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TMS320F28374D: how to measure PSRR of ADC

Yale Li 李耀先
Expert 4660 points
Part Number: TMS320F28374D


Hi Team,

https://www.ti.com/lit/ds/symlink/tms320f28374d.pdf P104 8.10.1.2.2 ADC Characteristics (16-Bit Differential Mode)

How to measure PSRR of ADC module?

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Thanks & Regards

Yale

  • +1
    TI__Mastermind 30185 points

    Hello Yale,

    The PSRR (Power Supply Rejection Ratio) measures the noise that propagates to the ADC by varying the power signal to inject noise:

    1. Low frequency (1 kHz) and high frequency (1 MHz) noise signal with 200 mV is applied to the power rail
    2. The input amplitude of the injected noise signal is measured
    3. ADC conversions on a DC voltage is performed; the output amplitude is measured by taking an FFT of the ADC results
    4. The rejection ration is then computed as a ration of the output amplitude over the input amplitude

    Let me know if you have further questions.

    Best regards,

    Omer Amir

  • 0 in reply to Omer Amir
    TI__Expert 4660 points

    Hi Omer,

    Thanks for your help!

    So the PSRR of ADC module is the influence that power rail's noise takes to ADC conversion.

    Could you please take a further explain for "DC up to Sine at 1 kHz"? What is the difference from "Sine at 800 kHz"?

    Omer Amir said:
    Low frequency (1 kHz) and high frequency (1 MHz) noise signal with 200 mV is applied to the power rail

    Where did the 1 MHz comes from?

  • +1 in reply to Yale Li 李耀先
    TI__Mastermind 30185 points
    Yale Li 李耀先 said:
    Could you please take a further explain for "DC up to Sine at 1 kHz"? What is the difference from "Sine at 800 kHz"?

    The difference is the performance; the DC to 1 kHz is the approximate flat attenuation and rolls off beyond a few hundreds of kHz, so we separate them out in the data sheet to emphasize this.

    Yale Li 李耀先 said:
    Where did the 1 MHz comes from?

    1 kHz and 1 MHz are regions that represent the bode plot attenuation, and at the 1 MHz region noise attenuation starts to drop off.