Low Noise, Micropower
5.0 V Precision Voltage Reference
ADR293
Rev. D
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FEATURES
6.0 V to 15 V supply range
Supply current: 15 μA maximum
Low noise: 15 μV p-p typical (0.1 Hz to 10 Hz)
High output current: 5 mA
Temperature range: −40°C to +125°C
Pin-compatible with the REF02/REF19x
APPLICATIONS
Portable instrumentation
Precision reference for 5 V systems
ADC and DAC reference
Solar-powered applications
Loop-current powered instruments
PIN CONFIGURATIONS
NC
1
V
IN 2
NC
3
GND
4
NC
8
NC
7
V
OUT
6
NC
5
NC = NO CONNECT
ADR293
TOP VIEW
(Not to Scale)
00164-001
Figure 1. 8-Lead Narrow Body SOIC (R-8)
TOP VIEW
(Not to Scale)
1
2
3
4
ADR293
V
IN
NC
GND
NC
8
7
6
5
NC
V
OUT
NC
NC
NC = NO CONNECT
00164-002
Figure 2. 8-Lead TSSOP (RU-8)
GENERAL DESCRIPTION
The ADR293 is a low noise, micropower precision voltage
reference that utilizes an XFET® (eXtra implanted junction FET)
reference circuit. The XFET architecture offers significant
performance improvements over traditional band gap and
buried Zener-based references. Improvements include one
quarter the voltage noise output of band gap references
operating at the same current, very low and ultralinear
temperature drift, low thermal hysteresis, and excellent long-
term stability.
The ADR293 is a series voltage reference providing stable and
accurate output voltage from a 6.0 V supply. Quiescent current
is only 15 μA maximum, making this device ideal for battery
powered instrumentation. Three electrical grades are available
offering initial output accuracy of ±3 mV, ±6 mV, and ±10 mV.
Temperature coefficients for the three grades are 8 ppm/°C,
15 ppm/°C, and 25 ppm/°C maximum. Line regulation and load
regulation are typically 30 ppm/V and 30 ppm/mA, respectively,
maintaining the reference’s overall high performance.
The ADR293 is specified over the extended industrial
temperature range of –40°C to +125°C. This device is available
in the 8-lead SOIC and 8-lead TSSOP packages.
Table 1. ADR29x Products
Device
Output
Voltage (V)
Initial
Accuracy (%)
Temperature
Coefficient
(ppm/°C max)
ADR291 2.500 0.08, 0.12, 0.24 8, 15, 25
ADR292 4.096 0.07, 0.10, 0.15 8, 15, 25
ADR293 5.000 0.06, 0.12, 0.20 8, 15, 25
ADR293
Rev. D | Page 2 of 12
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications ....................................................................................... 1
Pin Configurations ........................................................................... 1
General Description ......................................................................... 1
Revision History ............................................................................... 2
Specifications ..................................................................................... 3
Electrical Specifications ............................................................... 3
Absolute Maximum Ratings ............................................................ 5
Thermal Resistance ...................................................................... 5
ESD Caution .................................................................................. 5
Typical Performance Characteristics ............................................. 6
Terminology .......................................................................................9
Theory of Operation ...................................................................... 10
Device Power Dissipation Considerations .............................. 10
Basic Voltage Reference Connections ..................................... 10
Noise Performance ..................................................................... 10
Turn-On Time ............................................................................ 10
Applications ..................................................................................... 11
Kelvin Connections .................................................................... 11
Voltage Regulator for Portable Equipment ............................. 11
Outline Dimensions ....................................................................... 12
Ordering Guide .......................................................................... 12
REVISION HISTORY
5/11—Rev. C to Rev. D
Delete Negative Precision Reference Without Precision
Resistors Section ............................................................................. 11
Delete Figure 23 and Figure 24, Renumbered Sequentially ...... 11
9/10—Rev. B to Rev. C
Changes to Table 2 and Table 3 ....................................................... 3
Changes to Table 4 ............................................................................ 4
Changes to Figure 10, Figure 11, Figure 13 ................................... 7
Changes to Captions for Figure 17 to Figure 19 ........................... 8
6/07—Rev. A to Rev. B
Updated Format .................................................................. Universal
Changes to Table 1 ............................................................................. 1
Updated Outline Dimensions ....................................................... 13
Changes to Ordering Guide .......................................................... 13
3/01—Rev. 0 to Rev. A
ADR293
Rev. D | Page 3 of 12
SPECIFICATIONS
ELECTRICAL SPECIFICATIONS
VS = 6.0 V, TA = 25°C, unless otherwise noted.
