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dc1908af

DEMO MANUAL DC1908A

DC1908A SETUP

Data Collection

For SINAD, THD or SNR testing a low noise, low distortion

generator such as the Stanford Research DS360 should

be used. A low jitter RF oscillator such as the Rohde &

Schwarz SMB100A is used as the clock source. This demo

board is tested in house by attempting to duplicate the

FFT plot shown on the front page of the LTC2338-18 data

sheet. This involves using a 62MHz clock source, along

with a sinusoidal generator at a frequency of 2.0kHz. The

input signal level is approximately –1dBFS. A typical FFT

obtained with DC1908A is shown in Figure 4. Note that

to calculate the real SNR, the signal level (F1 amplitude =

–1.030dB) has to be added back to the SNR that PScope

displays. With the example shown in Figure 4 this means

that the actual SNR would be 99.54dB instead of the

98.51dB that PScope displays. Taking the RMS sum of the

recalculated SNR and the THD yields a SINAD of 99.27dB

which is fairly close to the typical number for this ADC.

Figure 4. DC1908A PScope Screen Shot