2.5 V/3.0 V
High Precision Reference
AD780
Rev. E
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 that may result from its use.
Specifications subject to change without notice. No license is granted by implication
or otherwise under any patent or patent rights of Analog Devices. Trademarks and
registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 www.analog.com
Fax: 781.326.8703 © 2004 Analog Devices, Inc. All rights reserved.
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)
FUNCTIONAL BLOCK DIAGRAM
00841-001
R16
R10
+V
IN
R4
R5
Q6 Q7
R11
R14
R13
R15
NC
V
OUT
TRIM
GND O/P SELECT
2.5V – NC
3.0V – GND
T
EMP
NC
NC = NO CONNECT
AD780
72
1
3
48
5
6
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.
AD780
Rev. E | Page 2 of 12
ABLE OF CONTENTS
.................................................... 3
Th
Supply Current Over Temperature .............................................8
O
EVISION HISTORY
ed from Rev. D to Rev. E
....Universal
..................2
....................10
T
Specifications.................................
Absolute Maximum Ratings............................................................ 4
Notes............................................................................................... 4
ESD Caution.................................................................................. 4
eory of Operation ........................................................................ 5
Applying the AD780......................................................................... 6
Noise Performance ....................................................................... 6
Noise Comparison........................................................................ 7
Temperature Performance........................................................... 7
Temperature Output Pin ............................................................. 7
Temperature Transducer Circuit................................................ 8
Turn-On Time ...............................................................................8
Dynamic Performance..................................................................8
Line Regulation..............................................................................9
Precision Reference for High Resolution 5 V Data Converters
..........................................................................................................9
4.5 V Reference from 5 V Supply ............................................. 10
Negative (–2.5 V) Reference ..................................................... 10
utline Dimensions....................................................................... 11
Ordering Guide............................................................................... 12
R
5/04—Data Sheet Chang
Updated Format..............................................................
Changes to Temperature Transducer Circuit section...................8
Changes to Ordering Guide ...........................................................12
1/04—Data Sheet Changed from Rev. C to Rev. D.
Changes to SPECIFICATIONS......................................
Updated ORDERING GUIDE.........................................................3
Updated OUTLINE DIMENSIONS .............................................10
5/02—Data Sheet Changed from Rev. B to Rev. C.
Updates to packages ........................................................
AD780
Rev. E | Page 3 of 12
SPECIFICATIONS
TA = 25°C, VIN = 5 V, unless otherwise noted.
Table 1.
