AD780BNZ [ADI]
2.5 V/3.0 V High Precision Reference; 2.5 V / 3.0 V高精密基准
| 型号： | AD780BNZ |
| 厂家： | 
ADI |
| 描述： | 2.5 V/3.0 V High Precision Reference |
| 文件： | 总12页 (文件大小：264K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
2.5 V/3.0 V
High Precision Reference
Data Sheet
AD780
FUNCTIONAL BLOCK DIAGRAM
FEATURES
+V
NC
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
IN
2
7
AD780
Low noise: 100 nV/√
Hz
R10
R11
Q7
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)
1
NC
6
5
V
OUT
R13
Q6
R16
TRIM
R5
R4
R14
TEMP
3
R15
4
8
O/P SELECT
2.5V – NC
3.0V – GND
GND
NC = NO CONNECT
Figure 1.
PRODUCT DESCRIPTION
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 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 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.
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.
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
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.
typically 100 nV/√ . This can be further reduced, if
Hz
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. F
Document Feedback
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responsibilityisassumedbyAnalog Devices for its use, nor for anyinfringements of patents or other
rights of third partiesthat may result from its use. Specifications subject to change without notice. No
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One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
Technical Support
©2012 Analog Devices, Inc. All rights reserved.
www.analog.com
AD780
Data Sheet
TABLE OF CONTENTS
Specifications..................................................................................... 3
Supply Current Over Temperature .............................................8
Turn-On Time ...............................................................................8
Dynamic Performance..................................................................8
Line Regulation..............................................................................9
Absolute Maximum Ratings............................................................ 4
Notes............................................................................................... 4
ESD Caution.................................................................................. 4
Theory of Operation ........................................................................ 5
Applying the AD780......................................................................... 6
Noise Performance ....................................................................... 6
Noise Comparison........................................................................ 7
Temperature Performance........................................................... 7
Temperature Output Pin ............................................................. 7
Temperature Transducer Circuit................................................ 8
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
Outline Dimensions....................................................................... 11
Ordering Guide............................................................................... 12
REVISION HISTORY
12/12—Rev. E to Rev. F
Updated Outline Dimensions........................................................11
Changes to Ordering Guide ...........................................................12
5/04—Data Sheet Changed from Rev. D to Rev. E
Updated Format..................................................................Universal
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........................................................2
Updated ORDERING GUIDE.........................................................3
Updated OUTLINE DIMENSIONS .............................................10
5/02—Data Sheet Changed from Rev. B to Rev. C.
Updates to packages ............................................................................10
Rev. F | Page 2 of 12
Data Sheet
AD780
SPECIFICATIONS
TA = 25°C, VIN = 5 V, unless otherwise noted.
Table 1.
AD780AN/AD780AR
AD780CR
Typ Max
AD780BN/AD780BR
Parameter
Min
Typ Max
Min
Min
Typ Max
Unit
OUTPUT VOLTAGE
2.5 V Out
3.0 V Out
2.495
2.995
2.505 2.4985
3.005 2.9950
2.5015 2.499
3.0050 2.999
2.501
3.001
V
V
OUTPUT VOLTAGE DRIFT1
−40°C to +85°C
−55°C to +125°C
7
20
7
20
3
ppm/°C
ppm/°C
LINE REGULATION
2.5 V Output, 4 V ≤+VIN ≤ 36 V, TMIN to TMAX
3.0 V Output, 4.5 V ≤+VIN ≤ 36 V, TMIN to TMAX
LOAD REGULATION, SERIES MODE
Sourcing 0 mA < IOUT< 10 mA
TMIN to TMAX
Sinking −10 mA < IOUT< 0 mA
−40°C to +85°C
−55°C to +125°C
10
10
10
10
10
10
µV/V
µV/V
50
75
75
75
150
50
75
75
75
150
50
75
75
75
150
µV/mA
µV/mA
µV/mA
µV/mA
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
−55°C to +125°C
0.75 1.0
0.75 1.0
0.75 1.0
mA
mA
mA
0.8
0.7
1.3
1.0
0.8
0.7
1.3
1.0
0.8
0.7
1.3
1.0
MINIMUM SHUNT CURRENT
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
Temperature Sensitivity
Output Resistance
500
560
1.9
3
620
+85
500
560 620
1.9
3
500
560 620
1.9
3
mV
mV/°C
kΩ
SHORT-CIRCUIT CURRENT TO GROUND
TEMPERATURE RANGE
Specified Performance (A, B, C)
Operating Performance (A, B, C)4
30
30
30
mA
–40
–55
–40
+85
+125
–40
–55
+85
+125 °C
°C
+125 –55
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.
