a
Low Noise Micropower
Precision Voltage References
ADR290/ADR291/ADR292
PIN CONFIGURATIONS
8-Lead Narrow Body SO (R Suffix)
FEATURES
Voltage Options 2.048 V, 2.500 V and 4.096 V
2.7 V to 15 V Supply Range
Supply Current 12 mA max
Initial Accuracy 62 mV max
Temperature Coefficient 8 ppm/8C max
Low-Noise 6 mV p-p (0.1 – 10 Hz)
High Output Current 5 mA min
Temperature Range 2408C to 11258C
REF02/REF19x Pinout
ADR29x
7
TOP VIEW
(Not
to
Scale)
6 VOUT
3
GND 4
OBS
5
8-Lead TSSOP (RU Suffix)
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
8
1
VIN 2
OLE
8
1
VIN 2
ADR29x
7
TOP VIEW
3 (Not to Scale) 6 VOUT
GND 4
5
TE
3-Pin TO-92 (T9 Suffix)
The ADR290, ADR291 and ADR292 are low noise, micropower precision voltage references that use an XFET™ reference circuit. The new XFET™ architecture offers significant
performance improvements over traditional bandgap and Zenerbased 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.
PIN 1
VIN
PIN 2
PIN 3
GND
VOUT
BOTTOM VIEW
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 instrumentation. 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.
Part Number
Nominal Output Voltage (V)
ADR290
ADR291
ADR292
2.048
2.500
4.096
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.
XFET is a trademark of Analog Devices, Inc.
REV. 0
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., 1997
ADR290/ADR291/ADR292
ADR290–SPECIFICATIONS
Electrical Specifications (V = 12.7 V, T = 1258C unless otherwise noted)
A
S
Parameter
Symbol
Conditions
Min
Typ
INITIAL ACCURACY
“E” Grade
“F” Grade
“G” Grade
VO
IOUT = 0 mA
2.046
2.045
2.042
2.048 2.050
2.051
2.054
V
V
V
LINE REGULATION
“E/F” Grades
“G” Grade
∆VO/∆VIN
2.7 V to 15 V, IOUT = 0 mA
30
40
100
125
ppm/V
ppm/V
100
125
ppm/mA
ppm/mA
OBS
Max
Units
LOAD REGULATION
“E/F” Grades
“G” Grade
∆VO/∆ILOAD
VS = 5.0 V, 0 mA to 5 mA
30
40
LONG TERM STABILITY
∆VO
1000 hrs @ +25°C, VS = +15 V
0.2
ppm
NOISE VOLTAGE
eN
0.1 Hz to 10 Hz
6
µV p-p
WIDEBAND NOISE DENSITY
en
at 1 kHz
420
nV/√Hz
OLE
Electrical Specifications (V = 12.7 V, T = 2258C ≤ T ≤ 1858C unless otherwise noted)
S
A
A
Parameter
Symbol
Conditions
TEMPERATURE COEFFICIENT
“E” Grade
“F” Grade
“G” Grade
TCVO/°C
IOUT = 0 mA
LINE REGULATION
“E/F” Grades
“G” Grade
∆VO/∆VIN
2.7 V to 15 V, IOUT = 0 mA
LOAD REGULATION
“E/F” Grades
“G” Grade
∆VO/∆ILOAD
VS = 5.0 V, 0 mA to 5 mA
TE
Min
Typ
Max
Units
3
6
10
8
15
25
ppm/°C
ppm/°C
ppm/°C
35
50
125
150
ppm/V
ppm/V
20
30
125
150
ppm/mA
ppm/mA
Typ
Max
Units
Electrical Specifications (V = 12.7 V, T = 2408C ≤ T ≤ 11258C unless otherwise noted)
A
S
A
Parameter
Symbol
Conditions
Min
TEMPERATURE COEFFICIENT
“E” Grade
“F” Grade
“G” Grade
TCVO/°C
IOUT = 0 mA
3
5
10
10
20
30
ppm/°C
ppm/°C
ppm/°C
LINE REGULATION
“E/F” Grades
“G” Grade
∆VO/∆VIN
2.7 V to 15 V, IOUT = 0 mA
40
70
200
250
ppm/V
ppm/V
LOAD REGULATION
“E/F” Grades
“G” Grade
∆VO/∆ILOAD
VS = 5.0 V, 0 mA to 5 mA
20
30
200
300
ppm/mA
ppm/mA
SUPPLY CURRENT
@ +25°C
8
12
12
15
µA
µA
THERMAL HYSTERESIS
TO-92, SO-8, TSSOP-8
50
ppm
NOTE
Specifications subject to change without notice.
