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Электронный компонент: ADR381

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REV. A
Information furnished by Analog Devices is believed to be accurate and
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may result from its use. No license is granted by implication or otherwise
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Tel: 781/329-4700
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Fax: 781/326-8703
2004 Analog Devices, Inc. All rights reserved.
ADR380/ADR381
Precision Low-Drift 2.048 V/2.500 V
SOT-23 Voltage Reference
FEATURES
Initial Accuracy: 5 mV/ 6 mV max
Initial Accuracy Error: 0.24%/ 0.24%
Low TCV
O
: 25 ppm/ C max
Load Regulation: 70 ppm/mA
Line Regulation: 25 ppm/V
Wide Operating Range:
2.4 V to 18 V for ADR380
2.8 V to 18 V for ADR381
Low Power: 120
A max
High Output Current: 5 mA
Wide Temperature Range: 40 C to +85 C
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
PIN CONFIGURATION
3-Lead SOT-23
(RT Suffix)
1
2
ADR380/
ADR381
(Not to Scale)
3
V
IN
GND
V
OUT
GENERAL DESCRIPTION
The ADR380 and ADR381 are precision 2.048 V and 2.500 V
band gap voltage references featuring high accuracy, high stabil-
ity, 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 to 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 +85C) temperature
range. ADR380/ADR381 is available in the tiny 3-lead SOT-23
package.
Table I. ADR38x Products
Part Number
Nominal Output Voltage (V)
ADR380
2.048
ADR381
2.500
REV. A
2
ADR380/ADR381SPECIFICATIONS
ADR380 ELECTRICAL CHARACTERISTICS
(@ V
IN
= 5.0 V, T
A
= 25 C unless otherwise noted.)
ADR380 ELECTRICAL CHARACTERISTICS
(@ V
IN
= 15.0 V, T
A
= 25 C unless otherwise noted.)
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
Output Voltage
V
O
2.043 2.048
2.053
V
Initial Accuracy Error
V
OERR
5
+5
mV
0.24
+0.24
%
Temperature Coefficient
TCV
O
40
C < T
A
< +85
C
5
25
ppm/
C
0
C < T
A
< 70
C
3
21
ppm/
C
Minimum Supply Voltage Headroom
V
IN
V
O
I
L
3 mA
300
mV
Line Regulation
V
O
/DV
IN
V
IN
= 2.5 V to 15 V
10
25
ppm/V
40
C < T
A
< +85
C
Load Regulation
V
O
/DI
LOAD
V
IN
= 3 V, I
LOAD
= 0 mA to 5 mA
70
ppm/mA
40
C < T
A
< +85
C
Quiescent Current
I
IN
No Load
100
120
A
40
C < T
A
< +85
C
140
A
Voltage Noise
e
N
0.1 Hz to 10 Hz
5
V p-p
Turn-On Settling Time
t
R
20
s
Long-Term Stability
V
O
1,000 Hrs
50
ppm
Output Voltage Hysteresis
V
O_HYS
40
ppm
Ripple Rejection Ratio
RRR
f
IN
= 60 Hz
85
dB
Short Circuit to GND
I
SC
25
mA
Specifications subject to change without notice.
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
Output Voltage
V
O
2.043 2.048
2.053
V
Initial Accuracy Error
V
OERR
5
+5
mV
0.24
+0.24
%
Temperature Coefficient
TCV
O
40
C < T
A
< +85
C
5
25
ppm/
C
0
C < T
A
< 70
C
3
21
ppm/
C
Minimum Supply Voltage Headroom
V
IN
V
O
I
L
3 mA
300
mV
Line Regulation
V
O
/DV
IN
V
IN
= 2.5 V to 15 V
40
C < T
A
< +85
C
10
25
ppm/V
Load Regulation
V
O
/DI
LOAD
V
IN
= 3 V, I
LOAD
= 0 mA to 5 mA
40
C < T
A
< +85
C
70
ppm/mA
Quiescent Current
I
IN
No Load
100
120
A
40
C < T
A
< +85
C
140
A
Voltage Noise
e
N
0.1 Hz to 10 Hz
5
V p-p
Turn-On Settling Time
t
R
20
s
Long-Term Stability
V
O
1,000 Hrs
50
ppm
Output Voltage Hysteresis
V
O_HYS
40
ppm
Ripple Rejection Ratio
RRR
f
IN
= 60 Hz
85
dB
Short Circuit to GND
I
SC
25
mA
Specifications subject to change without notice.