Rev. F | Page 3 of 12
AD780
Data Sheet
ABSOLUTE MAXIMUM RATINGS
Table 2.
GND
TEMP
+V
IN
Parameter
Values
36 V
+VIN to Ground
TRIM Pin to Ground
TEMP Pin to Ground
36 V
36 V
Power Dissipation (25°C) 500 mW
Storage Temperature
−65°C to +150°C
Lead Temperature
(Soldering 10 sec)
Output Protection
300°C
GND
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.
TRIM
V
2.5V/3.0V
OUT
O/P SELECT
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.
2.5V/3.0V O/PSELECT
NC
1
2
3
4
8
7
6
5
(NC OR GND)
Die Dimensions: The dimensions given have a tolerance of
2 mil.
+V
NC
IN
AD780
TEMP
V
TOP VIEW
OUT
(Not to Scale)
GND
TRIM
Backing: The standard backside surface is silicon (not plated).
Analog Devices does not recommend gold-backed dice for most
applications.
NC = NO CONNECT
Figure 2. Pin Configuration, 8-Lead PDIP and SOIC Packages
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 Surface: 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.
Rev. F | Page 4 of 12
Data Sheet
AD780
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.
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.
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.
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.
+V
2
NC
7
IN
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.
AD780
R10
R11
Q7
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.
1
NC
6
5
V
OUT
R13
Q6
R16
TRIM
R5
R4
R14
TEMP
3
R15
4
8
O/P SELECT
2.5V – NC
3.0V – GND
GND
NC = NO CONNECT
Figure 4. Schematic Diagram
Rev. F | Page 5 of 12
AD780
Data Sheet
APPLYING THE AD780
100
10
1
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.
2
7
+V
IN
NC
0.1
V
6
5
OUT
0.1
1
10
100
1
3
NC
LOAD CAPACITOR, C1 (µF)
AD780
1µF
R
NULL
R POT
TRIM
Figure 6. Compensation and Load Capacitor Combinations
TEMP
O/P SELECT
2.5V – NC
3.0V – GND
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.
GND
4
8
NC = NO CONNECT
AMPLIFIER GAIN = 100
Figure 5. Optional Fine-Trim Circuit
100µV
1s
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
100
90
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.
10
0%
0.1 TO 10Hz
The external null resistor affects the overall temperature
coefficient by a factor equal to the percentage of VOUT nulled.
Figure 7. Standalone Noise Performance
NO AMPLIFIER
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).
20µV
10ms
100
90
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.
10
0%
10Hz TO 10kHz
Figure 8. Standalone Noise Performance
Rev. F | Page 6 of 12
Data Sheet
AD780
2.0
1.6
1.2
0.8
0.4
0
2
7
NC
+V
IN
V
6
5
OUT
1
3
NC
AD780
1F
TRIM
TEMP
C1
O/P SELECT
2.5V – NC
3.0V – GND
C2
GND
4
8
–0.4
NC = NO CONNECT
–0.8
–60 –40 –20
Figure 9. Noise Reduction Circuit
0
20
40
60
80
100 120 140
TEMPERATURE (C)
NOISE COMPARISON
Figure 11. Typical AD780BN Temperature Drift
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.
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.
This performance is, respectively, 7× and 3× lower than the
specified performance of the LT1019.
NO AMPLIFIER
Figure 12 shows the typical VTEMP characteristic curve over
temperature taken at the output of the op amp with a
noninverting gain of 5.
20V
10ms
100
90
4.25
CIRCUIT CALIBRATED AT 25C
REFER TO FIGURE 13
4.00
3.75
3.50
10mV PER C
10
0%
3.25
3.00
2.75
2.50
2.25
2.00
10Hz TO 10kHz
Figure 10. Reduced Noise Performance with C1 = 100 μF, C2 = 100 nF
TEMPERATURE PERFORMANCE
–75
–50
–25
0
25
50
75
100
125
150
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.
