Precision Low Drift SOT-23
Voltage Reference with Shutdown
ADR318
Initial accuracy: ±5 mV maximum, ±0.27% maximum
Low temperature coefficient: 25 ppm/°C maximum
Load regulation: 100 ppm/mA
Line regulation: 25 ppm/V
Low supply headroom: 0.6 V
Wide operating range: (VOUT + 0.6 V) to 15 V
Low power: 120 μA maximum
Shutdown to less than 3 μA maximum
Output current: 5 mA
Wide temperature range: 0°C to 70°C
Tiny 5-lead SOT-23 package
PIN CONFIGURATION
SHDN
1
VIN
2
VOUT(SENSE)
3
5
GND
4
VOUT(FORCE)
ADR318
TOP VIEW
(Not to Scale)
03431-001
FEATURES
Figure 1. 5-Lead SOT-23
APPLICATIONS
Battery-powered instrumentation
Portable medical instruments
Data acquisition systems
Industrial process control systems
Fault protection critical systems
GENERAL DESCRIPTION
The ADR3181 is a precision 1.8 V band gap voltage reference
featuring high accuracy, high stability, and low power
consumption in a tiny footprint. Patented temperature drift
curvature correction techniques minimize nonlinearity of the
voltage change with temperature. The wide operating range and
low power consumption with additional shutdown capability
make the part ideal for battery-powered applications. The
VOUT (SENSE) pin enables greater accuracy by supporting full
Kelvin operation in PCBs employing thin or long traces.
above the output voltage. This device is specified over the
industrial operating range of 0°C to 70°C, and is available in a
tiny 5-lead SOT-23 package.
The combination of VOUT (SENSE) and shutdown functions also
enables a number of unique applications, combining precision
reference/regulation with fault decision and overcurrent
protection.
See the Applications section for details.
The ADR318 is a low dropout voltage (LDV) device that
provides a stable output voltage from supplies as low as 600 mV
1
Protected by U.S. Patent No. 5,969,657; other patents pending.
Rev. A
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: 781.461.3113
©2006 Analog Devices, Inc. All rights reserved.
ADR318
TABLE OF CONTENTS
Features .............................................................................................. 1
Theory of Operation .........................................................................9
Applications....................................................................................... 1
Device Power Dissipation Considerations.................................9
Pin Configuration............................................................................. 1
Shutdown Mode Operation .........................................................9
General Description ......................................................................... 1
Applications..................................................................................... 10
Revision History ............................................................................... 2
Basic Voltage Reference Connection ....................................... 10
Specifications..................................................................................... 3
Electrical Characteristics............................................................. 3
Precision Negative Voltage Reference Without Precision
Resistors....................................................................................... 10
Absolute Maximum Ratings............................................................ 4
General-Purpose Current Source ............................................ 10
Thermal Resistance ...................................................................... 4
High Power Performance with Current Limit ........................... 10
ESD Caution.................................................................................. 4
Outline Dimensions ....................................................................... 12
Typical Performance Characteristics ............................................. 5
Ordering Guide .......................................................................... 12
Terminology ...................................................................................... 8
REVISION HISTORY
10/06—Rev. 0 to Rev. A
Updated Format..................................................................Universal
Changes to Ordering Guide .......................................................... 12
Updated Outline Dimensions ....................................................... 12
1/03—Revision 0: Initial Version
Rev. A | Page 2 of 12
ADR318
SPECIFICATIONS
ELECTRICAL CHARACTERISTICS
TA = TMIN to TMAX, VIN = 5 V, unless otherwise noted 1 .
Table 1.
Parameter
Initial Accuracy
Initial Accuracy Error
Temperature Coefficient
Minimum Supply Voltage Headroom
Line Regulation
Symbol
VO
VOERR
TCVO
VIN – VOUT
ΔVOUT/ΔVIN
Load Regulation
ΔVOUT/ΔILOAD
Quiescent Current
ISY
Voltage Noise
Turn-On Settling Time
Long-Term Stability 2
Output Voltage Hysteresis
Ripple Rejection Ratio
Short Circuit to Ground
eN
tR
ΔVOUT
VO_HYS
RRR
ISC
Shutdown Supply Current
Shutdown Logic Input Current
Shutdown Logic Low
Shutdown Logic High
ISHDN
ILOGIC
VINL
VINH
1
2
Conditions
Min
1.795
−0.27
0°C to 70°C
Typ
1.8
5
Max
1.802
+0.27
25
10
25
Unit
V
%
ppm/°C
mV
ppm/V
100
ppm/mA
120
140
μA
μA
μV p-p
μs
ppm/1000 hours
ppm
dB
mA
mA
μA
nA
V
V
600
VIN = 2.5 V to 15 V,
0°C < TA < 70°C
VIN = 3 V, ILOAD = 0 mA to 5 mA,
0°C < TA < 70°C
No load
0°C < TA < 70°C
0.1 Hz to 10 Hz
100
5
20
50
40
85
25
30
fIN = 60 Hz
VIN = 5.0 V
VIN = 15.0 V
3
500
0.8
2.4
TMIN = 0°C, TMAX = 70°C.
