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Original question:

ADS8556: -

ADS8556: -

SD
Prodigy 65 points
Part Number: ADS8556
Other Parts Discussed in Thread: ADS8586S, SN74LVC1G32

Hi,

Please can I get schematic reviewed for ADS8556.

Regards

  • 0
    TI__Mastermind 35480 points

    Hi Shweta,

    You want us to review your schematic if my understanding is correct. If so, please send it to me in private message if you do not share it on the E2E forum. Also, can you please let me know your requirements about the ADC? I'm considering if ADS8586S which has more benefits can meet them.

    Best regards,

    Dale

  • 0 in reply to Dale Li
    TI__Mastermind 35480 points

    Hi Shweta,

    I have received your schematic, below is my feedback:

    1. ADS8556 is a switch-capacitor input structure ADC and it usually requires a high BW amplifier to drive and settle the signal, also the front-end resistor and capacitor are important to achieve the performance specified in the datasheet. Please refer to the videos of Precision Labs ADCs - Input Driver Design for the details. ADS8586s integrates an analog-front-end (AFE) with high input impedance which usually eliminate the need of driving amplifier, you can consider this ADC if its internal 24kHz or 16kHz BW LPF can be accepted in your design.

    2. Your REFEN (pin63) is connected to GND which indicates that the internal reference is disabled and an external voltage reference is expected on REFIO for hardware and serial mode. However, you did not design an external voltage reference.

    3. BUSY/INT is an output signal from the ADS8556, you connected the BUSY/INT signals from two ADS8556s together, it's not a practical design even two diodes are used especially when both both signals are available. You can use a single 2-input positive-OR gate (for example, SN74LVC1G32) to monitor two BUSY signals from two ADS8556 ADCs. R8 pull-down resistor is not necessary.

    4. A pull-down resistor can be used on RESET signal.

    5.R7 can be replaced with two small value resistors (49.9ohm) for each ADC in case any impact from two CONVST signals.

    6.I guess you are using a short connection between AGND and DGND for your actual digital ground (GND). It's not easy to achieve a good performance for splitting ground when multiple ADCs are designed in one circuit board. A solid ground plane can be used for all AGND and GND pins.

    Let me know if you have questions.

    Regards,

    Dale