Ultralow Noise XFET Voltage References
with Current Sink and Source Capability
ADR430/ADR431/ADR433/ADR434/ADR435/ADR439
FEATURES
PIN CONFIGURATIONS
Low noise (0.1 Hz to 10.0 Hz): 3.5 μV p-p @ 2.5 V output
No external capacitor required
Low temperature coefficient
A Grade: 10 ppm/°C maximum
B Grade: 3 ppm/°C maximum
Load regulation: 15 ppm/mA
Line regulation: 20 ppm/V
Wide operating range
ADR430: 4.1 V to 18 V
ADR431: 4.5 V to 18 V
ADR433: 5.0 V to 18 V
ADR434: 6.1 V to 18 V
ADR435: 7.0 V to 18 V
ADR439: 6.5 V to 18 V
High output source and sink current: +30 mA and −20 mA
Wide temperature range: −40°C to +125°C
TP 1
ADR43x
8
TP
COMP
TOP VIEW
6 VOUT
(Not to Scale)
5 TRIM
GND 4
VIN 2
7
NOTES
1. NC = NO CONNECT
2. TP = TEST PIN (DO NOT CONNECT)
04500-001
NC 3
Figure 1. 8-Lead MSOP (RM-8)
TP 1
VIN 2
ADR43x
8
TP
COMP
TOP VIEW
6 VOUT
(Not to Scale)
GND 4
5 TRIM
7
NOTES
1. NC = NO CONNECT
2. TP = TEST PIN (DO NOT CONNECT)
04500-041
NC 3
Figure 2. 8-Lead SOIC_N (R-8)
APPLICATIONS
Precision data acquisition systems
High resolution data converters
Medical instruments
Industrial process control systems
Optical control circuits
Precision instruments
GENERAL DESCRIPTION
The ADR43x series is a family of XFET® voltage references
featuring low noise, high accuracy, and low temperature drift
performance. Using Analog Devices, Inc., patented temperature
drift curvature correction and XFET (eXtra implanted junction
FET) technology, voltage change vs. temperature nonlinearity in
the ADR43x is minimized.
The XFET references operate at lower current (800 μA) and
lower supply voltage headroom (2 V) than buried Zener
references. Buried Zener references require more than 5 V
headroom for operation. The ADR43x XFET references are
the only low noise solutions for 5 V systems.
The ADR43x family has the capability to source up to 30 mA of
output current and sink up to 20 mA. It also comes with a trim
terminal to adjust the output voltage over a 0.5% range without
compromising performance.
Table 1. Selection Guide
Model
ADR430A
ADR430B
ADR431A
ADR431B
ADR433A
ADR433B
ADR434A
ADR434B
ADR435A
ADR435B
ADR439A
ADR439B
Output
Voltage (V)
2.048
2.048
2.500
2.500
3.000
3.000
4.096
4.096
5.000
5.000
4.500
4.500
Accuracy (mV)
±3
±1
±3
±1
±4
±1.5
±5
±1.5
±6
±2
±5.5
±2
Temperature
Coefficient
(ppm/°C)
10
3
10
3
10
3
10
3
10
3
10
3
The ADR43x is available in 8-lead MSOP and 8-lead narrow
SOIC packages. All versions are specified over the extended
industrial temperature range of −40°C to +125°C.
Rev. G
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 ©2003–2010 Analog Devices, Inc. All rights reserved.