REV. A
3
ADR381 ELECTRICAL CHARACTERISTICS
SPECIFICATIONS
(continued)
(@ V
IN
= 5.0 V, T
A
= 25 C unless otherwise noted.)
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
Output Voltage
V
O
2.494 2.5
2.506
V
Initial Accuracy Error
V
OERR
6
+6
mV
0.24
+0.24
%
Temperature Coefficient
TCV
O
40
C < T
A
< +85
C
5
25
ppm/
C
0
C < T
A
< 70
C
3
21
ppm/
C
Minimum Supply Voltage Headroom
V
IN
V
O
I
L
2 mA
300
mV
Line Regulation
V
O
/DV
IN
V
IN
= 2.8 V to 15 V
10
25
ppm/V
40
C < T
A
< +85
C
Load Regulation
V
O
/DI
LOAD
V
IN
= 3.5 V, I
LOAD
= 0 mA to 5 mA
70
ppm/mA
40
C < T
A
< +85
C
Quiescent Current
I
IN
No Load
100
120
A
40
C < T
A
< +85
C
140
A
Voltage Noise
e
N
0.1 Hz to 10 Hz
5
V p-p
Turn-On Settling Time
t
R
20
s
Long-Term Stability
V
O
1,000 Hrs
50
ppm
Output Voltage Hysteresis
V
O_HYS
75
ppm
Ripple Rejection Ratio
RRR
f
IN
= 60 Hz
85
dB
Short Circuit to GND
I
SC
25
mA
Specifications subject to change without notice.
ADR381 ELECTRICAL CHARACTERISTICS
(@ V
IN
= 15.0 V, T
A
= 25 C unless otherwise noted.)
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
Output Voltage
V
O
2.494 2.5
2.506
V
Initial Accuracy Error
V
OERR
6
+6
mV
0.24
+0.24
%
Temperature Coefficient
TCV
O
40
C < T
A
< +85
C
5
25
ppm/
C
0
C < T
A
< 70
C
3
21
ppm/
C
Minimum Supply Voltage Headroom
V
IN
V
O
I
L
2 mA
300
mV
Line Regulation
V
O
/DV
IN
V
IN
= 2.8 V to 15 V
10
25
ppm/V
40
C < T
A
< +85
C
Load Regulation
V
O
/DI
LOAD
V
IN
= 3.5 V, I
LOAD
= 0 mA to 5 mA
70
ppm/mA
40
C < T
A
< +85
C
Quiescent Current
I
IN
No Load
100
120
A
40
C < T
A
< +85
C
140
A
Voltage Noise
e
N
0.1 Hz to 10 Hz
5
V p-p
Turn-On Settling Time
t
R
20
s
Long-Term Stability
V
O
1,000 Hrs
50
ppm
Output Voltage Hysteresis
V
O_HYS
75
ppm
Ripple Rejection Ratio
RRR
f
IN
= 60 Hz
85
dB
Short Circuit to GND
I
SC
25
mA
Specifications subject to change without notice.
ADR380/ADR381
REV. A
4
ADR380/ADR381
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4,000 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.
ABSOLUTE MAXIMUM RATINGS
1
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 V
Output Short-Circuit Duration to GND
V
IN
> 15 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 sec
V
IN
15 V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Indefinite
Storage Temperature Range
RT Package . . . . . . . . . . . . . . . . . . . . . . . . 65
C to +150C
Operating Temperature Range
ADR380/ADR381 . . . . . . . . . . . . . . . . . . . . 40
C to +85C
Junction Temperature Range
RT Package . . . . . . . . . . . . . . . . . . . . . . . . 65
C to +150C
Lead Temperature Range (Soldering, 60 Sec) . . . . . . . . 300
C
Package Type
JA
2
JC
Unit
3-Lead SOT-23 (RT)
333
--
C/W
NOTES
1
Absolute maximum ratings apply at 25
C, unless otherwise noted.
2
JA
is specified for the worst-case conditions, i.e.,
JA
is specified for device
soldered in circuit board for surface-mount packages.
