ADR1581

Rev. 0 | Page 6 of 12

THEORY OF OPERATION

The ADR1581 uses the band gap concept to produce a stable,

low temperature coefficient voltage reference suitable for high

accuracy data acquisition 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 transistors have an approximately −2 mV/°C temperature

coefficient, which is 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 collector current

to approximately the silicon band gap voltage. Therefore, if a

voltage could be developed with an opposing temperature

The ADR1581 circuit in

Figure 11 shows a typical connection of the ADR1581BRT

operating at a minimum of 100 μA. This connection can

provide ±1 mA to the load while accommodating ±10%

power supply variations.

Figure 10. Typical Connection Diagram

Figure 9 provides such a compensating

voltage, V1, by driving two transistors at different current densities

reference.

+5V(+3V) ±10%

2.94kΩ

(1.30kΩ)

V+

V–

V1

Figure 11. Typical Connection Diagram

TEMPERATURE PERFORMANCE

The ADR1581 is designed for reference applications where stable

temperature performance is important. Extensive temperature

testing and characterization ensure that the device’s performance

is maintained over the specified temperature range.

Some confusion exists in the area of defining and specifying refer-

ence voltage error over temperature. Historically, references have

been characterized using a maximum deviation per degree Celsius,

for example, 50 ppm/°C. However, because of nonlinearities in

temperature characteristics that originated in standard Zener

references (such as S type characteristics), most manufacturers

now use a maximum limit error band approach to specify devices.

This technique involves the measurement of the output at three

or more temperatures to guarantee that the voltage falls within

the given error band. The proprietary curvature correction design

techniques used to minimize the ADR1581 nonlinearities allow

the temperature performance to be guaranteed using the maximum

deviation method. This method is more useful to a designer than

one that simply guarantees the maximum error band over the

entire temperature change.

Figure 9. Schematic Diagram

APPLYING THE ADR1581

The ADR1581 is simple to use in virtually all applications.

To operate the ADR1581 as a conventional shunt regulator (see

Figure 10), an external series resistor is connected between the

supply voltage and the ADR1581. For a given supply voltage, the

Figure 12 shows a typical output voltage drift for the ADR1581

and illustrates the methodology. The maximum slope of the two

diagonals drawn from the initial output value at +25°C to the

output values at +85°C and −40°C determines the performance

grade of the device. For a given grade of the ADR1581, the designer

can easily determine the maximum total error from the initial

tolerance plus the temperature variation.

the minimum acceptable reverse current.