Datasheet ADR381ART-REEL7, ADR381ART-REEL, ADR380ART-REEL7, ADR380ART-REEL Datasheet (Analog Devices)

Precision Low-Drift 2.048 V/2.500 V

1

2

ADR380/

ADR381

(Not to Scale)

3

V

IN

GND

V

OUT

a

FEATURES
Initial Accuracy: ⴞ5 mV/ⴞ6 mV max
Initial Accuracy Error: ⴞ0.24%/ⴞ0.24%
Low TCV
Load Regulation: 70 ppm/mA
Line Regulation: 25 ppm/V
Wide Operating Range:

2.4 V–18 V for ADR380

2.8 V–18 V for ADR381
Low Power: 120 ␮A max
High Output Current: 5 mA
Wide Temperature Range: –40ⴗC to +85ⴗC
Tiny 3-Lead SOT-23 Package with Standard Pinout

APPLICATIONS
Battery-Powered Instrumentation
Portable Medical Instruments
Data Acquisition Systems
Industrial Process Control Systems
Hard Disk Drives
Automotive

: 25 ppm/ⴗC max

O

SOT-23 Voltage References

ADR380/ADR381

PIN CONFIGURATION

3-Lead SOT-23

(RT Suffix)

Table I. ADR38x Products

Part Number Nominal Output Voltage (V)

ADR380 2.048
ADR381 2.500

GENERAL DESCRIPTION

The ADR380 and ADR381 are precision 2.048 V and 2.500 V
bandgap voltage references featuring high accuracy, high stabil­ity, and low-power consumption in a tiny footprint. Patented
temperature drift curvature correction techniques minimize
nonlinearity of the voltage change with temperature. The wide
operating range and low-power consumption make them ideal
for 3 V–5 V battery-powered applications.

The ADR380 and ADR381 are micropower, Low Dropout
Voltage (LDV) devices that provide a stable output voltage
from supplies as low as 300 mV above the output voltage.
They are specified over the industrial (–40°C to +85°C) tem­perature range. ADR380/ADR381 is available in the tiny 3-lead
SOT-23 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 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: [phone] World Wide Web Site: http://www.analog.com
Fax: [phone] © Analog Devices, Inc., 2001

ADR380/ADR381–SPECIFICATIONS

ADR380 ELECTRICAL CHARACTERISTICS

(@ VIN = 5.0 V, TA = 25ⴗC unless otherwise noted.)

Parameter Symbol Conditions Min Typ Max Unit

Output Voltage V
Initial Accuracy Error V

O

OERR

2.043 2.048 2.053 V
–5 +5 mV
–0.24 +0.24 %

Temperature Coefficient TCV

Minimum Supply Voltage Headroom V
Line Regulation ∆V

Load Regulation ∆V

Quiescent Current I

Voltage Noise e
Turn-On Settling Time t
Long-Term Stability ∆V
Output Voltage Hysteresis V

– V

IN

O

O

IN

N

R

O

O_HYS

O

/∆V

/∆I

O

IN

LOAD

Ripple Rejection Ratio RRR f
Short Circuit to GND I

Specifications subject to change without notice.

SC

ADR380 ELECTRICAL CHARACTERISTICS

–40°C < TA < +85°C 5 25 ppm/°C
0°C < T

< 70°C 3 21 ppm/°C

A

IL ≤ 3 mA 300 mV
VIN = 2.5 V to 15 V 10 25 ppm/V
–40°C < T
VIN = 3 V, I
–40°C < T

< +85°C

A

= 0 mA to 5 mA 70 ppm/mA

LOAD

< +85°C

A

No Load 100 120 µA
–40°C < T

< +85°C 140 µA

A

0.1 Hz to 10 Hz 5 µV p-p
20 µs

1000 Hrs 50 ppm

40 ppm

= 60 Hz 85 dB

IN

25 mA

(@ VIN = 15.0 V, TA = 25ⴗC unless otherwise noted.)

