Precision Low Drift SOT-23
Voltage Reference with Shutdown
ADR318
Rev. A
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Tel: 781.329.4700 www.analog.com
Fax: 781.461.3113 ©2006 Analog Devices, Inc. All rights reserved.
FEATURES PIN CONFIGURATION
1
SHDN
5
GND
2
V
IN
3
V
OUT(SENSE) 4
V
OUT(FORCE)
ADR318
TOP VIEW
(Not to Scale)
03431-001
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
Figure 1. 5-Lead SOT-23
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
APPLICATIONS
Battery-powered instrumentation
Portable medical instruments
Data acquisition systems
Industrial process control systems
Fault protection critical systems
GENERAL DESCRIPTION
The ADR318 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.
The ADR318 is a low dropout voltage (LDV) device that
provides a stable output voltage from supplies as low as 600 mV
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.
ADR318
Rev. A | Page 2 of 12
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications....................................................................................... 1
Pin Configuration............................................................................. 1
General Description......................................................................... 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Electrical Characteristics............................................................. 3
Absolute Maximum Ratings............................................................ 4
Thermal Resistance ...................................................................... 4
ESD Caution.................................................................................. 4
Typical Performance Characteristics ............................................. 5
Terminology ...................................................................................... 8
Theory of Operation .........................................................................9
Device Power Dissipation Considerations.................................9
Shutdown Mode Operation .........................................................9
Applications..................................................................................... 10
Basic Voltage Reference Connection ....................................... 10
Precision Negative Voltage Reference Without Precision
Resistors....................................................................................... 10
General-Purpose Current Source ............................................ 10
High Power Performance with Current Limit ........................... 10
Outline Dimensions ....................................................................... 12
Ordering Guide .......................................................................... 12
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
ADR318
Rev. A | Page 3 of 12
SPECIFICATIONS
ELECTRICAL CHARACTERISTICS
TA = TMIN to TMAX, VIN = 5 V, unless otherwise noted1.
Table 1.
Parameter Symbol Conditions Min Typ Max Unit
Initial Accuracy VO 1.795 1.8 1.802 V
Initial Accuracy Error VOERR −0.27 +0.27 %
Temperature Coefficient TCVO 0°C to 70°C 5 25 ppm/°C
Minimum Supply Voltage Headroom VIN – VOUT 600 mV
Line Regulation ΔVOUT/ΔVIN VIN = 2.5 V to 15 V, 10 25 ppm/V
0°C < TA < 70°C
Load Regulation ΔVOUT/ΔILOAD VIN = 3 V, ILOAD = 0 mA to 5 mA,
0°C < TA < 70°C
100 ppm/mA
Quiescent Current ISY No load 100 120 μA
0°C < TA < 70°C 140 μA
Voltage Noise eN 0.1 Hz to 10 Hz 5 μV p-p
Turn-On Settling Time tR 20 μs
Long-Term Stability2ΔVOUT 50 ppm/1000 hours
Output Voltage Hysteresis VO_HYS 40 ppm
Ripple Rejection Ratio RRR fIN = 60 Hz 85 dB
Short Circuit to Ground ISC VIN = 5.0 V 25 mA
V
IN = 15.0 V 30 mA
Shutdown Supply Current ISHDN 3 μA
Shutdown Logic Input Current ILOGIC 500 nA
Shutdown Logic Low VINL 0.8 V
Shutdown Logic High VINH 2.4 V
1 TMIN = 0°C, TMAX = 70°C.
2 The long-term stability specification is noncumulative. The drift in subsequent 1000-hour periods is significantly lower than in the first 1000-hour period.
ADR318
Rev. A | Page 4 of 12
ABSOLUTE MAXIMUM RATINGS
At 25°C, unless otherwise noted.
Table 2.
Parameter Rating
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.