–2–
REV. 0
ADR291–SPECIFICATIONS
ADR290/ADR291/ADR292
Electrical Specifications (V = 13.0 V, T = 1258C unless otherwise noted)
A
S
Parameter
Symbol
Conditions
Min
Typ
INITIAL ACCURACY
“E” Grade
“F” Grade
“G” Grade
VO
IOUT = 0 mA
2.498
2.497
2.494
2.500 2.502
2.503
2.506
V
V
V
LINE REGULATION
“E/F” Grades
“G” Grade
∆VO/∆VIN
3.0 V to 15 V, IOUT = 0 mA
30
40
100
125
ppm/V
ppm/V
LOAD REGULATION
“E/F“ Grades
“G“ Grade
∆VO/∆ILOAD
VS = 5.0 V, 0 mA to 5 mA
30
40
100
125
ppm/mA
ppm/mA
LONG TERM STABILITY
∆VO
1000 hrs @ +25°C, VS = +15 V
0.2
ppm
NOISE VOLTAGE
eN
0.1 Hz to 10 Hz
8
µV p-p
WIDEBAND NOISE DENSITY
en
at 1 kHz
480
nV/√Hz
OBS
OLE
Max
Units
Electrical Specifications (V = 13.0 V, T = 2258C ≤ T ≤ 1858C unless otherwise noted)
S
A
A
Parameter
Symbol
Conditions
TEMPERATURE COEFFICIENT
“E” Grade
“F” Grade
“G” Grade
TCVO/°C
IOUT = 0 mA
LINE REGULATION
“E/F” Grades
“G” Grade
∆VO/∆VIN
3.0 V to 15 V, IOUT = 0 mA
LOAD REGULATION
“E/F” Grades
“G” Grade
∆VO/∆ILOAD
VS = 5.0 V, 0 mA to 5 mA
Min
Typ
Max
Units
TE
3
5
10
8
15
25
ppm/°C
ppm/°C
ppm/°C
35
50
125
150
ppm/V
ppm/V
20
30
125
150
ppm/mA
ppm/mA
Typ
Max
Units
Electrical Specifications (V = 13.0 V, T = 2408C ≤ T ≤ 11258C unless otherwise noted)
A
S
A
Parameter
Symbol
Conditions
TEMPERATURE COEFFICIENT
“E” Grade
“F” Grade
“G” Grade
TCVO/°C
IOUT = 0 mA
3
5
10
10
20
30
ppm/°C
ppm/°C
ppm/°C
LINE REGULATION
“E/F” Grades
“G” Grade
∆VO/∆VIN
3.0 V to 15 V, IOUT = 0 mA
40
70
200
250
ppm/V
ppm/V
LOAD REGULATION
“E/F” Grades
“G” Grade
∆VO/∆ILOAD
VS = 5.0 V, 0 mA to 5 mA
20
30
200
300
ppm/mA
ppm/mA
SUPPLY CURRENT
@ +25°C
9
12
12
15
µA
µA
THERMAL HYSTERESIS
TO-92, SO-8, TSSOP-8
50
NOTE
Specifications subject to change without notice.
