Datasheet ADR121, ADR125 Datasheet (ANALOG DEVICES)

Precision, Micropower LDO Voltage

FEATURES

Initial accuracy

A grade: ±0.24%
B grade: ±0.12%

Maximum temperature coefficient

A grade: 25 ppm/°C

B grade: 9 ppm/°C
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 for ADR127
Temperature range: −40°C to +125°C
Tiny TSOT (UJ-6) package

APPLICATIONS

Battery-powered instrumentation
Portable medical equipment
Data acquisition systems
Automotive

References in TSOT

ADR121/ADR125/ADR127

PIN CONFIGURATION

1

1

NC

GND

ADR12x

2

TOP VIEW

(Not to Scale)

V

3

IN

NC = NO CONNECT

1

MUST BE LEFT FLOATING

Figure 1.

1

6

NC

1

NC

5

V

4

OUT

05725-001

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 the ADR121/ADR125 and 1.45 V for the 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 ADR121/ADR125/ADR127 are housed in the
tiny TSOT (UJ-6) package.

Rev. B

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: [phone] www.analog.com
Fax: [phone] ©2006–2008 Analog Devices, Inc. All rights reserved.

ADR121/ADR125/ADR127

TABLE OF CONTENTS

Features .............................................................................................. 1

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

Typical Performance Characteristics ............................................. 7

REVISION HISTORY

1/08—Rev. A to Rev. B

Changes to Table 1 ............................................................................ 3

Changes to Table 2 ............................................................................ 4

Changes to Table 3 .............................................................................5

Changes to Figure 52 ...................................................................... 17

Changes to Ordering Guide ......................................................... 18

Terminology .................................................................................... 15

Theory of Operation ...................................................................... 16

Power Dissipation Considerations ........................................... 16

Input Capacitor ........................................................................... 16

Output Capacitor ........................................................................ 16

Applications Information .............................................................. 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

5/07—Rev. 0 to Rev. A

Changes to Table 1 ............................................................................ 3

Changes to Table 2 ............................................................................ 4

Changes to Table 3 ............................................................................ 5

Added Thermal Hysteresis Equation ............................................. 7

Changes to Ordering Guide .......................................................... 18

6/06—Revision 0: Initial Version

Rev. B | Page 2 of 20

ADR121/ADR125/ADR127

SPECIFICATIONS

ADR121 ELECTRICAL CHARACTERISTICS

TA = 25°C, VIN = 2.8 V to 18 V, I

Table 1.

Parameter Symbol Conditions/Comments Min Typ Max Unit

OUTPUT VOLTAGE V

B Grade 2.497 2.5 2.503 V

A Grade 2.494 2.5 2.506 V

INITIAL ACCURACY ERROR V

B Grade −0.12 +0.12 %

A Grade −0.24 +0.24 %

TEMPERATURE COEFFICIENT TCV

B Grade 3 9 ppm/°C

A Grade 15 25 ppm/°C

DROPOUT (V

− VIN) VDO I

OUT

LOAD REGULATION

LINE REGULATION 2.8 V to 18 V, I
PSRR f = 60 Hz −90 dB
QUIESCENT CURRENT IQ −40°C < TA < +125°C, no load
V
V
SHORT-CIRCUIT CURRENT TO GROUND VIN = 2.8 V 18 mA
V
VOLTAGE NOISE f = 10 kHz 500 nV/√Hz
f = 0.1 Hz to 10 Hz 18 μV p-p
TURN-ON SETTLING TIME To 0.1%, CL = 0.2 μF 100 μs
LONG-TERM STABILITY 1000 hours @ 25°C 150 ppm/1000 hrs
OUTPUT VOLTAGE HYSTERESIS See the Terminology section 300 ppm

= 0 mA, unless otherwise noted.

OUT

OUT

OERR

−40°C < TA < +125°C

OUT

OUT

−40°C < T
0 mA < I

−40°C < T

−2 mA < I

= 0 mA 300 mV

< +125°C; VIN = 5.0 V,

A

< 5 mA

OUT

< +125°C; VIN = 5.0 V,

A

< 0 mA

OUT

= 0 mA −50 +3 +50 ppm/V

OUT

= 18 V 95 125 μA

IN

= 2.8 V 80 95 μA

IN

= 18 V 40 mA

IN

80 300 ppm/mA

50 300 ppm/mA

Rev. B | Page 3 of 20

ADR121/ADR125/ADR127

ADR125 ELECTRICAL CHARACTERISTICS

TA = 25°C, VIN = 5.3 V to 18 V, I

Table 2.

