AD588BQ Просмотр технического описания (PDF) - Analog Devices

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AD588BQ

High Precision Voltage Reference

Analog Devices 

AD588

ABSOLUTE MAXIMUM RATINGS*

+VS to –VS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 V

Power Dissipation (+25°C)

Q Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 600 mW

Storage Temperature Range . . . . . . . . . . . . . –65°C to +150°C

Lead Temperature Range (Soldering 10 sec) . . . . . . . . +300°C

Package Thermal Resistance

Q (θJA/θJC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .90/25°C/W

Output Protection: All Outputs Safe If Shorted to Ground

*Stresses above those listed under “Absolute Maximum Ratings” may cause

permanent damage to the device. This is a stress rating only and functional

operation of the device at these or any other conditions above those indicated in the

operational sections of this specification is not implied. Exposure to absolute

maximum rating conditions for extended periods may affect device reliability.

PIN CONFIGURATIONS

REDUCTION pin (Pin 7) to form a low-pass filter and reduce

the noise contribution of the Zener to the circuit. Two matched

10 kΩ nominal thin-film resistors (R4 and R5) divide the 10 V

output in half. Pin VCT (Pin 11) provides access to the center of

the voltage span and Pin 12 (BALANCE ADJUST) can be used

for fine adjustment of this division.

Ground sensing for the circuit is provided by amplifier A2. The

noninverting input (Pin 9) senses the system ground which will

be transferred to the point on the circuit where the inverting

input (Pin 10) is connected. This may be Pin 6, 8 or 11. The

output of A2 drives Pin 8 to the appropriate voltage. Thus, if

Pin 10 is connected to Pin 8, the VLOW pin will be the same

voltage as the system ground. Alternatively, if Pin 10 is con-

nected to the VCT pin, it will be ground and Pin 6 and Pin 8 will

be +5 V and –5 V respectively.

Amplifiers A3 and A4 are internally compensated and are used

to buffer the voltages at Pins 6, 8, and 11 as well as to provide a

full Kelvin output. Thus, the AD588 has a full Kelvin capability

by providing the means to sense a system ground and provide

forced and sensed outputs referenced to that ground.

THEORY OF OPERATION

The AD588 consists of a buried Zener diode reference, amplifi-

ers used to provide pin programmable output ranges, and asso-

ciated thin-film resistors as shown in the block diagram of

Figure 1. The temperature compensation circuitry provides the

device with a temperature coefficient of 1.5 ppm/°C or less.

APPLYING THE AD588

The AD588 can be configured to provide +10 V and –10 V ref-

erence outputs as shown in Figures 2a and 2c respectively. It

can also be used to provide +5 V, –5 V or a ± 5 V tracking refer-

ence as shown in Figure 2b. Table I details the appropriate pin

connections for each output range. In each case, Pin 9 is con-

nected to system ground and power is applied to Pins 2 and 16.

The architecture of the AD588 provides ground sense and

uncommitted output buffer amplifiers which offer the user a

great deal of functional flexibility. The AD588 is specified and

tested in the configurations shown in Figure 2. The user may

choose to take advantage of the many other configuration op-

tions available with the AD588. However, performance in these

configurations is not guaranteed to meet the extremely stringent

data sheet specifications.

As indicated in Table I, a +5 V buffered output can be provided

using amplifier A4 in the +10 V configuration (Figure 2a). A

–5 V buffered output can be provided using amplifier A3 in the

–10 V configuration (Figure 2c). Specifications are not guaran-

teed for the +5 V or –5 V outputs in these configurations. Per-

formance will be similar to that specified for the +10 V or –10 V

outputs.

As indicated in Table I, unbuffered outputs are available at Pins

6, 8 and 11. Loading of these unbuffered outputs will impair

circuit performance.

Amplifiers A3 and A4 can be used interchangeably. However,

the AD588 is tested (and the specifications are guaranteed) with

the amplifiers connected as indicated in Figure 2 and Table I.

When either A3 or A4 is unused, its output force and sense pins

should be connected and the input tied to ground.

Figure 1. AD588 Functional Block Diagram

Amplifier A1 performs several functions. A1 primarily acts to

amplify the Zener voltage from 6.5 V to the required 10 V out-

put. In addition, A1 also provides for external adjustment of the

10 V output through Pin 5, the GAIN ADJUST. Using the bias

compensation resistor between the Zener output and the nonin-

verting input to A1, a capacitor can be added at the NOISE

Two outputs of the same voltage may be obtained by connecting

both A3 and A4 to the appropriate unbuffered output on Pins 6,

8 or 11. Performance in these dual output configurations will

typically meet data sheet specifications.

CALIBRATION

Generally, the AD588 will meet the requirements of a precision

system without additional adjustment. Initial output voltage

error of 1 mV and output noise specs of 10 µV p-p allow for

REV. B

–3–

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