Page 1
Low Noise Micropower
a
FEATURES
Voltage Options 2.048 V, 2.500 V and 4.096 V
2.7 V to 15 V Supply Range
Supply Current 12 A max
Initial Accuracy ⴞ2 mV max
Temperature Coefficient 8 ppm/ⴗC max
Low-Noise 6 V p-p (0.1 Hz–10 Hz)
High Output Current 5 mA min
Temperature Range ⴚ40ⴗC to ⴙ125ⴗC
REF02/REF19x Pinout
APPLICATIONS
Portable Instrumentation
Precision Reference for 3 V and 5 V Systems
A/D and D/A Converter Reference
Solar Powered Applications
Loop-Current Powered Instruments
GENERAL DESCRIPTION
The ADR290, ADR291 and ADR292 are low noise, micropower precision voltage references that use an XFET
circuit. The new XFET
architecture offers significant performance improvements over traditional bandgap and Zener-based
references. Improvements include: one quarter the voltage noise
output of bandgap references operating at the same current,
very low and ultralinear temperature drift, low thermal hysteresis and excellent long-term stability.
The ADR29x family are series voltage references providing stable
and accurate output voltages from supplies as low as 2.7 V. Output voltage options are 2.048 V, 2.5 V and 4.096 V for the
ADR290, ADR291 and ADR292 respectively. Quiescent current
is only 12 µA, making these devices ideal for battery powered in-
strumentation. Three electrical grades are available offering initial
output accuracies of ±2 mV, ±3 mV and ±6 mV max for the
ADR290 and ADR291 and ±3 mV, ±4 mV and ±6 mV max for
the ADR292. Temperature coefficients for the three grades are
8 ppm/°C, 15 ppm/°C and 25 ppm/°C max, respectively. Line
regulation and load regulation are typically 30 ppm/V and
30 ppm/mA, maintaining the reference’s overall high performance. For a device with 5.0 V output, refer to the ADR293
data sheet.
The ADR290, ADR291 and ADR292 references are specified
over the extended industrial temperature range of –40°C to
+125°C. Devices are available in the 8-lead SOIC, 8-lead TSSOP
and the TO-92 package.
™
reference
Precision Voltage References
ADR290/ADR291/ADR292
PIN CONFIGURATIONS
8-Lead Narrow Body SO (R Suffix)
PIN 3
V
OUT
8
7
V
6
OUT
5
8
7
V
6
OUT
5
1
ADR29x
V
2
IN
TOP VIEW
(Not to Scale)
3
GND
4
8-Lead TSSOP (RU Suffix)
1
ADR29x
V
2
IN
TOP VIEW
(Not to Scale)
3
GND
4
3-Pin TO-92 (T9 Suffix)
PIN 1
PIN 2
V
GND
IN
BOTTOM VIEW
Part Number Nominal Output Voltage (V)
ADR290 2.048
ADR291 2.500
ADR292 4.096
XFET is a trademark of Analog Devices, Inc.
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
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood. MA 02062-9106, U.S.A.
Tel: 617/329-4700 World Wide Web Site: http://www.analog.com
Fax: 617/326-8703 © Analog Devices, Inc., 2000
Page 2
ADR290/ADR291/ADR292
ADR290–SPECIFICATIONS
Electrical Specifications
(VS = ⴙ2.7 V, TA = ⴙ25ⴗC unless otherwise noted)
Parameter Symbol Conditions Min Typ Max Units
INITIAL ACCURACY
“E” Grade V
O
I
= 0 mA 2.046 2.048 2.050 V
OUT
“F” Grade 2.045 2.051 V
“G” Grade 2.042 2.054 V
LINE REGULATION
“E/F” Grades ∆V
O
/∆V
IN
2.7 V to 15 V, I
= 0 mA 30 100 ppm/V
OUT
“G” Grade 40 125 ppm/V
