AD588TQ Analog Devices, AD588TQ Datasheet - Page 6

• Manufacturer Part Number: AD588TQ
• Description: High Precision Voltage Reference
• Manufacturer: Analog Devices

AD588
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.
If further noise reduction is desired, an optional capacitor, C
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 R
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 3. 0.1 Hz to 10 Hz Noise (0.1 Hz to 10 Hz BPF
with Gain of 1000 Applied)
R3
B
0.1 F
0.1 F
on the output of the Zener cell. A 1 µF capacitor will
GROUND
SYSTEM
R
B
R2
A2
NOISE
REDUCTION
A1
R1
Figure 2c. –10 V Output
R4
R5
R6
AD588
A3
A4
+V
–V
S
S
0.1 F
0.1 F
GROUND
SYSTEM
–10V
–5V
+15V
–15V
N
,
–6–
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.
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.
Output turn-on time is modified when an external noise reduc-
tion capacitor is used. When present, this capacitor presents an
Figure 4. Effect of 1 µ F Noise Reduction Capacitor
on Broadband Noise
Figure 5b. Extended Time Scale Turn-On
Figure 5a. Electrical Turn-On
REV. D