Parameter Symbol Conditions/Comments Min Typ Max Unit

OUTPUT VOLTAGE V

B Grade 4.994 5.0 5.006 V
A Grade 4.988 5.0 5.012 V

INITIAL ACCURACY ERROR V

B Grade −0.12 +0.12 %
A Grade −0.24 +0.24 %

TEMPERATURE COEFFICIENT TCV

B Grade 3 9 ppm/°C
A Grade 15 25 ppm/°C

DROPOUT (V

− VIN) VDO I

OUT

LOAD REGULATION

LINE REGULATION 5.3 V to 18 V, I
PSRR

QUIESCENT CURRENT IQ −40°C < TA < +125°C, no load
V
V
SHORT-CIRCUIT CURRENT TO GROUND VIN = 5.3 V 25 mA
V
VOLTAGE NOISE f = 10 kHz 900 nV/√Hz
f = 0.1 Hz to 10 Hz 36 μV p-p
TURN-ON SETTLING TIME To 0.1%, CL = 0.2 μF 100 μs
LONG-TERM STABILITY 1000 hours @ 25°C 150 ppm/1000 hrs
OUTPUT VOLTAGE HYSTERESIS See the Terminology section 300 ppm

= 0 mA, unless otherwise noted.

OUT

OUT

OERR

−40°C < TA < +125°C

OUT

OUT

−40°C < T
0 mA < I

−40°C < T

−2 mA < I

f = 60 Hz −90 dB

= 18 V 95 125 μA

IN

= 5.3 V 80 95 μA

IN

= 18 V 40 mA

IN

= 5 mA 300 mV

< +125°C; VIN = 6.0 V,

A

< 5 mA

OUT

< +125°C; VIN = 6.0 V,

A

< 0 mA

OUT

= 0 mA 30 ppm/V

OUT

35 200 ppm/mA

35 200 ppm/mA

Rev. B | Page 4 of 20

ADR121/ADR125/ADR127

ADR127 ELECTRICAL CHARACTERISTICS

TA = 25°C, VIN = 2.7 V to 18 V, I

Table 3.

Parameter Symbol Conditions/Comments Min Typ Max Unit

OUTPUT VOLTAGE V

B Grade 1.2485 1.25 1.2515 V

A Grade 1.2470 1.25 1.2530 V

INITIAL ACCURACY ERROR V

B Grade −0.12 +0.12 %

A Grade −0.24 +0.24 %

TEMPERATURE COEFFICIENT TCV

B Grade 3 9 ppm/°C

A Grade 15 25 ppm/°C

DROPOUT (V

− VIN) VDO I

OUT

LOAD REGULATION

LINE REGULATION 2.7 V to 18 V, I
PSRR

QUIESCENT CURRENT IQ −40°C < TA < +125°C, no load
V
V
SHORT-CIRCUIT CURRENT TO GROUND VIN = 2.7 V 15 mA
V
VOLTAGE NOISE f = 10 kHz 300 nV/√Hz

f = 0.1 Hz to 10 Hz 9 μV p-p

TURN-ON SETTLING TIME To 0.1%, CL = 0.2 μF 80 μs
LONG-TERM STABILITY 1000 hours @ 25°C 150 ppm/1000 hrs
OUTPUT VOLTAGE HYSTERESIS See the Terminology section 300 ppm

= 0 mA, unless otherwise noted.

OUT

OUT

OERR

−40°C < TA < +125°C

OUT

OUT

−40°C < T
0 mA < I

−40°C < T

−2 mA < I

f = 60 Hz −90 dB

IN

IN

IN

= 0 mA 1.45 V

< +125°C; VIN = 3.0 V,

A

< 5 mA

OUT

< +125°C; VIN = 3.0 V,

A

< 0 mA

OUT

= 0 mA 30 90 ppm/V

OUT

85 400 ppm/mA

65 400 ppm/mA

= 18 V 95 125 μA
= 2.7 V 80 95 μA

= 18 V 30 mA

Rev. B | Page 5 of 20

ADR121/ADR125/ADR127

ABSOLUTE MAXIMUM RATINGS

Table 4.