LOAD REGULATION
“E/F” Grades ∆V
O
/∆I
LOAD
VS = 5.0 V, 0 mA to 5 mA 30 100 ppm/mA
“G” Grade 40 125 ppm/mA
LONG TERM STABILITY ∆V
NOISE VOLTAGE e
WIDEBAND NOISE DENSITY e
Electrical Specifications
N
n
(V
= ⴙ2.7 V, T
S
O
1000 hrs @ +25°C, V
= +15 V 0.2 ppm
S
0.1 Hz to 10 Hz 6 µV p-p
at 1 kHz 420 nV/√Hz
= ⴚ25ⴗC ≤ TA ≤ ⴙ85ⴗC unless otherwise noted)
A
Parameter Symbol Conditions Min Typ Max Units
TEMPERATURE COEFFICIENT
“E” Grade TCV
/°CI
O
= 0 mA 3 8 ppm/°C
OUT
“F” Grade 6 15 ppm/°C
“G” Grade 10 25 ppm/°C
LINE REGULATION
“E/F” Grades ∆V
O
/∆V
IN
2.7 V to 15 V, I
= 0 mA 35 125 ppm/V
OUT
“G” Grade 50 150 ppm/V
LOAD REGULATION
“E/F” Grades ∆V
O
/∆I
LOAD
VS = 5.0 V, 0 mA to 5 mA 20 125 ppm/mA
“G” Grade 30 150 ppm/mA
Electrical Specifications
(VS = ⴙ2.7 V, T
= ⴚ40ⴗC ≤ TA ≤ ⴙ125ⴗC unless otherwise noted)
A
Parameter Symbol Conditions Min Typ Max Units
TEMPERATURE COEFFICIENT
“E” Grade TCV
/°CI
O
= 0 mA 3 10 ppm/°C
OUT
“F” Grade 5 20 ppm/°C
“G” Grade 10 30 ppm/°C
LINE REGULATION
“E/F” Grades ∆V
O
/∆V
IN
2.7 V to 15 V, I
= 0 mA 40 200 ppm/V
OUT
“G” Grade 70 250 ppm/V
LOAD REGULATION
“E/F” Grades ∆V
O
/∆I
LOAD
VS = 5.0 V, 0 mA to 5 mA 20 200 ppm/mA
“G” Grade 30 300 ppm/mA
SUPPLY CURRENT @ +25°C812µA
12 15 µA
THERMAL HYSTERESIS TO-92, SO-8, TSSOP-8 50 ppm
NOTE
Specifications subject to change without notice.
–2–
REV. A
Page 3
ADR291–SPECIFICATIONS
ADR290/ADR291/ADR292
Electrical Specifications
(VS = ⴙ3.0 V, TA = ⴙ25ⴗC unless otherwise noted)
Parameter Symbol Conditions Min Typ Max Units
INITIAL ACCURACY
“E” Grade V
O
I
= 0 mA 2.498 2.500 2.502 V
OUT
“F” Grade 2.497 2.503 V
“G” Grade 2.494 2.506 V
LINE REGULATION
“E/F” Grades ∆V
O
/∆V
IN
3.0 V to 15 V, I
= 0 mA 30 100 ppm/V
OUT
“G” Grade 40 125 ppm/V
LOAD REGULATION
“E/F“ Grades ∆V
O
/∆I
LOAD
VS = 5.0 V, 0 mA to 5 mA 30 100 ppm/mA
“G“ Grade 40 125 ppm/mA
LONG TERM STABILITY ∆V
NOISE VOLTAGE e
WIDEBAND NOISE DENSITY e
Electrical Specifications
N
n
(V
= ⴙ3.0 V, T
S
O
1000 hrs @ +25°C, V
= +15 V 0.2 ppm
S
0.1 Hz to 10 Hz 8 µV p-p
at 1 kHz 480 nV/√Hz
= ⴚ25ⴗC ≤ TA ≤ ⴙ85ⴗC unless otherwise noted)
A
Parameter Symbol Conditions Min Typ Max Units
TEMPERATURE COEFFICIENT
“E” Grade TCV
/°CI
O
= 0 mA 3 8 ppm/°C
OUT
“F” Grade 5 15 ppm/°C
“G” Grade 10 25 ppm/°C
LINE REGULATION
“E/F” Grades ∆V
O
/∆V
IN
3.0 V to 15 V, I
= 0 mA 35 125 ppm/V
OUT
“G” Grade 50 150 ppm/V
LOAD REGULATION
“E/F” Grades ∆V
O
/∆I
LOAD
VS = 5.0 V, 0 mA to 5 mA 20 125 ppm/mA
“G” Grade 30 150 ppm/mA
Electrical Specifications
(VS = ⴙ3.0 V, T
= ⴚ40ⴗC ≤ TA ≤ ⴙ125ⴗC unless otherwise noted)
A
Parameter Symbol Conditions Min Typ Max Units
TEMPERATURE COEFFICIENT
“E” Grade TCV
/°CI
O
= 0 mA 3 10 ppm/°C
OUT
“F” Grade 5 20 ppm/°C
“G” Grade 10 30 ppm/°C
LINE REGULATION
“E/F” Grades ∆V
O
/∆V
IN
3.0 V to 15 V, I
= 0 mA 40 200 ppm/V
OUT
“G” Grade 70 250 ppm/V
LOAD REGULATION
“E/F” Grades ∆V
O
/∆I
LOAD
VS = 5.0 V, 0 mA to 5 mA 20 200 ppm/mA
“G” Grade 30 300 ppm/mA
SUPPLY CURRENT @ +25°C912µA
12 15 µA
THERMAL HYSTERESIS TO-92, SO-8, TSSOP-8 50 ppm
NOTE
Specifications subject to change without notice.
