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PDF AD780 Data sheet ( Hoja de datos )
| Número de pieza | AD780 | |
| Descripción | 2.5 V/3.0 V High Precision Reference | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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Data Sheet
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)
GENERAL 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 analog-to-digital converters (ADCs) and
digital-to-analog converters (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.
2.5 V/3.0 V
High Precision Reference
AD780
FUNCTIONAL BLOCK DIAGRAM
+VIN
2
DNC
7
AD780
DNC 1
R10
R11
TEMP 3
Q6
R5
Q7
R4
6 VOUT
R13
R16
5 TRIM
R14
R15
48
GND
O/P SELECT
2.5V – DNC
DNC = DO NOT CONNECT TO THIS PIN 3.0V – GND
Figure 1.
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. H
Document Feedback
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.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 ©1993–2015 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com
1 page  
AD780
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter
+VIN to Ground
TRIM Pin to Ground
TEMP Pin to Ground
Power Dissipation (25°C)
Storage Temperature
Lead Temperature
(Soldering 10 sec)
Output Protection
ESD Classification
Values
36 V
36 V
36 V
500 mW
−65°C to +150°C
300°C
Output safe for indefinite short to
ground and momentary short to VIN.
Class 1 (1000 V)
Stresses at or above those listed under Absolute Maximum
Ratings may cause permanent damage to the product. This is a
stress rating only; functional operation of the product at these
or any other conditions above those indicated in the operational
section of this specification is not implied. Operation beyond
the maximum operating conditions for extended periods may
affect product reliability.
DNC 1
2.5V/3.0V O/PSELECT
8 (DNC OR GND)
+VIN 2 AD780 7 DNC
TEMP 3 TOP VIEW 6 VOUT
GND 4 (Not to Scale) 5 TRIM
NOTES
1. DNC = DO NOT CONNECT TO THIS PIN.
Figure 2. Pin Configuration, 8-Lead PDIP and SOIC Packages
Table 3. Die Physical Characteristics
Parameter
Value
Die Size
67 × 96
Back Grind Thickness
10
Bond Pad Opening Size
89 × 136
Top Metal Composition
AlCu (0.5%)
Passivation
Oxynitride
Polyimide
None
Die Marker
780
Substrate Bias
GND
Units
mil
mil
µm
%
µm
V
Data Sheet
GND TEMP
96 mils
+VIN
67 mils
GND
TRIM
VOUT
2.5V/3.0V
O/P SELECT
Figure 3. Die Layout
NOTES
Both VOUT pads must be connected to the output.
Die Thickness: The standard thickness of Analog Devices, Inc.
bipolar dice is 10 mil ± 1 mil.
Die Dimensions: The dimensions given are the maximum possible
die size.
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 Surface: The standard top surface of the die is covered by a
layer of passivation. All areas are covered except bonding pads
and scribe lines.
Surface Metallization: The metallization to Analog Devices
bipolar dice is aluminum/copper. The 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 3.5 mil by 5.3 mil.
ESD CAUTION
Rev. H | Page 4 of 12
5 Page 
AD780
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.
5V
AD7884
2
+VIN
VOUT 6
VREF + F
1µF AD780
GND
4
2.5V/3.0V
SELECT
8
VREF + S
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.
5V
AD7710
1µF
100nF
2
+VIN
VOUT 6
AD780
3
2.5V/3.0V
GND O/P SELECT
48
REF IN+
100µF
REF IN–
Figure 22. Precision 2.5 V or 3.0 V Reference for the
AD7710 High Resolution, Σ-Δ 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.
Data Sheet
VSUPPLY
2
6
AD780
4
0.1µF 1kΩ
3+ 7
OP90
2– 4
6
0.1µF
2N2907
2.5kΩ
10µF
3.9Ω
VOUT
0.1µF
5kΩ
0.01%
4kΩ
0.01%
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 GND pin of the AD780 to a negative supply via a bias resistor,
as shown in Figure 25.
2
+VIN
7
DNC
1 DNC
VOUT 6
1µF AD780
TRIM 5
3 TEMP
GND
4
O/P SELECT
2.5V – DNC
3.0V – GND
8
R
=
VOUT – (V–)
IL + IS MIN
V–
–2.5 VOUT
NOTES
1. IL = LOAD CURRENT
2. IS MIN = MINIMUM SHUNT CURRENT
3. DNC = DO NOT CONNECT TO THIS PIN
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.
+5V
+VIN
2
1kΩ
+5V
OUT AD780
68
4
–
OP07
+
2N3906
CONNECT IF
–3V OUTPUT
DESIRED
–2.5V (IL ≤ 100mA)
–5V
–5V
1000pF
Figure 25. −2.5 V High Load Current Reference
Rev. H | Page 10 of 12
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet AD780.PDF ] | |
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