The long-term stability specification is noncumulative. The drift in subsequent 1000-hour periods is significantly lower than in the first 1000-hour period.
Rev. A | Page 3 of 12
ADR318
ABSOLUTE MAXIMUM RATINGS
At 25°C, unless otherwise noted.
Table 2.
Parameter
Supply Voltage
Output Short-Circuit Duration to GND
Storage Temperature Range: RJ-5 Package
Operating Temperature Range
Junction Temperature Range: RJ-5 Package
Lead Temperature Range (Soldering, 60 sec)
Rating
18 V
Observe derating
curves
–65°C to +125°C
0°C to 70°C
–65°C to +150°C
300°C
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
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
THERMAL RESISTANCE
θJA is specified for the worst-case conditions, that is, a device
soldered in a circuit board for surface-mount packages.
Table 3. Thermal Resistance
Package Type
5-Lead SOT-23 (RJ-5)
ESD CAUTION
Rev. A | Page 4 of 12
θJA
230
θJC
146
Unit
°C/W
ADR318
TYPICAL PERFORMANCE CHARACTERISTICS
1.802
0
1.801
1.800
MEAN
1.799
1.798
MEAN – STANDARD DEVIATION
0
10
20
30
40
50
60
70
TEMPERATURE (°C)
–10
–15
–20
–25
03431-002
VOUT (V)
MEAN + STANDARD DEVIATION
–5
0
10
20
30
40
50
60
70
TEMPERATURE (°C)
Figure 2. Typical Output Voltage vs. Temperature
03431-005
LINE REGULATION (ppm/mV)
VIN = 2.5V TO 15V
Figure 5. Line Regulation vs. Temperature
110
2.5
2.3
0°C
VIN_MIN (V)
25°C
90
0°C
25°C
2.1
70°C
70
2.5
5.0
7.5
10.0
15.0
12.5
INPUT VOLTAGE (V)
1.7
0
1
2
3
4
5
LOAD CURRENT (mA)
Figure 3. Supply Current vs. Input Voltage
Figure 6. Minimum Input Voltage vs. Load Current
VOLTAGE (2mV/DIV)
–40
10V
–50
–60
2.5V
–80
0
10
20
30
40
50
TEMPERATURE (°C)
60
70
TIME (400ms/DIV)
Figure 7. Typical Output Voltage Noise 0.1 Hz to 10 Hz
Figure 4. Load Regulation vs. Temperature
Rev. A | Page 5 of 12
03431-007
–70
03431-004
LOAD REGULATION (ppm/mA)
–30
03431-006
1.9
80
03431-003
SUPPLY CURRENT (µA)
70°C
100
ADR318
VL
LOAD ON
IL = 5mA
IL = 0mA
03431-011
TIME (10ms/DIV)
LOAD OFF
03431-008
VOLTAGE (10mV/DIV)
VOLTAGE (200mV/DIV)
VOUT
TIME (200µs/DIV)
Figure 8. Typical Output Voltage Noise 10 Hz to 10 kHz
Figure 11. Load Transient Response, CL = 0 nF
VIN
TIME (40µs/DIV)
LOAD OFF
VL
LOAD ON
IL = 5mA
IL = 0mA
03431-012
VOLTAGE (200mV/DIV)
VOUT
03431-009
VOLTAGE (50mV/DIV)
VOUT
TIME (200µs/DIV)
Figure 9. Line Transient Response, CBYPASS = 0 μF
Figure 12. Load Transient Response, CL = 1 nF
VIN
TIME (40µs/DIV)
LOAD OFF
VL
LOAD ON
IL = 5mA
IL = 0mA
TIME (200µs/DIV)
Figure 10. Line Transient Response, CBYPASS = 0.1 μF
Figure 13. Load Transient Response, CL = 100 nF
Rev. A | Page 6 of 12
03431-013
VOLTAGE (200mV/DIV)
VOUT
03431-010
VOLTAGE (50mV/DIV)
VOUT
ADR318
VOUT
TIME (40µs/DIV)
TIME (4µs/DIV)
Figure 14. Turn-On/Turn-Off Response at 5 V, RLOAD = 1.8 kΩ
Figure 16. Shutdown Pin Response
VOUT
03431-015
VOLTAGE (2V/DIV)
VIN
TIME (100µs/DIV)
SHUTDOWN PIN
Figure 15. Turn-On/Turn-Off Response at 5 V, RLOAD = 1.8 kΩ, CBYPASS = 0.1 μF
Rev. A | Page 7 of 12
03431-016
VOLTAGE (1V/DIV)
VOUT
03431-014
VOLTAGE (50mV/DIV)
VIN
ADR318
TERMINOLOGY
Temperature Coefficient
Temperature coefficient is the change of output voltage with
respect to operating temperature changes, normalized by the
output voltage at 25°C. This parameter is expressed in ppm/°C,
and can be determined with the following equation:
VO (T2 ) − VO (T1 )
ppm ⎤
=
× 10 6
TCVO ⎡⎢
⎥
⎣ °C ⎦ VO (25°C ) × (T2 − T1 )
(1)
where:
where:
VO(t0) = VO at 25°C at Time 0.