TEMPERATURE (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
OUT. 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
V
ΔVOUT = 5.8 mV/μA ITEMP (2.5 V Range)
or
ΔVOUT = 6.9 mV/μA ITEMP (3.0 V Range)
Rev. F | Page 7 of 12
AD780
Data Sheet
0.85
0.80
0.75
0.70
0.65
0.60
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.
–55°C
+25°C
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
+125°C
capacitance can sometimes cause oscillation. In any case, the
user should follow the recommendation in Figure 6.
4
36
INPUT VOLTAGE (V)
TEMPERATURE TRANSDUCER CIRCUIT
Figure 14. Typical Supply Current over Temperature
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.
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.
To minimize resistance changes with temperature, resistors with
low temperature coefficients, such as metal film resistors,
should be used.
5V
V
IN
2
5V
0V
+V
IN
TEMP
3
10mV/°C
AD820
1µF
AD780
V
OUT
2.500V
2.499V
2.498V
GND
4
R
B
R
F
1.27kΩ
(1%)
6.04kΩ (1%)
R
BP
200Ω
10µs/DIV
Figure 15. Turn-On Settling Time Performance
Figure 13. Differential Temperature Transducer
DYNAMIC PERFORMANCE
SUPPLY CURRENT OVER TEMPERATURE
The output stage of the AD780 has been designed to provide
superior static and dynamic load regulation.
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.
Figure 16 and Figure 17 show the performance of the AD780
while driving a 0 mA to 10 mA load.
Rev. F | Page 8 of 12
Data Sheet
AD780
+V
2
IN
I
LOAD
0mA
10mA
V
OUT
(C = 1000pF)
6
V
AD780
OUT
L
1µF
249Ω
4
V
0V
OUT
V
L
Figure 16. Transient Resistive Load Test Circuit
10µs/DIV
I
LOAD
Figure 19. Settling under Dynamic Capacitive Load
0mA
10mA
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
V
(C = 0pF)
L
OUT
µV /V. Figure 20 shows typical performance with 4.0 V < VIN
<
15.0 V.
200
T = 25°C
100
0
10µs/DIV
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.
–100
–200
+V
IN
4
10
15
2
INPUT VOLTAGE (V)
Figure 20. Output Voltage Change vs. Input Voltage
6
V
OUT
AD780
C
L
PRECISION REFERENCE FOR HIGH RESOLUTION
5 V DATA CONVERTERS
1000pF
1µF
249Ω
The AD780 is ideally suited to be the reference for most 5 V
high resolution ADCs. The AD780 is stable under any
4
V
0V
OUT
V
L
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.
Figure 18. Capacitive Load Transient Response Test Circuit
Rev. F | Page 9 of 12
AD780
Data Sheet
V
5V
2
SUPPLY
AD7884
0.1F
1k
+V
IN
2N2907
2
V
6
V
V
+ F
+ S
OUT
REF
REF
7
+
3
6
1F
6
OP90
AD780
AD780
V
OUT
2.5k
2
–
4
10F
0.1F
2.5V/3.0V
SELECT
4
GND
4
0.1F
3.9
8
4k
0.01%
5k
0.01%
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.
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.
5V
2
7
AD7710
NC
+V
IN
2
+V
IN
V
6
5
OUT
1
3
NC
V
6
REF IN+
AD780
OUT
1F
1F
TRIM
AD780
TEMP
3
100F
O/P SELECT
2.5V – NC
3.0V – GND
2.5V/3.0V
GND O/P SELECT
100nF
GND
4
4
8
8
REF IN–
–2.5 V
OUT
V
– (V–)
OUT
+ I MIN
NOTES
R =
I
1. I = LOAD CURRENT
L
S
L
Figure 22. Precision 2.5 V or 3.0 V Reference for the
AD7710 High Resolution, Σ-Δ ADC
2. I MIN = MINIMUM SHUNT CURRENT
3. NC = NO CONNECT
S
V–
4.5 V REFERENCE FROM 5 V SUPPLY
Figure 24. Negative (−2.5 V Shunt Mode Reference)
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.