ADR430/ADR431/ADR433/ADR434/ADR435/ADR439
TABLE OF CONTENTS
Features .............................................................................................. 1
Noise Performance ..................................................................... 15
Applications ....................................................................................... 1
High Frequency Noise ............................................................... 15
Pin Configurations ........................................................................... 1
Turn-On Time ............................................................................ 16
General Description ......................................................................... 1
Applications Inforamtion .............................................................. 17
Revision History ............................................................................... 2
Output Adjustment .................................................................... 17
Specifications..................................................................................... 3
Reference for Converters in Optical Network Control
Circuits......................................................................................... 17
ADR430 Electrical Characteristics............................................. 3
ADR431 Electrical Characteristics............................................. 4
ADR433 Electrical Characteristics............................................. 5
ADR434 Electrical Characteristics............................................. 6
ADR435 Electrical Characteristics............................................. 7
ADR439 Electrical Characteristics............................................. 8
Absolute Maximum Ratings............................................................ 9
Thermal Resistance ...................................................................... 9
ESD Caution .................................................................................. 9
Typical Performance Characteristics ........................................... 10
Theory of Operation ...................................................................... 15
Negative Precision Reference Without Precision Resistors .. 17
High Voltage Floating Current Source .................................... 18
Kelvin Connection ..................................................................... 18
Dual Polarity References ........................................................... 18
Programmable Current Source ................................................ 19
Programmable DAC Reference Voltage .................................. 19
Precision Voltage Reference for Data Converters .................. 20
Precision Boosted Output Regulator ....................................... 20
Outline Dimensions ....................................................................... 21
Ordering Guide .......................................................................... 22
Basic Voltage Reference Connections ...................................... 15
REVISION HISTORY
7/10—Rev. F to Rev. G
Changes to Storage Temperature Range in Table 9 ...................... 9
6/10—Rev. E to Rev. F
Updated Pin Name NC to COMP Throughout............................ 1
Changes to Figure 1 and Figure 2 ................................................... 1
Changes to Figure 30 and High Frequency Noise Section ........ 15
Updated Outline Dimensions ....................................................... 21
Changes to Ordering Guide .......................................................... 22
1/09—Rev. D to Rev. E
Added High Frequency Noise Section and Equation 3;
Renumbered Sequentially.............................................................. 15
Inserted Figure 31, Figure 32, and Figure 33; Renumbered
Sequentially ..................................................................................... 16
Changes to the Ordering Guide.................................................... 22
12/07—Rev. C to Rev. D
Changes to Initial Accuracy and Ripple Rejection Ratio
Parameters in Table 2 through Table 7 .......................................... 3
Changes to Table 9 ............................................................................ 9
Changes to Theory of Operation Section .................................... 15
Updated Outline Dimensions ....................................................... 20
8/06—Rev. B to Rev. C
Updated Format .................................................................. Universal
Changes to Table 1.............................................................................1
Changes to Table 3.............................................................................4
Changes to Table 4.............................................................................5
Changes to Table 7.............................................................................8
Changes to Figure 26...................................................................... 14
Changes to Figure 31...................................................................... 16
Updated Outline Dimensions ....................................................... 20
Changes to Ordering Guide .......................................................... 21
9/04—Rev. A to Rev. B
Added New Grade .............................................................. Universal
Changes to Specifications .................................................................3
Replaced Figure 3, Figure 4, Figure 5........................................... 10
Updated Ordering Guide .............................................................. 21
6/04—Rev. 0 to Rev. A
Changes to Format ............................................................. Universal
Changes to the Ordering Guide ................................................... 20
12/03—Revision 0: Initial Version
Rev. G | Page 2 of 24
ADR430/ADR431/ADR433/ADR434/ADR435/ADR439
SPECIFICATIONS
ADR430 ELECTRICAL CHARACTERISTICS
VIN = 4.1 V to 18 V, IL = 0 mA, TA = 25°C, unless otherwise noted.
Table 2.
Parameter
OUTPUT VOLTAGE
A Grade
B Grade
INITIAL ACCURACY
A Grade
Symbol
VO
Conditions
Min
Typ
Max
Unit
2.045
2.047
2.048
2.048
2.051
2.049
V
V
±3
±0.15
±1
±0.05
mV
%
mV
%
10
3
20
15
15
800
ppm/°C
ppm/°C
ppm/V
ppm/mA
ppm/mA
μA
μV p-p
nV/√Hz
μs
ppm
ppm
dB
mA
18
V
V
VOERR
B Grade
TEMPERATURE COEFFICIENT
A Grade
B Grade
LINE REGULATION
LOAD REGULATION
QUIESCENT CURRENT
VOLTAGE NOISE
VOLTAGE NOISE DENSITY
TURN-ON SETTLING TIME
LONG-TERM STABILITY 1
OUTPUT VOLTAGE HYSTERESIS
RIPPLE REJECTION RATIO
SHORT CIRCUIT TO GND
SUPPLY VOLTAGE
OPERATING RANGE
SUPPLY VOLTAGE HEADROOM
1
TCVO
∆VO/∆VIN
∆VO/∆IL
∆VO/∆IL
IIN
eN p-p
eN
tR
∆VO
VO_HYS
RRR
ISC
−40°C < TA < +125°C
−40°C < TA < +125°C
VIN = 4.1 V to 18 V, −40°C < TA < +125°C
IL = 0 mA to 10 mA, VIN = 5.0 V, −40°C < TA < +125°C
IL = −10 mA to 0 mA, VIN = 5.0 V, −40°C < TA < +125°C
No load, −40°C < TA < +125°C
0.1 Hz to 10.0 Hz
1 kHz
CL = 0 μF
1000 hours
2
1
5
560
3.5
60
10
40
20
–70
40
fIN = 1 kHz
VIN
VIN − VO
4.1
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.
