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Design ultralow power, narrow band ADC

  1. Jul 11, 2013 #1
    Hi,
    I want to design an ADC with these specifications:
    Fin = 20MHz
    BW= 20MHz
    ENOB > 4
    Power consumption P < 1mW
    Could anyone suggest me some ADC for this kind? I have searched a lot in
    IEEE but there are only two ADC with SAR ADC and time-interleaved ADC.
    The ultralow power consumption makes it hard for me to find a
    architecture. I have little experience about this. Kindly help me.
     
  2. jcsd
  3. Jul 14, 2013 #2

    Baluncore

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    Science Advisor

    You like a challenge don't you !

    To convert a 20MHz signal Nyquist says you will need one converter at 40Msps or two at 20Msps.
    The best commercial unit would be 8 bits at about 50mW. But you only want 4 bits.

    A resistive divider with 15 comparators might be possible but 15 comparators at 40MHz (= 25ns) will draw about 15ma at 3 volts = 45mW. You might minimise the power slightly by using 15 AC coupled single transistors as your comparators. A sample pulse switches AC inputs from reference to signal at 40Msps.

    Maybe some knowledge of your signal characteristics could reduce power by pre-processing. Can you tell me how the signal is modulated ?

    Take a look at;
    http://www.ti.com/lsds/ti/analog/dataconverters/data_converter.page
    http://www.linear.com/products/Analog-to-Digital_Converters_(ADC)
    http://www.linear.com/products/Comparators
     
  4. Jul 15, 2013 #3
    By design an ADC do you mean design an IC? If so, you didn't look that hard in IEEE.

    Harpe, P.J.A., Zhou, C., Bi, Y., Meijs, N.P. van der, Wang, X., Philips, K.J.P., Dolmans, G. & Groot, H. de (2011). A 26μ W 8 bit 10 MS/s asynchronous SAR ADC for low energy radios. IEEE Journal of Solid-State Circuits, 46(7), 1585-1595.

    http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=05771068

    Reduce the 8-bits to 4 and you can get the power no problem.

    For a four-bit ADC though, maybe a straight flash is the way to go since you only need 15 comparators. Depends on the process you're using, of course.
     
  5. Jul 16, 2013 #4

    Baluncore

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    Science Advisor

    This is slow but includes discussion of different methods including switched capacitors.
    Very Low Power SAR ADC
     
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