AD589
APPLICATION INFORMATION
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The AD589 functions as a 2-terminal shunt-type regulator. It
provides a constant 1.23 V output for a wide range of input
current from 50
A
to 5 mA. Figure 5 shows the simplest con-
figuration for an output voltage of 1.2 V or less. Note that no
frequency compensation is required. If additional filtering is
desired for ultralow noise applications, minimum recommended
capacitance is 1000 pF.
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a. With 7109 12-Bit Binary ADC
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Figure 5. Basic Configuration for 1.2 V or Less
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The AD589 can also be used as a building block to generate
other values of reference voltage. Figure 6 shows a circuit that
produces a buffered 10 V output. Total supply current for this
circuit is approximately 2 mA.
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b. With 7107 Panel Meter ADC
Figure 7. AD589 Used as Reference for CMOS ADCs
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The AD589 also is useful as a reference for CMOS multiplying
DACs, such as the AD7533. These DACs require a negative
reference voltage in order to provide a positive output range.
Figure 8 shows the AD589 used to supply an equivalent –1.0 V
reference to an AD7533.
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Figure 6. Single-Supply Buffered 10 V Reference
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The low power operation of the AD589 makes it ideal for use in
battery-operated portable equipment. It is especially useful as a
reference for CMOS analog-to-digital converters. Figure 7 shows
the AD589 used in conjunction with two popular integrating type
CMOS ADCs.
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Figure 8. AD589 as Reference for 10-Bit CMOS DAC
REV. C
–5–
AD [ ANALOG DEVICES ]