REV. A
–3–
Page 4
ADR290/ADR291/ADR292
ADR292–SPECIFICATIONS
Electrical Specifications
(V
= ⴙ5 V, TA = ⴙ25ⴗC unless otherwise noted)
S
Parameter Symbol Conditions Min Typ Max Units
INITIAL ACCURACY
“E” Grade V
O
I
= 0 mA 4.093 4.096 4.099 V
OUT
“F” Grade 4.092 4.100 V
“G” Grade 4.090 4.102 V
LINE REGULATION
“E/F” Grades ∆V
O
/∆V
IN
4.5 V to 15 V, I
= 0 mA 30 100 ppm/V
OUT
“G” Grade 40 125 ppm/V
LOAD REGULATION
“E/F” Grades ∆V
O
/∆I
LOAD
VS = 5.0 V, 0 mA to 5 mA 30 100 ppm/mA
“G” Grade 40 125 ppm/mA
LONG TERM STABILITY ∆V
NOISE VOLTAGE e
WIDEBAND NOISE DENSITY e
Electrical Specifications
(VS = ⴙ5 V, T
O
N
N
= ⴚ25ⴗC ≤ TA ≤ ⴙ85ⴗC unless otherwise noted)
A
1000 hrs @ +25°C, V
= +15 V 0.2 ppm
S
0.1 Hz to 10 Hz 12 µV p-p
at 1 kHz 640 nV/√Hz
Parameter Symbol Conditions Min Typ Max Units
TEMPERATURE COEFFICIENT
“E” Grade TCV
/°CI
O
= 0 mA 3 8 ppm/°C
OUT
“F” Grade 5 15 ppm/°C
“G” Grade 10 25 ppm/°C
LINE REGULATION
“E/F” Grades ∆V
O
/∆V
IN
4.5 V to 15 V, I
= 0 mA 35 125 ppm/V
OUT
“G” Grade 50 150 ppm/V
LOAD REGULATION
“E/F” Grades ∆V
O
/∆I
LOAD
VS = 5.0 V, 0 mA to 5 mA 20 125 ppm/mA
“G” Grade 30 150 ppm/mA
Electrical Specifications
(VS = ⴙ5 V, T
= ⴚ40ⴗC ≤ TA ≤ ⴙ125ⴗC unless otherwise noted)
A
Parameter Symbol Conditions Min Typ Max Units
TEMPERATURE COEFFICIENT
“E” Grade TCV
/°CI
O
= 0 mA 3 10 ppm/°C
OUT
“F” Grade 5 20 ppm/°C
“G” Grade 10 30 ppm/°C
LINE REGULATION
“E/F” Grades ∆V
O
/∆V
IN
4.5 V to 15 V, I
= 0 mA 40 200 ppm/V
OUT
“G” Grade 70 250 ppm/V
LOAD REGULATION
“E/F” Grades ∆V
O
/∆I
LOAD
VS = 5.0 V, 0 mA to 5 mA 20 200 ppm/mA
“G” Grade 30 300 ppm/mA
SUPPLY CURRENT @ +25°C1015µA
12 18 µA
THERMAL HYSTERESIS TO-92, SO-8, TSSOP-8 50 ppm
NOTE
Specifications subject to change without notice.
–4–
REV. A
Page 5
ADR290/ADR291/ADR292
WAFER TEST LIMITS
(@ I
= 0 mA, TA = ⴙ25ⴗC unless otherwise noted)
LOAD
Parameter Symbol Conditions Limits Units
INITIAL ACCURACY
ADR290 V
ADR291 V
ADR292 V
O
O
O
LINE REGULATION ∆VO/∆V
LOAD REGULATION ∆VO/∆I
IN
LOAD
VO + 1 V < VIN < 15 V, I
= 0 mA 125 ppm/V
OUT
0 to 5 mA, VIN = VO + 1 V 125 ppm/mA
2.042/2.054 V
2.494/2.506 V
4.090/4.102 V
SUPPLY CURRENT ADR290, ADR291, No Load 12 µA
ADR292, No Load 15 µA
NOTES
Electrical tests are performed as wafer probe to the limits shown. Due to variations in assembly methods and normal yield loss, yield after packaging is not guaranteed
for standard product dice. Consult factory to negotiate specifications based on dice lot qualification through sample lot assembly and testing.
Specifications subject to change without notice.
DICE CHARACTERISTICS
Die Size 0.074 ⴛ 0.052 inch, 3848 sq. mils
(1.88 ⴛ 1.32 mm, 2.48 sq. mm)
Transistor Count: 52
1. V
IN
2. GND
3. V
4. V
OUT(FORCE)
OUT(SENSE)
For additional DICE ordering information, refer to databook.
