 14, 2008
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    I'm not sure you'll ever find a small processor with the A/D precision you want. And with a home-built circuit, you'd have a hard time keeping the signal quiet enough to make any use of that kind of conversion anyway.
     
  3. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    I agree on the lack of 16 bit A2D converters inside micros. Either there is no (market) need for such, or the noise floor inside a micro will not support the extra bits. Microchip does have five devices (dsPIC33's), the smallest in a QFN-S, SOIC, SPDIP (28) package.

    As far as getting extra bits, I breadborded a separate 4 channel A2D, forget offhand if it was 16 or 18 bits, in a PIC project, no ground layer. It may have occasionally changed the least sig bit from time to time.

    I've soldered small (8 pin) QFN's by hand using a hot air tip. That should work for larger packages too.
     
  4. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    I'd re-evaluate the need for a 16-24bit ADC, or think about how accurately you expect it to read.

    From what I've seen most people posting questions here who want a 16-24bit ADC simply don't need it, or don't understand that it's not going to give them the real world accuracy that they imagined.
     
  5. embedded.world

    Thread Starter Member

    Feb 27, 2014
    36
    0
    @THE_RB I want to learn who to calculate ENOB & accurate measurement mathematically.

    For example I have selected ADS1247 with 24 bit adc, I need to measure minium step of 75uV & reference = 2.048V & other parameters are also defined.

    Can you guide me right literature from where I can learn how accurately I will read, ENOB & other related parameters?
     
  6. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    If you selected a precision ADC chip already (ADS1247) then you no longer need to have a "16 to 24bit ADC" inside your microcontroller.

    Now your micro just needs these;
    "1. Debug/program on chip
    2. 6 I/o
    3. Uart"
    which should be very easy to find.
     
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