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ADC32RF55: Nyquist zone during device configuration

Shunya Matsushima
Prodigy 80 points
Part Number: ADC32RF55


Tool/software:

The Nyquist Zone settings in Table 8-5 "Register Programming Sequence for Device Configuration" on page P114 of the datasheet are divided into three cases based on the sampling rate, with the options starting from 640 MSPS.

On the other hand, in section 6.6 "Electrical Characteristics - DC Specifications," the minimum value for the input clock frequency is 500 MSPS.

Should the settings for the 500~640 MSPS range be "640-2250"?

  • +1
    TI__Mastermind 23830 points

    Hi Shunya,

    Yes, use this section for between 500MSPS-2250MSPS.

    Thanks, Chase

  • 0 in reply to Chase W
    Prodigy 80 points

    Excuse me, I have an additional question. Could you please explain the usage of 1st and 2nd?

    • In the range of Sampling Rate 640-2250, there are two types of Nyquist Zones: 1st and 2nd. Does this mean that the value is set to 1st in the range of 640-1400, and to 2nd in the range of 1500-2200?
    • For a Sampling Rate of 2250-2800 MSPS, is it correct to consider 2300-2500 as 1st and 2600-2800 as 2nd?
  • 0 in reply to Shunya Matsushima
    TI__Mastermind 23830 points

    Hi Shunya,

    The nyquist zone registers are to trim device performance to within that nyquist zone. If sampling at 2.6GSPS and a tone is at 1.2GHz, then this falls within the first nyquist zone. If the tone was at 1.5GHz, this will be in second nyquist zone, so choose the second nyquist registers.

    The 2250-2800MSPS example you provided is not clear as sample rate is not dynamic for this device. At each configuration, it will be clear which nyquist region the analog signal is within because if spread across multiple nyquist zones, you cannot determine what the frequency is due to aliasing. The nyquist selection for that configuration should be set accordingly.

    Thanks, Chase

  • 0 in reply to Chase W
    Prodigy 80 points

    Should we select one of the Nyquist zones even when the frequency of the signal to be sampled is uncertain?

    Also, should this register be considered for dynamic operation?

    Thank you. Shunya