Parameter Symbol Conditions Min Typ Max Unit

Output Voltage V
Initial Accuracy Error V

O

OERR

2.043 2.048 2.053 V
–5 +5 mV
–0.24 +0.24 %

Temperature Coefficient TCV

Minimum Supply Voltage Headroom V
Line Regulation ∆V

Load Regulation ∆V

Quiescent Current I

Voltage Noise e
Turn-On Settling Time t
Long-Term Stability ∆V
Output Voltage Hysteresis V

– V

IN

O

O

IN

N

R

O

O_HYS

O

/∆V

/∆I

O

IN

LOAD

Ripple Rejection Ratio RRR f
Short Circuit to GND I

Specifications subject to change without notice.

SC

–40°C < TA < +85°C 5 25 ppm/°C
0°C < T

< 70°C 3 21 ppm/°C

A

IL ≤ 3 mA 300 mV
VIN = 2.5 V to 15 V
–40°C < T
VIN = 3 V, I
–40°C < T

< +85°C 10 25 ppm/V

A

= 0 mA to 5 mA

LOAD

< +85°C 70 ppm/mA

A

No Load 100 120 µA
–40°C < T

< +85°C 140 µA

A

0.1 Hz to 10 Hz 5 µV p-p
20 µs

1000 Hrs 50 ppm

40 ppm

= 60 Hz 85 dB

IN

25 mA

–2–

REV. 0

SPECIFICATIONS

ADR380/ADR381

ADR381 ELECTRICAL CHARACTERISTICS

(@ VIN = 5.0 V, TA = 25ⴗC unless otherwise noted.)

Parameter Symbol Conditions Min Typ Max Unit

Output Voltage V
Initial Accuracy Error V

O

OERR

2.494 2.5 2.506 V
–6 +6 mV
–0.24 +0.24 %

Temperature Coefficient TCV

Minimum Supply Voltage Headroom V
Line Regulation ∆V

Load Regulation ∆V

Quiescent Current I

Voltage Noise e
Turn-On Settling Time t
Long-Term Stability ∆V
Output Voltage Hysteresis V

– V

IN

O

O

IN

N

R

O

O_HYS

O

O

/∆V

/∆I

LOADVIN

Ripple Rejection Ratio RRR f
Short Circuit to GND I

Specifications subject to change without notice.

SC

ADR381 ELECTRICAL CHARACTERISTICS

–40°C < TA < +85°C 5 25 ppm/°C
0°C < T

< 70°C 3 21 ppm/°C

A

IL ≤ 2 mA 300 mV
VIN = 2.8 V to 15 V 10 25 ppm/V

IN

–40°C < T

= 3.5 V, I

–40°C < T

< +85°C

A

LOAD

< +85°C

A

= 0 mA to 5 mA 70 ppm/mA

No Load 100 120 µA
–40°C < T

< +85°C 140 µA

A

0.1 Hz to 10 Hz 5 µV p-p
20 µs

1000 Hrs 50 ppm

75 ppm

= 60 Hz 85 dB

IN

25 mA

(@ VIN = 15.0 V, TA = 25ⴗC unless otherwise noted.)

Parameter Symbol Conditions Min Typ Max Unit

Output Voltage V
Initial Accuracy Error V

O

OERR

2.494 2.5 2.506 V
–6 +6 mV
–0.24 +0.24 %

Temperature Coefficient TCV

Minimum Supply Voltage Headroom V
Line Regulation ∆V

Load Regulation ∆V

Quiescent Current I

Voltage Noise e
Turn-On Settling Time t
Long-Term Stability ∆V
Output Voltage Hysteresis V

– V

IN

O

O

IN

N

R

O

O_HYS

O

O

/∆V

/∆I

LOADVIN

Ripple Rejection Ratio RRR f
Short Circuit to GND I

Specifications subject to change without notice.