REV. A –5–
Page 6
ADR290/ADR291/ADR292
*
ABSOLUTE MAXIMUM RATINGS*
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ⴙ18 V
Output Short-Circuit Duration . . . . . . . . . . . . . . . . . Indefinite
Storage Temperature Range
T9, R, RU Package . . . . . . . . . . . . . . . . . ⫺65°C to ⴙ150°C
Operating Temperature Range
ADR290/ADR291/ADR292 . . . . . . . . . . . ⫺40°C to ⴙ125°C
Junction Temperature Range
T9, R, RU Package . . . . . . . . . . . . . . . . . ⫺65°C to ⴙ125°C
Lead Temperature (Soldering, 60 sec) . . . . . . . . . . . . ⴙ300°C
Package Type
1
JA
JC
Units
8-Lead SOIC (R) 158 43 °C/W
8-Lead TO-92 (T9) 162 120 °C/W
3-Pin TSSOP (RU) 240 43 °C/W
NOTE
1
θJA is specified for worst case conditions, i.e. θ
for PDIP, and θ
packages.
is specified for a device soldered in circuit board for SOIC
JA
is specified for device in socket
JA
ORDERING GUIDE
Model Temperature Range Package
CAUTION
1. Stresses above those listed under Absolute Maximum
Ratings may cause permanent damage to the device. This is a
stress rating only; functional operation at or above this specification is not implied. Exposure to the above maximum rating
conditions for extended periods may affect device
reliability.
2. Remove power before inserting or removing units from their
sockets.
3. Ratings apply to both DICE and packaged parts, unless otherwise noted
ADR290ER, ADR290FR, ADR290GR ⫺40°C to ⴙ125°C 8-Lead SOIC
ADR290ER-REEL, ADR290FR-REEL, ADR290GR-REEL ⫺40°C to ⴙ125°C 8-Lead SOIC
ADR290ER-REEL7, ADR290FR-REEL7, ADR290GR-REEL7 ⫺40°C to ⴙ125°C 8-Lead SOIC
ADR290GT9 ⫺40°C to ⴙ125°C 3-Pin TO-92
ADR290GT9-REEL ⫺40°C to ⴙ125°C 3-Pin TO-92
ADR290GRU-REEL ⫺40°C to ⴙ125°C 8-Lead TSSOP
ADR290GRU-REEL7 ⫺40°C to ⴙ125°C 8-Lead TSSOP
ADR290GBC ⫹25°C DICE
ADR291ER, ADR291FR, ADR291GR ⫺40°C to ⴙ125°C 8-Lead SOIC
ADR291ER-REEL, ADR291FR-REEL, ADR291GR-REEL ⫺40°C to ⴙ125°C 8-Lead SOIC
ADR291ER-REEL7, ADR291FR-REEL7, ADR291GR-REEL7 ⫺40°C to ⴙ125°C 8-Lead SOIC
ADR291GT9 ⫺40°C to ⴙ125°C 3-Pin TO-92
ADR291GT9-REEL ⫺40°C to ⴙ125°C 3-Pin TO-92
ADR291GRU-REEL ⫺40°C to ⴙ125°C 8-Lead TSSOP
ADR291GRU-REEL7 ⫺40°C to ⴙ125°C 8-Lead TSSOP
ADR291GBC ⫹25°C DICE
ADR292ER, ADR292FR, ADR292GR ⫺40°C to ⴙ125°C 8-Lead SOIC
ADR292ER-REEL, ADR292FR-REEL, ADR292GR-REEL ⫺40°C to ⴙ125°C 8-Lead SOIC
ADR292ER-REEL7, ADR292FR-REEL7, ADR292GR-REEL7 ⫺40°C to ⴙ125°C 8-Lead SOIC
ADR292GT9 ⫺40°C to ⴙ125°C 3-Pin TO-92
ADR292GT9-REEL ⫺40°C to ⴙ125°C 3-Pin TO-92
ADR292GRU-REEL ⫺40°C to ⴙ125°C 8-Lead TSSOP
ADR292GRU-REEL7 ⫺40°C to ⴙ125°C 8-Lead TSSOP
ADR292GBC ⫹25°C DICE
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
the ADR290/ADR291/ADR292 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.
–6–
WARNING!