AD780AN/AD780AR AD780CR AD780BN/AD780BR
Parameter Min Typ Max Min Typ Max Min Typ Max Unit
OUTPUT VOLTAGE
2.5 V Out 2.495 2.505 2.4985 2.5015 2.499 2.501 V
3.0 V Out 2.995 3.005 2.9950 3.0050 2.999 3.001 V
OUTPUT VOLTAGE DRIFT1
−40°C to +85°C 7 7 3 ppm/°C
−55°C to +125°C 20 20 ppm/°C
LINE REGULATION
2.5 V Output, 4 V ≤+VIN ≤ 36 V, TMIN to TMAX 10 10 10 µV/V
3.0 V Output, 4.5 V ≤+VIN ≤ 36 V, TMIN to TMAX 10 10 10 µV/V
LOAD REGULATION, SERIES MODE
Sourcing 0 mA < IOUT< 10 mA 50 50 50 µV/mA
TMIN to TMAX 75 75 75 µV/mA
Sinking −10 mA < IOUT< 0 mA 75 75 75 µV/mA
−40°C to +85°C 75 75 75 µV/mA
−55°C to +125°C 150 150 150 µV/mA
LOAD REGULATION, SHUNT MODE
I < ISHUNT< 10 mA 75 75 75 µV/mA
QUIESCENT CURRENT, 2.5 V SERIES MODE2
–40°C to +85°C 0.75 1.0 0.75 1.0 0.75 1.0 mA
−55°C to +125°C 0.8 1.3 0.8 1.3 0.8 1.3 mA
MINIMUM SHUNT CURRENT 0.7 1.0 0.7 1.0 0.7 1.0 mA
OUTPUT NOISE
0.1 Hz to 10 Hz 4 4 4 µV p-p
Spectral Density, 100 Hz 100 100 100 nV/√Hz
LONG-TERM STABILITY3 20 20 20 ± ppm/1000 Hr
TRIM RANGE 4.0 4.0 4.0 ± %
TEMPERATURE PIN
Voltage Output @ 25°C 500 560 620 500 560 620 500 560 620 mV
Temperature Sensitivity 1.9 1.9 1.9 mV/°C
Output Resistance 3 3 3 kΩ
SHORT-CIRCUIT CURRENT TO GROUND 30 30 30 mA
TEMPERATURE RANGE
Specified Performance (A, B, C) –40 +85 –40 +85 –40 +85 °C
Operating Performance (A, B, C)4–55 +125 –55 +125 –55 +125 °C
1 Maximum output voltage drift is guaranteed for all packages.
23.0 V mode typically adds 100 µA to the quiescent current. Also, Iq increases by 2 µA/V above an input voltage of 5 V.
3The long-term stability specification is noncumulative. The drift in subsequent 1,000 hour periods is significantly lower than in the first 1,000 hour period.
4The operating temperature range is defined as the temperature extremes at which the device will still function. Parts may deviate from their specified performance
outside their specified temperature range.
AD780
Rev. E | Page 4 of 12
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter Values
+VIN to Ground 36 V
TRIM Pin to Ground 36 V
TEMP Pin to Ground 36 V
Power Dissipation (25°C) 500 mW
Storage Temperature −65°C to +150°C
Lead Temperature
(Soldering 10 sec)
300°C
Output Protection Output safe for indefinite short to
ground and momentary short to VIN.
ESD Classification Class 1 (1000 V)
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
conditions above those indicated in the operational sections of
this specification is not implied. Exposure to absolute maximum
specifications for extended periods may affect device reliability.
00841-002
NC = NO CONNECT
AD780
TOP VIEW
(Not to Scale)
NC
1
+V
IN 2
T
EMP
3
GND
4
2.5V/3.0V O/PSELECT
(NC OR GND)
NC
V
OUT
TRIM
8
7
6
5
Figure 2. Pin Configuration, 8-Lead PDIP and SOIC Packages
00841-003
GND TEMP +V
IN
TRIM 2.5V/3.0V
O/P SELECT
V
OUT
GND
Figure 3. Die Layout
NOTES
Both VOUT pads should be connected to the output.
Die Thickness: The standard thickness of Analog Devices
bipolar dice is 24 mil ± 2 mil.
Die Dimensions: The dimensions given have a tolerance of
±2 mil.
Backing: The standard backside surface is silicon (not plated).
Analog Devices does not recommend gold-backed dice for most
applications.
Edges: A diamond saw is used to separate wafers into dice, thus
providing perpendicular edges halfway through the die. In
contrast to scribed dice, this technique provides a more uniform
die shape and size. The perpendicular edges facilitate handling
(such as tweezer pickup), while the uniform shape and size
simplify substrate design and die attach.
Top Surfac e: The standard top surface of the die is covered by a
layer of glassivation. All areas are covered except bonding pads
and scribe lines.
Surface Metallization: The metallization to Analog Devices
bipolar dice is aluminum. Minimum thickness is 10,000 Å.
Bonding Pads: All bonding pads have a minimum size of
4.0 mil by 6.0 mil. The passivation windows have a minimum
size of 3.6 mil by 5.6 mil.
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on
the human body and test equipment and can discharge without detection. Although this product features
proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy
electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance
degradation or loss of functionality.