SC

–40°C < TA < +85°C 5 25 ppm/°C
0°C < T

< 70°C 3 21 ppm/°C

A

IL ≤ 2 mA 300 mV
VIN = 2.8 V to 15 V 10 25 ppm/V

IN

–40°C < T

= 3.5 V, I

–40°C < T

< +85°C

A

LOAD

< +85°C

A

= 0 mA to 5 mA 70 ppm/mA

No Load 100 120 µA
–40°C < T

< +85°C 140 µA

A

0.1 Hz to 10 Hz 5 µV p-p
20 µs

1000 Hrs 50 ppm

75 ppm

= 60 Hz 85 dB

IN

25 mA

REV. 0

–3–

ADR380/ADR381

WARNING!

ESD SENSITIVE DEVICE

1

2

ADR380/

ADR381

(Not to Scale)

3

V

IN

GND

V

OUT

ABSOLUTE MAXIMUM RATINGS

1

PIN CONFIGURATION

Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 V

Output Short-Circuit Duration to GND

> 15 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 sec

V

IN

V

≤ 15 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Indefinite

IN

3-Lead SOT-23

(RT Suffix)

Storage Temperature Range

RT Package . . . . . . . . . . . . . . . . . . . . . . . –65°C to +150°C

Operating Temperature Range

ADR380/ADR381 . . . . . . . . . . . . . . . . . . . –40°C to +85°C

Junction Temperature Range

RT Package . . . . . . . . . . . . . . . . . . . . . . . –65°C to +150°C

Lead Temperature Range (Soldering, 60 Sec) . . . . . . . . 300°C

Package Type ␪

2

JA

␪

JC

Unit

3-Lead SOT-23 (RT) 333 — °C/W

NOTES

1

Absolute maximum ratings apply at 25°C, unless otherwise noted.

2

θJA is specified for the worst case conditions, i.e., θJA is specified for device soldered

in circuit board for surface-mount packages.

ORDERING GUIDE

Temperature Package Package Top Output Number of

Model Range Description Option Mark Voltage Parts per Reel

ADR380ART-REEL7 –40°C to +85°C SOT-23 RT-3 R2A 2.048 3,000
ADR380ART-REEL –40°C to +85°C SOT-23 RT-3 R2A 2.048 10,000
ADR381ART-REEL7 –40°C to +85°C SOT-23 RT-3 R3A 2.500 3,000
ADR381ART-REEL –40°C to +85°C SOT-23 RT-3 R3A 2.500 10,000

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 ADR380/ADR381 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.

–4–

REV. 0

ADR380/ADR381

PARAMETER DEFINITIONS
Temperature Coefficient

The change of output voltage over the operating temperature
change and normalized by the output voltage at 25°C, expressed
in ppm/°C. The equation follows:

VT VT

21

OO

TCV ppm C

/ °

O

[]

()−()

=

VCTT

°

25

O

()

×−

21

()

6

10

×

where:

V

(25°C) = VO at 25°C.

O

V

) = VO at Temperature 1.

O (T1

V

) = VO at Temperature 2.

O (T2

Line Regulation

The change in output voltage due to a specified change in input
voltage. It includes the effects of self-heating. Line Regulation is
expressed in either percent per volt, parts-per-million per volt,
or microvolts per volt change in input voltage.

Load Regulation

The change in output voltage due to a specified change in load
current. It includes the effects of self-heating. Load Regulation
is expressed in either microvolts per milliampere, parts-per­million per milliampere, or ohms of dc output resistance.

Long-Term Stability

A typical shift in output voltage over 1000 hours at a controlled
temperature. The graphs (TPC 24 and TPC 25) show a sample
of parts measured at different intervals in a controlled envi­ronment of 50°C for 1000 hours.

∆VVtVt

=

OO O

∆V ppm

O

[]

01

()−()

Vt Vt

01

OO

()−()

=

Vt

0

O

()

6

×

10

where:

)= VO at Time 0.

V

O(t0

V

)= VO after 1000 hours’ operation at a

O(t1

controlled temperature.

Note that 50°C was chosen since most applications we have
experienced run at a higher temperature than 25°C.

Thermal Hysteresis

The change of output voltage after the device is cycled through
temperature from +25°C to –40°C to +85°C and back to +25°C.
This is a typical value from a sample of parts put through
such a cycle.

