AD7226KN(RevA) 查看數據表（PDF） - Analog Devices

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AD7226KN
(Rev.:RevA)

LC2MOS Quad 8-Bit D/A Converter

Analog Devices 

AD7226

STAIRCASE WINDOW COMPARATOR

In many test systems, it is important to be able to determine

whether some parameter lies within defined limits. The staircase

window comparator of Figure 18a is a circuit which can be

used, for example, to measure the VOH and VOL thresholds of a

TTL device under test. Upper and lower limits on both VOH

and VOL can be programmably set using the AD7226. Each ad-

jacent pair of comparators forms a window of programmable

size. If VTEST lies within a window then the output for that win-

dow will be high. With a reference of +2.56 V applied to the

VREF input, the minimum window size is 10 mV.

Figure 19a. Overlapping Windows

Figure 19b. Window Structure

Figure 18a. Logic Level Measurement

Figure 18b. Window Structure

The circuit can easily be adapted to allow for overlapping of

windows as shown in Figure 19a. If the three outputs from this

circuit are decoded then five different nonoverlapping program-

mable windows can again be defined.

Figure 20. Varying Reference Signal

VARYING REFERENCE SIGNAL

In some applications, it may be desirable to have a varying sig-

nal applied to the reference input of the AD7226. The AD7226

has multiplying capability within upper and lower limits of refer-

ence voltage when operated with dual supplies. The upper and

lower limits are those required by the AD7226 to achieve its lin-

earity specification. Figure 20 shows a sine wave signal applied

to the reference input of the AD7226. For input signal frequen-

cies up to 50 kHz the output distortion typically remains less

than 0.1%. Typical 3 dB bandwidth figure is 700 kHz.

–10–

REV. A

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