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dc2071afc

DEMO MANUAL DC2071A

To change the default settings for the LTC2373-18 se-

quencer in PScope, click on the Set Demo Bd Options

button in the PScope tool bar shown in Figure 8. This will

open the Configure Sequencer menu of Figure 9. In this

menu it is possible to set the number of sequences up to

16, the channel configuration, format and gain compres-

sion setting for each sequence. There is also a button to

return PScope to the default DC2071 settings which are

optimizedforthedefaulthardwaresettingsoftheDC2071A.

Thereareanumberofscenariosthatcanproducemislead-

ing results when evaluating an ADC. One that is common

is feeding the converter with an input frequency that is

a sub-multiple of the sample rate and which will only

exercise a small subset of the possible output codes.

The proper method is to pick an M/N frequency for the

input sine wave frequency. N is the number of samples

in the FFT. M is a prime number between one and N/2.

Multiply M/N by the sample rate to obtain the input sine

wave frequency. Another scenario that can yield poor

results is if you do not have a signal generator capable of

ppm frequency accuracy or if it cannot be locked to the

clock frequency. You can use an FFT with windowing to

reduce the leakage, or spreading of the fundamental, to

get a close approximation of the ADC performance. If an

amplifier or clock source with poor phase noise is used,

the windowing will not improve the SNR.

Figure 8. PScope Tool Bar

DC2071A SETUP

Figure 9. PScope Configure Sequencer Menu