AD780
Rev. E | Page 5 of 12
THEORY OF OPERATION
Band gap references are the high performance solution for low
supply voltage and low power voltage reference applications. In
this technique, a voltage with a positive temperature coefficient
is combined with the negative coefficient of a transistor’s Vbe to
produce a constant band gap voltage.
In the AD780, the band gap cell contains two NPN transistors
(Q6 and Q7) that differ in emitter area by 12×. The difference in
their Vbes produces a PTAT current in R5. This, in turn,
produces a PTAT voltage across R4 that, when combined with
the Vbe of Q7, produces a voltage (Vbg) that does not vary with
temperature. Precision laser trimming of the resistors and other
patented circuit techniques are used to further enhance the drift
performance.
00841-004
R16
R10
+V
IN
R4
R5
Q6 Q7
R11
R14
R13
R15
NC
V
OUT
TRIM
GND O/P SELECT
2.5V – NC
3.0V – GND
T
EMP
NC
NC = NO CONNECT
AD780
72
1
3
48
5
6
Figure 4. Schematic Diagram
The output voltage of the AD780 is determined by the
configuration of Resistors R13, R14, and R15 in the amplifier’s
feedback loop. This sets the output to either 2.5 V or 3.0 V,
depending on whether R15 (Pin 8) is grounded or not
connected.
A unique feature of the AD780 is the low headroom design of
the high gain amplifier, which produces a precision 3 V output
from an input voltage as low as 4.5 V (or 2.5 V from a 4.0 V
input). The amplifier design also allows the part to work with
+VIN = VOUT when current is forced into the output terminal.
This allows the AD780 to work as a 2-terminal shunt regulator,
providing a −2.5 V or −3.0 V reference voltage output without
external components.
The PTAT voltage is also used to provide the user with a
thermometer output voltage (at Pin 3) that increases at a rate of
approximately 2 mV/°C.
The AD780’s NC (Pin 7) is a 20 kΩ resistor to +VIN that is used
solely for production test purposes. Users who are currently
using the LT1019 self-heater pin (Pin 7) must take into account
the different load on the heater supply.
AD780
Rev. E | Page 6 of 12
APPLYING THE AD780
The AD780 can be used without any external components to
achieve specified performance. If power is supplied to Pin 2 and
Pin 4 is grounded, Pin 6 provides a 2.5 V or 3.0 V output
depending on whether Pin 8 is left unconnected or grounded.
A bypass capacitor of 1 µF (+VIN to GND) should be used if the
load capacitance in the application is expected to be greater
than 1 nF. The AD780 in 2.5 V mode typically draws 700 µA of
Iq at 5 V. This increases by ~2 µA/V up to 36 V.
00841-005
NC
TEMP
+V
IN
R
NULL
V
OUT
TRIM
GND
O/P SELECT
2.5V – NC
3.0V – GND
NC
R POT
1µF
AD780
NC = NO CONNECT
1
7
6
5
84
2
3
Figure 5. Optional Fine-Trim Circuit
Initial error can be nulled using a single 25 kΩ potentiometer
connected between VOUT, TRIM, and GND. This is a coarse trim
with an adjustment range of 4%, and is only included here for
compatibility purposes with other references. A fine trim can be
implemented by inserting a large value resistor (e.g., 1 MΩ to
5 MΩ) in series with the wiper of the potentiometer (see
Figure 5). The trim range, expressed as a fraction of the output,
is simply greater than or equal to 2.1 kΩ/RNULL for either the
2.5 V or 3.0 V mode.
The external null resistor affects the overall temperature
coefficient by a factor equal to the percentage of VOUT nulled.
For example, a 1 mV (0.03%) shift in the output caused by the
trim circuit, with a 100 ppm/°C null resistor, adds less than
0.06 ppm/°C to the output drift (0.03% × 200 ppm/°C, since the
resistors internal to the AD780 also have temperature
coefficients of less than 100 ppm/°C).
