Data Sheet

ADA4932-1/ADA4932-2

APPLICATIONS INFORMATION

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Rev. F | 24 of 27

input to the AD7626 yielded the results shown in Figure 63 of 88.49

dB SNR and −86.17 dBc THD. At this input level, the ADC limits the

SFDR to 83.8 dB. As can be seen from the plot, the harmonics of

the fundamental alias back into the pass band. For example, when

sampling at 10 MSPS, the third harmonic (7.206 MHz) is aliased

into the pass band at 10.000 MHz – 7.206 MHz = 2.794 MHz.

Figure 63. AD7626 Output, 64,000 Point, FFT Plot −1 dBFS Amplitude

2.40173 MHz Input Ton, 10.000 MSPS Sampling Rate

The nonharmonic noise admitted through the pass band of the

band-pass filter used in the circuit is replaced by the average

noise across the Nyquist bandwidth when calculating the SNR and

THD. The performance of this or any high speed circuit is highly

dependent on proper PCB layout. This includes, but is not limited

to, power supply bypassing, controlled impedance lines (where

required), component placement, signal routing, and power and

ground planes. For a more detailed analysis of this circuit, refer to

Circuit Note CN-0105.

Figure 64. ADA4932-1 Driving the AD7626 (All Connections and Decoupling Not Shown)