REV. 0
–3–
Min
ppm
ADR290/ADR291/ADR292
ADR292–SPECIFICATIONS
Electrical Specifications
(VS = 15 V, TA = 1258C unless otherwise noted)
Parameter
Symbol
Conditions
Min
Typ
INITIAL ACCURACY
“E” Grade
“F” Grade
“G” Grade
VO
IOUT = 0 mA
4.093
4.092
4.090
4.096 4.099
4.100
4.102
V
V
V
LINE REGULATION
“E/F” Grades
“G” Grade
∆VO/∆VIN
4.5 V to 15 V, IOUT = 0 mA
30
40
100
125
ppm/V
ppm/V
100
125
ppm/mA
ppm/mA
OBS
Max
Units
LOAD REGULATION
“E/F” Grades
“G” Grade
∆VO/∆ILOAD
VS = 5.0 V, 0 mA to 5 mA
30
40
LONG TERM STABILITY
∆VO
1000 hrs @ +25°C, VS = +15 V
0.2
ppm
NOISE VOLTAGE
eN
0.1 Hz to 10 Hz
µV p-p
WIDEBAND NOISE DENSITY
eN
OLE
12
at 1 kHz
640
nV/√Hz
Electrical Specifications
(VS = 15 V, TA = 2258C ≤ TA ≤ 1858C unless otherwise noted)
Parameter
Symbol
Conditions
TEMPERATURE COEFFICIENT
“E” Grade
“F” Grade
“G” Grade
TCVO/°C
IOUT = 0 mA
LINE REGULATION
“E/F” Grades
“G” Grade
∆VO/∆VIN
4.5 V to 15 V, IOUT = 0 mA
LOAD REGULATION
“E/F” Grades
“G” Grade
∆VO/∆ILOAD
VS = 5.0 V, 0 mA to 5 mA
Electrical Specifications
TE
Min
Typ
Max
Units
3
5
10
8
15
25
ppm/°C
ppm/°C
ppm/°C
35
50
125
150
ppm/V
ppm/V
20
30
125
150
ppm/mA
ppm/mA
Typ
Max
Units
(VS = 15 V, TA = 2408C ≤ TA ≤ 11258C unless otherwise noted)
Parameter
Symbol
Conditions
Min
TEMPERATURE COEFFICIENT
“E” Grade
“F” Grade
“G” Grade
TCVO/°C
IOUT = 0 mA
3
5
10
10
20
30
ppm/°C
ppm/°C
ppm/°C
LINE REGULATION
“E/F” Grades
“G” Grade
∆VO/∆VIN
4.5 V to 15 V, IOUT = 0 mA
40
70
200
250
ppm/V
ppm/V
LOAD REGULATION
“E/F” Grades
“G” Grade
∆VO/∆ILOAD
VS = 5.0 V, 0 mA to 5 mA
20
30
200
300
ppm/mA
ppm/mA
SUPPLY CURRENT
@ +25°C
10
12
15
18
µA
µA
THERMAL HYSTERESIS
TO-92, SO-8, TSSOP-8
50
ppm
NOTE
Specifications subject to change without notice.
–4–
REV. 0
ADR290/ADR291/ADR292
WAFER TEST LIMITS (@ I
LOAD
= 0 mA, TA = 1258C unless otherwise noted)
Parameter
Symbol
Conditions
INITIAL ACCURACY
ADR290
ADR291
ADR292
VO
VO
VO
LINE REGULATION
∆VO/∆VIN
LOAD REGULATION
∆VO/∆ILOAD
SUPPLY CURRENT
OBS
Limits
Units
2.042/2.054
2.494/2.506
4.090/4.102
V
V
V
VO + 1 V < VIN < 15 V, IOUT = 0 mA
125
ppm/V
0 to 5 mA, VIN = VO + 1 V
125
ppm/mA
ADR290, ADR291, no load
ADR292, no load
12
15
µA
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.
1
OLE
DICE CHARACTERISTICS
Die Size 0.074 3 0.052 inch, 3848 sq. mils
(1.88 3 1.32 mm, 2.48 sq. mm)
Transistor Count: 52
4
TE
3
2
For additional DICE ordering information, refer to databook.
REV. 0
–5–
1. V IN
2. GND
3. VOUT(FORCE)
4. VOUT(SENSE)
ADR290/ADR291/ADR292
ABSOLUTE MAXIMUM RATINGS*
*CAUTION
Supply Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 V
Output Short-Circuit Duration . . . . . . . . . . . . . . . . . Indefinite
Storage Temperature Range
T9, R, RU Package . . . . . . . . . . . . . . . . . 265°C to 1150°C
Operating Temperature Range
ADR290/ADR291/ADR292 . . . . . . . . . . . 240°C to 1125°C
Junction Temperature Range
T9, R, RU Package . . . . . . . . . . . . . . . . . 265°C to 1125°C
Lead Temperature (Soldering, 60 sec) . . . . . . . . . . . . 1300°C
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.
Package Type
uJA1
uJC
Units
8-Lead SOIC (R)
8-Lead TO-92 (T9)
3-Pin TSSOP (RU)
158
162
240
43
120
43
°C/W
°C/W
°C/W
OBS
2. Remove power before inserting or removing units from their
sockets.