Table 2.
Parameter Symbol Conditions Min Typ Max Unit
OUTPUT VOLTAGE VOUT I
OUT = 0 mA
E Grade 4.997 5.000 5.003 V
F Grade 4.994 5.000 5.006 V
G Grade 4.990 5.000 5.010 V
INITIAL ACCURACY IOUT = 0 mA
E Grade –3 +3 mV
0.06 %
F Grade –6 +6 mV
0.12 %
G Grade –10 +10 mV
0.20 %
LINE REGULATION ΔVOUT /ΔVIN 6.0 V to 15 V, IOUT = 0 mA
E, F Grades 30 100 ppm/V
G Grade 40 150 ppm/V
LOAD REGULATION ΔVOUT /ΔILOAD V
S = 6.0 V, IOUT = 0 mA to 5 mA
E, F Grades 30 100 ppm/mA
G Grade 40 150 ppm/mA
LONG-TERM STABILITY ΔVOUT After 1000 hours of operation @ 125°C 50 ppm
VOLTAGE NOISE eN p-p f = 0.1 Hz to 10 Hz 15 μV p-p
VOLTAGE NOISE DENSITY eN f = 1 kHz 640 nV/√Hz
VS = 6.0 V, TA = −25°C to +85°C, unless otherwise noted.
Table 3.
Parameter Symbol Conditions Min Typ Max Unit
TEMPERATURE COEFFICIENT TCVOUT I
OUT = 0 mA
E Grade 3 8 ppm/°C
F Grade 5 15 ppm/°C
G Grade 10 25 ppm/°C
LINE REGULATION ΔVOUT/ΔVIN 6.0 V to 15 V, IOUT = 0 mA
E, F Grades 35 150 ppm/V
G Grade 50 200 ppm/V
LOAD REGULATION ΔVOUT/ΔILOAD V
S = 6.0 V, IOUT = 0 mA to 5 mA
E, F Grades 20 150 ppm/mA
G Grade 30 200 ppm/mA
ADR293
Rev. D | Page 4 of 12
VS = 6.0 V, TA = −40°C to +125°C, unless otherwise noted.
Table 4.
Parameter Symbol Conditions Min Typ Max Unit
TEMPERATURE COEFFICIENT TCVOUT I
OUT = 0 mA
E Grade 3 10 ppm/°C
F Grade 5 20 ppm/°C
G Grade 10 30 ppm/°C
LINE REGULATION ΔVOUT/ΔVIN 6.0 V to 15 V, IOUT = 0 mA
E, F Grades 40 200 ppm/V
G Grade 70 250 ppm/V
LOAD REGULATION ΔVOUT/ΔILOAD V
S = 6.0 V, IOUT = 0 mA to 5 mA
E, F Grades 20 200 ppm/mA
G Grade 30 300 ppm/mA
SUPPLY CURRENT IS @ 25°C 11 15 μA
15 20 μA
THERMAL HYSTERESIS VOUT-HYS 8-lead SOIC_N 72 ppm
8-lead TSSOP 157 ppm
ADR293
Rev. D | Page 5 of 12
ABSOLUTE MAXIMUM RATINGS
THERMAL RESISTANCE
Table 5.