Parameter Rating

VIN to GND 20 V
Internal Power Dissipation

TSOT (UJ-6) 40 mW
Storage Temperature Range −65°C to +150°C
Operating Temperature Range −40°C to +125°C
Lead Temperature, Soldering

Vapor Phase (60 sec) 215°C

Infrared (15 sec) 220°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.

THERMAL RESISTANCE

θJA is specified for the worst-case conditions, that is, a device
soldered in a circuit board for surface-mount packages.

Table 5.

Package Type θJA θ

6-Lead TSOT (UJ-6) 230 146 °C/W

Unit

JC

ESD CAUTION

Rev. B | Page 6 of 20

ADR121/ADR125/ADR127

TYPICAL PERFORMANCE CHARACTERISTICS

1.256

5

1.254

1.252

(V)

1.250

OUT

V

1.248

1.246

1.244
–25 –10 5 20 35 50 65 80 95 110

–40 125

TEMPERATURE ( °C)

Figure 2. ADR127 V

2.510

2.508

2.506

2.504

2.502

(V)

2.500

OUT

V

2.498

2.496

2.494

2.492

2.490
–40 125

–25–105 203550658095110

Figure 3. ADR121 V

vs. Temperature

OUT

TEMPERATURE (°C)

vs. Temperature

OUT

4

3

2

NUMBER OF PARTS

1

0

–50 50

–40–30–20–100 10203040

05725-006

TEMPERATURE CO EFFICIENT (ppm/°C)

05725-009

Figure 5. ADR127 Temperature Coefficient

5

4

3

2

NUMBER OF PARTS

1

0

–50 50

–40–30–20–100 10203040

05725-007

TEMPERATURE CO EFFICIENT (ppm/°C)

05725-011

Figure 6. ADR121 Temperature Coefficient

5.020

5.015

5.010

5.005

(V)

5.000

OUT

V

4.995

4.990

4.985

4.980
–40 125

–25–105 203550658095110

TEMPERATURE (°C)

Figure 4. ADR125 V

vs. Temperature

OUT

05725-008

Rev. B | Page 7 of 20

5

4

3

2

NUMBER OF PARTS

1

0

–50 50

–40–30–20–100 10203040

TEMPERATURE CO EFFICIENT (ppm/°C)

Figure 7. ADR125 Temperature Coefficient

05725-010

ADR121/ADR125/ADR127

3.0

120

2.8

–40°C

2.6

_MIN (V)

IN

2.4

V

2.2

2.0
–2–1012345

+25°C

+125°C

LOAD CURRENT (mA)

Figure 8. ADR127 Minimum Input Voltage vs. Load Current

3.5

3.4

3.3

3.2

3.1

3.0

_MIN (V)

IN

2.9

V

2.8

2.7

2.6

2.5

–2–1012345

LOAD CURRENT (mA)

+125°C

+25°C

–40°C

Figure 9. ADR121 Minimum Input Voltage vs. Load Current

6.2

100

+25°C

80

+125°C

–40°C

60

40

SUPPLY CURRENT ( µA)

20

0

3 4 5 6 7 8 9 1011121314151617

21

5725-012

INPUT VOLTAG E (V)

8

5725-015

Figure 11. ADR127 Supply Current vs. Input Voltage

120

100

SUPPLY CURRENT ( µA)

05725-013

+125°C

+25°C

80

60

40

20

0

21

–40°C

3 4 5 6 7 8 9 1011121314151617

INPUT VOLTAGE (V)

8

05725-016

Figure 12. ADR121 Supply Current vs. Input Voltage

120

6.0

5.8

5.6

_MIN (V)

IN

V

5.4

5.2

5.0

–2–1012345

LOAD CURRENT (mA)

+125°C

+25°C

–40°C

Figure 10. ADR125 Minimum Input Voltage vs. Load Current

05725-014

Rev. B | Page 8 of 20

100

+25°C

80

+125°C

–40°C

60

40

SUPPLY CURRENT (µA)

20

0

51

6 7 8 9 1011121314151617

INPUT VOLTAG E (V)

8

5725-017

Figure 13. ADR125 Supply Current vs. Input Voltage

ADR121/ADR125/ADR127

6

5

— +125°C

— +25°C

— –40°C

0

–10

4

3

2

SUPPLY CURRENT (mA)

1

0

–2 5

–101234

LOAD CURRENT (mA)