3. Ratings apply to both DICE and packaged parts, unless otherwise noted
NOTE
1
θJA is specified for worst case conditions, i.e. θJA is specified for device in socket
for PDIP, and θJA is specified for a device soldered in circuit board for SOIC
packages.
Model
OLE
ORDERING GUIDE
Temperature Range
Package
ADR290ER, ADR290FR, ADR290GR
ADR290ER-REEL, ADR290FR-REEL, ADR290GR-REEL
ADR290ER-REEL7, ADR290FR-REEL7, ADR290GR-REEL7
ADR290GT9
ADR290GT9-REEL
ADR290GRU-REEL
ADR290GRU-REEL7
ADR290GBC
240°C to 1125°C
240°C to 1125°C
240°C to 1125°C
240°C to 1125°C
240°C to 1125°C
240°C to 1125°C
240°C to 1125°C
125°C
8-Lead SOIC
8-Lead SOIC
8-Lead SOIC
3-Pin TO-92
3-Pin TO-92
8-Lead TSSOP
8-Lead TSSOP
DICE
ADR291ER, ADR291FR, ADR291GR
ADR291ER-REEL, ADR291FR-REEL, ADR291GR-REEL
ADR291ER-REEL7, ADR291FR-REEL7, ADR291GR-REEL7
ADR291GT9
ADR291GT9-REEL
ADR291GRU-REEL
ADR291GRU-REEL7
ADR291GBC
240°C to 1125°C
240°C to 1125°C
240°C to 1125°C
240°C to 1125°C
240°C to 1125°C
240°C to 1125°C
240°C to 1125°C
125°C
ADR292ER, ADR292FR, ADR292GR
ADR292ER-REEL, ADR292FR-REEL, ADR292GR-REEL
ADR292ER-REEL7, ADR292FR-REEL7, ADR292GR-REEL7
ADR292GT9
ADR292GT9-REEL
ADR292GRU-REEL
ADR292GRU-REEL7
ADR292GBC
240°C to 1125°C
240°C to 1125°C
240°C to 1125°C
240°C to 1125°C
240°C to 1125°C
240°C to 1125°C
240°C to 1125°C
125°C
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–
TE
8-Lead SOIC
8-Lead SOIC
8-Lead SOIC
3-Pin TO-92
3-Pin TO-92
8-Lead TSSOP
8-Lead TSSOP
DICE
8-Lead SOIC
8-Lead SOIC
8-Lead SOIC
3-Pin TO-92
3-Pin TO-92
8-Lead TSSOP
8-Lead TSSOP
DICE
WARNING!
ESD SENSITIVE DEVICE
REV. 0
ADR290/ADR291/ADR292
2.054
14
VS = 5V
3 TYPICAL PARTS
12
QUIESCENT CURRENT –
OUTPUT VOLTAGE – V
A
2.052
2.050
2.048
2.046
2.044
2.042
–50
10
TA = +125 C
8
TA = +25 C
TA = –40 C
6
4
2
OBS
–25
0
25
50
75
100
0
125
0
2
4
TEMPERATURE – C
Figure 1. ADR290 VOUT vs. Temperature
VS = 5V
16
14
2.502
2.500
2.498
A
12
QUIESCENT CURRENT –
OUTPUT VOLTAGE – V
14
3 TYPICAL PARTS
2.504
2.496
10
8
6
4
2
–25
12
Figure 4. ADR290 Quiescent Current vs. Input Voltage
OLE
2.506
2.494
–50
6
8
10
INPUT VOLTAGE – V
0
25
50
75
100
0
125
0
2
4
TEMPERATURE – C
Figure 2. ADR291 VOUT vs. Temperature
TA = +125 C
TE
TA = +25 C
TA = –40 C
6
8
10
INPUT VOLTAGE – V
12
14
16
Figure 5. ADR291 Quiescent Current vs. Input Voltage
4.102
16
VS = 5V
3 TYPICAL PARTS
14
QUIESCENT CURRENT –
OUTPUT VOLTAGE – V
A
4.100
4.098
4.096
4.094
12
TA = +125 C
10
TA = +25 C
TA = –40 C
8
6
4
4.092
2
4.090
–50
–25
0
25
50
75
100
0
125
TEMPERATURE – C
Figure 3. ADR292 VOUT vs. Temperature
REV. 0
0
2
4
6
8
10
INPUT VOLTAGE – V
12
14
16
Figure 6. ADR292 Quiescent Current vs. Input Voltage
–7–
ADR290/ADR291/ADR292
0.7
14
VS = 5V
0.6
ADR291
SUPPLY CURRENT –
A
ADR292
DIFFERENTIAL VOLTAGE – V
12
10
8
ADR290
6
TA = –40 C
0.5
TA = +125 C
0.4
0.3
TA = +25 C
0.2
0.1
4
–50
OBS
–25
0
25
50
75
100
0
125
0
0.5
1.0
1.5
TEMPERATURE – C
Figure 7. ADR290/ADR291/ADR292 Supply Current vs.
