AD592

REV. A

–8–

To minimize the number of MUXs required when a large num-

ber of AD592s are being used, the circuit can be configured in a

matrix. That is, a decoder can be used to switch the supply volt-

age to a column of AD592s while a MUX is used to control

which row of sensors are being measured. The maximum num-

ber of AD592s which can be used is the product of the number

of channels of the decoder and MUX.

An example circuit controlling 80 AD592s is shown in Figure

16. A 7-bit digital word is all that is required to select one of

the sensors. The enable input of the multiplexer turns all the

sensors off for minimum dissipation while idling.

+15V

COLUMN

SELECT

4028 BCD TO DECIMAL DECODER

ROW

SELECT

+15V

–15V

80 – AD592s

10k

Ω

Figure 16. Matrix Multiplexer

To convert the AD592 output to

°C or °F a single inexpensive

reference and op amp can be used as shown in Figure 17. Al-

though this circuit is similar to the two temperature trim circuit

shown in Figure 6, two important differences exist. First, the

gain resistor is fixed alleviating the need for an elevated tem-

perature trim. Acceptable accuracy can be achieved by choosing

an inexpensive resistor with the correct tolerance. Second, the

AD592 calibration error can be trimmed out at a known conve-

nient temperature (i.e., room temperature) with a single pot ad-

justment. This step is independent of the gain selection.

R

AD741

+5V

AD1403

V–

≈ 9.1kΩ

≈ 9.8kΩ

100k

Ω

180k

Ω

AD592

2.5V

Figure 17. Celsius or Fahrenheit Thermometer

OUTLINE DIMENSIONS

Dimensions shown in inches and (mm).

0.105 (2.66)

0.080 (2.42)

0.105 (2.66)

0.080 (2.42)

0.165 (4.19)

0.125 (3.94)

SQUARE

0.019 (0.482)

0.016 (0.407)

0.105 (2.66)

0.095 (2.42)

0.055 (1.39)

0.045 (1.15)

SEATING

PLANE

0.500

(12.70)

MIN

0.205 (5.20)

0.175 (4.96)

0.210 (5.33)

0.170 (4.32)

12

3

BOTTOM VIEW

0.135

(3.43)

MIN

0.050

(1.27)

MAX