ESD SENSITIVE DEVICE
REV. A
Page 7
ADR290/ADR291/ADR292
2.054
VS = 5V
2.052
2.050
2.048
2.046
OUTPUT VOLTAGE – V
2.044
2.042
–50 125–25
Figure 1. ADR290 V
2.506
VS = 5V
2.504
2.502
2.500
2.498
OUTPUT VOLTAGE – V
2.496
3 TYPICAL PARTS
0 25 50 75 100
TEMPERATURE – 8C
vs. Temperature
OUT
3 TYPICAL PARTS
14
12
10
QUIESCENT CURRENT – mA
8
6
4
2
0
0162
468101214
INPUT VOLTAGE – V
TA = +1258C
TA = +258C
TA = –408C
Figure 4. ADR290 Quiescent Current vs. Input Voltage
14
12
10
8
6
4
QUIESCENT CURRENT – mA
2
TA = +1258C
TA = +258C
TA = –408C
2.494
–50 125–25
Figure 2. ADR291 V
4.102
VS = 5V
4.100
4.098
4.096
4.094
OUTPUT VOLTAGE – V
4.092
4.090
–50 125–25
Figure 3. ADR292 V
0 25 50 75 100
TEMPERATURE – 8C
vs. Temperature
OUT
3 TYPICAL PARTS
0 25 50 75 100
TEMPERATURE – 8C
vs. Temperature
OUT
0
0162
468101214
INPUT VOLTAGE – V
Figure 5. ADR291 Quiescent Current vs. Input Voltage
16
14
12
10
QUIESCENT CURRENT – mA
8
6
4
2
0
0162
468101214
INPUT VOLTAGE – V
TA = +1258C
TA = +258C
TA = –408C
Figure 6. ADR292 Quiescent Current vs. Input Voltage
REV. A –7–
Page 8
ADR290/ADR291/ADR292
14
VS = 5V
12
10
8
SUPPLY CURRENT – mA
6
4
–50 125–25
ADR292
0 255075100
TEMPERATURE – 8C
ADR291
ADR290
Figure 7. ADR290/ADR291/ADR292 Supply Current vs.
Temperature
100
ADR290: VS = 2.7V TO 15V
ADR291: V
ADR292: V
80
60
= 3.0V TO 15V
S
= 4.5V TO 15V
S
ADR292
I
OUT
= 0mA
0.7
0.6
0.5
TA = +1258C
0.4
0.3
0.2
DIFFERENTIAL VOLTAGE – V
0.1
0
0 5.00.5
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
LOAD CURRENT – mA
TA = –408C
TA = +258C
Figure 10. ADR290 Minimum Input-Output Voltage
Differential vs. Load Current
0.7
0.6
0.5
0.4
TA = +1258C
TA = +258C
40
LINE REGULATION – ppm/V
20
0
–50 125–25
0 255075100
TEMPERATURE – 8C
ADR290
ADR291
Figure 8. ADR290/ADR291/ADR292 Line Regulation vs.
Temperature
100
ADR290: VS = 2.7V TO 7.0V
ADR291: VS = 3.0V TO 7.0V
ADR292: V
80
60
40
LINE REGULATION – ppm/V
20
0
–50 125–25
ADR291
= 4.5V TO 9.0V
S
0 255075100
TEMPERATURE – 8C
I
ADR290
= 0mA
OUT
ADR292
Figure 9. ADR290/ADR291/ADR292 Line Regulation vs.
Temperature
0.3
0.2
DIFFERENTIAL VOLTAGE – V
0.1
0
0 5.00.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
LOAD CURRENT – mA
TA = –408C
Figure 11. ADR291 Minimum Input-Output Voltage
Differential vs. Load Current
0.7
0.6
0.5
0.4
0.3
0.2
DIFFERENTIAL VOLTAGE – V
0.1
0
0 5.00.5
TA = +1258C
TA = +258C
TA = –408C
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
LOAD CURRENT – mA
Figure 12. ADR292 Minimum Input-Output Voltage
Differential vs. Load Current
–8–
REV. A
Page 9
200
SOURCING LOAD CURRENT – mA
500
–250
–1000
0.1 101
D V
OUT
FROM NOMINAL – mV
–750
–500
0
250
TA = +258C
TA = +1258C
TA = –408C
SOURCING LOAD CURRENT – mA
0
–1250
–2000
0.1 101
D V
OUT
FROM NOMINAL – mV
–1750
–1500
–500
–250
TA = +258C
TA = +1258C
TA = –408C
–1000
–750
SOURCING LOAD CURRENT – mA
0
–2500
–4000
0.1 101
D V
OUT
FROM NOMINAL – mV
–3500
–3000
–1000
–500
TA = +258C
TA = +1258C
TA = –408C
–2000
–1500
160
ADR290/ADR291/ADR292
VS = 5V
120
80
LINE REGULATION – ppm/mA
40
0
–50 125–25
0 255075100
TEMPERATURE – 8C
I
OUT
I
OUT
= 1mA
= 5mA
Figure 13. ADR290 Line Regulation vs. Temperature
200
VS = 5V
160
I
= 1mA
120
80
40
LOAD REGULATION – ppm/mA
OUT
I
OUT
= 5mA
Figure 16. ADR290 ∆V
from Nominal vs. Load Current
OUT
Figure 14. ADR291 Load Regulation vs. Temperature
Figure 15. ADR292 Load Regulation vs. Temperature
REV. A –9–
0
–50 125–25
200
