ADR121 [ADI]
Precision, Micropower LDO Voltage References in TSOT; 在TSOT精密，微功耗LDO电压基准
| 型号： | ADR121 |
| 厂家： | 
ADI |
| 描述： | Precision, Micropower LDO Voltage References in TSOT |
| 文件： | 总20页 (文件大小：588K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Precision, Micropower LDO Voltage
References in TSOT
ADR121/ADR125/ADR127
FEATURES
PIN CONFIGURATION
Initial accuracy
A grade: 0.24%
B grade: 0.12%
Maximum tempco
1
1
1
NC
GND
1
2
3
6
5
4
NC
NC
ADR12x
TOP VIEW
(Not to Scale)
V
V
OUT
IN
A grade: 25 ppm/°C
B grade: 9 ppm/°C
NC = NO CONNECT
1
MUST BE LEFT FLOATING
Low dropout: 300 mV for ADR121, ADR125
High output current: +5 mA/−2 mA
Low typical operating current: 85 μA
Input range: 2.7 V to 18 V
Temperature range: −40°C to +125°C
Tiny TSOT (UJ-6) package
Figure 1.
APPLICATIONS
Battery-powered instrumentation
Portable medical equipment
Data acquisition systems
Automotive
GENERAL DESCRIPTION
The ADR121/ADR125/ADR127 are a family of micropower,
high precision, series mode, band gap references with sink and
source capability. The parts feature high accuracy and low
power consumption in a tiny package. The ADR12x design
includes a patented temperature drift curvature correction
technique that minimizes the nonlinearities in the output
voltage vs. temperature characteristics.
The ADR12x is a low dropout voltage reference, requiring only
300 mV for ADR121/ADR125 and 1.45 V for ADR127 above
the nominal output voltage on the input to provide a stable
output voltage. This low dropout performance coupled with the
low 85 μA operating current makes the ADR12x ideal for
battery-powered applications.
Available in an extended industrial temperature range of −40°C
to +125°C, the ADR12x is housed in the tiny TSOT (UJ-6)
package.
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 ofthird parties that may result fromits 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 registeredtrademarks arethe property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
Fax: 781.461.3113
www.analog.com
©2006 Analog Devices, Inc. All rights reserved.
ADR121/ADR125/ADR127
TABLE OF CONTENTS
Features .............................................................................................. 1
Terminology.......................................................................................7
Typical Performance Characteristics ..............................................8
Theory of Operation ...................................................................... 16
Power Dissipation Considerations........................................... 16
Notes ............................................................................................ 16
Applications..................................................................................... 17
Basic Voltage Reference Connection....................................... 17
Stacking Reference ICs for Arbitrary Outputs ....................... 17
Negative Precision Reference Without Precision Resistors.. 17
General-Purpose Current Source ............................................ 17
Outline Dimensions....................................................................... 18
Ordering Guide .......................................................................... 18
Applications....................................................................................... 1
Pin Configuration............................................................................. 1
General Description......................................................................... 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
ADR121 Electrical Characteristics............................................. 3
ADR125 Electrical Characteristics............................................. 4
ADR127 Electrical Characteristics............................................. 5
Absolute Maximum Ratings............................................................ 6
Thermal Resistance ...................................................................... 6
ESD Caution.................................................................................. 6
REVISION HISTORY
6/06—Revision 0: Initial Version
Rev. 0 | Page 2 of 20
ADR121/ADR125/ADR127
SPECIFICATIONS
ADR121 ELECTRICAL CHARACTERISTICS
@ TA = 25°C, VIN = 2.8 V to 18 V, IOUT = 0 mA, unless otherwise noted.
Table 1.
