2.5 V/3.0 V
High Precision Reference
a
AD780
FUNCTIONAL BLOCK DIAGRAM
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
+VIN
NC
2
7
Low Noise: 100 nV/√Hz
Noise Reduction Capability
AD780
Low Quiescent Current: 1 mA max
Output Trim Capability
R10
R11
Plug-In Upgrade for Present References
Temperature Output Pin
Series or Shunt Mode Operation (ꢁ2.5 V, ꢁ3.0 V)
1
NC
VOUT
6
5
R13
Q6
Q7
TRIM
R5
R4
R16
R14
R15
PRODUCT DESCRIPTION
3
TEMP
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.
4
8
O/P SELECT
2.5V - NC
GND
NC = NO CONNECT
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.
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.
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.
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.
5. The temperature output pin enables the AD780 to be config-
ured as a temperature transducer while providing a stable
output reference voltage.
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.
REV. B
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