REV. B

Information furnished by Analog Devices is believed to be accurate and

reliable. However, no responsibility is assumed by Analog Devices for its

use, nor for any infringements of patents or other rights of third parties

which may result from its use. No license is granted by implication or

otherwise under any patent or patent rights of Analog Devices.

a

2.5 V/3.0 V

High Precision Reference

AD780

FUNCTIONAL BLOCK DIAGRAM

NC

TEMP

TRIM

GND

O/P SELECT

2.5V - NC

3.0V - GND

Q6

Q7

R10

R11

R5

R4

R14

R15

R16

R13

NC = NO CONNECT

NC

7

2

1

3

4

8

6

5

AD780

PRODUCT DESCRIPTION

The AD780 is an ultrahigh precision bandgap reference voltage

which provides a 2.5 V or 3.0 V output from inputs between

4.0 V and 36 V. Low initial error and temperature drift com-

bined with low output noise and the ability to drive any value of

capacitance make the AD780 the ideal choice for enhancing the

performance of high resolution ADCs and DACs and for any

general purpose precision reference application. A unique low

headroom design facilitates a 3.0 V output from a 5.0 V

± 10%

input, providing a 20% boost to the dynamic range of an ADC,

over performance with existing 2.5 V references.

The AD780 can be used to source or sink up to 10 mA and can

be used in series or shunt mode, thus allowing positive or nega-

tive output voltages without external components. This makes it

suitable for virtually any high performance reference application.

Unlike some competing references, the AD780 has no “region

of possible instability.” The part is stable under all load condi-

tions when a 1

µF bypass capacitor is used on the supply.

A temperature output pin is provided on the AD780. This pro-

vides an output voltage that varies linearly with temperature, al-

lowing the AD780 to be configured as a temperature transducer

while providing a stable 2.5 V or 3.0 V output.

The AD780 is a pin-compatible performance upgrade for the

LT1019(A)–2.5 and the AD680. The latter is targeted toward

low power applications.

The AD780 is available in three grades in plastic DIP, SOIC,

and cerdip packages. The AD780AN, AD780AR, AD780BN,

AD780BR, and AD780CR are specified for operation from –40

°C

to +85

°C.

FEATURES

Pin-Programmable 2.5 V or 3.0 V Output

Ultralow Drift: 3 ppm/ C max

High Accuracy: 2.5 V or 3.0 V

1 mV max

Low Noise: 100 nV/

√Hz

Noise Reduction Capability

Low Quiescent Current: 1 mA max

Output Trim Capability

Plug-In Upgrade for Present References

Temperature Output Pin

Series or Shunt Mode Operation ( 2.5 V,

3.0 V)

PRODUCT HIGHLIGHTS

1. The AD780 provides a pin-programmable 2.5 V or 3.0 V

output from a 4 V to 36 V input.

2. Laser trimming of both initial accuracy and temperature

coefficients results in low errors over temperature without the

use of external components. The AD780BN has a maximum

variation of 0.9 mV from –40

°C to +85°C.

3. For applications requiring even higher accuracy, an optional

fine-trim connection is provided.

4. The AD780 noise is extremely low, typically 4

µV p-p from

0.1 Hz to 10 Hz and a wideband spectral noise density of

typically 100 nV/

√Hz. This can be further reduced if desired,

by simply using two external capacitors.

5. The temperature output pin enables the AD780 to be config-

ured as a temperature transducer while providing a stable

output reference voltage.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Tel: 781/329-4700

World Wide Web Site: http://www.analog.com

Fax: 781/326-8703

© Analog Devices, Inc., 2000