Rev. G | Page 3 of 24
ADR430/ADR431/ADR433/ADR434/ADR435/ADR439
ADR431 ELECTRICAL CHARACTERISTICS
VIN = 4.5 V to 18 V, IL = 0 mA, TA = 25°C, unless otherwise noted.
Table 3.
Parameter
OUTPUT VOLTAGE
A Grade
B Grade
INITIAL ACCURACY
A Grade
Symbol
VO
Conditions
Min
Typ
Max
Unit
2.497
2.499
2.500
2.500
2.503
2.501
V
V
±3
±0.12
±1
±0.04
mV
%
mV
%
10
3
20
15
15
800
ppm/°C
ppm/°C
ppm/V
ppm/mA
ppm/mA
μA
μV p-p
nV/√Hz
μs
ppm
ppm
dB
mA
18
V
V
VOERR
B Grade
TEMPERATURE COEFFICIENT
A Grade
B Grade
LINE REGULATION
LOAD REGULATION
QUIESCENT CURRENT
VOLTAGE NOISE
VOLTAGE NOISE DENSITY
TURN-ON SETTLING TIME
LONG-TERM STABILITY 1
OUTPUT VOLTAGE HYSTERESIS
RIPPLE REJECTION RATIO
SHORT CIRCUIT TO GND
SUPPLY VOLTAGE
OPERATING RANGE
SUPPLY VOLTAGE HEADROOM
1
TCVO
∆VO/∆VIN
∆VO/∆IL
∆VO/∆IL
IIN
eN p-p
eN
tR
∆VO
VO_HYS
RRR
ISC
−40°C < TA < +125°C
−40°C < TA < +125°C
VIN = 4.5 V to 18 V, −40°C < TA < +125°C
IL = 0 mA to 10 mA, VIN = 5.0 V, −40°C < TA < +125°C
IL = −10 mA to 0 mA, VIN = 5.0 V, −40°C < TA < +125°C
No load, −40°C < TA < +125°C
0.1 Hz to 10.0 Hz
1 kHz
CL = 0 μF
1000 hours
2
1
5
580
3.5
80
10
40
20
−70
40
fIN = 1 kHz
VIN
VIN − VO
4.5
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.
Rev. G | Page 4 of 24
ADR430/ADR431/ADR433/ADR434/ADR435/ADR439
ADR433 ELECTRICAL CHARACTERISTICS
VIN = 5.0 V to 18 V, IL = 0 mA, TA = 25°C, unless otherwise noted.
Table 4.
Parameter
OUTPUT VOLTAGE
A Grade
B Grade
INITIAL ACCURACY
A Grade
Symbol
VO
Conditions
Min
Typ
Max
Unit
2.996
2.9985
3.000
3.000
3.004
3.0015
V
V
±4
±0.13
±1.5
±0.05
mV
%
mV
%
10
3
20
15
15
800
ppm/°C
ppm/°C
ppm/V
ppm/mA
ppm/mA
μA
μV p-p
nV/√Hz
μs
ppm
ppm
dB
mA
18
V
V
VOERR
B Grade
TEMPERATURE COEFFICIENT
A Grade
B Grade
LINE REGULATION
LOAD REGULATION
QUIESCENT CURRENT
VOLTAGE NOISE
VOLTAGE NOISE DENSITY
TURN-ON SETTLING TIME
LONG-TERM STABILITY 1
OUTPUT VOLTAGE HYSTERESIS
RIPPLE REJECTION RATIO
SHORT CIRCUIT TO GND
SUPPLY VOLTAGE
OPERATING RANGE
SUPPLY VOLTAGE HEADROOM
1
TCVO
∆VO/∆VIN
∆VO/∆IL
∆VO/∆IL
IIN
eN p-p
eN
tR
∆VO
VO_HYS
RRR
ISC
−40°C < TA < +125°C
−40°C < TA < +125°C
VIN = 5 V to 18 V, −40°C < TA < +125°C
IL = 0 mA to 10 mA, VIN = 6 V, −40°C < TA < +125°C
IL = −10 mA to 0 mA, VIN = 6 V, −40°C < TA < +125°C
No load, −40°C < TA < +125°C
0.1 Hz to 10.0 Hz
1 kHz
CL = 0 μF
1000 hours
2
1
5
590
3.75
90
10
40
20
−70
40
fIN = 1 kHz
VIN
VIN − VO
5.0
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.
