Datasheet AD688 (Analog Devices) - 8
| Manufacturer | Analog Devices |
| Description | High Precision ±10 V Reference |
| Pages / Page | 16 / 8 — AD688. NOISE PERFORMANCE AND REDUCTION. 10V. 1mV. 100. +VS. –VS. +VOUT. … |
| Revision | B |
| File Format / Size | PDF / 495 Kb |
| Document Language | English |
AD688. NOISE PERFORMANCE AND REDUCTION. 10V. 1mV. 100. +VS. –VS. +VOUT. 2ms. 200. CN = 1. NO CN. 20ms. TURN ON TIME
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AD688 NOISE PERFORMANCE AND REDUCTION
any thermal tails when the horizontal scale is expanded to The noise generated by the AD688 is typically less than 2 ms/cm in Figure 9. 6 µV p-p over the 0.1 Hz to 10 Hz band. Noise in a 1 MHz bandwidth is approximately 840 µV p-p. The dominant source
10V 1mV 100
µ
s
of this noise is the buried Zener which contributes
+VS 100
approximately 140 nV/√Hz. In comparison, the op amp’s
90
contribution is negligible. Figure 6 shows the 0.1 Hz to 10 Hz noise of a typical AD688.
–VS 1mV 5s +VOUT 10 100 0% 90 10V 1
µ
V
00815-008 Figure 8. Turn On Characteristics: Electrical Turn On
10V 1mV 2ms 10 0% +VS 100 90
00815-006 Figure 6. 0.1 Hz to 10 Hz Noise
–VS
If further noise reduction is desired, an optional capacitor can be added between the noise reduction pin and ground as shown
+VOUT
in Figure 5. This will form a low-pass filter with the 5 kΩ RB on
10
the output of the Zener cell. A 1 µF capacitor will have a 3 dB
0%
point at 32 Hz and will reduce the high frequency noise (to
10V
1 MHz) to about 250 µV p-p. Figure 7 shows the 1 MHz noise of 00815-009 a typical AD688 both with and without a 1 µF capacitor. Figure 9. Turn On Characteristics: Extended Time Scale Output turn on time is modified when an external noise
200
µ
V 50
µ
s
reduction capacitor is used. When present, this capacitor presents an additional load to the internal Zener diode’s current source, resulting in a somewhat longer turn on time. In the case
CN = 1
µ
F
of a 1 µF capacitor, the initial turn on time is approximately 100 ms (Figure 10). When the noise reduction feature is used, a 20 kΩ resistor between Pin 6 and Pin 2 is required for proper startup.
NO CN 10V 1mV 20ms +VS 100
00815-007
90
Figure 7. Effect of 1 µF Noise Reduction Capacitor on Broadband Noise
TURN ON TIME –V
Upon application of power (cold start), the time required for
S
the output voltage to reach its final value within a specified error is the turn on settling time. Two components normally
+VOUT 10
associated with this are: time for active circuits to settle and
0%
time for thermal gradients on the chip to stabilize. Figure 8 and Figure 9 show the turn on characteristics of the AD688. They
10V
00815-010 show the settling time to be about 600 µs. Note the absence of Figure 10. Turn On With 1 µF CN Rev. B | Page 8 of 16 Document Outline FEATURES GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAM PRODUCT HIGHLIGHTS SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS THEORY OF OPERATION APPLICATIONS CALIBRATION NOISE PERFORMANCE AND REDUCTION TURN ON TIME TEMPERATURE PERFORMANCE KELVIN CONNECTIONS DYNAMIC PERFORMANCE BRIDGE DRIVER CIRCUIT OUTLINE DIMENSIONS ORDERING GUIDE
AD688 NOISE PERFORMANCE AND REDUCTION
any thermal tails when the horizontal scale is expanded to The noise generated by the AD688 is typically less than 2 ms/cm in Figure 9. 6 µV p-p over the 0.1 Hz to 10 Hz band. Noise in a 1 MHz bandwidth is approximately 840 µV p-p. The dominant source
10V 1mV 100
µ
s
of this noise is the buried Zener which contributes
+VS 100
approximately 140 nV/√Hz. In comparison, the op amp’s
90
contribution is negligible. Figure 6 shows the 0.1 Hz to 10 Hz noise of a typical AD688.
–VS 1mV 5s +VOUT 10 100 0% 90 10V 1
µ
V
00815-008 Figure 8. Turn On Characteristics: Electrical Turn On
10V 1mV 2ms 10 0% +VS 100 90
00815-006 Figure 6. 0.1 Hz to 10 Hz Noise
–VS
If further noise reduction is desired, an optional capacitor can be added between the noise reduction pin and ground as shown
+VOUT
in Figure 5. This will form a low-pass filter with the 5 kΩ RB on
10
the output of the Zener cell. A 1 µF capacitor will have a 3 dB
0%
point at 32 Hz and will reduce the high frequency noise (to
10V
1 MHz) to about 250 µV p-p. Figure 7 shows the 1 MHz noise of 00815-009 a typical AD688 both with and without a 1 µF capacitor. Figure 9. Turn On Characteristics: Extended Time Scale Output turn on time is modified when an external noise
200
µ
V 50
µ
s
reduction capacitor is used. When present, this capacitor presents an additional load to the internal Zener diode’s current source, resulting in a somewhat longer turn on time. In the case
CN = 1
µ
F
of a 1 µF capacitor, the initial turn on time is approximately 100 ms (Figure 10). When the noise reduction feature is used, a 20 kΩ resistor between Pin 6 and Pin 2 is required for proper startup.
NO CN 10V 1mV 20ms +VS 100
00815-007
90
Figure 7. Effect of 1 µF Noise Reduction Capacitor on Broadband Noise
TURN ON TIME –V
Upon application of power (cold start), the time required for
S
the output voltage to reach its final value within a specified error is the turn on settling time. Two components normally
+VOUT 10
associated with this are: time for active circuits to settle and
0%
time for thermal gradients on the chip to stabilize. Figure 8 and Figure 9 show the turn on characteristics of the AD688. They
10V
00815-010 show the settling time to be about 600 µs. Note the absence of Figure 10. Turn On With 1 µF CN Rev. B | Page 8 of 16 Document Outline FEATURES GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAM PRODUCT HIGHLIGHTS SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS THEORY OF OPERATION APPLICATIONS CALIBRATION NOISE PERFORMANCE AND REDUCTION TURN ON TIME TEMPERATURE PERFORMANCE KELVIN CONNECTIONS DYNAMIC PERFORMANCE BRIDGE DRIVER CIRCUIT OUTLINE DIMENSIONS ORDERING GUIDE
