App note: dsPIC33E simultaneous analog sampling

Some new PIC 33E and 24E microcontrollers can take simultaneous samples from multiple analog to digital converters. Most chips measure analog values sequentially, but this ADC can sample 4 signals at once. Samples are still converted one after the other, but they’re collected at the same moment. More in the reference manual for dsPic33E and PIC24E 16bit devices:

This document describes the features and associated operational modes of one of the successive approximation (SAR) Analog-to-Digital Converter (ADC) modules available on the dsPIC33E/PIC24E families of devices. This ADC module can be configured by the user application to function as a 10-bit, 4-channel ADC or a 12-bit, single-channel ADC. On devices with DMA, this ADC module can be configured to use DMA or use a dedicated 16-word memory mapped buffer instead of DMA.

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5 Comments

  1. Its not 33E nor 24E specific.
    At least PIC24F (which Im more familiar with) supports simultaneous sampling. See PIC24F ADC reference document:
    (pg.2) “The ADC module supports simultaneous sampling using multiple S&H channels to sample the
    inputs at the same time, and then performs the conversion for each channel sequentially. By
    default, the multiple channels are sampled and converted sequentially.”

  2. SAR ADC requires S&H anyway, so this simultaneous feature only requires the additional circuits for multiple S&H. I suppose another FET switch, capacitor and op-amp for each input adds little cost, especially since they can share the same ADC (via the typical mux).

  3. This is neither special nor unique. It is just hardware clock triggering of multiple sample & hold stages at the same time. Simultaneous sampling is quite useful for conversion of quadrature signals.

  4. Some new PIC 33E and 24E microcontrollers can take simultaneous samples
    So can do other (older) PIC24H and dsPIC33FJ microcontrollers as well! There are excellent example programs and periheral library support in the book Microcontrollers: From Assembly Language to C Using the PIC24 Family, by R. Reese, B. Jones, and J. W. Bruce. Further information, example program, video lectures and an updated version of the supporting software package is available at http://www.reesemicro.com.

    I am just working on the adoptation of that chapter dealing with the ADC of the above mentioned course material. The adoptedd version is available in Hungarian at my homepage.

  5. Perhaps the simultanius sampeling is not so distinctive, but this ADC on E-type devices does go up to 1.1Ms/s @ 10bits, which I haven’t seen before..

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