NOISE PERFORMANCE
The impressive noise performance of the AD780 can be further
improved, if desired, by adding two capacitors: a load capacitor
(C1) between the output and ground, and a compensation
capacitor (C2) between the TEMP pin and ground. Suitable
values are shown in Figure 6.
100
10
1
0.1
0.1 1 10 100
00841-006
LOAD CAPACITOR, C1 (µF)
COMPENSATION CAPACITOR, C2 (nF)
Figure 6. Compensation and Load Capacitor Combinations
C1 and C2 also improve the settling performance of the AD780
when subjected to load transients. The improvement in noise
performance is shown in Figure 7, Figure 8, Figure 9, and
Figure 10.
00841-007
0.1 TO 10Hz
AMPLIFIER GAIN = 100
1s100µV
100
90
10
0%
Figure 7. Standalone Noise Performance
00841-008
10Hz TO 10kHz
NO AMPLIFIER
10ms20µV
100
90
10
0%
Figure 8. Standalone Noise Performance
AD780
Rev. E | Page 7 of 12
00841-009
NC
TEMP
+VIN
VOUT
TRIM
GND
O/P SELECT
2.5V – NC
3.0V – GND
NC
1µF
AD780
NC = NO CONNECT
1
7
6
5
8
4
2
3
C2
C1
Figure 9. Noise Reduction Circuit
NOISE COMPARISON
The wideband noise performance of the AD780 can also be
expressed in ppm. The typical performance with C1 and C2 is
0.6 ppm; without external capacitors, typical performance is
1.2 ppm.
This performance is, respectively, 7× and 3× lower than the
specified performance of the LT1019.
00841-010
10Hz TO 10kHz
NO AMPLIFIER
10ms20µV
100
90
10
0%
Figure 10. Reduced Noise Performance with C1 = 100 µF, C2 = 100 nF
TEMPERATURE PERFORMANCE
The AD780 provides superior performance over temperature by
means of a combination of patented circuit design techniques,
precision thin-film resistors, and drift trimming. Temperature
performance is specified in terms of ppm/°C; because of
nonlinearity in the temperature characteristic, the box test
method is used to test and specify the part. The nonlinearity
takes the form of the characteristic S-shaped curve shown in
Figure 11. The box test method forms a rectangular box around
this curve, enclosing the maximum and minimum output
voltages over the specified temperature range. The specified
drift is equal to the slope of the diagonal of this box.
2.0
–0.8
–0.4
0
0.4
0.8
1.2
1.6
–60 –40 –20 0 20 40 60 80 100 120 140
00841-011
TEMPERATURE (°C)
ERROR (mV)
Figure 11. Typical AD780BN Temperature Drift
TEMPERATURE OUTPUT PIN
The AD780 provides a TEMP output (Pin 3) that varies linearly
with temperature. This output can be used to monitor changes
in system ambient temperature, and to initiate calibration of the
system, if desired. The voltage VTEMP is 560 mV at 25°C, and the
temperature coefficient is approximately 2 mV/°C.
Figure 12 shows the typical VTEMP characteristic curve over
temperature taken at the output of the op amp with a
noninverting gain of 5.
4.25
4.00
3.75
3.50
3.25
3.00
2.75
2.50
2.25
2.00
–75 –50 –25 0 25 50 75 100 125 150
00841-012
TEMPERATURE (°C)
VOLTAGE (V
OUT
)
CIRCUIT CALIBRATED AT 25°C
REFER TO FIGURE 13
10mV PER °C
Figure 12. Temperature Pin Transfer Characteristic
Since the TEMP voltage is acquired from the band gap core
circuit, current pulled from this pin has a significant effect on
VOUT. Care must be taken to buffer the TEMP output with a
suitable op amp, e.g., an OP07, AD820, or AD711 (all of which
would result in less than a 100 µV change in VOUT). The
relationship between ITEMP and VOUT is
∆VOUT = 5.8 mV/µA ITEMP (2.5 V Range)
or
∆VOUT = 6.9 mV/µA ITEMP (3.0 V Range)
AD780
Rev. E | Page 8 of 12
Notice how sensitive the current dependent factor on VOUT is. A
large amount of current, even in tens of microamp, drawn from
the TEMP pin can cause the VOUT and TEMP output to fail.