Parameter
Symbol
Conditions/Comments
Min
Typ
Max
Unit
OUTPUT VOLTAGE
B Grade
A Grade
VO
@ 25°C
2.497
2.494
2.5
2.5
2.503
2.506
V
V
INITIAL ACCURACY ERROR
B Grade
A Grade
VOERR
TCVO
VDO
@ 25°C
−0.12
−0.24
+0.12
+0.24
%
%
TEMPERATURE COEFFICIENT
B Grade
A Grade
−40°C < TA < +125°C
3
15
9
25
ppm/°C
ppm/°C
mV
DROPOUT (VOUT − VIN)
LOAD REGULATION
IOUT = 0 mA
300
−50
−40°C < TA < +125°C; VIN = 3.0 V,
0 mA < IOUT < 5 mA
−40°C < TA < +125°C; VIN = 3.0 V,
−2 mA < IOUT < 0 mA
2.8 V to 18 V
80
50
300
300
+50
ppm/mA
ppm/mA
LINE REGULATION
IOUT = 0 mA
+3
ppm/V
dB
PSRR
f = 1 Khz
−90
60
RIPPLE REJECTION
QUIESCENT CURRENT
f = 60 Hz
dB
ΔVOUT/ΔVIN
IQ
−40°C < TA < +125°C, no load
VIN = 18 V
VIN = 2.8 V
95
80
18
40
125
95
μA
μA
SHORT-CIRCUIT CURRENT TO GROUND
VOLTAGE NOISE
VIN = 2.8 V
VIN = 18 V
mA
mA
@ 25°C
f = 10 KHz
500
10
nV/√Hz
μV p-p
μs
0.1 Hz to 10 Hz
To 0.1%, CL = 0.2 μF
1000 hours @ 25°C
See the Terminology section
TURN-ON SETTLING TIME
LONG-TERM STABILITY
100
150
300
ppm/1000 hrs
ppm
OUTPUT VOLTAGE HYSTERESIS
Rev. 0 | Page 3 of 20
ADR121/ADR125/ADR127
ADR125 ELECTRICAL CHARACTERISTICS
@ TA = 25°C, VIN = 5.3 V to 18 V, IOUT = 0 mA, unless otherwise noted.
Table 2.
Parameter
Symbol
Condition
Min
Typ
Max
Unit
OUTPUT VOLTAGE
B Grade
A Grade
VO
@ 25°C
4.994
4.988
5.0
5.0
5.006
5.012
V
V
2.497
INITIAL ACCURACY ERROR
B Grade
A Grade
VOERR
TCVO
VDO
@ 25°C
−0.12
−0.24
+0.12
+0.24
%
%
TEMPERATURE COEFFICIENT
B Grade
A Grade
−40°C < TA < +125°C
3
15
9
25
ppm/°C
ppm/°C
mV
DROPOUT (VOUT − VIN)
LOAD REGULATION
IOUT = 5 mA
300
−40°C < TA < +125°C; VIN = 3.0 V,
0 mA < IOUT < 5 mA
−40°C < TA < +125°C; VIN = 3.0 V,
−2 mA < IOUT < 0 mA
5.3 V < VIN < 18 V
35
35
200
200
30
ppm/mA
ppm/mA
LINE REGULATION
IOUT = 0 mA
ppm/V
dB
PSRR
f = 60 Hz
−90
60
RIPPLE REJECTION
QUIESCENT CURRENT
f = 60 Hz
dB
ΔVOUT/ΔVIN
IQ
−40°C < TA < +125°C, no load
VIN = 18 V
VIN = 3.0 V
95
80
25
40
125
95
μA
μA
SHORT-CIRCUIT CURRENT TO GROUND
VOLTAGE NOISE
VIN = 5.3 V
VIN = 18 V
mA
mA
@ 25°C
f = 10 Khz
900
20
nV/√Hz
μV p-p
μs
0.1 Hz to 10 Hz
To 0.1%, CL = 0.2 μF
1000 hours @ 25°C
See the Terminology section
TURN-ON SETTLING TIME
LONG-TERM STABILITY
100
150
300
ppm/1000 hrs
ppm
OUTPUT VOLTAGE HYSTERESIS
Rev. 0 | Page 4 of 20
ADR121/ADR125/ADR127
ADR127 ELECTRICAL CHARACTERISTICS
@ TA = 25°C, 2.7 V to 18 V, IOUT = 0 mA, unless otherwise noted.