VVCV

__=°

O HYS O O TC

−25

()

Typical Performance Characteristics

2.054

2.052

SAMPLE 1

SAMPLE 2

SAMPLE 3

– V

OUT

V

2.050

2.048

2.046

2.044

V ppm

O HYS

_

where:

VO(25°C) = VO at 25°C.
V

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

O_TC

–40°C to +85°C and back to +25°C.

2.506

2.504

– V

V

2.502

2.500

OUT

2.498

2.496

SAMPLE 1

SAMPLE 2

VCV

°

25

OOTC

()

=

[]

VC

O

SAMPLE 3

25

()

−

_

6

10

×

°

2.042
–40

–15 10 35 60 85

TEMPERATURE – ⴗC

TPC 1. ADR380 Output Voltage vs. Temperature

REV. 0

–5–

2.494

–40

–15 10 35 60 85

TEMPERATURE – ⴗC

TPC 2. ADR381 Output Voltage vs. Temperature

12/07/00 1.45 PM

ADR380/ADR381–Typical Performance Characteristics

30

TEMPERATURE +25ⴗC –40ⴗC +85ⴗC +25ⴗC

25

20

15

FREQUENCY

10

5

0

–11 –9 –7 –5 –3 –113

PPM – ⴗC

TOTAL NUMBER
OF DEVICES = 130

5 7 9 11 13 15 17 19

TPC 3. ADR380 Output Voltage Temperature Coefficient

60

TEMPERATURE +25ⴗC

50

40

30

FREQUENCY

20

10

–40ⴗC +85ⴗC +25ⴗC

TOTAL NUMBER
OF DEVICES IN
SAMPLE = 450

140

120

100

80

60

40

SUPPLY CURRENT – ␮A

20

0

+85ⴗC

2.5 5.0 7.5 10.0 12.5 15.0

+25ⴗC

–40ⴗC

INPUT VOLTAGE – V

TPC 6. ADR381 Supply Current vs. Input Voltage

70

IL = 0mA TO 5mA

60

50

40

30

VIN = 5V

20

LOAD REGULATION – ppm/mA

10

VIN = 3V

0

–11 –9 –7 –5 –3 –11 3

PPM – ⴗC

579111315–15 –13

TPC 4. ADR381 Output Voltage Temperature Coefficient

140

120

100

80

60

40

SUPPLY CURRENT – ␮A

20

+85ⴗC

0

2.5 5.0 7.5 10.0 12.5 15.0

+25ⴗC

–40ⴗC

INPUT VOLTAGE – V

TPC 5. ADR380 Supply Current vs. Input Voltage

0

–40 –15 10 35 60

TEMPERATURE – ⴗC

85

TPC 7. ADR380 Load Regulation vs. Temperature

70

IL = 5mA

60

50

40

30

20

LOAD REGULATION – ppm/mA

10

0

–40 –15 10 35 60 85

VIN = 3.5V

VIN = 5V

TEMPERATURE – ⴗC

TPC 8. ADR381 Load Regulation vs. Temperature

–6–

REV. 0

5

–40ⴗC

LOAD CURRENT – mA

012345

0

DIFFERENTIAL VOLTAGE – V

0.2

0.4

0.6

0.8

+85ⴗC

+25ⴗC

V

OUT

DEVIATION – ppm

–260

0

FREQUENCY

10

20

30

40

50

60

–200

–140

–80 –20

40 100

160 220 340 400

280

TEMPERATURE +25ⴗC –40ⴗC 85ⴗC +25ⴗC

VIN = 2.5V TO 15V

4

3

2

LINE REGULATION – ppm/V

1

0

–40 –15 10 35 60

TEMPERATURE – ⴗC

85

TPC 9. ADR380 Line Regulation vs. Temperature

5

VIN = 2.8V TO 15V

4

ADR380/ADR381

TPC 12. ADR381 Minimum Input/Output Voltage
Differential vs. Load Current

3

2

LINE REGULATION – ppm/V

1

0

–40 –15 10 35 60 85

TPC 10. ADR381 Line Regulation vs. Temperature

0.8

0.6

0.4

0.2

DIFFERENTIAL VOLTAGE – V

0

012 34

TPC 11. ADR380 Minimum Input/Output Voltage
Differential vs. Load Current

TEMPERATURE – ⴗC

–40ⴗC

LOAD CURRENT – mA