VS = 5V
160
120
80
LOAD REGULATION – ppm/mA
40
0
–50 125–25
0 255075100
TEMPERATURE – 8C
I
= 1mA
OUT
0 255075100
TEMPERATURE – 8C
I
OUT
= 5mA
Figure 17. ADR291 ∆V
Figure 18. ADR292 ∆V
from Nominal vs. Load Current
OUT
from Nominal vs. Load Current
OUT
Page 10
ADR290/ADR291/ADR292
1000
900
800
700
600
500
400
300
200
VOLTAGE NOISE DENSITY – nV/!Hz
100
0
10 1000100
ADR292
ADR291
ADR290
FREQUENCY – Hz
V
T
IN
A
= 15V
= 258C
Figure 19. Voltage Noise Density vs. Frequency
120
VS = 5V
100
80
60
40
RIPPLE REJECTION – dB
20
50
VS = 5V
I
= 0 mA
L
40
30
20
OUTPUT IMPEDANCE – V
10
0
0 10k10
100 1k
FREQUENCY – Hz
Figure 22. ADR290 Output Impedance vs. Frequency
50
VS = 5V
I
= 0 mA
L
40
30
20
OUTPUT IMPEDANCE – V
10
0
10 1000100
FREQUENCY – Hz
Figure 20. ADR290/ADR291/ADR292 Ripple Rejection vs.
Frequency
1s
100
90
2mV
P–P
10
0%
TIME – sec
Figure 21. ADR290 0.1 Hz to 10 Hz Noise
0
0 10k10
100 1k
FREQUENCY – Hz
Figure 23. ADR291 Output Impedance vs. Frequency
50
VS = 5V
I
= 0 mA
L
40
30
20
OUTPUT IMPEDANCE – V
10
0
0 10k10
100 1k
FREQUENCY – Hz
Figure 24. ADR292 Output Impedance vs. Frequency
–10–
REV. A
Page 11
ADR290/ADR291/ADR292
100
IL = 5mA
90
10
0%
OFF
ON
Figure 25. ADR291 Load Transient
IL = 5mA
CL = 1nF
100
90
OFF
ON
10
0%
1ms
1V
1ms
1V
IL = 5mA
100
90
10
0%
Figure 28. ADR291 Turn-On Time
IL = 0mA
100
90
10
0%
500ms
1V
10ms
1V
Figure 26. ADR291 Load Transient
IL = 5mA
100
OFF
ON
0%
CL = 100nF
90
10
Figure 27. ADR291 Load Transient
Figure 29. ADR291 Turn-Off Time
5ms
1V
REV. A –11–
Page 12
ADR290/ADR291/ADR292
THEORY OF OPERATION
The ADR29x series of references uses a new reference generation
technique known as XFET (eXtra implanted junction FET). This
technique yields a reference with low noise, low supply current
and very low thermal hysteresis.
The core of the XFET reference consists of two junction fieldeffect 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 compensated by adding a correction term generated in
the same fashion as the proportional-to-temperature (PTAT)
term used to compensate bandgap references. The big advantage over a bandgap reference is that the intrinsic temperature
coefficient is some thirty times lower (therefore less correction is
needed) and this results in much lower noise since most of the
noise of a bandgap reference comes from the temperature compensation circuitry.
The simplified schematic below shows the basic topology of the
ADR29x series. The temperature correction term is provided by
a current source with value designed to be proportional to absolute temperature. The general equation is:
Device Power Dissipation Considerations
The ADR29x family of references is guaranteed to deliver load
currents to 5 mA with an input voltage that ranges from 2.7 V
to 15 V (minimum supply voltage depends on output voltage
option). When these devices are 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:
TT
−
JA
P
=
D
θ
JA
In this equation, TJ and TA are the junction and ambient temperatures, respectively, P
is the device package thermal resistance.
θ
JA
is the device power dissipation, and
D
Basic Voltage Reference Connections
References, in general, require a bypass capacitor connected
from the V
pin to the GND pin. The circuit in Figure 31
OUT
illustrates the basic configuration for the ADR29x family of references. Note that the decoupling capacitors are not required
for circuit stability.