Table 3.
Parameter
Symbol
Condition
Min
Typ
Max
Unit
OUTPUT VOLTAGE
B Grade
A Grade
VO
@ 25°C
1.2485 1.25
1.2470 1.25
1.2515
1.2530
V
V
INITIAL ACCURACY ERROR
B Grade
A Grade
VOERR
TCVO
VDO
@ 25°C
−0.12
−0.24
+0.12
+0.24
%
%
TEMPERATURE COEFFICIENT
B Grade
A Grade
−40°C < TA < +125°C
3
15
9
25
ppm/°C
ppm/°C
V
DROPOUT (VOUT − VIN)
LOAD REGULATION
IOUT = 0 mA
1.45
−40°C < TA < +125°C; VIN = 3.0 V,
0 mA < IOUT < 5 mA
−40°C < TA < +125°C; VIN = 3.0 V,
−2 mA < IOUT < 0 mA
2.7 V to 18 V
85
65
400
400
90
ppm/mA
ppm/mA
LINE REGULATION
IOUT = 0 mA
30
ppm/V
dB
PSRR
F = 60 Hz
−90
60
RIPPLE REJECTION
QUIENSCENT CURRENT
f = 60 Hz
dB
ΔVOUT/ΔVIN
IQ
−40°C < TA < +125°C, no load
VIN = 18 V
VIN = 2.7 V
95
80
15
30
125
95
μA
μA
SHORT-CIRCUIT CURRENT TO GROUND
VIN = 2.7 V
mA
mA
V
IN = 18 V
VOLTAGE NOISE
Noise Density
@ 25°C
f = 10 kHz
0.1 Hz to 10 Hz
To 0.1%, CL = 0.2 μF
1000 hours @ 25°C
See the Terminology section
300
5
nV/√Hz
μV p-p
μs
TURN-ON SETTLING TIME
LONG-TERM STABILITY
80
150
300
ppm/1000 hrs
ppm
OUTPUT VOLTAGE HYSTERESIS
Rev. 0 | Page 5 of 20
ADR121/ADR125/ADR127
ABSOLUTE MAXIMUM RATINGS
Table 4.
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.
Parameter
Ratings
VIN to GND
20 V
Internal Power Dissipation
TSOT (UJ-6)
40 mW
Storage Temperature Range
Specified Temperature Range
Lead Temperature, Soldering
Vapor Phase (60 sec)
Infrared (15 sec)
−65°C to +150°C
−40°C to +125°C
THERMAL RESISTANCE
215°C
220°C
θJA is specified for the worst-case conditions, that is, a device
soldered in a circuit board for surface-mount packages.
Table 5. Thermal Resistance
Package Type
θJA
θJC
Unit
TSOT (UJ-6)
230
146
°C/W
ESD 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 this product 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.
Rev. 0 | Page 6 of 20
ADR121/ADR125/ADR127
TERMINOLOGY
Temperature Coefficient
Long-Term Stability
The change of output voltage with respect to operating
temperature change normalized by the output voltage at 25°C.
This parameter is expressed in ppm/°C and can be determined
by
Typical shift of output voltage at 25°C on a sample of parts
subjected to a test of 1000 hours at 25°C.
ΔVO =VO
tO
−VO
VO tO
VO
t1
)
(
)
−VO
t1
( )
ΔVO ppm
[
]
=
×106
VO
(
T2
)
−VO
(
T
)
tO
( )
1
TCVO
[ppm/°C
]
=
×106
VO
(
25°C
)
×
(
T2 −T
)
1
where:
where:
VO(25°C) = VO at 25°C.
VO(t0) = VO at 25°C at Time 0.
VO(t1) = VO at 25°C after 1000 hours operating at 25°C.
VO(T1) = VO at Temperature 1.
VO(T2) = VO at Temperature 2.
Thermal Hysteresis
The change of output voltage after the device is cycled through
temperatures from +25°C to −40°C to +125°C and back to
+25°C. This is a typical value from a sample of parts put
through such a cycle.