Parameter Rating
Supply Voltage 18 V
Output Short-Circuit Duration to GND Indefinite
Storage Temperature Range −65°C to +150°C
Operating Temperature Range −40°C to +125°C
Junction Temperature Range −65°C to +150°C
Lead Temperature (Soldering, 60 sec) 300°C
θJA is specified for worst-case conditions; that is, θJA is specified
for the device in socket testing. In practice, θJA is specified for
the device soldered in a circuit board.
Table 6. Thermal Resistance
Package Type θJA θ
JC Unit
8-Lead SOIC_N (R-8) 158 43 °C/W
8-Lead TSSOP (RU-8) 240 43 °C/W
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.
ESD CAUTION
ADR293
Rev. D | Page 6 of 12
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, unless otherwise noted.
5.006
5.004
5.002
5.000
4.998
4.996
4.994
OUTPUT VOL
T
AGE (V)
–50 –25 0 25 50 75 100 125
TEMPERATURE (°C)
V
S
= 6V 3 TYPICAL PARTS
00164-003
Figure 3. VOUT vs. Temperature
16
14
12
10
8
6
4
2
0
SUPPLY CURRENT (µA)
0 2 4 6 8 10 12 14 16
INPUT VOLTAGE (V)
T
A
= +125°C
T
A
= +25°C
T
A
= –40°C
00164-004
Figure 4. Supply Current vs. Input Voltage
VS = 6V
16
14
12
10
8
6
SUPPLY CURRENT (µA)
–50 –25 0 25 50 75 100 125
TEMPERATURE (°C)
00164-005
Figure 5. Supply Current vs. Temperature
100
80
60
40
20
0
LINE REGUL
A
TION (ppm/V)
–50 –25 0 25 50 75 100 125
TEMPERATURE (°C)
VS = 6V TO 15V
00164-006
Figure 6. Line Regulation vs. Temperature
100
80
60
40
20
0
LINE REGUL
A
TION (ppm/V)
–50 –25 0 25 50 75 100 125
TEMPERATURE (°C)
V
S
= 6V TO 9V
00164-007
I
OUT
= 0mA
Figure 7. Line Regulation vs. Temperature
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
DIFFERENTI
A
L VOLTAGE (V)
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
LOAD CURRENT (mA)
00164-008
T
A
= +125°C
T
A
= +25°C
T
A
= –40°C
Figure 8. Minimum Input/Output Voltage Differential vs. Load Current
ADR293
Rev. D | Page 7 of 12
200
160
120
80
40
0
LOAD REGUL
A
TION (ppm/mA)
–50 –25 0 25 50 75 100 125
TEMPERATURE (°C)
00164-009
V
S
= 6V
I
OUT
= 5mA
I
OUT
= 1mA
Figure 9. Load Regulation vs. Temperature
2
1
0
–1
–2
–3
–4
∆V
OUT
FROM NOMIN
A
L (mV)
0.1 1 10
SOURCING LOAD CURRENT (mA)
00164-010
T
A
= +125°C
T
A
= +25°C
T
A
= –40°C
Figure 10. ΔVOUT from Nominal vs. Load Current
1k
100
10 100 1k
FREQUENCY (Hz)
00164-011
VOLTAGE NOISE DENSITY (nV/ Hz)
VIN = 15V
TA = 25°C
Figure 11. Voltage Noise Density vs. Frequency
120
100
80
60
40
20
0
RIPPLE REJECTION (dB)
10 100 1k
FREQUENCY (Hz)
00164-012
V
S
= 6V
Figure 12. Ripple Rejection vs. Frequency
100
10
1
OUTPUT IMPEDANCE (Ω)
10 100 1k 10k
FREQUENCY (Hz)
00164-013
V
S
= 6V
I
L
= 0mA
Figure 13. Output Impedance vs. Frequency
10µV p-p
00164-014
1s/DIV
Figure 14. 0.1 Hz to 10 Hz Noise
ADR293
Rev. D | Page 8 of 12
0
0164-015
50µs/DIV
I
L
= 5mA
2V/DIV
5V/DIV
Figure 15. Turn-On Time
00164-016
50µs/DIV
IL = 5mA
2V/DIV
5V/DIV
Figure 16. Turn-Off Time
00164-017
1ms/DIV
I
L
= 5mA
Figure 17. Load Transient Response
00164-018
1ms/DIV
I
I
= 5mA
C
L
= 1nF
Figure 18. Load Transient Response
00164-019
1ms/DIV
I
I
= 5mA
C
L
= 100nF
Figure 19. Load Transient Response
18
16
14
12
10
8
6
4
2
0
FREQUENCY IN NUMBER OF UNITS
–200 –160 –120 –80 –40 0 40 80 120 160 200 240
V
OUT
DEVIATION (ppm)
TEMPERATURE
+25°C → –40°C →
+85°C → +25°C
00164-020
Figure 20. Typical Hysteresis for the ADR29x Product
ADR293
Rev. D | Page 9 of 12
TERMINOLOGY
Line Regulation
The change in output voltage due to a specified change in input
voltage. It includes the effects of self-heating. Line regulation is
expressed in percent per volt, parts per million per volt, or
microvolts per volt change in input voltage.