VO(t1) = VO at 25°C after 1000 hours of operation at 25°C.
Thermal Hysteresis
Thermal hysteresis is the change of output voltage after the
device is cycled through temperature from +25°C to −40°C to
+125°C and back to +25°C. This is a typical value from a sample
of parts put through such a cycle.
VO_HYS = VO(25°C) − VO_TC
VO(25°C) = VO at 25°C.
VO _ HYS [ppm ] =
VO(T1) = VO at Temperature 1.
VO (25°C ) − VO _ TC
VO(T2) = VO at Temperature 2.
Long-Term Stability
Long-term stability is the typical shift of output voltage at 25°C
on a sample of parts subjected to a test of 1000 hours at 25°C.
ΔVO = VO(t0) − VO(t1)
ΔVO [ppm ] =
VO (t 0 ) − VO (t1 )
VO (t 0 )
× 106
VO (25°C )
× 10 6
(3)
where:
VO(25°C) = VO at 25°C.
VO_TC = VO at 25°C after temperature cycle at +25°C to −40°C to
+125°C and back to +25°C.
(2)
Rev. A | Page 8 of 12
ADR318
THEORY OF OPERATION
Band gap references are the high performance solution for low
supply voltage and low power voltage reference applications,
and the ADR318 is no exception. The uniqueness of this lies in
its architecture. By observing Figure 17, the ideal zero
temperature coefficient (TC) band gap voltage is referenced to
the output, not to ground. Therefore, if noise exists on the
ground line, it is greatly attenuated on VOUT. The band gap cell
consists of the PNP pair, Q51 and Q52, running at unequal
current densities. The difference in voltage base emitter (VBE)
results in a voltage with a positive TC that is amplified by the
ratio of 2 × (R58/R54). This proportional-to-absolute
temperature (PTAT) voltage, combined with VBE Q51 and VBE
Q52, produces the stable band gap voltage.
Reduction in band gap curvature is performed by the ratio of
the resistors R44 and R59, one of which is linearly temperature
dependent. Precision laser-trimming and other patented circuit
techniques are used to further enhance the drift performance.
VIN
Q1
Q51
R49
R53
TA = the ambient temperatures.
PD = the device power dissipation.
03431-017
GND
(4)
TJ = the junction temperature.
Q52
R61
θ JA
where:
R48
R60
T J − TA
The ADR318 includes a shutdown feature that is TTL/CMOS
compatible. A logic low or a 0 V condition on the SHDN pin is
required to turn the device off. During shutdown, the output of
the reference becomes a high impedance state where its
potential would then be determined by external circuitry. If the
shutdown feature is not used, the SHDN pin should be
connected to VIN (Pin 2).
R44
R54
SHDN
PD =
SHUTDOWN MODE OPERATION
VOUT(FORCE)
R58
The ADR318 is capable of delivering load currents up to 5 mA
with an input voltage that ranges from 2.4 V to 15 V. When this
device is used in applications with high input voltages, care
should be taken to avoid exceeding the specified maximum
power dissipation or junction temperature. Doing so results in
premature device failure. The following formula should be used
to calculate the device’s maximum junction temperature or
dissipation:
θJA = the device package thermal resistance.
VOUT(SENSE)
R59
DEVICE POWER DISSIPATION CONSIDERATIONS
Figure 17. Simplified Schematic
Rev. A | Page 9 of 12
ADR318
APPLICATIONS
BASIC VOLTAGE REFERENCE CONNECTION
GENERAL-PURPOSE CURRENT SOURCE
The circuit in Figure 18 illustrates the basic configuration for
the ADR318. Decoupling capacitors are not required for circuit
stability. The ADR318 is capable of driving capacitative loads
from 0 μF to 10 μF. However, a 0.1 μF ceramic output capacitor
is recommended to absorb and deliver the charge as is required
by a dynamic load.
