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ADS8634: ADS8634SRGER

sandeep kothapally
Prodigy 100 points
Part Number: ADS8634

I am using ADS8634SRGER. I am interfacing ADC SPI to ESP32-wroom-32 ble module. Please find modified ADC circuit diagram. 1)Pin no 23 and 24 connected through 10uF cap. Does it need to connect to GND? 2) pin number 22 should be pull up as per circuit? 3) how to know whether ADC working on internal reference ? is it works with internal reference default? please let me know if ckt have any mistakes?

  • 0 in reply to sandeep kothapally
    TI__Mastermind 45365 points

    Hi Sandeep,

    Please see my answers below:

    1. Pin 23 should be directly connected to the AGND ground plane. Please see the Figure 74 in the data sheet.
    2. Pin 22 is a input pin in default condition which is active low power-down, so this pin should be pulled up to DVDD through a pull-up resistor because you do not want the device in a power-down condition.
    3. After the device is powered up, the internal voltage reference is powered down by default, see the bit 2 in the Aux-Config register for ADS8634 in page 54 of the data sheet. You will have to turn on the internal voltage reference by programming the Aux-Config register, then you will be able to see the 2.5V on the pin 24 from next frame.

    Regarding your schematic, a solid ground plane is recommended for both AGND and DGND.Pin 23 should be shorted the the ground plane as mentioned above. The pin 22 (AL_PD) should be pulled up to DVDD not AVDD. Input op-amp drivers may be needed and it depends on your ADC sampling rate and input signal. You are connecting HVSS to the ground so you will not be able to sample a bipolar signal.

    I would suggest you to use ADS8664 for your design, which is a 12-bit, 4-ch input ADC with a lot of features and benefits for you including integrated ADC drivers and a single 5V power supply to support +/-10.24V bipolar, 0-10.24V or 0-5.12V unipolar input range.

    Regards,

    Dale