NC
1
8
NC
VV
where ∆V
is the difference in pinch-off voltage between the two
P
FETs, and I
RR R
++
∆
123
R
=
OUT P PTAT
is the positive temperature coefficient correc-
PTAT
IR
+
()()
1
3
tion current. The various versions of the ADR29x family are
created by on-chip adjustment of R1 and R3 to achieve 2.048 V,
2.500 V or 4.096 V at the reference output.
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 drop-out voltage.
V
IN
I1I
1
*
∆V
P
*EXTRA CHANNEL IMPLANT
ⴙⴙ
V
ⴝ
OUT
R3R2R1
ⴛ ∆VPⴙ I
R1
PTAT
R1
R2
R3
ⴛ
R3
I
PTAT
GND
V
OUT
Figure 30. ADR290/ADR291/ADR292 Simplified Schematic
+
10F 0.1F
NC
2
3
4
ADR29x
7
6
5
NC
OUTPUT
NC
0.1F
Figure 31. Basic Voltage Reference Configuration
Noise Performance
The noise generated by the ADR29x family of references is typi-
cally less than 12 µV p-p over the 0.1 Hz to 10 Hz band. Figure
21 shows the 0.1 Hz to 10 Hz noise of the ADR290 which is
only 6 µV p-p. The noise measurement is made with a bandpass
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 28 shows the turn-on settling time for the
ADR291.
APPLICATIONS SECTION
A Negative Precision Reference without Precision Resistors
In many current-output CMOS DAC applications, where the
output signal voltage must be of the same polarity as the reference voltage, it is often required to reconfigure a current-switching DAC into a voltage-switching DAC through the use of a
1.25 V reference, an op amp and a pair of resistors. Using a current-switching DAC directly requires the need for an additional
operational amplifier at the output to reinvert the signal. A
negative voltage reference is then desirable from the point that
–12–
REV. A
Page 13
an additional operational amplifier is not required for either
ADR29x
4
6
2
V
IN
GND
V
OUT
R
L
1F
I
OUT
冧
P
1
R
1
R
SET
I
SY
ADJUST
ADR290
V
IN
GND
–V
S
OP90
2N3904
2.10k⍀
+V
S
E231
SILICONIX
reinversion (current-switching mode) or amplification (voltageswitching mode) of the DAC output voltage. In general, any
positive voltage reference can be converted into a negative voltage reference through the use of an operational amplifier and a
pair of matched resistors in an inverting configuration. The disadvantage to that approach is that the largest single source of
error in the circuit is the relative matching of the resistors used.
The circuit illustrated in Figure 32 avoids the need for tightly
matched resistors with the use of an active integrator circuit. In
this circuit, the output of the voltage reference provides the
input drive for the integrator. The integrator, to maintain circuit
equilibrium adjusts its output to establish the proper relationship
between the reference’s V
and GND. Thus, any negative
OUT
output voltage desired can be chosen by simply substituting for
the appropriate reference IC. One caveat with this approach
should be mentioned: although rail-to-rail output amplifiers
work best in the application, these operational amplifiers require
a finite amount (mV) of headroom when required to provide
any load current. The choice for the circuit’s negative supply
should take this issue into account.
V
IN
ADR290/ADR291/ADR292
Figure 33. A Precision Current Source
High Voltage Floating Current Source
The circuit of Figure 34 can be used to generate a floating current source with minimal self heating. This particular configuration can operate on high supply voltages determined by the
breakdown voltage of the N-channel JFET.
2
ADR29x
GND
4
6
V
OUT
100k⍀
1k⍀
1F
1F
+5V
A
1
–5V
A
= 1/2 OP291,
1
100⍀
1/2 OP295
–V
REF
Figure 32. A Negative Precision Voltage Reference Uses
No Precision Resistors
A Precision Current Source
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 33, any one of the devices in the ADR29x
family of references can be configured as a precision current
source. The circuit configuration illustrated is a floating current
source with a grounded load. The reference’s output voltage is
bootstrapped across R
load. With this configuration, circuit precision is maintained for
load currents in the range from the reference’s supply current,
typically 12 µA to approximately 5 mA.
REV. A –13–
which sets the output current into the
SET,
Figure 34. High Voltage Floating Current Source
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 mW/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 (V
= R ⫻ IL ) at
ERROR
the load. However, the Kelvin connection of Figure 35, overcomes
the problem by including the wiring resistance within the forcing
loop of the op amp. Since 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.