+85ⴗC

+25ⴗC

TPC 13. ADR381 V

2␮V/DIV

5

TIME – 1s/DIV

Hysteresis

OUT

TPC 14. ADR381 Typical Noise Voltage 0.1 Hz to 10 Hz

REV. 0

–7–

ADR380/ADR381

␮

␮

100␮V/DIV

LOAD OFF

CL = 0␮F

V

OUT

V

LOAD

LOAD = 1mA

ON

1V/DIV

2V/DIV

TIME – 10ms/DIV

TPC 15. ADR381 Typical Noise Voltage 10 Hz to 10 kHz

C

= 0␮F

BYPASS

V

OUT

LINE INTERRUPTION

0.5V/DIV

TIME – 10␮s/DIV

V

IN

1V/DIV

0.5V/DIV

TPC 16. ADR381 Line Transient Response

C

= 0.1␮F

BYPASS

V

OUT

1V/DIV

TIME – 200

s/DIV

TPC 18. ADR381 Load Transient Response with CL = 0 µF

CL = 1nF

V

LOAD OFF

TIME – 200

s/DIV

OUT

V

LOAD

LOAD = 1mA

1V/DIV

ON

2V/DIV

TPC 19. ADR381 Load Transient Response with CL = 1 nF

CL = 100nF

V

OUT

1V/DIV

0.5V/DIV

LINE INTERRUPTION

TIME – 10␮s/DIV

TPC 17. ADR381 Line Transient Response

0.5V/DIV

LOAD OFF

V

ON

LOAD

LOAD = 1mA

TIME – 200␮s/DIV

TPC 20. ADR381 Load Transient Response with CL = 100 nF

–8–

2V/DIV

REV. 0

C

HOURS

0

–150

0

100

DRIFT – ppm

–100

–50

50

100

150

200 300 400

500

600 700 800 900

1000

CONDITIONS: VIN = 6V IN A CONTROLLED
ENVIRONMENT 50ⴗC +/– 1ⴗC

HOURS

0

–150

0

100

DRIFT – ppm

–100

–50

50

100

150

200 300 400

500

600 700 800 900

1000

CONDITIONS: VIN = 6V IN A CONTROLLED
ENVIRONMENT 50ⴗC +/– 1ⴗC

BYPASS

ADR380/ADR381

= 0.1␮F

V

OUT

2V/DIV

TIME – 200␮s/DIV

V

IN

5V/DIV

TPC 21. ADR381 Turn-On/Turn-Off Response at 5 V

C

= 0.1␮F

BYPASS

V

OUT

TIME – 200␮s/DIV

V

IN

2V/DIV

5V/DIV

TPC 22. ADR381 Turn-On/Turn-Off Response at 5 V

TPC 24. ADR380 Long-Term Drift

TPC 25. ADR381 Long-Term Drift

CB = 0.1␮F

CL = 40pF

– 10⍀/DIV

OUT

Z

CL = 1␮F

CL = 0.1␮F

10

100

1k 10k 100k

FREQUENCY – Hz

1M

TPC 23. ADR381 Output Impedance vs. Frequency

REV. 0

–9–

ADR380/ADR381

THEORY OF OPERATION

Bandgap references are the high-performance solution for low­supply voltage and low-power voltage reference applications,
and the ADR380/ADR381 is no exception. But the uniqueness
of this product lies in its architecture. By observing Figure 1, the
ideal zero TC bandgap voltage is referenced to the output, not
to ground. The bandgap cell consists of the pnp pair Q51 and
Q52, running at unequal current densities. The difference in

results in a voltage with a positive TC which is amplified up

V

BE

by the ratio of 2 × R58/R54. This PTAT voltage, combined with
V

of Q51 and Q52, produce the stable bandgap voltage. Reduc-

BEs

tion in the bandgap curvature is performed by the ratio of the
two resistors R44 and R59. Precision laser trimming and other
patented circuit techniques are used to further enhance the drift
performance.