Temperature
IOUT = 0mA
80
60
ADR292
40
ADR290
25
50
75
100
TA = +125 C
0.5
0.4
0.3
0.2
0.1
ADR291
0
Figure 8. ADR290/ADR291/ADR292 Line Regulation vs.
Temperature
TE
TA = +25 C
TA = –40 C
0
125
0
0.5
1.0
1.5
TEMPERATURE – C
2.0
2.5
3.0 3.5
LOAD CURRENT – mA
4.0
4.5
5.0
Figure 11. ADR291 Minimum Input-Output Voltage
Differential vs. Load Current
0.7
100
ADR290: VS = 2.7V TO 7.0V
ADR291: VS = 3.0V TO 7.0V
ADR292: VS = 4.5V TO 9.0V
IOUT = 0mA
0.6
80
DIFFERENTIAL VOLTAGE – V
LINE REGULATION – ppm/V
5.0
0.6
20
–25
4.5
0.7
DIFFERENTIAL VOLTAGE – V
LINE REGULATION – ppm/V
ADR290: VS = 2.7V TO 15V
ADR291: VS = 3.0V TO 15V
ADR292: VS = 4.5V TO 15V
4.0
Figure 10. ADR290 Minimum Input-Output Voltage
Differential vs. Load Current
OLE
100
0
–50
2.0
2.5
3.0 3.5
LOAD CURRENT – mA
60
ADR290
ADR291
40
ADR292
20
TA = +125 C
0.5
TA = +25 C
0.4
0.3
0.2
TA = –40 C
0.1
0
–50
–25
0
25
50
75
100
0
125
0
TEMPERATURE – C
Figure 9. ADR290/ADR291/ADR292 Line Regulation vs.
Temperature
0.5
1.0
1.5
2.0
2.5
3.0 3.5
LOAD CURRENT – mA
4.0
4.5
5.0
Figure 12. ADR292 Minimum Input-Output Voltage
Differential vs. Load Current
–8–
REV. 0
ADR290/ADR291/ADR292
500
200
250
V
160
∆ VOUT FROM NOMINAL –
LINE REGULATION – ppm/mA
VS = 5V
120
IOUT = 1mA
80
40
0
TA = +25 C
–250
TA = +125 C
–500
TA = –40 C
–750
IOUT = 5mA
0
–50
OBS
0
–25
25
50
75
100
–1000
0.1
125
TEMPERATURE – C
OLE
160
IOUT = 1mA
120
–250
V
LOAD REGULATION – ppm/mA
VS = 5V
0
∆ VOUT FROM NOMINAL –
200
IOUT = 5mA
80
40
0
25
50
75
100
–750
–100
–1250
–1500
–2000
0.1
125
TEMPERATURE – C
TE
TA = –40 C
TA = +125 C
1
SOURCING LOAD CURRENT – mA
10
Figure 17. ADR291 ∆VOUT from Nominal vs. Load Current
Figure 14. ADR291 Load Regulation vs. Temperature
0
200
VS = 5V
–500
V
160
∆ VOUT FROM NOMINAL –
LOAD REGULATION – ppm/mA
TA = +25 C
–500
–1750
–25
10
Figure 16. ADR290 ∆VOUT from Nominal vs. Load Current
Figure 13. ADR290 Load Regulation vs. Temperature
0
–50
1
SOURCING LOAD CURRENT – mA
120
IOUT = 1mA
IOUT = 5mA
80
–1000
–1500
TA = +25 C
TA = –40 C
TA = +125 C
–2000
–2500
–3000
40
–3500
0
–50
–25
0
25
50
75
100
–4000
0.1
125
TEMPERATURE – C
10
Figure 18. ADR292 ∆VOUT from Nominal vs. Load Current
Figure 15. ADR292 Load Regulation vs. Temperature
REV. 0
1
SOURCING LOAD CURRENT – mA
–9–
ADR290/ADR291/ADR292
1000
50
ADR292
900
VS = 5V
IL = 0 mA
VIN = 15V
TA = 25 C
40
OUTPUT IMPEDANCE – Ω
VOLTAGE NOISE DENSITY – µV/√Hz
800
700
ADR291
600
500
400
300
ADR290
200
20
10
100
0
10
OBS
100
FREQUENCY – Hz
0
1000
Figure 19. Voltage Noise Density
VS = 5V
100
80
60
40
0
10
1k
10k
OLE
50
VS = 5V
IL = 0 mA
40
30
20
10
20
0
10
100
FREQUENCY – Hz
Figure 22. ADR290 Output Impedance vs. Frequency
OUTPUT IMPEDANCE – Ω
120
RIPPLE REJECTION – dB
30
100
FREQUENCY – Hz
0
1000
Figure 20. ADR290/ADR291/ADR292 Ripple Rejection vs.