Rev. G | Page 5 of 24
ADR430/ADR431/ADR433/ADR434/ADR435/ADR439
ADR434 ELECTRICAL CHARACTERISTICS
VIN = 6.1 V to 18 V, IL = 0 mA, TA = 25°C, unless otherwise noted.
Table 5.
Parameter
OUTPUT VOLTAGE
A Grade
B Grade
INITIAL ACCURACY
A Grade
Symbol
VO
Conditions
Min
Typ
Max
Unit
4.091
4.0945
4.096
4.096
4.101
4.0975
V
V
±5
±0.12
±1.5
±0.04
mV
%
mV
%
10
3
20
15
15
800
ppm/°C
ppm/°C
ppm/V
ppm/mA
ppm/mA
μA
μV p-p
nV/√Hz
μs
ppm
ppm
dB
mA
18
V
V
VOERR
B Grade
TEMPERATURE COEFFICIENT
A Grade
B Grade
LINE REGULATION
LOAD REGULATION
QUIESCENT CURRENT
VOLTAGE NOISE
VOLTAGE NOISE DENSITY
TURN-ON SETTLING TIME
LONG-TERM STABILITY 1
OUTPUT VOLTAGE HYSTERESIS
RIPPLE REJECTION RATIO
SHORT CIRCUIT TO GND
SUPPLY VOLTAGE
OPERATING RANGE
SUPPLY VOLTAGE HEADROOM
1
TCVO
∆VO/∆VIN
∆VO/∆IL
∆VO/∆IL
IIN
eN p-p
eN
tR
∆VO
VO_HYS
RRR
ISC
−40°C < TA < +125°C
−40°C < TA < +125°C
VIN = 6.1 V to 18 V, −40°C < TA < +125°C
IL = 0 mA to 10 mA, VIN = 7 V, −40°C < TA < +125°C
IL = −10 mA to 0 mA, VIN = 7 V, −40°C < TA < +125°C
No load, −40°C < TA < +125°C
0.1 Hz to 10.0 Hz
1 kHz
CL = 0 μF
1000 hours
2
1
5
595
6.25
100
10
40
20
−70
40
fIN = 1 kHz
VIN
VIN − VO
6.1
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.
Rev. G | Page 6 of 24
ADR430/ADR431/ADR433/ADR434/ADR435/ADR439
ADR435 ELECTRICAL CHARACTERISTICS
VIN = 7.0 V to 18 V, IL = 0 mA, TA = 25°C, unless otherwise noted.
Table 6.
Parameter
OUTPUT VOLTAGE
A Grade
B Grade
INITIAL ACCURACY
A Grade
Symbol
VO
Conditions
Min
Typ
Max
Unit
4.994
4.998
5.000
5.000
5.006
5.002
V
V
±6
±0.12
±2
±0.04
mV
%
mV
%
10
3
20
15
15
800
ppm/°C
ppm/°C
ppm/V
ppm/mA
ppm/mA
μA
μV p-p
nV/√Hz
μs
ppm
ppm
dB
mA
V
V
VOERR
B Grade
TEMPERATURE COEFFICIENT
A Grade
B Grade
LINE REGULATION
LOAD REGULATION
QUIESCENT CURRENT
VOLTAGE NOISE
VOLTAGE NOISE DENSITY
TURN-ON SETTLING TIME
LONG-TERM STABILITY 1
OUTPUT VOLTAGE HYSTERESIS
RIPPLE REJECTION RATIO
SHORT CIRCUIT TO GND
SUPPLY VOLTAGE OPERATING RANGE
SUPPLY VOLTAGE HEADROOM
1
TCVO
∆VO/∆VIN
∆VO/∆IL
∆VO/∆IL
IIN
eN p-p
eN
tR
∆VO
VO_HYS
RRR
ISC
VIN
VIN − VO
−40°C < TA < +125°C
−40°C < TA < +125°C
VIN = 7 V to 18 V, −40°C < TA < +125°C
IL = 0 mA to 10 mA, VIN = 8 V, −40°C < TA < +125°C
IL = −10 mA to 0 mA, VIN = 8 V, −40°C < TA < +125°C
No load, −40°C < TA < +125°C
0.1 Hz to 10 Hz
1 kHz
CL = 0 μF
1000 hours
2
1
5
620
8
115
10
40
20
−70
40
fIN = 1 kHz
7.0
2
18
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. G | Page 7 of 24
ADR430/ADR431/ADR433/ADR434/ADR435/ADR439
ADR439 ELECTRICAL CHARACTERISTICS
VIN = 6.5 V to 18 V, IL = 0 mV, TA = 25°C, unless otherwise noted.
