AD580

REV. A

–3–

ABSOLUTE MAXIMUM RATINGS

Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 V

Power Dissipation @ +25

°C

Ambient Temperature . . . . . . . . . . . . . . . . . . . . . . . 350 mW

Derate above +25

°C . . . . . . . . . . . . . . . . . . . . . . . 2.8 mW/°C

Lead Temperature (Soldering 10 sec) . . . . . . . . . . . . . +300

°C

Thermal Resistance

Junction-to-Case . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

°C

Junction-to-Ambient . . . . . . . . . . . . . . . . . . . . . . . 360

°C/W

AD580 CHIP DIMENSIONS

AND PAD LAYOUT

Dimensions shown in inches and (mm).

The AD580 is also available in chip form. Consult the factory

for specifications and applications information.

THEORY OF OPERATION

The AD580 family (AD580, AD581, AD584, AD589) uses

the “bandgap” concept to produce a stable, low temperature

coefficient voltage reference suitable for high accuracy data ac-

quisition components and systems. The device makes use of the

underlying physical nature of a silicon transistor base-emitter

voltage in the forward-biased operating region. All such transis-

tors have approximately a –2 mV/

°C temperature coefficient,

unsuitable for use directly as a low TC reference; however,

extrapolation of the temperature characteristic of any one of

these devices to absolute zero (with emitter current proportional

volts at 0K, as shown in Figure 1. Thus, if a voltage could be

developed with an opposing temperature coefficient to sum with

operation from a single, low voltage supply would be possible.

Figure 2, by driving two transistors at different current densities

up to 2.5 volts to provide a usable reference-voltage output. Fig-

ure 3 is the schematic diagram of the AD580.

The AD580 operates as a three-terminal reference, which means

that no additional components are required for biasing or cur-

rent setting. The connection diagram, Figure 4 is quite simple.

Figure 1. Extrapolated Variation of Base-Emitter Voltage

Shown for Two Different Devices

Figure 2. Basic Bandgap-Reference Regulator Circuit