Supply Voltage 18 V
Output Short-Circuit Duration to GND Observe derating
curves
Storage Temperature Range: RJ-5 Package –65°C to +125°C THERMAL RESISTANCE
Operating Temperature Range 0°C to 70°C θJA is specified for the worst-case conditions, that is, a device
soldered in a circuit board for surface-mount packages.
Junction Temperature Range: RJ-5 Package –65°C to +150°C
Lead Temperature Range (Soldering, 60 sec) 300°C
Table 3. Thermal Resistance
Package Type θJA θ
JC Unit
5-Lead SOT-23 (RJ-5) 230 146 °C/W
ESD CAUTION
ADR318
Rev. A | Page 5 of 12
TYPICAL PERFORMANCE CHARACTERISTICS
1.802
1.801
1.800
1.799
1.798
0 10203040506070
V
OUT
(V)
TEMPERATURE (°C)
03431-002
MEAN + STANDARD DEVIATION
MEAN
MEAN – STANDARD DEVIATION
Figure 2. Typical Output Voltage vs. Temperature
110
100
90
80
70
2.5 15.0
70°C
25°C
0°C
12.510.07.55.0
SUPPLY CURRENT (µA)
INPUT VOLTAGE (V)
03431-003
Figure 3. Supply Current vs. Input Voltage
–
30
–40
–50
–60
–70
–80
07
0605040302010
LOAD REGULATION (ppm/mA)
TEMPERATURE (°C)
2.5V
10V
03431-004
0
0
–5
–10
–15
–20
–25
07605040302010
LINE REGULATION (ppm/mV)
TEMPERATURE (°C)
03431-005
V
IN
= 2.5V TO 15V
Figure 5. Line Regulation vs. Temperature
2.5
70°C
25°C
0°C
2.3
2.1
1.9
1.7
054321
V
IN_MIN
(V)
LOAD CURRENT (mA)
03431-006
Figure 6. Minimum Input Voltage vs. Load Current
VOLTAGE (2mV/DIV)
TIME (400ms/DIV)
03431-007
Figure 7. Typical Output Voltage Noise 0.1 Hz to 10 Hz Figure 4. Load Regulation vs. Temperature
ADR318
Rev. A | Page 6 of 12
VOLTAGE (200mV/DIV)
TIME (200µs/DIV)
LOAD OFF LOAD ON
V
OUT
V
L
03431-011
I
L
= 5mA
I
L
= 0mA
VOLTAGE (10mV/DIV)
TIME (10ms/DIV)
03431-008
Figure 8. Typical Output Voltage Noise 10 Hz to 10 kHz Figure 11. Load Transient Response, CL = 0 nF
VOLTAGE (200mV/DIV)
TIME (200µs/DIV)
LOAD OFF LOAD ON
03431-012
V
OUT
V
L
I
L
= 5mA
I
L
= 0mA
VOLTAGE (50mV/DIV)
TIME (40µs/DIV)
03431-009
V
IN
V
OUT
Figure 9. Line Transient Response, CBYPASS = 0 μF Figure 12. Load Transient Response, CL = 1 nF
VOLTAGE (200mV/DIV)
TIME (200µs/DIV)
LOAD OFF LOAD ON
03431-013
V
OUT
V
L
I
L
= 5mA
I
L
= 0mA
VOLTAGE (50mV/DIV)
TIME (40µs/DIV)
03431-010
V
IN
V
OUT
Figure 10. Line Transient Response, CBYPASS = 0.1 μF Figure 13. Load Transient Response, CL = 100 nF
ADR318
Rev. A | Page 7 of 12
VOLTAGE (50mV/DIV)
TIME (40µs/DIV)
V
IN
V
OUT
03431-014
VOLTAGE (1V/DIV)
TIME (4µs/DIV)
V
OUT
SHUTDOWN PIN
03431-016
Figure 14. Turn-On/Turn-Off Response at 5 V, RLOAD = 1.8 kΩ Figure 16. Shutdown Pin Response
VOLTAGE (2V/DIV)
TIME (100µs/DIV)
V
IN
V
OUT
03431-015
Figure 15. Turn-On/Turn-Off Response at 5 V, RLOAD = 1.8 kΩ, CBYPASS = 0.1 μF
ADR318
Rev. A | Page 8 of 12
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:
() ()
()
()
6
10
C25C
ppm ×
−×°
−
=
⎥
⎦
⎤
⎢
⎣
⎡
°12
O
1
O
2
O
OTTV
TVTV
TCV (1)
where:
VO(25°C) = VO at 25°C.