Table 7.
Parameter
OUTPUT VOLTAGE
A Grade
B Grade
INITIAL ACCURACY
A Grade
Symbol
VO
Conditions
Min
Typ
Max
Unit
4.4946
4.498
4.500
4.500
4.5054
4.502
V
V
±5.5
±0.12
±2
±0.04
mV
%
mV
%
10
3
20
15
15
800
ppm/°C
ppm/°C
ppm/V
ppm/mA
ppm/mA
μA
μV p-p
nV/√Hz
μs
ppm
ppm
dB
mA
V
V
VOERR
B Grade
TEMPERATURE COEFFICIENT
A Grade
B Grade
LINE REGULATION
LOAD REGULATION
QUIESCENT CURRENT
VOLTAGE NOISE
VOLTAGE NOISE DENSITY
TURN-ON SETTLING TIME
LONG-TERM STABILITY 1
OUTPUT VOLTAGE HYSTERESIS
RIPPLE REJECTION RATIO
SHORT CIRCUIT TO GND
SUPPLY VOLTAGE OPERATING RANGE
SUPPLY VOLTAGE HEADROOM
1
TCVO
∆VO/∆VIN
∆VO/∆IL
∆VO/∆IL
IIN
eN p-p
eN
tR
∆VO
VO_HYS
RRR
ISC
VIN
VIN − VO
−40°C < TA < +125°C
−40°C < TA < +125°C
VIN = 6.5 V to 18 V, −40°C < TA < +125°C
IL = 0 mA to 10 mA, VIN = 6.5 V, −40°C < TA < +125°C
IL = −10 mA to 0 mA, VIN = 6.5 V, −40°C < TA < +125°C
No load, −40°C < TA < +125°C
0.1 Hz to 10.0 Hz
1 kHz
CL = 0 μF
1000 hours
2
1
5
600
7.5
110
10
40
20
−70
40
fIN = 1 kHz
6.5
2
18
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. G | Page 8 of 24
ADR430/ADR431/ADR433/ADR434/ADR435/ADR439
ABSOLUTE MAXIMUM RATINGS
TA = 25°C, unless otherwise noted.
THERMAL RESISTANCE
Table 8.
θJA is specified for the worst-case conditions, that is, a device
soldered in a circuit board for surface-mount packages.
Parameter
Supply Voltage
Output Short-Circuit Duration to GND
Storage Temperature Range
Operating Temperature Range
Junction Temperature Range
Lead Temperature, Soldering (60 sec)
Rating
20 V
Indefinite
−65°C to +150°C
−40°C to +125°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.
Table 9. Thermal Resistance
Package Type
8-Lead SOIC_N (R)
8-Lead MSOP (RM)
ESD CAUTION
Rev. G | Page 9 of 24
θJA
130
142
θJC
43
44
Unit
°C/W
°C/W
ADR430/ADR431/ADR433/ADR434/ADR435/ADR439
TYPICAL PERFORMANCE CHARACTERISTICS
Default conditions: ±5 V, CL = 5 pF, G = 2, RG = RF = 1 kΩ, RL = 2 kΩ, VO = 2 V p-p, f = 1 MHz, TA = 25°C, unless otherwise noted.
