Datasheet AD586 (Analog Devices) - 7

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AD586 THEORY OF OPERATION V
The AD586 consists of a proprietary buried Zener diode refer-
IN
ence, an amplifier to buffer the output, and several high stability
2
thin-film resistors, as shown in the block diagram in Figure 5.
VIN
This design results in a high precision monolithic 5 V output
AD586 VO 6 OUTPUT NOISE
reference with initial offset of 2.0 mV or less. The temperature
8 REDUCTION TRIM 5 10k
Ω
OPTIONAL
compensation circuitry provides the device with a temperature
NOISE CN GND REDUCTION 1
µ
F
coefficient of under 2 ppm/°C.
CAPACITOR 4
Using the bias compensation resistor between the Zener output 00529-005 and the noninverting input to the amplifier, a capacitor can be Figure 6. Optional Fine-Trim Configuration added at the noise reduction pin (Pin 8) to form a low-pass
NOISE PERFORMANCE AND REDUCTION
filter and reduce the noise contribution of the Zener to the circuit. The noise generated by the AD586 is typically less than 4 µV p-p over the 0.1 Hz to 10 Hz band. Noise in a 1 MHz bandwidth is
VIN NOISE REDUCTION
approximately 200 µV p-p. The dominant source of this noise is
2 8
the buried Zener, which contributes approximately 100 nV/√Hz.
AD586
By comparison, contribution by the op amp is negligible. Figure 7 shows the 0.1 Hz to 10 Hz noise of a typical AD586. The noise
RZ1 RS
measurement is made with a band-pass filter made of a 1-pole
A1 6 R V Z2 OUT
high-pass filter with a corner frequency at 0.1 Hz, and a 2-pole
RF RT
low-pass filter with a corner frequency at 12.6 Hz, to create a
5 TRIM
filter with a 9.922 Hz bandwidth.
RI
If further noise reduction is desired, an external capacitor can
4
be added between the noise reduction pin and ground, as
GND
shown in Figure 6. This capacitor, combined with the 4 kΩ RS
NOTES
and the Zener resistances, forms a low-pass filter on the output
1. PINS 1, 3, AND 7 ARE INTERNAL TEST POINTS. MAKE NO CONNECTIONS TO THESE POINTS.
00529-001 of the Zener cell. A 1 µF capacitor will have a 3 dB point at Figure 5. Functional Block Diagram 12 Hz, and will reduce the high frequency (to 1 MHz) noise to about 160 µV p-p. Figure 8 shows the 1 MHz noise of a typical
APPLYING THE AD586
AD586, both with and without a 1 µF capacitor. The AD586 is simple to use in virtually all precision reference applications. When power is applied to Pin 2 and Pin 4 is
1
µ
F 5s
grounded, Pin 6 provides a 5 V output. No external components are required; the degree of desired absolute accuracy is achieved simply by selecting the required device grade. The AD586 requires less than 3 mA quiescent current from an operating
1
µ
F
supply of 12 V or 15 V. An external fine trim may be desired to set the output level to exactly 5.000 V (calibrated to a main system reference). System calibration may also require a reference voltage that is slightly different from 5.000 V, for example, 5.12 V for binary applica- tions. In either case, the optional trim circuit shown in Figure 6 00529-006 can offset the output by as much as 300 mV with minimal effect Figure 7. 0.1 Hz to 10 Hz Noise on other device characteristics. Rev. G | Page 7 of 16 Document Outline FEATURES GENERAL DESCRIPTION PRODUCT HIGHLIGHTS SPECIFICATIONS AD586J, AD586K/AD586A, AD586L/AD586B AD586M, AD586S, AD586T ABSOLUTE MAXIMUM RATINGS ESD CAUTION PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS THEORY OF OPERATION APPLYING THE AD586 NOISE PERFORMANCE AND REDUCTION TURN-ON TIME DYNAMIC PERFORMANCE LOAD REGULATION TEMPERATURE PERFORMANCE NEGATIVE REFERENCE VOLTAGE FROM AN AD586 USING THE AD586 WITH CONVERTERS 5 V REFERENCE WITH MULTIPLYINGCMOS DACs OR ADCs STACKED PRECISION REFERENCES FORMULTIPLE VOLTAGES PRECISION CURRENT SOURCE PRECISION HIGH CURRENT SUPPLY OUTLINE DIMENSIONS ORDERING GUIDE