The choice of C1 and C2 was dictated primarily by the need for
a relatively flat response that rolled off early in the high
frequency noise at the output. However, there is considerable
margin in the choice of these capacitors. For example, the user
can actually put a huge C2 on the TEMP pin with none on the
output pin. However, one must either put very little or a lot of
capacitance at the TEMP pin. Intermediate values of
capacitance can sometimes cause oscillation. In any case, the
user should follow the recommendation in Figure 6.
TEMPERATURE TRANSDUCER CIRCUIT
The circuit shown in Figure 13 is a temperature transducer that
amplifies the TEMP output voltage by a gain of a little over +5
to provide a wider full-scale output range. The digital
potentiometer can be used to adjust the output so it varies by
exactly 10 mV/°C.
To minimize resistance changes with temperature, resistors with
low temperature coefficients, such as metal film resistors,
should be used.
00841-013
AD780
GND R
B
1.27kΩ
(1%)
R
F
6.04kΩ(1%)
4
+V
IN
2
3
1µF
TEMP
R
BP
200Ω
AD820 10mV/°C
5V
Figure 13. Differential Temperature Transducer
SUPPLY CURRENT OVER TEMPERATURE
The AD780’s quiescent current varies slightly over temperature
and input supply range. The test limit is 1 mA over the
industrial and 1.3 mA over the military temperature range.
Typical performance with input voltage and temperature
variation is shown in Figure 14.
0.85
0.80
0.75
0.70
0.65
0.60 43
00841-014
INPUT VOLTAGE (V)
QUIESCENT CURRENT (mA)
–55°C
+25°C
+125°C
6
Figure 14. Typical Supply Current over Temperature
TURN-ON TIME
The time required for the output voltage to reach its final value
within a specified error band is defined as the turn-on settling
time. The two major factors that affect this are the active circuit
settling time and the time for the thermal gradients on the chip
to stabilize. Typical settling performance is shown in Figure 15.
The AD780 settles to within 0.1% of its final value within 10 µs.
5V
0V
2.500V
2.499V
2.498V
00841-015
10µs/DIV
V
IN
V
OUT
Figure 15. Turn-On Settling Time Performance
DYNAMIC PERFORMANCE
The output stage of the AD780 has been designed to provide
superior static and dynamic load regulation.
Figure 16 and Figure 17 show the performance of the AD780
while driving a 0 mA to 10 mA load.
AD780
Rev. E | Page 9 of 12
00841-016
AD780
4
+V
IN
2
6
1µF
V
OUT
249Ω
V
L
V
OUT
0V
Figure 16. Transient Resistive Load Test Circuit
0mA
10mA
00841-017
10µs/DIV
OUTPUT CHANGE (50mV/DIV)
I
LOAD
V
OUT
(C
L
= 0pF)
Figure 17. Settling under Transient Resistive Load
The dynamic load may be resistive and capacitive. For example,
the load may be connected via a long capacitive cable. Figure 18
and Figure 19 show the performance of the AD780 driving a
1000 pF, 0 mA to 10 mA load.