Load Regulation
The change in output voltage due to a specified change in load
current. It includes the effects of self-heating. Load regulation is
expressed in microvolts per milliampere, parts per million per
milliampere, or ohms of dc output resistance.
Long-Term Stability
Typical shift of output voltage of 25°C on a sample of parts
subjected to high temperature operating life test of 1000 hours
at 125°C.
(
)
()
1
OUT
0
OUTOUT tVtVV −=Δ
[]
()
()
()
6
10ppm ×
−
=Δ
0
OUT
1
OUT
0
OUT
OUT tV
tVtV
V
where:
VOUT (t0) = VOUT at 25°C at time 0.
VOUT (t1) = VOUT at 25°C after 1000 hours operation at 125°C.
NC = No Connect
There are in fact connections at NC pins, which are reserved for
manufacturing purposes. Users should not connect anything at
NC pins.
Temperature Coefficient
The change of output voltage over the operating temperature
change and normalized by the output voltage at 25°C, expressed
in ppm/°C.
[]
()
(
)
()
()
6
10Cppm/ ×
−×°
−
=°
12
OUT
1
OUT
2
OUT
OUT TTC25V
TVΤV
VTC
where:
VOUT (25°C) = VOUT at 25°C.
VOUT (T1) = VOUT at Temperature 1.
VOUT (T2) = VOUT at Temperature 2.
Thermal Hysteresis
Thermal hysteresis is defined as the change of output voltage
after the device is cycled through temperatures from +25°C to
–40°C to +85°C and back to +25°C. This is a typical value from
a sample of parts put through such a cycle.
(
)
TCOUTOUTHYSOUT VC25VV −− −°
=
[]
()
()
6
10ppm ×
°
−°
=−
−C25V
VC25V
V
OUT
TCOUTOUT
HYSOUT
where:
VOUT (25°C) = VOUT at 25°C.
VOUT-TC = VOUT (25°C) after temperature cycle at +25°C to –40°C
to +85°C and back to +25°C.
ADR293
Rev. D | Page 10 of 12
THEORY OF OPERATION
The ADR293 uses a new reference generation technique known
as XFET, which yields a reference with low noise, low supply
current, and very low thermal hysteresis.
The core of the XFET reference consists of two junction field
effect transistors, one of which has an extra channel implant to
raise its pinch-off voltage. By running the two JFETs at the same
drain current, the difference in pinch-off voltage can be amplified
and used to form a highly stable voltage reference. The intrinsic
reference voltage is around 0.5 V with a negative temperature
coefficient of about –120 ppm/K. This slope is essentially locked
to the dielectric constant of silicon and can be closely compen-
sated by adding a correction term generated in the same fashion
as the proportional-to-temperature (PTAT) term used to
compensate band gap references. The big advantage over a band
gap reference is that the intrinsic temperature coefficient is
some 30 times lower (therefore, less correction is needed) and
this results in much lower noise, because most of the noise of a
band gap reference comes from the temperature compensation
circuitry.
