a
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)
2.5 V/3.0 V
High Precision Reference
AD780
FUNCTIONAL BLOCK DIAGRAM
+V
IN
2
NC
7
AD780
R10
R11
NC 1
6
V
OUT
R13
Q6
Q7
5
R5
R16
R14
R4
R15
TRIM
PRODUCT DESCRIPTION
TEMP
3
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.
4
GND
NC = NO CONNECT
8
O/P SELECT
2.5V - NC
3.0V - GND
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.
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.
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
AD [ ANALOG DEVICES ]