Figure 14. ADR127 Supply Current vs. Load Current

6

— +125°C

— +25°C

— –40°C

5

4

3

2

SUPPLY CURRENT (mA)

1

0

–2 5

–101234

LOAD CURRENT (mA)

Figure 15. ADR121 Supply Current vs. Load Current

6

— +125°C

— +25°C

— –40°C

5

–20

–30

LINE REGUL ATION (ppm/V)

–40

–50

–40 125

05725-018

VIN = 2.7V TO 18V

–25 –10 5 20 35 50 65 80 95 110

TEMPERATURE ( °C)

05725-021

Figure 17. ADR127 Line Regulation vs. Temperature

3

2

1

0

–1

LINE REGUL ATION (ppm/V)

–2

–3

–40 125

–25 –10 5 20 35 50 65 80 95 110

05725-019

VIN = 2.8V TO 18V

TEMPERATURE ( °C)

05725-022

Figure 18. ADR121 Line Regulation vs. Temperature

6

4

4

3

2

SUPPLY CURRENT (mA)

1

0

–2 5

–101234

LOAD CURRENT (mA)

Figure 16. ADR125 Supply Current vs. Load Current

05725-020

Rev. B | Page 9 of 20

2

0

–2

LINE REGUL ATION (p pm/V)

–4

–6

VIN = 5.3V TO 18V

–40 125

–25 –10 5 20 35 50 65 80 95 110

TEMPERATURE ( °C)

Figure 19. ADR125 Line Regulation vs. Temperature

05725-023

ADR121/ADR125/ADR127

200

150

CIN = C

OUT

= 0.1µF

100

50

0

–50

–100

LOAD REGULAT ION (pp m/mA)

–150

–200

–40 125

2mA SINKING, VIN = 3V

5mA SOURCING, VIN = 3V

–25 –10 5 20 35 50 65 80 95 110

TEMPERATURE ( °C)

Figure 20. ADR127 Load Regulation vs. Temperature

100

80

60

40

20

0

–20

–40

LOAD REGULAT ION (pp m/mA)

–60

–80

–100

–40 125

–25 –10 5 20 35 50 65 80 95 110

2mA SINKING, VIN = 5V

5mA SOURCING, VIN = 5V

TEMPERATURE ( °C)

Figure 21. ADR121 Load Regulation vs. Temperature

CH1 p-p

5.76µV

1

2µV/DIV

05725-024

TIME (1s/ DIV)

CH1 rms

0.862µV

05725-027

Figure 23. ADR127 0.1 Hz to 10 Hz Noise

CIN = C

1

05725-025

= 0.1µF

OUT

5µV/DIV TIME (1s/DIV )

CH1 p-p

10.8µV

CH1 rms

1.75µV

05725-028

Figure 24. ADR121 0.1 Hz to 10 Hz Noise

50

40

30

20

10

–10

–20

LOAD REGULAT ION (pp m/mA)

–30

–40

–50

2mA SINKING, VIN = 6V

0

5mA SOURCING, VIN = 6V

–40 125

–25 –10 5 20 35 50 65 80 95 110

TEMPERATURE ( °C)

Figure 22. ADR125 Load Regulation vs. Temperature

05725-026

Rev. B | Page 10 of 20

CIN = C

1

= 0.1µF

OUT

10µV/DIV TIME (1s/DIV)

CH1 p-p

20.6µV

CH1 rms

3.34µV

05725-029

Figure 25. ADR125 0.1 Hz to 10 Hz Noise

ADR121/ADR125/ADR127

CIN = C

OUT

= 0.1µF

CH1 p-p
287µV

VIN 1V/DIV
C

= C

IN

OUT

= 0.1µF

1

50µV/DIV

TIME (1s/ DIV)

CH1 rms

38.8µV

05725-030

Figure 26. ADR127 10 Hz to 10 kHz Noise

CIN = C

1

= 0.1µF

OUT

100µV/DIV TIME (1s/DI V)

CH1 p-p
450µV

CH1 rms

58.1µV

05725-031

Figure 27. ADR121 10 Hz to 10 kHz Noise

1

V

OUT

2

500mV/DIV

TIME (200µs/ DIV)

05725-033

Figure 29. ADR127 Turn-On Response

VIN 1V/DIV
C

= C

= 0.1µF

IN

OUT

1

V

OUT

500mV/ DIV

TIME (40µs/DIV)