The simplified schematic in Figure 21 shows the basic topology
of the ADR293. The temperature correction term is provided by
a current source with value designed to be proportional to
absolute temperature. The general equation is
()
()
R3I
R1
R3R2R1
VV PTAT
P
OUT +
⎟
⎠
⎞
⎜
⎝
⎛++
Δ=
where:
ΔVP is the difference in pinch-off voltage between the two FETs.
IPTAT is the positive temperature coefficient correction current.
The process used for the XFET reference also features vertical
NPN and PNP transistors, the latter of which are used as output
devices to provide a very low dropout voltage.
V
OUT
V
IN
I
PTAT
GND
R1
R2
R3
I
1
I
1
1
1
EXTRA CHANNEL IMPLANT
V
OUT
=×∆V
P
+ I
PTAT
× R3
R1 + R2 + R3
R1
∆V
P
00164-021
Figure 21. Simplified Schematic
DEVICE POWER DISSIPATION CONSIDERATIONS
The ADR293 is guaranteed to deliver load currents to 5 mA
with an input voltage that ranges from 5.5 V to 15 V. When
this device is used in applications with large input voltages,
care should be exercised to avoid exceeding the published
specifications for maximum power dissipation or junction
temperature that could result in premature device failure.
The following formula should be used to calculate a device’s
maximum junction temperature or dissipation:
JA
A
J
D
TT
Pθ
−
=
where:
TJ and TA are the junction temperature and ambient
temperature, respectively.
PD is the device power dissipation.
θJA is the device package thermal resistance.
BASIC VOLTAGE REFERENCE CONNECTIONS
References, in general, require a bypass capacitor connected
from the VOUT pin to the GND pin. The circuit in Figure 22
illustrates the basic configuration for the ADR293. Note that the
decoupling capacitors are not required for circuit stability.
NC
NC
NC
NC
V
OUT
NC
0.1µF
0.1µF
10µF
+
NC = NO CONNECT
1
2
3
4
8
7
6
5
00164-022
ADR293
Figure 22. Basic Voltage Reference Configuration
NOISE PERFORMANCE
The noise generated by the ADR293 is typically less than
15 μV p-p over the 0.1 Hz to 10 Hz band. The noise measure-
ment is made with a band-pass filter made of a 2-pole high-pass
filter with a corner frequency at 0.1 Hz and a 2-pole low-pass
filter with a corner frequency at 10 Hz.
TURN-ON TIME
Upon application of power (cold start), 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. Two
components normally associated with this are the time for the
active circuits to settle and the time for the thermal gradients on
the chip to stabilize. Figure 15 shows the typical turn-on time
for the ADR293.
ADR293
Rev. D | Page 11 of 12
APPLICATIONS
KELVIN CONNECTIONS
In many portable instrumentation applications where PC board
cost and area go hand-in-hand, circuit interconnects are very often
of dimensionally minimum width. These narrow lines can cause
large voltage drops if the voltage reference is required to provide
load currents to various functions. In fact, a circuit’s interconnects
can exhibit a typical line resistance of 0.45 mΩ/square (1 oz. Cu,
for example). Force and sense connections, also referred to as
Kelvin connections, offer a convenient method of eliminating
the effects of voltage drops in circuit wires. Load currents flowing
through wiring resistance produce an error (VERROR = R × IL) at
the load. However, the Kelvin connection in Figure 23 overcomes
the problem by including the wiring resistance within the forcing
loop of the op amp. Because the op amp senses the load voltage,
op amp loop control forces the output to compensate for the
wiring error and to produce the correct voltage at the load.
