ANALOG DEVICES AD780 Service Manual
2.5 V/3.0 V
T
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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/√
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)
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.
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.
Hz
High Precision Reference
FUNCTIONAL BLOCK DIAGRAM
+V
IN
AD780
R10
1
NC
3
EMP
NC = NO CONNECT
Q6
R11
Q7
R5
R4
48
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/√
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.
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.
. This can be further reduced, if
Hz
NC
72
R14
O/P SELECT
2.5V – NC
3.0V – GND
R13
R16
R15
AD780
6
V
OUT
5
TRIM
00841-001
AD780
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ABLE OF CONTENTS
T
Specifications.................................
.................................................... 3
Supply Current Over Temperature .............................................8
Absolute Maximum Ratings............................................................ 4
Notes............................................................................................... 4
ESD Caution.................................................................................. 4
Th
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
EVISION HISTORY
R
5/04—Data Sheet Chang
Updated Format..............................................................
Changes to Temperature Transducer Circuit section...................8
C
hanges to Ordering Guide...........................................................12
ed from Rev. D to Rev. E
....Universal
Turn -On Ti me ...............................................................................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
O
utline Dimensions....................................................................... 11
Ordering Guide............................................................................... 12
1/04—Data Sheet Changed from Rev. C to Rev. D.
Changes to SPECIFICATIONS......................................
Updated ORDERING GUIDE.........................................................3
pdated OUTLINE DIMENSIONS .............................................10
U
5/02—Data Sheet Changed from Rev. B to Rev. C.
Updates to packages........................................................
..................2
....................10
Rev. E | Page 2 of 12
AD780
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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 DRIFT
−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, T
3.0 V Output, 4.5 V ≤+VIN ≤ 36 V, T
LOAD REGULATION, SERIES MODE
Sourcing 0 mA < I
T
to T
MIN
MAX
Sinking −10 mA < I
−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 < I
< 10 mA 75 75 75 µV/mA
SHUNT
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
LONG-TERM STABILITY
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)
1
Maximum output voltage drift is guaranteed for all packages.
2
3.0 V mode typically adds 100 µA to the quiescent current. Also, Iq increases by 2 µA/V above an input voltage of 5 V.
3
The 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.
4
The 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.
1
to T
MIN
to T
MIN
< 10 mA 50 50 50 µV/mA
OUT
10 10 10 µV/V
MAX
10 10 10 µV/V
MAX
75 75 75 µV/mA
< 0 mA 75 75 75 µV/mA
OUT
3
4
20 20 20 ± ppm/1000 Hr
–55 +125 –55 +125 –55 +125 °C
nV/√Hz
Rev. E | Page 3 of 12
AD780
T
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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)
Output Protection
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.
NC
1
2
+V
IN
EMP
3
4
GND
300°C
Output safe for indefinite short to
ground and momentary short to V
2.5V/3.0V O/PSELECT
8
(NC OR GND)
7
AD780
TOP VIEW
(Not to Scale)
NC
V
6
OUT
5
TRIM
.
IN
GND TEMP +V
TRIM 2.5V/3.0V
V
OUT
Figure 3. Die Layout
IN
GND
O/P SELECT
NOTES
Both V
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.
pads should be connected to the output.
OUT
00841-003
NC = NO CONNECT
Figure 2. Pin Configuration, 8-Lead PDIP and SOIC Packages
00841-002
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 S ur fa ce: 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. E | Page 4 of 12
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