2.5 V/3.0 V
High Precision Reference
AD780
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)
FUNCTIONAL BLOCK DIAGRAM
+VIN
NC
2
7
AD780
R10
R11
NC 1
6
VOUT
5
TRIM
R13
Q6
Q7
R16
R5
R14
TEMP 3
R15
R4
4
GND
NC = NO CONNECT
8
O/P SELECT
2.5V – NC
3.0V – GND
00841-001
FEATURES
Figure 1.
PRODUCT DESCRIPTION
The AD780 is an ultrahigh precision band gap reference voltage
that 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 combined 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
negative 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
conditions when a 1 µF bypass capacitor is used on the supply.
A temperature output pin on the AD780 provides an output
voltage that varies linearly with temperature, allowing the part
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 PDIP and SOIC
packages. The AD780AN, AD780AR, AD780BN, AD780BR, and
AD780CR are specified for operation from −40°C to +85°C.
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 that require even higher accuracy, an
optional fine-trim connection is provided.
4. The AD780 noise is extremely low, typically 4 mV 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 using two external capacitors.
5. The temperature output pin enables the AD780 to be
configured as a temperature transducer while providing a
stable output reference.
Rev. E
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