Line Regulation
The change in the output due to a specified change in input
voltage. This parameter accounts for the effects of self-heating.
Line regulation is expressed in either percent per volt, parts-
per-million per volt, or microvolts per voltage changes in input
voltage.
where:
VO (25°C) = VO at 25°C.
V
OTC = VO at 25°C after temperature cycle at +25°C to −40°C to
+125°C and back to +25°C.
Load Regulation
The change in output voltage due to a specified change in load
current. This parameter accounts for the effects of self-heating.
Load regulation is expressed in either microvolts per milliam-
pere, parts-per-million per milliampere, or ohms of dc output
resistance.
Rev. 0 | Page 7 of 20
ADR121/ADR125/ADR127
TYPICAL PERFORMANCE CHARACTERISTICS
1.256
5
4
3
2
1
0
1.254
1.252
1.250
1.248
1.246
1.244
–40 –25 –10
5
20
35
50
65
80
95 110 125
95 110 125
95 110 125
–50 –40 –30 –20 –10
0
10
20
30
40
40
40
50
50
50
TEMPERATURE (°C)
TEMPERATURE COEFFICIENT (ppm/°C)
Figure 2. ADR127 VOUT vs. Temperature
Figure 5. ADR127 Temperature Coefficient
2.510
2.508
2.506
2.504
2.502
2.500
2.498
2.496
2.494
2.492
2.490
5
4
3
2
1
0
–40 –25 –10
5
20
35
50
65
80
–50 –40 –30 –20 –10
0
10
20
30
TEMPERATURE (°C)
TEMPERATURE COEFFICIENT (ppm/°C)
Figure 3. ADR121 VOUT vs. Temperature
Figure 6. ADR125 Temperature Coefficient
5.020
5.015
5.010
5.005
5.000
4.995
4.990
4.985
4.980
5
4
3
2
1
0
–40 –25 –10
5
20
35
50
65
80
–50 –40 –30 –20 –10
0
10
20
30
TEMPERATURE (°C)
TEMPERATURE COEFFICIENT (ppm/°C)
Figure 4. ADR125 VOUT vs. Temperature
Figure 7. ADR121 Temperature Coefficient
Rev. 0 | Page 8 of 20
ADR121/ADR125/ADR127
3.0
2.8
2.6
2.4
2.2
2.0
120
100
80
60
40
20
0
+25°C
–40°C
+25°C
+125°C
–40°C
+125°C
–2
–1
0
1
2
3
4
5
5
5
2
2
5
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18
LOAD CURRENT (mA)
INPUT VOLTAGE (V)
Figure 8. ADR127 Minimum Input Voltage vs. Load Current
Figure 11. ADR127 Supply Current vs. Input Voltage
3.5
120
100
80
60
40
20
0
3.4
3.3
3.2
3.1
3.0
2.9
2.8
2.7
2.6
2.5
+125°C
+25°C
+125°C
+25°C
–40°C
–40°C
–2
–1
0
1
2
3
4
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18
LOAD CURRENT (mA)
INPUT VOLTAGE (V)
Figure 9. ADR121 Minimum Input Voltage vs. Load Current
Figure 12. ADR121 Supply Current vs. Input Voltage
120
100
80
60
40
20
0
6.2
6.0
5.8
5.6
5.4
5.2
5.0
+125°C
+25°C
–40°C
+25°C
+125°C
–40°C
6
7
8
9
10 11 12 13 14 15 16 17 18
INPUT VOLTAGE (V)
–2
–1
0
1
2
3
4
LOAD CURRENT (mA)
Figure 13. ADR125 Supply Current vs. Input Voltage
Figure 10. ADR125 Minimum Input Voltage vs. Load Current