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.
+5V
+V
IN
2
OUT
1k
+5V
AD780
6
8
CONNECT IF
–3V OUTPUT
DESIRED
4
–
+
–2.5V (IL 100mA)
2N3906
OP07
–5V
–5V
1000pF
Figure 25. −2.5 V High Load Current Reference
Rev. F | Page 10 of 12
Data Sheet
AD780
OUTLINE DIMENSIONS
5.00 (0.1968)
4.80 (0.1890)
8
1
5
4
6.20 (0.2441)
5.80 (0.2284)
4.00 (0.1574)
3.80 (0.1497)
0.50 (0.0196)
0.25 (0.0099)
1.27 (0.0500)
BSC
45°
1.75 (0.0688)
1.35 (0.0532)
0.25 (0.0098)
0.10 (0.0040)
8°
0°
0.51 (0.0201)
0.31 (0.0122)
COPLANARITY
0.10
1.27 (0.0500)
0.40 (0.0157)
0.25 (0.0098)
0.17 (0.0067)
SEATING
PLANE
COMPLIANT TO JEDEC STANDARDS MS-012-AA
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.
Figure 26. 8-Lead Standard Small Outline Package [SOIC_N]
Narrow Body (R-8)
Dimensions shown in millimeters and (inches)
0.400 (10.16)
0.365 (9.27)
0.355 (9.02)
8
1
5
4
0.280 (7.11)
0.250 (6.35)
0.240 (6.10)
0.325 (8.26)
0.310 (7.87)
0.300 (7.62)
0.100 (2.54)
BSC
0.060 (1.52)
MAX
0.195 (4.95)
0.130 (3.30)
0.115 (2.92)
0.210 (5.33)
MAX
0.015
(0.38)
MIN
0.150 (3.81)
0.130 (3.30)
0.115 (2.92)
0.015 (0.38)
GAUGE
0.014 (0.36)
0.010 (0.25)
0.008 (0.20)
PLANE
SEATING
PLANE
0.022 (0.56)
0.018 (0.46)
0.014 (0.36)
0.430 (10.92)
MAX
0.005 (0.13)
MIN
0.070 (1.78)
0.060 (1.52)
0.045 (1.14)
COMPLIANT TO JEDEC STANDARDS MS-001
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.
CORNER LEADS MAY BE CONFIGURED AS WHOLE OR HALF LEADS.
Figure 27. 8-Lead Plastic Dual-In-Line Package [PDIP]
Narrow Body
(N-8)
Dimensions shown in inches and (millimeters)
Rev. F | Page 11 of 12
AD780
Data Sheet
ORDERING GUIDE
Temperature
Qty. per
Model1
Initial Error Range
Temperature Coefficient
7 ppm/°C
7 ppm/°C
7 ppm/°C
7 ppm/°C
7 ppm/°C
3 ppm/°C
3 ppm/°C
3 ppm/°C
3 ppm/°C
3 ppm/°C
3 ppm/°C
3 ppm/°C
7 ppm/°C
7 ppm/°C
Package Description Package Option Tube/Reel
AD780ANZ
AD780AR
AD780AR-REEL7
AD780ARZ
AD780ARZ-REEL7
AD780BNZ
5.0 mV
5.0 mV
5.0 mV
5.0 mV
5.0 mV
1.0 mV
1.0 mV
1.0 mV
1.0 mV
1.0 mV
1.0 mV
1.0 mV
1.5 mV
1.5 mV
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
8-Lead PDIP
N-8
R-8
R-8
R-8
R-8
N-8
R-8
R-8
R-8
R-8
R-8
R-8
R-8
R-8
50
98
750
98
1,000
50
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead PDIP
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead SOIC_N
AD780BR
98
AD780BR-REEL
AD780BR-REEL7
AD780BRZ
AD780BRZ-REEL
AD780BRZ-REEL7
AD780CRZ
2,500
750
98
2,500
750
98
AD780CRZ-REEL7
1,000
1 Z = RoHS Compliant Part.
©2012 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D00841-0-12/12(F)
Rev. F | Page 12 of 12
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