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AD588
(Rev.:RevD)

High Precision Voltage Reference

Analog Devices 

AD588

0.1␮F

0.1␮F

NOISE

REDUCTION

Note that a second capacitor is needed in order to implement

the NOISE REDUCTION feature when using the AD588 in

the –10 V mode (Figure 2c.). The NOISE REDUCTION capaci-

tor is limited to 0.1 µF maximum in this mode.

RB

A1

R1

R2

R3

A2

R4

R5

R6

A3

A4

+VS

AD588

–VS

SYSTEM

GROUND

–5V

–10V

+15V

0.1␮F

SYSTEM

GROUND

0.1␮F

–15V

Figure 2c. –10 V Output

Trimming the AD588 introduces no additional errors over

temperature, so precision potentiometers are not required.

For single-output voltage ranges, or in cases when BALANCE

ADJUST is not required, Pin 12 should be connected to Pin 11.

If GAIN ADJUST is not required, Pin 5 should be left floating.

NOISE PERFORMANCE AND REDUCTION

The noise generated by the AD588 is typically less than 6 µV p-p

over the 0.1 Hz to 10 Hz band. Noise in a 1 MHz bandwidth is

approximately 600 µV p-p. The dominant source of this noise is

the buried Zener, which contributes approximately 100 nV/√Hz.

In comparison, the op amp’s contribution is negligible. Figure 3

shows the 0.1 Hz to 10 Hz noise of a typical AD588.

Figure 4. Effect of 1 µF Noise Reduction Capacitor

on Broadband Noise

TURN-ON TIME

Upon application of power (cold start), the time required for the

output voltage to reach its final value within a specified error

band is the turn-on settling time. Two components normally

associated with this are: time for active circuits to settle and

time for thermal gradients on the chip to stabilize. Figures 5a

and 5b show the turn-on characteristics of the AD588. It

shows the settling to be about 600 µs. Note the absence of any

thermal tails when the horizontal scale is expanded to 2 ms/cm in

Figure 5b.

Figure 5a. Electrical Turn-On

Figure 3. 0.1 Hz to 10 Hz Noise (0.1 Hz to 10 Hz BPF

with Gain of 1000 Applied)

If further noise reduction is desired, an optional capacitor, CN,

may be added between the NOISE REDUCTION pin and ground,

as shown in Figure 2b. This will form a low-pass filter with the

4 kΩ RB on the output of the Zener cell. A 1 µF capacitor will

have a 3 dB point at 40 Hz and will reduce the high frequency

(to 1 MHz) noise to about 200 µV p-p. Figure 4 shows the 1 MHz

noise of a typical AD588 both with and without a 1 µF capacitor.

Figure 5b. Extended Time Scale Turn-On

Output turn-on time is modified when an external noise reduc-

tion capacitor is used. When present, this capacitor presents an

–6–

REV. D

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