A1
1µF 100kΩ
+VOUT
SENSE
VIN
RLW
RL
RLW
+VOUT
FORCE
VOUT
GND
VIN
ADR293
2
6
4
0
0164-025
Figure 23. Advantage of Kelvin Connection
VOLTAGE REGULATOR FOR PORTABLE
EQUIPMENT
The ADR293 is ideal for providing a stable, low cost, and low
power reference voltage in portable equipment power supplies.
Figure 24 shows how the ADR293 can be used in a voltage
regulator that not only has low output noise (as compared to
switch mode design) and low power, but also a very fast
recovery after current surges. Some precautions should be taken
in the selection of the output capacitors. Too high an ESR
(effective series resistance) could endanger the stability of the
circuit. A solid tantalum capacitor, 16 V or higher, and an
aluminum electrolytic capacitor, 10 V or higher, are recom-
mended for C1 and C2, respectively. In addition, the path from
the ground side of C1 and C2 to the ground side of R1 should
be kept as short as possible.
ADR293
V
OUT
GND
V
IN
0.1µF
LEAD-ACID
BATTERY
+
6V
CHARGER
INPUT
R1
402kΩ
1%
C1
68µF
TANT
C2
1000µF
ELECT
R2
402kΩ
1%
++
5V, 100mA
IRF9530
R3
510kΩ
OP20
2
6 2 7
6
4
3
4
00164-026
Figure 24. Voltage Regulator for Portable Equipment
ADR293
Rev. D | Page 12 of 12
OUTLINE DIMENSIONS
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.
COMPLIANT TO JEDEC STANDARDS MS-012-AA
012407-A
0.25 (0.0098)
0.17 (0.0067)
1.27 (0.0500)
0.40 (0.0157)
0.50 (0.0196)
0.25 (0.0099) 45°
8°
0°
1.75 (0.0688)
1.35 (0.0532)
SEATING
PLANE
0.25 (0.0098)
0.10 (0.0040)
4
1
85
5.00 (0.1968)
4.80 (0.1890)
4.00 (0.1574)
3.80 (0.1497)
1.27 (0.0500)
BSC
6.20 (0.2441)
5.80 (0.2284)
0.51 (0.0201)
0.31 (0.0122)
COPLANARITY
0.10
Figure 25. 8-Lead Standard Small Outline Package [SOIC_N]
Narrow Body
(R-8)
Dimensions shown in millimeters and (inches)
85
41
PIN 1
0.65 BSC
SEATING
PLANE
0.15
0.05
0.30
0.19
1.20
MAX
0.20
0.09
8°
0°
6.40 BSC
4.50
4.40
4.30
3.10
3.00
2.90
COPLANARITY
0.10
0.75
0.60
0.45
COMPLIANT TO JEDEC STANDARDS MO-153-AA
Figure 26. 8-Lead Thin Shrink Small Outline Package [TSSOP]
(RU-8)
Dimensions shown in millimeters
ORDERING GUIDE
Model1
Output
Voltage (V)
Initial
Accuracy (%)
Temperature
Coefficient
(ppm/°C max)
Temperature
Range
Package
Description
Package
Option
Ordering
Quantity
ADR293ERZ 5.00 0.06 8 −40°C to +125°C 8-Lead SOIC_N R-8 98
ADR293ERZ-REEL 5.00 0.06 8 −40°C to +125°C 8-Lead SOIC_N R-8 2,500
ADR293GRZ 5.00 0.20 25 −40°C to +125°C 8-Lead SOIC_N R-8 98
ADR293GRZ-REEL7 5.00 0.20 25 −40°C to +125°C 8-Lead SOIC_N R-8 1,000
ADR293GRUZ 5.00 0.20 25 −40°C to +125°C 8-Lead TSSOP RU-8 96
ADR293GRUZ-REEL 5.00 0.20 25 −40°C to +125°C 8-Lead TSSOP RU-8 2,500
ADR293GRUZ-REEL7 5.00 0.20 25 −40°C to +125°C 8-Lead TSSOP RU-8 1,000
1 Z = RoHS Compliant Part.
©2001-2011 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D00164-0-5/11(D)
