XRD8794AB Просмотр технического описания (PDF) - Exar Corporation

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XRD8794AB

XRD8794AB Application Board

Exar Corporation 

XRD8794AB

CLOCK

AIN

Data

DB(0-11)

At DUT

N

Sample

Point

N

N-3

N+1

tAP

tDHZ

N+1

N-2

PTS

Data

DB (0-11)

at Connector

N-4

N-3

Figure 7. XRD8794AB Circuit Timing

DITHER with AIN

Setting AIN to a DC voltage and a signal applied to

DITHER, then the input to the ADC (ADCIN) is given by:

ADCIN = AIN + ( R5 / R3 )( AIN - DITHER )

Timing

Figure 7. demonstrates the circuit timing of the

XRD8794AB. The CLOCK is provided by the user as

specified on the XRD8794 data sheet. The PTS clock is

an output that allows for synchronization of external lab

equipment with the output data DB(0–11). DB(0–11) is

valid after the rising edge of the PTS clock.

Outputs

The parallel digital output of the A/D can be accessed on

the 28 pin connector. A system clock (PTS) is also

available on that connector. This output data, in

conjunction with various input stimuli, is used to evaluate

Rev. 1.00

the A/D and timing performance. The three common

methods are described below.

DIGITAL SIGNAL PROCESSING

A comprehensive dynamic performance evaluation is

most often done by using external hardware capable of

fast data acquisition and storage. The computation of

integral linearity, differential linearity, signal-to-noise and

distortion ratios, the effective number of bits, and other

useful figures of merit is done using software having

histogram and FFT capability. The accuracy of the test

results depends upon the quality of the input sinewave. A

low distortion sinewave generator with a band pass filter

will be necessary.

Commercial software packages with the needed

computational features are available. The Tektronix

PTS101 and other internally developed proprietary

systems are used by EXAR to acquire and analyze the

ADC data.

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