VO(T1) = VO at Temperature 1.
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)
[]
()
()
()
6
10ppm ×
−
=Δ
0
O
1
O
0
O
OtV
tVtV
V (2)
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
[]
(
)
()
6
_
_10
C25
C25
ppm ×
°
−°
=
O
TCO
O
HYSO V
VV
V (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.
ADR318
Rev. A | Page 9 of 12
THEORY OF OPERATION
DEVICE POWER DISSIPATION CONSIDERATIONS
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
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:
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.
JA
A
J
Dθ
T
T
P
−
= (4)
where:
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.
TJ = the junction temperature.
TA = the ambient temperatures.
PD = the device power dissipation.
SHDN
GND
Q51
R54
R59
Q1
R44
R49R58
R60 R61
R48
R53
Q52
V
OUT(FORCE)
V
OUT(SENSE)
V
IN
03431-017
θJA = the device package thermal resistance.
SHUTDOWN MODE OPERATION
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).
Figure 17. Simplified Schematic
ADR318
Rev. A | Page 10 of 12
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.
SHUTDOWN
INPUT
SHDN
ADR318
GND
V
OUT(F)
V
OUT(S)
V
IN
OUTPUT
C
I
0.1µF
C
O
0.1µF
03431-018
+VDD
U1
ADR318
SHDN VOUT(F)
VOUT(S)
GND R1
RL
ISY (ISET)
ISY
ADJ
0.1µF
IOUT = ISET + ISV (ISET)
ISET
VIN
03431-020
Figure 18. Voltage Reference Connection
PRECISION NEGATIVE VOLTAGE REFERENCE
WITHOUT PRECISION RESISTORS
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.
Figure 20. General-Purpose Current Source
HIGH POWER PERFORMANCE WITH CURRENT LIMIT
+V
DD
–VREF
OP1177
ADR318
SHDN
V
OUT(S)
V
OUT(F)
GND
V
IN
–V
SS
03431-019
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.
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
ADR318
Rev. A | Page 11 of 12
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.
ADR318
SHDN GND
V
OUT(F)
V
OUT(S)
V
IN
V
IN
R
S
R1
4.7kΩ
Q1
Q2
R
L
03431-022
ADR318
SHDN GND
V
OUT(F)
V
OUT(S)
V
IN
V
IN
R
S
R1
4.7kΩ
R
L
Q1
Q2
03431-021
Figure 22. High Output Current with Darlington Drive Configuration
Figure 21. High Power Performance with Current Limit
ADR318
Rev. A | Page 12 of 12
OUTLINE DIMENSIONS
PIN 1
1.60 BSC 2.80 BSC
1.90
BSC
0.95 BSC
5
123
4
0.22
0.08 10°
5°
0°
0.50
0.30
0.15 MAX SEATING
PLANE
1.45 MAX
1.30
1.15
0.90
2.90 BSC
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
Temperature
Range
Package
Description
Package
Option Branding
Output
Voltage
Ordering
Quantity
ADR318ARJ-R2 0°C to 70°C 5-Lead SOT-23 RJ-5 REA 1.800 V 250
ADR318ARJ-REEL 0°C to 70°C 5-Lead SOT-23 RJ-5 REA 1.800 V 10,000
ADR318ARJ-REEL7 0°C to 70°C 5-Lead SOT-23 RJ-5 REA 1.800 V 3,000
ADR318ARJZ-REEL71 0°C to 70°C 5-Lead SOT-23 RJ-5 L28 1.800 V 3,000
1 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)