Page 14
ADR290/ADR291/ADR292
V
IN
R
LW
+V
R
LW
A1
= 1/2 OP295
OUT
SENSE
+V
OUT
FORCE
R
L
2
ADR29x
GND
4
V
IN
6
V
OUT
1F
A1
100k⍀
Figure 35. Advantage of Kelvin Connection
Low Power, Low Voltage Reference For Data Converters
The ADR29x family has a number of features that makes it
ideally suited for use with A/D and D/A converters. The low
supply voltage required makes it possible to use the ADR29x
with today’s converters that run on 3 V supplies without having
to add a higher supply voltage for the reference. The low quies-
cent current (12 µA max) and low noise, tight temperature coef-
ficient, combined with the high accuracy of the ADR29x makes
it ideal for low power applications such as hand-held, battery
operated equipment.
One such ADC for which the ADR291 is well suited is the
AD7701. Figure 36 shows the ADR291 used as the reference
for this converter. The AD7701 is a 16-bit A/D converter with
on-chip digital filtering intended for the measurement of wide
dynamic range, low frequency signals such as those representing
chemical, physical or biological processes. It contains a charge
balancing (sigma-delta) ADC, calibration microcontroller with
on-chip static RAM, a clock oscillator and a serial communications port.
This entire circuit runs on ±5 V supplies. The power dissipation
of the AD7701 is typically 25 mW and, when combined with
the power dissipation of the ADR291 (60 µW), the entire circuit
still consumes about 25 mW.
Voltage Regulator For Portable Equipment
The ADR29x family of references is ideal for providing a stable,
low cost and low power reference voltage in portable equipment
power supplies. Figure 37 shows how the ADR290/ADR291/
ADR292 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 recommended for C1 and C2, respectively. Also, the
path from the ground side of C1 and C2 to the ground side of
R1 should be kept as short as possible.
CHARGER
INPUT
LEAD-ACID
BATTERY
0.1mF
2
V
IN
V
+
OUT
ADR29x
TEMP
GND
4
6V
2
6
3
3
R1
402kV
402kV
1%
7
4
1%
R3
510kV
68mF
TANT
C1
IRF9530
++
+5V, 100mA
C2
1000mF
ELECT
6
OP20
R2
Figure 37. Voltage Regulator for Portable Equipment
+5V
ANALOG
SUPPLY
RANGES
SELECT
CALIBRATE
ANALOG
ANALOG
GROUND
ANALOG
SUPPLY
0.1mF
INPUT
–5V
10mF0.1mF
V
ADR291
GND
0.1mF
V
OUT
AV
DD
DV
IN
V
REF
AD7701
BP/UP
CAL
A
IN
AGND
AV
SS
10mF0.1mF
SLEEP
MODE
DRDY
CS
SCLK
SDATA
CLKIN
CLKOUT
SC1
SC2
DGND
DV
DD
SS
0.1mF
DATA READY
READ
(TRANSMIT)
SERIAL
SERIAL
0.1mF
CLOCK
CLOCK
Figure 36. Low Power, Low Voltage Supply Reference for
the AD7701
–14–
REV. A
Page 15
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
8-Lead Narrow Body SO (R Suffix)
0.1968 (5.00)
0.1890 (4.80)
ADR290/ADR291/ADR292
0.2440 (6.20)
0.2284 (5.80)
0.0098 (0.25)
0.0040 (0.10)
SEATING
PLANE
0.006 (0.15)
0.002 (0.05)
SEATING
PLANE
85
PIN 1
0.0500
(1.27)
BSC
0.1574 (4.00)
0.1497 (3.80)
41
0.102 (2.59)
0.094 (2.39)
0.0192 (0.49)
0.0138 (0.35)
0.0098 (0.25)
0.0075 (0.19)
8-Lead TSSOP (RU Suffix)
0.122 (3.10)
0.114 (2.90)
8
5
0.177 (4.50)
0.169 (4.30)
PIN 1
1
0.0256 (0.65)
BSC
0.0118 (0.30)
0.0075 (0.19)
4
0.256 (6.50)
0.246 (6.25)
0.0433
(1.10)
MAX
0.0079 (0.20)
0.0035 (0.090)
8°
0°
0.0196 (0.50)
0.0099 (0.25)
8°
0°
0.0500 (1.27)
0.0160 (0.41)
0.028 (0.70)
0.020 (0.50)
x 45°
C3151–0–2/00 (rev. A)
3-Pin TO-92 (T9 Suffix)
0.135
(3.43)
MIN
SEATING
PLANE
0.500
(12.70)
MIN
0.105 (2.66)
0.095 (2.42)
0.105 (2.66)
0.080 (2.42)
0.105 (2.66)
0.080 (2.42)
123
BOTTOM VIEW
REV. A –15–
0.205 (5.20)
0.175 (4.96)
0.210 (5.33)
0.170 (4.38)
0.019 (0.482)
0.016 (0.407)
SQUARE
0.055 (1.39)
0.045 (1.15)
0.165 (4.19)
0.125 (3.94)
0.050
(1.27)
MAX
PRINTED IN U.S.A.
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