AD589

–4–

UNDERSTANDING THE SPECIFICATIONS

Voltage Variation Versus Temperature

Some confusion exists in the area of defining and specifying

reference voltage error over temperature. Historically, references

have been characterized using a maximum deviation per degree

Centigrade, i.e., 10 ppm/°C. However, because of nonlinearities

in temperature characteristics, which originated in standard Zener

references (such as S type characteristics), most manufacturers

have begun to use a maximum limit error band approach to specify

devices. This technique involves measurement of the output at

3, 5, or more different temperatures to guarantee that the output

voltage will fall within the given error band. The temperature

characteristics of the AD589 consistently follows the curve shown

in Figure 1. Three-point measurement guarantees the error band

over the specified temperature range. The temperature coefficients

specified in the Specifications section represent the slopes of the

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Figure 1.Typical AD589Temperature Characteristics

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Figure 2. Noise Spectral Density

Dynamic Performance

Many low power instrument manufacturers are becoming increas-

ingly concerned with the turn-on characteristics of the components

being used in their systems. Fast turn-on components often enable

the end user to keep power off when not needed and yet respond

quickly when the power is turned on for operation. Figure 3 dis-

plays the turn-on characteristics of the AD589. This characteristic

is generated from cold-start operation and represents the true turn-

on waveform after an extended period with the supplies off. The

figure shows both the coarse and fine transient characteristics of

the device; the total settling time to within ±1 mV is about 25 s,

and there is no long thermal tail appearing after that point.

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Figure 4. Schematic Diagram

REV. C