2

05725-034

Figure 30. ADR127 Turn-On Response

CIN = C

1

= 0.1µF

OUT

200µV/DIV TIME (1s/DI V)

Figure 28. ADR125 10 Hz to 10 kHz Noise

CH1 p-p
788µV

CH1 rms
115µV

05725-032

VIN 1V/DIV
C

= C

= 0.1µF

IN

OUT

1

2

V

OUT

500mV/DI V

TIME (100µs/ DIV)

05725-035

Figure 31. ADR127 Turn-Off Response

Rev. B | Page 11 of 20

ADR121/ADR125/ADR127

CIN = C

OUT

= 0.1µF

VIN 1V/DIV
C

= C

= 0.1µF

IN

OUT

1

V

OUT

1V/DIV

2

TIME (100µs/ DIV)

05725-036

1

2

Figure 32. ADR121 Turn-On Response

CIN = C

OUT

VIN 1V/DIV
C

= C

= 0.1µF

IN

OUT

1

V

OUT

2

1V/DIV

TIME (40µs/DIV)

05725-037

1

2

Figure 33. ADR121 Turn-On Response

V

IN

2V/DIV

V

OUT

2V/DIV

TIME (100µs/ DIV)

Figure 35. ADR125 Turn-On Response

= 0.1µF

V

IN

2V/DIV

V

OUT

2V/DIV

TIME (20µs/DIV)

Figure 36. ADR125 Turn-On Response

05725-039

05725-040

CIN = C

VIN 1V/DIV
C

= C

= 0.1µF

IN

OUT

1

V

OUT

1V/DIV

2

TIME (200µ s/DIV)

05725-038

1

2

Figure 34. ADR121 Turn-Off Response

= 0.1µF

OUT

V

IN

2V/DIV

V

OUT

2V/DIV

TIME (20µs/DIV)

Figure 37. ADR125 Turn-Off Response

05725-041

Rev. B | Page 12 of 20

ADR121/ADR125/ADR127

V

CIN = C

1

= 0.1µF

OUT

VIN 1V/DIV
LINE INTE RRUPTION

2.50V

VIN500mV/DIV
C

= C

= 0.1µF

IN

OUT

625Ω LOAD
2mA SINKING

2

1.25V

2

V

OUT

500mV/DIV

Figure 38. ADR127 Line Transient Response

CIN = C

1

2

= 0.1µF

OUT

VIN 1V/DIV
LINE INTERRUPT ION

V

OUT

500mV/DIV

Figure 39. ADR121 Line Transient Response

CIN = C

1

= 0.1µF

OUT

VIN 1V/DIV
LINE INTERRUPT ION

TIME (200µs/DIV)

TIME (400µ s/DIV)

1

05725-042

V

OUT

20mV/DIV

TIME (40µs/DIV)

05725-045

Figure 41. ADR127 Load Transient Response (Sinking)

VIN500mV/DIV
C

= C

= 0.1µF

IN

OUT

250Ω LOAD
5mA SOURCING

1

2

V

OUT

100mV/DIV

05725-043

TIME (40µs/DIV)

1.25

0V

05725-046

Figure 42. ADR127 Load Transient Response (Sourcing)

5V

VIN1V/DIV

= C

C
1250Ω LOAD
2mA SINKING

= 0.1µF

IN

OUT

2.5V

2

V

OUT

500mV/DIV

Figure 40. ADR125 Line Transient Response

TIME (400µ s/DIV)

05725-044

1

2

V

OUT

10mV/DIV

TIME (40µs/DIV)

Figure 43. ADR121 Load Transient Response (Sinking)

05725-047

Rev. B | Page 13 of 20

ADR121/ADR125/ADR127

0

–20

–40

–60

–100

(dB)

–120

–140

–160

–180

–200

–80

1

10 100M

100 1k 10k 100k 1M 10M

Figure 47. ADR121/ADR125/ADR127 PSRR

50

45

40

35

30

25

20

15

OUTPUT IMPEDANCE (Ω)

10

5

0

10

1

100

FREQUENCY (Hz)

1k 10k 100k

ADR127

ADR121

ADR125

Figure 48. ADR121/ADR125/ADR127 Output Impedance vs. Frequency

05725-051

5725-054

VIN1V/DIV
C

= C

= 0.1µF

IN

OUT

500Ω LOAD

1

2

V

OUT

100mV/DIV

5mA SOURCING

TIME (40µs/DIV)