0.8
2.5009
SUPPLY CURRENT (mA)
OUTPUT VOLTAGE (V)
2.5007
2.5005
2.5003
2.5001
2.4999
0.7
+125°C
0.6
+25°C
–40°C
0.5
0.4
–25
–10
5
20
35
50
65
80
95
110
125
TEMPERATURE (°C)
0.3
04500-015
2.4995
–40
4
8
10
12
14
16
INPUT VOLTAGE (V)
Figure 3. ADR431 Output Voltage vs. Temperature
Figure 6. ADR435 Supply Current vs. Input Voltage
4.0980
700
4.0975
650
SUPPLY CURRENT (µA)
4.0970
4.0965
4.0960
4.0955
600
550
500
–25
–10
5
20
35
50
65
80
95
110
125
TEMPERATURE (°C)
400
–40
04500-016
4.0950
–40
–25
–10
5
20
35
50
65
80
95
110
125
04500-019
450
18
04500-020
OUTPUT VOLTAGE (V)
6
04500-018
2.4997
TEMPERATURE (°C)
Figure 4. ADR434 Output Voltage vs. Temperature
Figure 7. ADR435 Supply Current vs. Temperature
0.60
5.0025
+125°C
0.58
5.0020
SUPPLY CURRENT (mA)
5.0010
5.0005
5.0000
0.54
0.52
+25°C
0.50
0.48
0.46
–40°C
0.44
4.9995
4.9990
–40
0.42
0.40
–25
–10
5
20
35
50
65
80
95
110
TEMPERATURE (°C)
125
04500-017
OUTPUT VOLTAGE (V)
0.56
5.0015
Figure 5. ADR435 Output Voltage vs. Temperature
6
8
10
12
14
16
INPUT VOLTAGE (V)
Figure 8. ADR431 Supply Current vs. Input Voltage
Rev. G | Page 10 of 24
ADR430/ADR431/ADR433/ADR434/ADR435/ADR439
2.5
610
DIFFERENTIAL VOLTAGE (V)
SUPPLY CURRENT (µA)
580
550
520
490
460
2.0
–40°C
1.5
+25°C
1.0
+125°C
0.5
–25
–10
5
20
35
50
65
80
95
110
125
TEMPERATURE (°C)
0
–10
04500-021
400
–40
0
5
10
LOAD CURRENT (mA)
Figure 9. ADR431 Supply Current vs. Temperature
15
–5
04500-024
430
Figure 12. ADR431 Minimum Input/Output
Differential Voltage vs. Load Current
1.9
IL = 0mA to 10mA
NO LOAD
12
MINIMUM HEADROOM (V)
LOAD REGULATION (ppm/mA)
1.8
9
6
3
1.7
1.6
1.5
1.4
1.3
1.2
5
20
35
50
65
80
95
110
125
TEMPERATURE (°C)
1.0
–40
DIFFERENTIAL VOLTAGE (V)
6
3
5
20
35
50
65
80
95
110
TEMPERATURE (°C)
125
04500-023
LOAD REGULATION (ppm/mA)
9
–10
20
35
50
65
80
95
110
125
2.5
12
–25
5
Figure 13. ADR431 Minimum Headroom vs. Temperature
IL = 0mA to 10mA
0
–40
–10
TEMPERATURE (°C)
Figure 10. ADR431 Load Regulation vs. Temperature
15
–25
Figure 11. ADR435 Load Regulation vs. Temperature
2.0
–40°C
1.5
+25°C
1.0
+125°C
0.5
0
–10
–5
0
5
LOAD CURRENT (mA)
Figure 14. ADR435 Minimum Input/Output
Differential Voltage vs. Load Current
Rev. G | Page 11 of 24
10
04500-026
–10
04500-022
–25
04500-025
1.1
0
–40
ADR430/ADR431/ADR433/ADR434/ADR435/ADR439
1.9
NO LOAD
MINIMUM HEADROOM (V)
1.7
CL = 0.01µF
NO INPUT CAPACITOR
VO = 1V/DIV
1.5
1.3
1.1
–25
–10
5
20
35
50
65
80
95
110
125
TEMPERATURE (°C)
TIME = 4µs/DIV
04500-027
0.9
–40
Figure 15. ADR435 Minimum Headroom vs. Temperature
04500-031
VIN = 2V/DIV
Figure 18. ADR431 Turn-On Response, 0.01 μF Load Capacitor
20
VIN = 7V TO 18V
VO = 1V/DIV
12
CIN = 0.01µF
NO LOAD
8
4
0
–25
–10
5
20
35
50
65
80
95
110
125
TEMPERATURE (°C)
04500-028
Figure 19. ADR431 Turn-Off Response
Figure 16. ADR435 Line Regulation vs. Temperature
CIN = 0.01µF
NO LOAD
BYPASS CAPACITOR = 0µF
LINE
INTERRUPTION
VO = 1V/DIV
VIN = 500mV/DIV
VO = 50mV/DIV
VIN = 2V/DIV
TIME = 4µs/DIV
TIME = 100µs/DIV
Figure 20. ADR431 Line Transient Response
Figure 17. ADR431 Turn-On Response
Rev. G | Page 12 of 24
04500-033
–4
–40
TIME = 4µs/DIV
04500-032
VIN = 2V/DIV
04500-030
LINE REGULATION (ppm/V)
16
ADR430/ADR431/ADR433/ADR434/ADR435/ADR439
BYPASS CAPACITOR = 0.1µF
LINE
INTERRUPTION
VIN = 500mV/DIV
VO = 50mV/DIV
TIME = 1s/DIV