Rev. 0 | Page 9 of 20
ADR121/ADR125/ADR127
6
0
–10
–20
–30
–40
–50
— +125°C
— +25°C
— –40°C
5
4
3
2
1
0
V
= 2.7V TO 18V
IN
–2
–1
0
1
2
3
4
5
5
5
–40 -25 -10
5
20
35
50
65
80
95 110 125
LOAD CURRENT (mA)
TEMPERATURE (°C)
Figure 14. ADR127 Supply Current vs. Load Current
Figure 17. ADR127 Line Regulation vs. Temperature
6
3
2
— +125°C
— +25°C
— –40°C
5
4
3
2
1
0
1
0
V
= 2.8V TO 18V
IN
–1
–2
–3
–2
–1
0
1
2
3
4
–40 –25 –10
5
20
35
50
65
80
95 110 125
LOAD CURRENT (mA)
TEMPERATURE (°C)
Figure 15. ADR121 Supply Current vs. Load Current
Figure 18. ADR121 Line Regulation vs. Temperature
6
5
4
3
2
1
0
6
4
— +125°C
— +25°C
— –40°C
2
V
= 5.3V TO 18V
IN
0
–2
–4
–6
–2
–1
0
1
2
3
4
–40 –25 –10
5
20
35
50
65
80
95 110 125
LOAD CURRENT (mA)
TEMPERATURE (°C)
Figure 16. ADR125 Supply Current vs. Load Current
Figure 19. ADR125 Line Regulation vs. Temperature
Rev. 0 | Page 10 of 20
ADR121/ADR125/ADR127
200
150
100
50
C
= C
= 0.1µF
IN
OUT
2mA SINKING, V = 3V
IN
CH1 p-p
5.76µV
0
1
–50
–100
–150
–200
CH1 rms
0.862µV
5mA SOURCING, V = 3V
IN
2µV/DIV
TIME (1s/DIV)
–40 –25 –10
5
20
35
50
65
80
95 110 125
TEMPERATURE (°C)
Figure 20. ADR127 Load Regulation vs. Temperature
Figure 23. ADR127 0.1 Hz to 10 Hz Noise
100
80
C
IN
= C
OUT
= 0.1µF
60
2mA SINKING, V = 5V
IN
40
20
CH1 p-p
10.8µV
0
–20
–40
–60
–80
–100
1
5mA SOURCING, V = 5V
IN
CH1 rms
1.75µV
5µV/DIV
TIME (1s/DIV)
–40 –25 –10
5
20
35
50
65
80
95 110 125
TEMPERATURE (°C)
Figure 24. ADR121 0.1 Hz to 10 Hz Noise
Figure 21. ADR121 Load Regulation vs. Temperature
50
40
C
= C
= 0.1µF
IN
OUT
30
2mA SINKING, V = 6V
IN
20
10
CH1 p-p
20.6µV
0
–10
–20
–30
–40
–50
1
CH1 rms
3.34µV
5mA SOURCING, V = 6V
IN
10µV/DIV
TIME (1s/DIV)
–40 –25 –10
5
20
35
50
65
80
95 110 125
TEMPERATURE (°C)
Figure 22. ADR125 Load Regulation vs. Temperature
Figure 25. ADR125 0.1 Hz to 10 Hz Noise
Rev. 0 | Page 11 of 20
ADR121/ADR125/ADR127
C
C
C
= C
= C
= C
= 0.1µF
IN
OUT
V
C
1V/DIV
IN
= C
= 0.1µF
IN
OUT
CH1 p-p
287µV
1
1
CH1 rms
38.8µV
V
OUT
500mV/DIV
2
TIME (200µs/DIV)
TIME (1s/DIV)
50µV/DIV
Figure 26. ADR127 10 Hz to 10 KHz Noise
Figure 29. ADR127 Turn-On Response
= 0.1µF
OUT
IN
V
1V/DIV
IN
C
= C
= 0.1µF
IN
OUT
CH1 p-p
450µV
1
1
CH1 rms
58.1µV
V
OUT
500mV/DIV
TIME (40µs/DIV)
100µV/DIV
TIME (1s/DIV)
2
Figure 27. ADR121 10 Hz to 10 KHz Noise
Figure 30. ADR127 Turn-On Response
= 0.1µF
OUT
IN
V
1V/DIV
IN
C
= C
= 0.1µF
IN
OUT
CH1 p-p
788µV
1
1
CH1 rms
115µV
200µV/DIV
TIME (1s/DIV)
2
V
OUT
500mV/DIV
TIME (100µs/DIV)
Figure 28. ADR125 10 Hz to 10 KHz Noise
Figure 31. ADR127 Turn-Off Response