Figure 44. ADR121 Load Transient Response (Sourcing)

VIN2V/DIV
C

= C

= 0.1µF

IN

OUT

2.5kΩ LOAD
2mA SINKING

1

2

V

OUT

20mV/DIV

TIME (40µs/DIV)

Figure 45. ADR125 Load Transient Response (Sinking)

2.5V

0V

05725-048

10V

5V

05725-049

5V

VIN2V/DIV
C

= C

= 0.1µF

IN

OUT

1kΩ LOAD

V

OUT

100mV/DIV

5mA SOURCING

TIME (40µs/DIV)

1

2

0V

05725-050

Figure 46. ADR125 Load Transient Response (Sourcing)

Rev. B | Page 14 of 20

ADR121/ADR125/ADR127

(

−

Δ

(

=

T

TERMINOLOGY

Temperature Coefficient

The change in 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
as follows:

−

TCV

[]

OUT

Cppm/ ×

()( )

C25

() ()

O

UT

=°

TVTV

1OUT2

−×°

TTV

6

(1)

10

12OUT

where:

V

OUT

V

OUT(T1

V

OUT(T2

(25°C) = V

) = V
) = V

at 25°C.

OUT

at Temperature 1.

OUT

at Temperature 2.

OUT

Line Regulation

The change in the output voltage due to a specified change
in input voltage. This parameter accounts for the effects of
self-heating. Line regulation is expressed in percent per volt,
parts-per-million per volt, or microvolts per voltage change in
input voltage.

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 microvolts per milliampere,
parts-per-million per milliampere, or ohms of dc output
resistance.

Long-Term Stability

Typical shift of output voltage at 25°C on a sample of parts
subjected to a test of 1000 hours at 25°C.

O

UT

[]

V

OUT

)()

=Δ

tVtVV

1

O0OUT

UT

() ()

−

tVtV

1OUT0OUT

()

tV

0OUT

(2)

6

10ppm ×

where:

V
V

OUT(t0

OUT(t1

) = V
) = V

at 25°C at Time 0.

OUT

at 25°C after 1000 hours operating at 25°C.

OUT

Thermal Hysteresis

The change in 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.

)

VVV

C25 −°

()

O

V

[]

ppm ×

_

HYSOUT

UT

=

V

OU

(3)

TCOUTOUTHYSOUT

__

VV

C25

−°

_

TCOUT

6

()

C25

°

10

where:

V
V

OUT

OUT_TC

(25°C) = V

= V

at 25°C.

OUT

at 25°C after temperature cycle at +25°C to

OUT

−40°C to +125°C and back to +25°C.

Rev. B | 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.

POWER DISSIPATION CONSIDERATIONS

The ADR12x family is capable of delivering load currents up 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.

Use the following formula to calculate a device’s maximum
junction temperature or dissipation:

TT

−

J

P

= (4)

D

where:

T

is the junction temperature.

J

T

is the ambient temperature.

A

P

is the device power dissipation.

D

θ

is the device package thermal resistance.

JA

A

θ

JA

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 may improve transient response
in applications where there is a sudden supply change. An
additional 0.1 μF capacitor in parallel also helps reduce noise
from the supply.

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.

Rev. B | Page 16 of 20

ADR121/ADR125/ADR127

–V

V

APPLICATIONS INFORMATION

BASIC VOLTAGE REFERENCE CONNECTION

The circuit in Figure 49 illustrates the basic configuration for
the ADR12x family voltage reference.

1

NC

ADR12x

GND

2

V

3

IN

+ +

0.1µF 0.1µF

Figure 49. Basic Configuration for the ADR12x Family

6

NC

NC

5

V

OUT

OUTPUTINPUT

4

05725-002

STACKING REFERENCE ICs FOR ARBITRARY OUTPUTS

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.

1

NC

ADR12x

2

GND

V

IN

V

3

IN

U2

1

NC

ADR12x

2

GND

V

3

IN

U1

Figure 50. Stacking References with the ADR12x

Two reference ICs are used and fed from an unregulated input,
V

. The outputs of the individual ICs are connected in series,

IN

which provides two output voltages, V
the terminal voltage of U1, whereas V
voltage and the terminal of U2. U1 and U2 are chosen for the
two voltages that supply the required outputs (see Tab le 6). For
example, if U1 and U2 are ADR127s and V

1.25 V and V

OUT2

is 2.5 V.