Figure 21. ADR431 Line Transient Response, 0.1 μF Bypass Capacitor
04500-037
TIME = 100µs/DIV
04500-034
2µV/DIV
Figure 24. ADR435 0.1 Hz to 10.0 Hz Voltage Noise
1µV/DIV
50µV/DIV
Figure 22. ADR431 0.1 Hz to 10.0 Hz Voltage Noise
04500-038
TIME = 1s/DIV
04500-035
TIME = 1s/DIV
Figure 25. ADR435 10 Hz to 10 kHz Voltage Noise
14
NUMBER OF PARTS
12
10
8
6
4
50µV/DIV
0
–110 –90
04500-036
TIME = 1s/DIV
–70
–50
–30
–10
10
30
50
DEVIATION (PPM)
Figure 23. ADR431 10 Hz to 10 kHz Voltage Noise
Figure 26. ADR431 Typical Hysteresis
Rev. G | Page 13 of 24
70
90
110
04500-029
2
ADR430/ADR431/ADR433/ADR434/ADR435/ADR439
50
10
45
–10
RIPPLE REJECTION (dB)
35
30
ADR435
20
15
ADR433
10
ADR430
5
0
100
1k
10k
FREQUENCY (Hz)
100k
–30
–50
–70
–90
–110
–130
–150
10
100
1k
10k
FREQUENCY (Hz)
Figure 27. Output Impedance vs. Frequency
Figure 28. Ripple Rejection
Rev. G | Page 14 of 24
100k
1M
04500-040
25
04500-039
OUTPUT IMPEDANCE (Ω)
40
ADR430/ADR431/ADR433/ADR434/ADR435/ADR439
THEORY OF OPERATION
The intrinsic reference voltage is around 0.5 V with a negative
temperature coefficient of about −120 ppm/°C. This slope is
essentially constant to the dielectric constant of silicon and can
be compensated closely by adding a correction term generated
in the same fashion as the proportional-to-temperature (PTAT)
term used to compensate band gap references. The primary
advantage of an XFET reference is its correction term, which is
~30 times lower and requires less correction than that of a band
gap reference. Because most of the noise of a band gap reference
comes from the temperature compensation circuitry, the XFET
results in much lower noise.
The ADR43x family of references is guaranteed to deliver load
currents to 10 mA with an input voltage that ranges from 4.1 V
to 18 V. When these devices are used in applications at higher
currents, use the following equation to account for the
temperature effects due to the power dissipation increases:
TJ = PD × θJA + TA
where:
TJ and TA are the junction and ambient temperatures, respectively.
PD is the device power dissipation.
θJA is the device package thermal resistance.
BASIC VOLTAGE REFERENCE CONNECTIONS
Voltage references, in general, require a bypass capacitor
connected from VOUT to GND. The circuit in Figure 30
illustrates the basic configuration for the ADR43x family
of references. Other than a 0.1 μF capacitor at the output to
help improve noise suppression, a large output capacitor at
the output is not required for circuit stability.
TP
VIN
Figure 29 shows the basic topology of the ADR43x series. The
temperature correction term is provided by a current source
with a value designed to be proportional to absolute temperature.
The general equation is
VOUT = G (ΔVP – R1 × IPTAT)
ADR43x devices are created by on-chip adjustment of R2 and R3 to
achieve 2.048 V or 2.500 V, respectively, at the reference output.
I1
VIN
I1
ADR43x
IPTAT
VOUT
R2
*
R1
*EXTRA CHANNEL IMPLANT
VOUT = G(ΔVP – R1 × IPTAT)
Figure 29. Simplified Schematic Device
Power Dissipation Considerations
R3
GND
04500-002
ΔVP
10µF
+
1
0.1µF
NC
GND
8
ADR43x
TP
COMP
VOUT
TOP VIEW
6
(Not to Scale)
4
5 TRIM
2
7
3
0.1µF
NOTES:
1. NC = NO CONNECT
2. TP = TEST PIN (DO NOT CONNECT)
(1)
where:
G is the gain of the reciprocal of the divider ratio.
