UNDERSTANDING THE SPECIFICATIONS
Voltage Variation Versus Temperature
Some confusion exists in the area of de ning 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 speci ed temperature range. The temperature coef cients
speci ed in the Speci cations section represent the slopes of the
diagonals of the error band from 25°C to T
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Figure 1. Typical AD589 Temperature Characteristics
Figure 2. Noise Spectral Density
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
gure shows both the coarse and ne transient characteristics of
the device; the total settling time to within ±1 mV is about 25
and there is no long thermal tail appearing after that point.
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Figure 3. Output Settling Characteristics
Figure 4. Schematic Diagram