6

NC

5

NC

V

4

OUT

6

NC

5

NC

V

4

OUT

and V

OUT1

OUT2

OUT2

is the sum of this

≥ 3.95 V, V

IN

V

0.1µF0.1µF

V

0.1µF0.1µF

. V

OUT2

OUT1

OUT1

OUT1

05725-003

is

is

Table 6. Required Outputs

U1/U2 V

V

OUT2

OUT1

ADR127/ADR121 1.25 V 3.75 V
ADR127/ADR125 1.25 V 6.25 V
ADR121/ADR125 2.5 V 7.5 V

NEGATIVE PRECISION REFERENCE WITHOUT PRECISION RESISTORS

A negative reference is easily generated by adding an op
amp, for example, the AD8603, and is configured as shown in
Figure 51. V

is at virtual ground and, therefore, the negative

OUT

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.

+V

DD

REF

AD8603

Figure 51. Negative Reference

1

2

3

–V

NC

ADR127

GND

V

IN

–

V+

V–

+

DD

2

3

0.1µF

6

NC

NC

5

V

4

OUT

1kΩ

05725-055

GENERAL-PURPOSE CURRENT SOURCE

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 R
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.

+

DD

, which sets the output current into the

SET

1

NC

NC

6

ADR12x

2

GND

V

3

IN

I

SY

5

NC

V

4

OUT

I

SET

R

SET

P1

R

L

05725-005

Figure 52. ADR12x Trim Configuration

Rev. B | Page 17 of 20

ADR121/ADR125/ADR127

R

OUTLINE DIMENSIONS

INDICATO

ORDERING GUIDE

Initial

Accuracy

mV ±%

Model

ADR121AUJZ-REEL7
ADR121AUJZ-R2

1

2.5 2.5 0.24 25 −40°C to +125°C 6-Lead TSOT UJ-6 250 R0N

ADR121BUJZ-REEL7
ADR125AUJZ-REEL7
ADR125AUJZ-R2

1

5.0 5.0 0.24 25 −40°C to +125°C 6-Lead TSOT UJ-6 250 R0Q

ADR125BUJZ-REEL7
ADR127AUJZ-REEL7
ADR127AUJZ-R2

1

1.25 3 0.24 25 −40°C to +125°C 6-Lead TSOT UJ-6 250 R0S

ADR127BUJZ-REEL7

1

Z = RoHS Compliant Part.

Output
Voltage

)

(V

OUT

1

2.5 2.5 0.24 25 −40°C to +125°C 6-Lead TSOT UJ-6 3,000 R0N

1

2.5 2.5 0.12 9 −40°C to +125°C 6-Lead TSOT UJ-6 3,000 R0P

1

5.0 5.0 0.24 25 −40°C to +125°C 6-Lead TSOT UJ-6 3,000 R0Q

1

5.0 5.0 0.12 9 −40°C to +125°C 6-Lead TSOT UJ-6 3,000 R0R

1

1.25 3 0.24 25 −40°C to +125°C 6-Lead TSOT UJ-6 3,000 R0S

1

1.25 1.5 0.12 9 −40°C to +125°C 6-Lead TSOT UJ-6 3,000 R0T

2.90 BSC

4526

1.60 BSC

13

PIN 1

*

0.90

0.87

0.84

0.10 MAX

*

COMPLIANT TO JEDEC STANDARDS MO-193-AA WITH

THE EXCEPTION OF PACKAGE HEIGHT AND THICKNESS.

1.90

BSC

0.50

0.30

2.80 BSC

0.95 BSC

*

1.00 MAX

SEATING
PLANE

0.20

0.08
8°
4°
0°

Figure 53. 6-Lead Thin Small Outline Transistor Package [TSOT]

(UJ-6)

Dimensions shown in millimeters

Temperature
Coefficient
(ppm/°C)

Temperature
Range

Package
Description

0.60

0.45

0.30

Package
Option

Ordering
Quantity Branding

Rev. B | Page 18 of 20

ADR121/ADR125/ADR127

NOTES

Rev. B | Page 19 of 20

ADR121/ADR125/ADR127

NOTES

©2006–2008 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D05725-0-1/08(B)

Rev. B | Page 20 of 20