00841-018
AD780
4
+VIN
2
6
1µF
VOUT
249Ω
VLVOUT
0V
CL
1000pF
Figure 18. Capacitive Load Transient Response Test Circuit
0mA
10mA
00841-019
10µs/DIV
OUTPUT CHANGE (50mV/DIV)
I
LOAD
V
OUT
(C
L
= 1000pF)
Figure 19. Settling under Dynamic Capacitive Load
LINE REGULATION
Line regulation is a measure of change in output voltage due to
a specified change in input voltage. It is intended to simulate
worst-case unregulated supply conditions and is measured in
µV/V. Figure 20 shows typical performance with 4.0 V < VIN <
15.0 V.
200
100
0
–100
–200 4110
00841-020
INPUT VOLTAGE (V)
OUTPUT CHANGE (µV)
T = 25°C
5
Figure 20. Output Voltage Change vs. Input Voltage
PRECISION REFERENCE FOR HIGH RESOLUTION
5 V DATA CONVERTERS
The AD780 is ideally suited to be the reference for most 5 V
high resolution ADCs. The AD780 is stable under any capacitive
load, has superior dynamic load performance, and its 3.0 V
output provides the converter with the maximum dynamic
range without requiring an additional and expensive buffer
amplifier. One of the many ADCs that the AD780 is suited for is
the AD7884, a 16-bit, high speed sampling ADC (see Figure 21).
This part previously needed a precision 5 V reference, resistor
divider, and buffer amplifier to do this function.
AD780
Rev. E | Page 10 of 12
00841-021
+VIN
AD780
AD7884
VOUT VREF + F
6
VREF + S
2.5V/3.0V
SELECT
8
GND
4
2
1µF
5V
Figure 21. Precision 3 V Reference for the AD7884 16-Bit, High Speed ADC
The AD780 is also ideal for use with higher resolution
converters, such as the AD7710/AD7711/AD7712 (see Figure
22. While these parts are specified with a 2.5 V internal
reference, the AD780 in 3 V mode can be used to improve the
absolute accuracy, temperature stability, and dynamic range. It is
shown in Figure 22 with the two optional noise reduction
capacitors.
00841-022
+V
IN
AD780
AD7710
V
OUT
REF IN+
6
2.5V/3.0V
O/P SELECT
8
GND
4
3
2
1µF
100nF
5V
REF IN–
100µF
Figure 22. Precision 2.5 V or 3.0 V Reference for the
AD7710 High Resolution, Σ-∆ ADC
4.5 V REFERENCE FROM 5 V SUPPLY
Some 5 V high resolution ADCs can accommodate reference
voltages up to 4.5 V. The AD780 can be used to provide a
precision 4.5 V reference voltage from a 5 V supply using the
circuit shown in Figure 23. This circuit provides a regulated
4.5 V output from a supply voltage as low as 4.7 V. The high
quality tantalum 10 µF capacitor, in parallel with the ceramic
AD780 0.1 µF capacitor and the 3.9 Ω resistor, ensures a low
output impedance around 50 MHz.
00841-023
AD780
2N2907
V
OUT
5kΩ
0.01% 4kΩ
0.01%
2.5kΩ
3.9Ω
1kΩ
0.1µF
0.1µF
10µF0.1µF
OP90
+
–
V
SUPPLY
2
4
637
6
4
2
Figure 23. 4.5 V Reference from a Single 5 V Supply
NEGATIVE (–2.5 V) REFERENCE
The AD780 can produce a negative output voltage in shunt
mode by connecting the input and output to ground, and
connecting the AD780’s GND pin to a negative supply via a bias
resistor, as shown in Figure 25.
00841-024
NC
TEMP
+V
IN
V
OUT
TRIM
GND
O/P SELECT
2.5V – NC
3.0V – GND
NC
1µF
AD780
NOTES
1. I
L
= LOAD CURRENT
2. I
S
MIN = MINIMUM SHUNT CURRENT
3. NC = NO CONNECT
1
7
6
5
84
2
3
R = V
OUT
– (V–)
I
L
+ I
S
MIN
–2.5 V
OUT
V–
Figure 24. Negative (−2.5 V Shunt Mode Reference)
A precise –2.5 V reference capable of supplying up to 100 mA to
a load can be implemented with the AD780 in series mode,
using the bootstrap circuit shown in Figure 25.