Rev. 0 | Page 12 of 20
ADR121/ADR125/ADR127
C
= C
= 0.1µF
IN
OUT
V
1V/DIV
V
IN
IN
C
= C
= 0.1µF
2V/DIV
IN
OUT
1
1
V
V
OUT
OUT
2V/DIV
1V/DIV
2
TIME (100µs/DIV)
2
TIME (100µs/DIV)
Figure 32. ADR121 Turn-On Response
Figure 35. ADR125 Turn-On Response
C
= C
= 0.1µF
IN
OUT
V
C
1V/DIV
IN
V
IN
= C
= 0.1µF
2V/DIV
IN
OUT
1
1
V
OUT
V
OUT
2V/DIV
TIME (20µs/DIV)
TIME (40µs/DIV)
1V/DIV
2
2
Figure 33. ADR121 Turn-On Response
Figure 36. ADR125 Turn-On Response
C
= C
= 0.1µF
IN
OUT
V
IN
V
IN
1V/DIV
2V/DIV
1
1
V
V
OUT
OUT
1V/DIV
2V/DIV
TIME (200µs/DIV)
2
2
TIME (20µs/DIV)
Figure 34. ADR121 Turn-Off Response
Figure 37. ADR125 Turn-Off Response
Rev. 0 | Page 13 of 20
ADR121/ADR125/ADR127
C
= C
= 0.1µF
IN
IN
IN
OUT
2.50V
1.25V
V
1V/DIV
IN
LINE INTERRUPTION
V
C
500mV/DIV
1
IN
= C
= 0.1µF
IN
OUT
625Ω LOAD
2mA SINKING
2
1
2
V
OUT
TIME (40µs/DIV)
20mV/DIV
V
OUT
TIME (200µs/DIV)
500mV/DIV
Figure 38. ADR127 Line Transient Response
Figure 41. ADR127 Load Transient Response (Sinking)
C
= C
= 0.1µF
OUT
LINE INTERRUPTION
1V/DIV
1.25V
0V
1
V
C
500mV/DIV
IN
= C
= 0.1µF
IN
OUT
250Ω LOAD
5mA SOURCING
1
TIME (400µs/DIV)
2
2
V
V
OUT
500mV/DIV
OUT
100mV/DIV
TIME (40µs/DIV)
Figure 39. ADR121 Line Transient Response
Figure 42. ADR127 Load Transient Response (Sourcing)
C
= C
= 0.1µF
OUT
5V
V
C
1V/DIV
V
IN
IN
= C
= 0.1µF
1V/DIV
IN
OUT
1
1250Ω LOAD
2mA SINKING
2.5V
1
2
2
V
V
OUT
OUT
TIME (40µs/DIV)
10mV/DIV
500mV/DIV
TIME (400µs/DIV)
Figure 40. ADR125 Line Transient Response
Figure 43. ADR121 Load Transient Response (Sinking)
Rev. 0 | Page 14 of 20
ADR121/ADR125/ADR127
0
–20
2.5V
0V
V
1V/DIV
–40
IN
C
= C
= 0.1µF
IN
OUT
500Ω LOAD
–60
5mA SOURCING
1
–80
1
–100
–120
–140
–160
–180
–200
2
V
OUT
100mV/DIV
TIME (40µs/DIV)
10
100
1k
10k
100k
1M
10M
100M
Figure 44. ADR121 Load Transient Response (Sourcing)
Figure 47. ADR121/ADR125/ADR127 PSRR
50
45
40
35
30
25
20
15
10
5
10V
5V
V
C
2V/DIV
IN
= C
= 0.1µF
IN
OUT
2.5kΩ LOAD
2mA SINKING
ADR127
ADR121
ADR125
1
2
V
OUT
1
TIME (40µs/DIV)
20mV/DIV
0
10
100
1k
10k
100k
FREQUENCY (Hz)
Figure 48. ADR121/ADR125/ADR127 Output Impedance vs. Frequency
Figure 45. ADR125 Load Transient Response (Sinking)
5V
0V
V
C
2V/DIV
IN
= C
= 0.1µF
IN
OUT
1kΩ LOAD
5mA SOURCING
1
2
V
OUT
100mV/DIV
TIME (40µs/DIV)
Figure 46. ADR125 Load Transient Response (Sourcing)
Rev. 0 | Page 15 of 20
ADR121/ADR125/ADR127
THEORY OF OPERATION
The ADR12x band gap references are the high performance
solution for low supply voltage and low power applications. The
uniqueness of these products lies in their architecture.