Frequency
0
10
TE
100
FREQUENCY – Hz
1k
10k
Figure 23. ADR291 Output Impedance vs. Frequency
50
VS = 5V
IL = 0 mA
1s
40
OUTPUT IMPEDANCE – Ω
100
90
2µVP–P
10
30
20
10
0%
TIME – sec
0
Figure 21. ADR290 0.1 Hz to 10 Hz Noise
0
10
100
FREQUENCY – Hz
1k
10k
Figure 24. ADR292 Output Impedance vs. Frequency
–10–
REV. 0
ADR290/ADR291/ADR292
IL = 5mA
1ms
500µs
IL = 5mA
OFF
ON
100
90
100
90
10
10
0%
0%
1V
1V
OBS
Figure 25. ADR291 Load Transient
IL = 5mA
CL = 1nF
OFF
100
90
ON
10
Figure 28. ADR291 Turn-On Time
OLE
1ms
IL = 0mA
100
90
10
0%
0%
1V
Figure 26. ADR291 Load Transient
IL = 5mA
CL = 100nF
OFF
TE
1V
Figure 29. ADR291 Turn-Off Time
5ms
100
90
ON
10
0%
1V
Figure 27. ADR291 Load Transient
REV. 0
10ms
–11–
ADR290/ADR291/ADR292
THEORY OF OPERATION
Device Power Dissipation Considerations
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 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:
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.
PD =
OBS
Basic Voltage Reference Connections
References, in general, require a bypass capacitor connected
from the VOUT pin to the GND pin. The circuit in Figure 31
illustrates the basic configuration for the ADR29x family of references. Note that the decoupling capacitors are not required
for circuit stability.
OLE
NC
R1 + R2 + R3
VOUT = ∆VP
+ I PTAT R3
R1
)( )
I1
TE
8
NC
7
NC
ADR29x
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.
VIN
1
2
where ∆VP is the difference in pinch-off voltage between the two
FETs, and IPTAT is the positive temperature coefficient correction 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.
I1
θ JA
In this equation, TJ and TA are the junction and ambient temperatures, respectively, PD is the device power dissipation, and
θJA is the device package thermal resistance.
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:
(
TJ − TA
NC
+
10µF
3
0.1µF
4
OUTPUT
6
5
NC
0.1µF
Figure 31. Basic Voltage Reference Configuration
Noise Performance
The noise generated by the ADR29x family of references is typically 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
*
VOUT
∆VP
R1
IPTAT
R2
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.
R3
*EXTRA CHANNEL IMPLANT
VOUT 5
R11 R2 1R3
R1
GND
3 ∆VP1 I PTAT 3R3
Figure 30. ADR290/ADR291/ADR292 Simplified Schematic
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. 0
ADR290/ADR291/ADR292
an additional operational amplifier is not required for either
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 VOUT and GND. Thus, any negative 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.
OBS
VIN
2
ADR29x
1kΩ
VOUT
+5V
2
ADR29x
6
VOUT
R1
GND
100kΩ
1µF
1µF
4
ISY
ADJUST
P1
IOUT
6
RSET
RL
Figure 33. A Precision Current Source
High Voltage Floating Current Source
OLE
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.