0
0841-025
AD780
2N3906
+5V
+5V
OP07
CONNECT IF
–3V OUTPUT
DESIRED
–2.5V (I
L
≤
100mA)
–5V
–5V
OUT
1kΩ
1000pF
+V
IN
–
+
2
4
68
Figure 25. −2.5 V High Load Current Reference
AD780
Rev. E | Page 11 of 12
OUTLINE DIMENSIONS
0.25 (0.0098)
0.17 (0.0067)
1.27 (0.0500)
0.40 (0.0157)
0.50 (0.0196)
0.25 (0.0099)× 45°
8°
0°
1.75 (0.0688)
1.35 (0.0532)
SEATING
PLANE
0.25 (0.0098)
0.10 (0.0040)
41
85
5.00 (0.1968)
4.80 (0.1890)
4.00 (0.1574)
3.80 (0.1497)
1.27 (0.0500)
BSC
6.20 (0.2440)
5.80 (0.2284)
0.51 (0.0201)
0.31 (0.0122)
COPLANARIT
Y
0.10
CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
COMPLIANT TO JEDEC STANDARDS MS-012AA
Figure 26. 8-Lead Standard Small Outline Package [SOIC]
Narrow Body (R-8)
Dimensions shown in millimeters and (inches)
SEATING
PLANE
0.015
(0.38)
MIN
0.180
(4.57)
MAX
0.150 (3.81)
0.130 (3.30)
0.110 (2.79) 0.060 (1.52)
0.050 (1.27)
0.045 (1.14)
8
14
5
0.295 (7.49)
0.285 (7.24)
0.275 (6.98)
0.100 (2.54)
BSC
0.375 (9.53)
0.365 (9.27)
0.355 (9.02)
0.150 (3.81)
0.135 (3.43)
0.120 (3.05)
0.015 (0.38)
0.010 (0.25)
0.008 (0.20)
0.325 (8.26)
0.310 (7.87)
0.300 (7.62)
0.022 (0.56)
0.018 (0.46)
0.014 (0.36)
CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN
COMPLIANT TO JEDEC STANDARDS MO-095AA
Figure 27. 8-Lead Plastic Dual-In-Line Package [PDIP]
(N-8)
Dimensions shown in inches and (millimeters)
AD780
Rev. E | Page 12 of 12
ORDERING GUIDE
Model Initial Error Temperature Range Temperature Coefficient Package Option Qty. per Tube/Reel
AD780AN ±5.0 mV −40°C to +85°C 7 ppm/°C PDIP 48
AD780AR ±5.0 mV −40°C to +85°C 7 ppm/°C SOIC 98
AD780AR-REEL7 ±5.0 mV −40°C to +85°C 7 ppm/°C SOIC 750
AD780ARZ1±5.0 mV −40°C to +85°C 7 ppm/°C SOIC 98
AD780BN ±1.0 mV −40°C to +85°C 3 ppm/°C PDIP 48
AD780BR ±1.0 mV −40°C to +85°C 3 ppm/°C SOIC 98
AD780BRZ1 ±1.0 mV −40°C to +85°C 3 ppm/°C SOIC 98
AD780BR-REEL ±1.0 mV −40°C to +85°C 3 ppm/°C SOIC 2,500
AD780BR-REEL7 ±1.0 mV −40°C to +85°C 3 ppm/°C SOIC 750
AD780BRZ1 ±1.0 mV −40°C to +85°C 3 ppm/°C SOIC 98
AD780BRZ-REEL71 ±1.0 mV −40°C to +85°C 3 ppm/°C SOIC 750
AD780CR ±1.5 mV −40°C to +85°C 7 ppm/°C SOIC 98
AD780CR-REEL7 ±1.5 mV −40°C to +85°C 7 ppm/°C SOIC 750
AD780CRZ1 ±1.5 mV −40°C to +85°C 7 ppm/°C SOIC 98
1 Z = Pb-free part.
© 2004 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
C00841–0–5/04(E)