V

R49

R48

IN

V

OUT

GND

Q1

R59

R54

+

Q51

–

R60

R53

R44

R58

Q52

R61

Figure 1. Simplified Schematic

Device Power Dissipation Considerations

The ADR380/ADR381 is capable of delivering load currents to
5 mA with an input voltage that ranges from 2.8 V (ADR381
only) to 15 V. When this device is used in applications with
large input voltages, care should be taken to avoid exceeding the
specified 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

−

A

J

P

=

D

θ

A

J

where:

P

is the device power dissipation,

D

and TA are junction and ambient temperatures, respec-

T

J

tively, and

θ

is the device package thermal resistance.

JA

Input Capacitor

Input capacitor is not required on the ADR380/ADR381.
There is no limit for the value of the capacitor used on the input,
but a capacitor on the input will improve transient response in
applications where the load current suddenly increases.

Output Capacitor

The ADR380/ADR381 does not need an output capacitor for
stability under any load condition. An output capacitor, typi­cally 0.1 µF, will take out any very low-level noise voltage, and
will not affect the operation of the part. The only parameter
that will degrade by putting an output capacitor here is turn-on

time. (This will vary depending on the size of the capacitor.)
Load transient response is also improved with an output capacitor.
A capacitor will act as a source of stored energy for a sudden
increase in load current.

APPLICATIONS
Stacking Reference ICs for Arbitrary Outputs

Some applications may require two reference voltage sources
which are a combined sum of standard outputs. The follow­ing circuit shows how this “stacked output” reference can be
implemented:

U2

GND

3

U1

GND

3

2

V

OUT

C2

␮

F

1

2

V

OUT

C4

␮

F

1

R1

3.9k

V

V

⍀

OUT2

OUT1

1

1

V

IN

ADR380/

ADR381

V

IN

ADR380/

ADR381

V

IN

C1

␮

F

0.1

C3

0.1

␮

F

Figure 2. Stacking Voltage References with the ADR380/
ADR381

Two ADR380s or ADR381s are used; the outputs of the indi­vidual references are simply cascaded to reduce the supply
current. Such configuration provides two output voltages V
and V

OUT2

. V

is the terminal voltage of U1, while V

OUT1

OUT2

OUT1

is
the sum of this voltage and the terminal voltage of U2. U1 and
U2 can be chosen for the two different voltages that supply the
required outputs.

While this concept is simple, a precaution is in order. Since the
lower reference circuit must sink a small bias current from U2,
plus the base current from the series PNP output transistor in
U2, the external load of either U1 or R1 must provide a path for
this current. If the U1 minimum load is not well-defined, the
resistor R1 should be used, set to a value that will conservatively
pass 600 µA of current with the applicable V

across it. Note

OUT1

that the two U1 and U2 reference circuits are locally treated as
macrocells, each having its own bypasses at input and output for
optimum stability. Both U1 and U2 in this circuit can source dc
currents up to their full rating. The minimum input voltage, V
is determined by the sum of the outputs, V

, plus the 300 mV

OUT2

,

S

dropout voltage of U2.

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 current­switching DAC directly requires an additional operational amplifier
at the output to reinvert the signal. A negative voltage reference
is then desirable from the point that an additional operational
amplifier is not required for either reinversion (current-switching
mode) or amplification (voltage-switching mode) of the DAC

–10–

REV. 0

ADR380/ADR381

GND

V

OUT

V

IN

U1
ADR380/
ADR381

3

V

O

2

R2

100⍀

1

C1

0.001␮F
Q1

2N7002

+8 –15V

R1

100k⍀

R

L

V

IN

A1

–V

+V

AD820

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 this approach is that the
largest single source of error in the circuit is the relative match­ing of the resistors used.

The circuit in Figure 3 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 output

OUT

voltage desired can be chosen by simply substituting for the
appropriate reference IC. A precaution should be noted with
this approach: 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.