100Ω
GND
4
1µF
6
VIN
A1
VIN
–VREF
TE
+VS
E231
SILICONIX
–5V
ADR290
2N3904
A1 = 1/2 OP291,
1/2 OP295
OP90
Figure 32. A Negative Precision Voltage Reference Uses
No Precision Resistors
GND
2.10k
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 RSET, which sets the output current into the
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. 0
–VS
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 (VERROR = R 3 IL ) at
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.
–13–
ADR290/ADR291/ADR292
Voltage Regulator For Portable Equipment
VIN
RLW
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.
+VOUT
SENSE
2
VIN
RLW
ADR29x
A1
6
VOUT
GND
+VOUT
FORCE
RL
1µF
100kΩ
4
A1 = 1/2 OP295
Figure 35. Advantage of Kelvin Connection
OBS
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 quiescent current (12 µA max) and low noise, tight temperature coefficient, combined with the high accuracy of the ADR29x makes
it ideal for low power applications such as hand-held, battery
operated equipment.
CHARGER
INPUT
0.1µF
R3
510kΩ
2
VIN
OLE
V OUT 6
6V
LEAD-ACID
BATTERY
+
2
7
3
4
ADR29x
TEMP 3
GND
4
OP-20
+5V, 100mA
TE
R2
R1
402kΩ 402kΩ
1%
1%
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.
IRF9530
6
C1
68µF
TANT
+
+ C2
1000µF
ELECT
Figure 37. Voltage Regulator for Portable Equipment
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.
+5V
ANALOG
SUPPLY
0.1µF
10µF
AVDD
V IN
VOUT
0.1µF
DV DD
VREF
ADR291
AD7701
BP/UP
DRDY
DATA READY
CS
SCLK
READ (TRANSMIT)
SDATA
SERIAL CLOCK
SERIAL DATA
CAL
CALIBRATE
ANALOG
INPUT
AIN
ANALOG
GROUND
AGND
CLKIN
CLKOUT
0.1µF
0.1µF
SC1
SC2
DGND
AVSS
–5V
ANALOG
SUPPLY
0.1µF
MODE
GND
RANGE
SELECT
SLEEP
0.1µF
DVSS
10µF
Figure 36. Low Power, Low Voltage Supply Reference for
the AD7701
–14–
REV. 0
ADR290/ADR291/ADR292
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
8-Lead Narrow Body SO (R Suffix)
0.1968 (5.00)
0.1890 (4.80)
0.2440 (6.20)
0.2284 (5.80)
OBS
8
5
1
4
0.1574 (4.00)
0.1497 (3.80)
0.102 (2.59)
0.094 (2.39)
PIN 1
0.0196 (0.50)
x 45°
0.0099 (0.25)
0.0098 (0.25)
0.0040 (0.10)
8°
0°
0.0500 0.0192 (0.49)
SEATING (1.27) 0.0138 (0.35) 0.0098 (0.25)
PLANE BSC
0.0075 (0.19)
0.0500 (1.27)
0.0160 (0.41)
OLE
8-Lead TSSOP (RU Suffix)
0.122 (3.10)
0.114 (2.90)
8
TE
0.256 (6.50)
0.246 (6.25)
0.177 (4.50)
0.169 (4.30)
5
1
4
PIN 1
0.0256 (0.65)
BSC
0.006 (0.15)
0.002 (0.05)
0.0433
(1.10)
MAX
SEATING
PLANE
0.0118 (0.30)
0.0075 (0.19)
0.0079 (0.20)
0.0035 (0.090)
8°
0°
0.028 (0.70)
0.020 (0.50)
3-Pin TO-92 (T9 Suffix)
0.205 (5.20)
0.175 (4.96)
0.135
(3.43)
MIN
0.210 (5.33)
0.170 (4.38)
0.050
(1.27)
MAX
SEATING
PLANE
0.019 (0.482)
0.016 (0.407)
SQUARE
0.500
(12.70)
MIN
0.055 (1.39)
0.045 (1.15)
0.105 (2.66)
0.095 (2.42)
0.105 (2.66)
0.080 (2.42)
0.105 (2.66)
0.080 (2.42)
1
2
3
BOTTOM VIEW
REV. 0
–15–
0.165 (4.19)
0.125 (3.94)
PRINTED IN U.S.A.
OBS
OLE
TE
–16–
C3151–12–7/97
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