Many times in low power applications, the need arises for a
precision current source that can operate on low supply
voltages. As shown in Figure 20, the ADR318 can be configured
as a precision current source. The illustrated circuit
configuration is a floating current source with a grounded load.
The reference output voltage is bootstrapped across R1 that sets
the output current into the load. With this configuration, circuit
precision is maintained for load currents in the range of the
reference supply current, typically 90 mA, to approximately 5 mA.
The supply current is a function of ISET and increases slightly at
a given ISET.
ADR318
GND
SHDN
SHUTDOWN
INPUT
VIN
CI
0.1µF
VOUT(S)
VOUT(F)
+VDD
OUTPUT
VIN
03431-018
U1
ADR318
Figure 18. Voltage Reference Connection
SHDN
VOUT(F)
VOUT(S)
PRECISION NEGATIVE VOLTAGE REFERENCE
WITHOUT PRECISION RESISTORS
GND
R1
0.1µF
A negative reference can be easily generated by combining the
ADR318 with an op amp. Figure 19 shows this simple negative
reference configuration. VOUT(F) and VOUT(S) are at virtual ground
and therefore the negative reference can be taken directly from
the output of the op amp. The op amp should be a dual-supply,
low offset, rail-to-rail amplifier, such as the OP1177.
ISY (ISET )
RL
ISET
ISY
ADJ
IOUT = ISET + ISV (ISET)
03431-020
CO
0.1µF
Figure 20. General-Purpose Current Source
+VDD
HIGH POWER PERFORMANCE WITH CURRENT LIMIT
VIN
In some cases, the user may want higher output current
delivered to a load and still achieve better than 0.5% accuracy
out of the ADR318. The accuracy for a reference is normally
specified with no load (see the Specifications section). However,
the output voltage changes with the load current.
ADR318
VOUT(F)
SHDN
VOUT(S)
GND
–VSS
03431-019
–VREF
OP1177
The circuit in Figure 21 provides high current without
compromising the accuracy of the ADR318. The power bipolar
junction transistor (BJT) Q1 provides the required current, up
to 1 A. The ADR318 delivers the base drive to Q1 through the
force pin. The sense pin of the ADR318 is a regulated output
and is connected to the load.
Figure 19. Negative Reference
Rev. A | Page 10 of 12
ADR318
The transistor Q2 protects Q1 during short-circuit limit faults
by robbing its base drive. The maximum current is IL, MAX =
0.6 V/RS.
A similar circuit function can also be achieved using the
Darlington transistor configuration, as shown in Figure 22.
VIN
VIN
R1
4.7kΩ
VIN
ADR318
SHDN
VIN
ADR318
SHDN
GND
GND
VOUT(S) VOUT(F)
VOUT(S) VOUT(F)
Q1
Q1
Q2
RS
Q2
RS
RL
03431-021
RL
03431-022
R1
4.7kΩ
Figure 22. High Output Current with Darlington Drive Configuration
Figure 21. High Power Performance with Current Limit
Rev. A | Page 11 of 12
ADR318
OUTLINE DIMENSIONS
2.90 BSC
5
4
2.80 BSC
1.60 BSC
1
2
3
PIN 1
0.95 BSC
1.90
BSC
1.30
1.15
0.90
1.45 MAX
0.15 MAX
0.50
0.30
0.22
0.08
SEATING
PLANE
10°
5°
0°
0.60
0.45
0.30
COMPLIANT TO JEDEC STANDARDS MO-178-AA
Figure 23. 5-Lead Small Outline Transistor Package [SOT-23]
(RJ-5)
Dimensions shown in millimeters
ORDERING GUIDE
Model
ADR318ARJ-R2
ADR318ARJ-REEL
ADR318ARJ-REEL7
ADR318ARJZ-REEL71
1
Temperature
Range
0°C to 70°C
0°C to 70°C
0°C to 70°C
0°C to 70°C
Package
Description
5-Lead SOT-23
5-Lead SOT-23
5-Lead SOT-23
5-Lead SOT-23
Package
Option
RJ-5
RJ-5
RJ-5
RJ-5
Z = Pb-free part.
©2006 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
C03431-0-10/06(A)
Rev. A | Page 12 of 12
Branding
REA
REA
REA
L28
Output
Voltage
1.800 V
1.800 V
1.800 V
1.800 V
Ordering
Quantity
250
10,000
3,000
3,000
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