R4

IN

U1

GND

3

2

V

OUT

100k⍀

1

V

IN

C1

1␮F

0.1␮F

V

C2

ADR380

1k⍀

R3

C3
1␮F

C4

1␮F

+5V

R5

U2

OP195

100⍀

–V

REF

+V

A1

–V

–5V

Figure 3. A Negative Precision Voltage Reference Uses No
Precision Resistors

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 4, the ADR380/ADR381 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

(R1 + P1), which

SET

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 90 µA to approxi-
mately 5 mA.

Precision High-Current Voltage Source

In some cases, the user may want higher output current delivered
to a load and still achieve better than 0.5% accuracy out of the
ADR380/ADR381. The accuracy for a reference is normally
specified on the data sheet with no load. However, the output
voltage changes with load current.

The circuit in Figure 5 provides high current without compro­mising the accuracy of the ADR380/ADR381. By op amp action,
V

follows V

O

with very low drop in R1. To maintain circuit

REF

equilibrium, the op amp also drives the N-Ch MOSFET Q1 into
saturation to maintain the current needed at different loads. R2
is optional to prevent oscillation at Q1. In such an approach, hun­dreds of milliamp of load current can be achieved and the current
is limited by the thermal limitation of Q1. V

= VO + 300 mV.

IN

Figure 5. ADR380/ADR381 for Precision High-Current
Voltage Source

1

V

IN

C1

0.1␮F

1␮F

V

IN

C2

ADR380

GND

U1

3

2

V

OUT

C3
1␮F

ADJUST

R1

P1

I

SY

I

OUT

R

L

Figure 4. A Precision Current Source

REV. 0

–11–

ADR380/ADR381

OUTLINE DIMENSIONS

Dimensions shown in inches and (mm).

Surface Mount Package

(RT-3)

0.1200 (3.048)

0.1102 (2.799)

0.014 (8.30)

0.012 (8.00)

0.010 (7.70)

0.161 (4.10)

0.157 (4.00)

0.061 (1.55)

0.059 (1.50)

0.059 (1.50)

0.126 (3.2)

0.122 (3.1)

0.114 (2.9)

DIRECTION OF UNREELING

0.154 (3.90)

0.0550 (1.397)

0.0470 (1.194)

0.0236 (0.599)

0.0177 (0.450)

0.0040 (0.102)

0.0005 (0.013)

0.081 (2.05)

0.080 (2.00)

0.077 (1.95)

0.039 (1.00)
MIN

PIN 1

SEATING

PLANE

0.073 (1.85)

0.069 (1.75)

0.065 (1.65)

0.140 (3.55)

0.138 (3.50)

0.136 (3.45)

0.030 (0.75)
MIN

3

1

0.0807 (2.050)

0.0701 (1.781)

0.0210 (0.533)

0.0146 (0.371)

0.1040 (2.642)

0.0827 (2.101)

2

0.0413 (1.049)

0.0374 (0.950)

0.0440 (1.118)

0.0320 (0.813)

0.0100 (0.254)

0.0050 (0.127)

0.027 (0.686)

TAPE AND REEL DIMENSIONS

Dimensions shown in inches and (mm).

0.043 (1.10)

0.110 (2.80)

0.106 (2.70)

0.102 (2.60)

0.039 (1.00)

0.035 (0.90)

0.014 (0.35)

0.012 (0.30)

0.010 (0.25)

7" REEL 3.937 (100)

13" REEL 12.992 (330)

0.059 (1.5) MIN

0.795

(20.2)

MIN

0.0059 (0.150)

0.0034 (0.086)

REF

OR

0.567 (14.4) MAX

0.520 (13.2)

0.511 (13.0)

0.504 (12.8)

0.390 (9.9)

0.331 (8.4)

0.331 (8.4)

7" REEL

1.968 (50) MIN
OR
13" REEL

3.937 (100) MIN

C02175–4.5–1/01 (rev. 0)

–12–

PRINTED IN U.S.A.

REV. 0