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ADS5294: need help for the low SNR result of ADS5294

user4290001
Intellectual 620 points
Part Number: ADS5294

Dear,

I have develop a data acquisition board using ADS5294. But my test result show the floor noise is very large(about 5 bits). According to the datasheet of ads5294, the noise floor should be small(about 2 bits)

Could you give me some advises about the low SNR?

Schematic: ADC driver: ADA4940 

Test condition:

  1. A8_P/A8_N have been connected to Ground.
  2. All the power in board have been supplied by very clean DC power supply equipment.
  3. The LVDS output of the ADC have been correctly de-serialized. The data is shown on the scope which is developed by myself(which is currently used in our product, its function is ok                                         

    Test result:

    no filter，no decimation. Floor noise PK to PK  value is about 40(about 5 bit).

    Fs/8 low pass filter，no decimation. Floor noise PK to PK  value is about 20(about 4 bit).

  • 0
    TI__Mastermind 49176 points
    Hello,

    We have received your inquiry regarding the device ADS5294 and will get back to you by next week.
  • 0
    TI__Genius 12025 points

    Hi, How are you!

    Thanks for using our ADS5294 device.

    As you can see from ADS5294 Datasheet, it shows

    our device noise performance is about 75.5dBFS (-1dBFS at fin=5MHz)

    When we are using ADS5294EVM board to measure the ADS5294 device performance,

    please refer to our ADS5294 users guide.

    You can see our test results show, one of test results show as:

    Here the device noise performance is about 75.68dBFS (-1dBFS at fin=5MHz)

    That is very consistent with our datasheet.

    Please also review our schematic from ADS5294 users guide.

    The low SNR result (due to the higher noise) issue may be caused by the input signal amplifier.

    Here is one example (in the users' guide) showing that you can create a filter (such as BP filter in this case)

    to reduce the noise coming from the input amplifier.

    Thank you very much!

    Best regards,

    Chen

  • 0 in reply to Chen Kung
    TI__Genius 12025 points

    Hi, How are you?

    Here are the photos for ADS5294 three diagrams.

    Please take a look.

    Thank you very much!