NOTES
Input Capacitor
Input capacitors are not required on the ADR12x. There is no
limit for the value of the capacitor used on the input, but a 1 μF
to 10 μF capacitor on the input improved transient response in
the applications where there is a sudden supply change. An
additional 0.1 μF capacitor in parallel also helps reduce noise
from the supply.
POWER DISSIPATION CONSIDERATIONS
The ADR12x family is capable of delivering load currents to
5 mA with an input range from 3.0 V to 18 V. When this device
is used in applications with large input voltages, care must be
taken to avoid exceeding the specified maximum power
dissipation or junction temperature, because this could result in
premature device failure.
Output Capacitor
The ADR12x requires a small 0.1 μF capacitor for stability.
Additional 0.1 μF to 10 μF capacitance in parallel can improve
load transient response. This acts as a source of stored energy
for a sudden increase in load current. The only parameter
affected with the additional capacitance is turn-on time.
Use the following formula to calculate a device’s maximum
junction temperature or dissipation:
TJ − TA
PD
=
θJA
where:
TJ is the junction temperature.
TA is the ambient temperature.
PD is the device power dissipation.
θJA is the device package thermal resistance.
Rev. 0 | Page 16 of 20
ADR121/ADR125/ADR127
APPLICATIONS
Table 6. Required Outputs
U1/U2
BASIC VOLTAGE REFERENCE CONNECTION
VOUT2
1.25 V
1.25 V
2.5 V
VOUT1
3.75 V
6.25 V
7.5 V
The circuit in Figure 4 illustrates the basic configuration for the
ADR12x family voltage reference.
ADR127/ADR121
ADR127/ADR125
ADR121/ADR125
1
6
NC
NC
NC
ADR12x
GND
NEGATIVE PRECISION REFERENCE WITHOUT
PRECISION RESISTORS
2
3
5
4
INPUT
OUTPUT
0.1µF
V
V
OUT
A negative reference is easily generated by adding an op amp,
A1, and is configured as shown in Figure 51. VOUT1 is at virtual
ground and, therefore, the negative reference can be taken
directly from the output of the op amp. The op amp must be
dual-supply, low offset, and rail-to-rail if the negative supply
voltage is close to the reference output.
IN
+
+
0.1µF
Figure 49. Basic Configuration for the ADR12x Family
STACKING REFERENCE ICs FOR ARBITRARY
OUTPUTS
1
6
NC
NC
NC
Some applications may require two reference voltage sources
that are a combined sum of the standard outputs. Figure 50
shows how this stacked output reference can be implemented.
ADR127
2
3
GND
5
4
V
V
OUT
+V
IN
DD
1
6
NC
NC
NC
0.1µF
ADR12x
GND
1kΩ
2
3
5
4
2
3
–
V+
–V
AD8603
OUTPUT1
0.1µF
REF
V
V
OUT
IN
V–
+
+
+
0.1µF
–V
DD
Figure 51. Negative Reference
INPUT
1
6
NC
NC
GENERAL-PURPOSE CURRENT SOURCE
ADR12x
OUTPUT2
In low power applications, the need can arise for a precision
current source that can operate on low supply voltages. The
ADR12x can be configured as a precision current source (see
Figure 52). The circuit configuration shown 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 ranging from the reference’s supply current,
typically 85 μA, to approximately 5 mA.
