Datasheet AD688 (Analog Devices) - 6
| Hersteller | Analog Devices |
| Beschreibung | High Precision ±10 V Reference |
| Seiten / Seite | 16 / 6 — AD688. THEORY OF OPERATION. NOISE. +10V OUT. REDUCTION. VHIGH. A3 IN. … |
| Revision | B |
| Dateiformat / Größe | PDF / 495 Kb |
| Dokumentensprache | Englisch |
AD688. THEORY OF OPERATION. NOISE. +10V OUT. REDUCTION. VHIGH. A3 IN. SENSE. FORCE. –10V OUT. 15 FORCE. +VS. 16 –VS. GAIN. GND. VLOW BAL. A4 IN. ADJ. +IN
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AD688 THEORY OF OPERATION
The AD688 consists of a buried Zener diode reference, Amplifiers A3 and A4 are internally compensated and are used amplifiers and associated thin-film resistors as shown in to buffer the voltages at Pin 6 and Pin 8 as well as to provide a Figure 3. The temperature compensation circuitry provides the full Kelvin output. Thus, the AD688 has a full Kelvin capability device with a temperature coefficient of 1.5 ppm/°C or less. by providing the means to sense a system ground, and forced and sensed outputs referenced to that ground. Amplifier A1 performs several functions. A1 primarily acts to amplify the Zener voltage to the required 20 V. In addition, A1
NOISE +10V OUT REDUCTION VHIGH A3 IN SENSE
also provides for external adjustment of the 20 V output
7 6 4 3
through Pin 5 (GAIN ADJ). Using the bias compensation resistor between the Zener output and the noninverting input to
+10V OUT A3 1 FORCE
A1, a capacitor can be added at the noise reduction pin (Pin 7)
RB
to form a low-pass filter and reduce the noise contribution of
A1 AD688 –10V OUT 14
the Zener to the circuit. Two matched 12 kΩ nominal thin-film
R1 R4 SENSE
resistors (R4 and R5) divide the 20 V output in half.
–10V OUT R2 A4 15 FORCE R5
Ground sensing for the circuit is provided by amplifier A2. The noninverting input (Pin 9) senses the system ground and forces
R6 2 +VS R3
the midpoint of resistors R4 and R5 to be a virtual ground.
A2
Pin 12 (BAL ADJ) can be used for fine adjustment of this
16 –VS
midpoint transfer.
5 9 10 8 12 11 13 GAIN GND NC VLOW BAL NC A4 IN ADJ SENSE ADJ
003
+IN NC = NO CONNECT
00815- Figure 3. Functional Block Diagram Rev. B | Page 6 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 THEORY OF OPERATION
The AD688 consists of a buried Zener diode reference, Amplifiers A3 and A4 are internally compensated and are used amplifiers and associated thin-film resistors as shown in to buffer the voltages at Pin 6 and Pin 8 as well as to provide a Figure 3. The temperature compensation circuitry provides the full Kelvin output. Thus, the AD688 has a full Kelvin capability device with a temperature coefficient of 1.5 ppm/°C or less. by providing the means to sense a system ground, and forced and sensed outputs referenced to that ground. Amplifier A1 performs several functions. A1 primarily acts to amplify the Zener voltage to the required 20 V. In addition, A1
NOISE +10V OUT REDUCTION VHIGH A3 IN SENSE
also provides for external adjustment of the 20 V output
7 6 4 3
through Pin 5 (GAIN ADJ). Using the bias compensation resistor between the Zener output and the noninverting input to
+10V OUT A3 1 FORCE
A1, a capacitor can be added at the noise reduction pin (Pin 7)
RB
to form a low-pass filter and reduce the noise contribution of
A1 AD688 –10V OUT 14
the Zener to the circuit. Two matched 12 kΩ nominal thin-film
R1 R4 SENSE
resistors (R4 and R5) divide the 20 V output in half.
–10V OUT R2 A4 15 FORCE R5
Ground sensing for the circuit is provided by amplifier A2. The noninverting input (Pin 9) senses the system ground and forces
R6 2 +VS R3
the midpoint of resistors R4 and R5 to be a virtual ground.
A2
Pin 12 (BAL ADJ) can be used for fine adjustment of this
16 –VS
midpoint transfer.
5 9 10 8 12 11 13 GAIN GND NC VLOW BAL NC A4 IN ADJ SENSE ADJ
003
+IN NC = NO CONNECT
00815- Figure 3. Functional Block Diagram Rev. B | Page 6 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