AD588TQ Просмотр технического описания (PDF) - Analog Devices

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AD588TQ

High Precision Voltage Reference

Analog Devices 

AD588

Figure 2c. –10 V Output

Trimming the AD588 introduces no additional errors over tem-

perature 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 as-

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

for thermal gradients on the chip to stabilize. Figure 5 shows 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.

a. Electrical Turn-On

Figure 3. 0.1 Hz to 10 Hz Noise

If further noise reduction is desired, an optional capacitor 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.

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

capacitor is limited to 0.1 µF maximum in this mode.

b. Extended Time Scale

Figure 5. Turn-On Characteristics

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

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

additional load to the internal Zener diode’s current source, re-

sulting in a somewhat longer turn-on time. In the case of a 1 µF

capacitor, the initial turn-on time is approximately 60 ms (see

Figure 6).

Note: If the NOISE REDUCTION feature is used in the ± 5 V

configuration, a 39 kΩ resistor between Pins 6 and 2 is required

for proper start up.

REV. B

–5–

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