ΔVP is the difference in pinch-off voltage between the two JFETs.
IPTAT is the positive temperature coefficient correction current.
(2)
04500-044
The ADR43x series of references uses a reference generation
technique known as XFET (eXtra implanted junction FET).
This technique yields a reference with low supply current, good
thermal hysteresis, and exceptionally low noise. The core of the
XFET reference consists of two junction field-effect transistors
(JFETs), 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.
Figure 30. Basic Voltage Reference Configuration
NOISE PERFORMANCE
The noise generated by the ADR43x family of references is
typically less than 3.75 μV p-p over the 0.1 Hz to 10.0 Hz band
for ADR430, ADR431, and ADR433. Figure 22 shows the 0.1 Hz
to 10.0 Hz noise of the ADR431, which is only 3.5 μV p-p. The
noise measurement 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 10.0 Hz.
HIGH FREQUENCY NOISE
The total noise generated by the ADR43x family of references is
composed of the reference noise and the op amp noise. Figure 31
shows the wideband noise from 10 Hz to 25 kHz. An internal node
of the op amp is brought out on Pin 7, and by overcompensating
the op amp, the overall noise can be reduced.
This is understood by considering that in a closed-loop
configuration, the effective output impedance of an op amp is
RO =
rO
1 + AVO β
where:
RO is the apparent output impedance.
rO is the output resistance of the op amp.
AVO is the open-loop gain at the frequency of interest.
β is the feedback factor.
Rev. G | Page 15 of 24
(3)
ADR430/ADR431/ADR433/ADR434/ADR435/ADR439
1000
ADR431
NO COMPENSATION
CL = 1µF
10µF
+
CL = 50µF
1
2
0.1µF
NC
GND
8
ADR43x
7
TP
COMP 82kΩ
VOUT
TOP VIEW
6
(Not to Scale)
4
5 TRIM
10nF
3
0.1µF
NOTES
1. NC = NO CONNECT
2. TP = TEST PIN (DO NOT CONNECT)
Figure 32. Compensated Reference
The 82 kΩ resistor and 10 nF capacitor can eliminate the noise
peaking (see Figure 33). The COMP pin should be left
unconnected if unused.
100
CL = 10µF
RC 82kΩ AND 10nF
CL = 1µF
RC 82kΩ AND 10nF
CL = 50µF
RC 82kΩ AND 10nF
10
10
CL = 0µF
100
1k
FREQUENCY (Hz)
10k
04500-043
100
Figure 33. Noise with Compensation Network
10
10
100
1k
10k
FREQUENCY (Hz)
Figure 31. Noise vs. Capacitive Loading
100k
04500-042
NOISE DENSITY (nV/√Hz)
CL = 10µF
TP
VIN
NOISE DENSITY (nV/√Hz)
However, references are used increasingly to drive the reference
input of an ADC that may present a dynamic, switching capacitive
load. Large capacitors, in the microfarad range, are used to reduce
the change in reference voltage to less than one-half LSB. Figure 31
shows the ADR431 noise spectrum with various capacitive values
to 50 μF. With no capacitive load, the noise spectrum is relatively
flat at approximately 60 nV/√Hz to 70 nV/√Hz. With various
values of capacitive loading, the predicted noise peaking
becomes evident.
The op amp within the ADR43x family uses the classic RC
compensation technique. Monolithic capacitors in an IC are
limited to tens of picofarads. With very large external capacitive
loads, such as 50 μF, it is necessary to overcompensate the op amp.
The internal compensation node is brought out on Pin 7, and
an external series RC network can be added between Pin 7 and
the output, Pin 6, as shown in Figure 32.
04500-003
Equation 3 shows that the apparent output impedance is reduced
by approximately the excess loop gain; therefore, as the frequency
increases, the excess loop gain decreases, and the apparent output
impedance increases. A passive element whose impedance
increases as its frequency increases is an inductor. When a
capacitor is added to the output of an op amp or a reference, it
forms a tuned circuit that resonates at a certain frequency and
results in gain peaking. This can be observed by using a model
of a semiperfect op amp with a single-pole response and some
pure resistance in series with the output. Changing capacitive
loads results in peaking at different frequencies. For most normal
op amp applications with low capacitive loading (
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