2
3
GND
NC
5
4
V
V
OUT
IN
+
+
0.1µF
0.1µF
Figure 50. Stacking References with ADR12x
Two reference ICs are used and fed from an unregulated input,
VIN. The outputs of the individual ICs are connected in series,
which provide two output voltages, VOUT1 and VOUT2. VOUT1 is the
terminal voltage of U1, while VOUT2 is the sum of this voltage
and the terminal of U2. U1 and U2 are chosen for the two
voltages that supply the required outputs (see Table 6). For
example, if U1 and U2 are ADR127 and VIN ≥ 3.95 V, VOUT1 is
1.25 V and VOUT2 is 2.5 V.
1
6
NC
NC
NC
ADR12x
GND
2
3
5
4
+V
V
V
OUT
DD
IN
I
SET
R1
RL
I
SY
P1
Figure 52. ADR12x Trim Configuration
Rev. 0 | Page 17 of 20
ADR121/ADR125/ADR127
OUTLINE DIMENSIONS
2.90 BSC
6
1
5
2
4
3
2.80 BSC
1.60 BSC
PIN 1
INDICATOR
0.95 BSC
1.90
BSC
*
0.90
0.87
0.84
*
1.00 MAX
0.20
0.08
8°
4°
0°
0.60
0.45
0.30
0.50
0.30
0.10 MAX
SEATING
PLANE
*
COMPLIANT TO JEDEC STANDARDS MO-193-AA WITH
THE EXCEPTION OF PACKAGE HEIGHT AND THICKNESS.
Figure 53. 6-Lead Thin Small Outline Transistor Package [TSOT]
(UJ-6)
Dimensions shown in millimeters
ORDERING GUIDE
Output
Initial
Temperature
Voltage
(VO)
Accuracy
(mV/%)
Coefficient
(ppm/°C)
Package
Description
Package
Option
Temperature
Range (°C)
Ordering
Quantity
3000
Model
Branding
ADR121AUJZ-
REEL71
ADR121AUJZ-
R21
ADR121BUJZ-
REEL71
ADR125AUJZ-
REEL71
ADR125AUJZ-
R21
ADR125BUJZ-
REEL71
ADR127AUJZ-
REEL71
ADR127AUJZ-
R21
2.5
2.5
2.5
2.5
5.0
5.0
5.0
3
0.24
25
25
9
6-Lead TSOT
6-Lead TSOT
6-Lead TSOT
6-Lead TSOT
6-Lead TSOT
6-Lead TSOT
6-Lead TSOT
6-Lead TSOT
6-Lead TSOT
UJ-6
UJ-6
UJ-6
UJ-6
UJ-6
UJ-6
UJ-6
UJ-6
UJ-6
−40°C to
+125°C
−40°C to
+125°C
−40°C to
+125°C
−40°C to
+125°C
−40°C to
+125°C
−40°C to
+125°C
−40°C to
+125°C
−40°C to
+125°C
R0N
2.5
0.24
0.12
0.24
0.24
0.12
0.24
0.24
0.12
250
R0N
R0P
R0Q
R0Q
R0R
R0S
R0S
R0T
2.5
3000
3000
250
5.0
25
25
9
5.0
5.0
3000
3000
250
1.25
1.25
1.25
25
25
9
3
ADR127BUJZ-
REEL71
1.5
−40°C to
+125°C
3000
1 Z = Pb-free part.
Rev. 0 | Page 18 of 20
ADR121/ADR125/ADR127
NOTES
Rev. 0 | Page 19 of 20
ADR121/ADR125/ADR127
NOTES
©2006 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D05725-0-6/06(0)
Rev. 0 | Page 20 of 20
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