• AD7691: Vref

    Question on AD7691: What should be Vref to convert of the maximal number of
    bits a difference between two signals which a little from each other differ?
    For example, Vin + = 4,5V, Vin-= 4,49V.


    As the absolute input range max is =Vref…
  • Different specification on AD7691

    I want to try an 18 bit ADC with an evaluation board and have thought of AD7691. However, when looking at it I find different specifications:

    Here it says 16 bits on the evaluation board:

    PulSAR ADC PMODs [Analog Devices Wiki]

    And then about the reference…

  • Repeated samples from AD7691

    I am currently testing the AD7691 18-bit SAR ADC. I have made a circuit with a 16-bit DAC that puts out a voltage for the AD7691 to sample. Then I programmed a micro controller to read and write bits to the DAC and ADC with SPI, and a serial port to transfer…

  • wrong conversion with AD7691


    we have a frustrating issue with the ADC AD7691:

    we use an FPGA that reads the ADC at 200 kHz (but we tested also at 100 kHz and it's the same) in "CS MODE" (3-WIRE WITHOUT BUSY INDICATOR).

    The ADC seem to works fine for almost…

  • ADM7150 as reference supply for AD7691


    I thought to use the ADM7150 as "reference" and power supply to AD7691 and the 350R bridge.
    As I want to do ratiometric measurement, accuracy and drift should be no problem?

    As the bridge will be chopped (+/-5V), I need a "reference" with…

  • AD7691 SDO status on Power Up

    We are using 2 AD7691 in 4 wire CS mode with 4 flash memory ICs using the same SPI bus, these 2 are connected to a TI TPS430 u Controller.  The power to the ADCs/flash is controlled by a FET and the TPS430.  The SDO pin on the ADCs is tied low after power…

  • Having difficulty in getting expected ad7691 output

    My application is using an STMicro ST32F4XX processor acting as a SPI Master, receive only. The SPI slave is an AD7691 in 3 wire, no busy indicator that is getting its input from 4 sources that is selected via an ADG704 MUX.

    SPI Master is configured…

  • Problems with multiple AD7691 in 4-wire CS-mode

    I am using four AD7691 in "CS MODE, 4-WIRE WITHOUT BUSY INDICATOR", as explained on page 20 in the datasheet.

    I have problems with the SDO (data output) that should be in high impedance mode, if SDI (used as Chip Select) is high (not selected…

  • AD7691 Pulsar Differential ADC Common Mode Input Spec

    AD7691 spec sheet says Common-Mode Range needs to be Vref/2 +-0.1V.

    I have a system who's inputs to the ADC is In-=0.1V In+=1.4V(up to 1.8V), and I don't see any issues due to this.

    Can someone help me understand when this specification is important…

  • How can we collect datas from the AD7691 via microcontroller ?


    I'm currently working with two AD7691, each of them are interfacing with a SDP-B card referenced SDP-CB1Z and the SDP-B card owns a BlackFin microcontroller.

    Theoretically we can send a signal of conversion through CNV and set the clock…