ORDERING GUIDE
Temperature
Package
Package
Output
Number of
Model
Range
Description
Option
Branding
Voltage
Parts per Reel
ADR380ART-R2
40
C to +85C
SOT-23
RT-3
R2A
2.048
250
ADR380ART-REEL7
40
C to +85C
SOT-23
RT-3
R2A
2.048
3,000
ADR380ARTZ-REEL7
*
40
C to +85C
SOT-23
RT-3
R2A
2.048
3,000
ADR381ART-R2
40
C to +85C
SOT-23
RT-3
R3A
2.500
250
ADR381ART-REEL7
40
C to +85C
SOT-23
RT-3
R3A
2.500
3,000
ADR381ARTZ-REEL7
*
40
C to +85C
SOT-23
RT-3
R3A
2.500
3,000
*Z = Pb-free part
PIN CONFIGURATION
3-Lead SOT-23
(RT Suffix)
1
2
ADR380/
ADR381
(Not to Scale)
3
V
IN
GND
V
OUT
REV. A
ADR380/ADR381
5
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:
TCV
ppm C
V T
V T
V
C
T
T
O
O
O
O
/
[
]
=
( )
( )
(
)
(
)
2
1
2
1
6
25
10
where:
V
O
(25
C) = V
O
at 25
C.
V
O
(T
1
) = V
O
at Temperature 1.
V
O
(T
2
) = V
O
at Temperature 2.
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-per-
million per milliampere, or ohms of dc output resistance.
Long-Term Stability
A typical shift in output voltage over 1,000 hours at a controlled
temperature. The graphs TPC 24 and TPC 25 show a sample
of parts measured at different intervals in a controlled environ-
ment of 50
C for 1,000 hours.
V
V
t
V
t
V
ppm
V
t
V
t
V
t
O
O
O
O
O
O
O
=
( )
( )
[ ]
=
( )
( )
( )
0
1
0
1
0
6
10
where:
V
O
(t
0
) = V
O
at Time 0.
V
O
(t
1
) = V
O
after 1,000 hours' operation at a 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 40C to +85C and back to +25C.
This is a typical value from a sample of parts put through
such a cycle.
V
V
C
V
V
ppm
V
C
V
V
C
O_HYS
O
O_TC
O_HYS
O
O_TC
O
=
(
)
[ ]
=
(
)
(
)
25
25
25
10
6
where:
V
O
(25
C) = V
O
at 25
C.
V
O_TC
= V
O
at 25
C after temperature cycle at +25C to 40C
to +85
C and back to +25C.
Typical Performance Characteristics
TEMPERATURE ( C)
2.042
40
V
OUT
(V)
2.044
2.046
2.048
2.050
2.052
2.054
15
10
35
60
85
SAMPLE 1
SAMPLE 2
SAMPLE 3
TPC 1. ADR380 Output Voltage vs. Temperature
TEMPERATURE( C)
2.494
40
V
OUT
(V)
2.496
2.498
2.500
2.502
2.504
2.506
15
10
35
60
85
SAMPLE 1
SAMPLE 2
SAMPLE 3
TPC 2. ADR381 Output Voltage vs. Temperature
REV. A
6
ADR380/ADR381
PPM ( C)
11 9 7 5
3 1
1
3
0
5
10
15
20
25
30
5
7
9
11 13
15 17 19
TOTAL NUMBER
OF DEVICES = 130
TEMPERATURE +25 C 40 C +85 C +25 C
FREQUENCY
TPC 3. ADR380 Output Voltage Temperature Coefficient
PPM ( C)
11 9 7 5
3 1
1
3
0
FREQUENCY
10
20
30
40
50
60
5
7
9
11 13
15
15 13
TOTAL NUMBER
OF DEVICES IN
SAMPLE = 450
TEMPERATURE +25 C
40 C +85 C +25 C
TPC 4. ADR381 Output Voltage Temperature Coefficient
INPUT VOLTAGE (V)
2.5
5.0
7.5
10.0
12.5
15.0
+85 C
+25 C
40 C
0
SUPPLY CURRENT (
A)
20
40
80
100
120
140
60
TPC 5. ADR380 Supply Current vs. Input Voltage
40 C
INPUT VOLTAGE (V)
2.5
5.0
7.5
10.0
12.5
15.0
+85 C
+25 C
0
SUPPLY CURRENT (
A)
20
40
80
100
120
140
60
TPC 6. ADR381 Supply Current vs. Input Voltage
V
IN
= 5V
V
IN
= 3V
TEMPERATURE ( C)
40
15
10
35
60
85
0
LOAD REGULATION (ppm/mA)
10
20
40
50
60
70
30
I
L
= 0mA TO 5mA
TPC 7. ADR380 Load Regulation vs. Temperature
V
IN
= 5V
V
IN
= 3.5V
TEMPERATURE ( C)
40
15
10
35
60
85
0
LOAD REGULATION (ppm/mA)
10
20
40
50
60
70
30
I
L
= 5mA
TPC 8. ADR381 Load Regulation vs. Temperature
REV. A
ADR380/ADR381
7
V
IN
= 2.5V TO 15V
TEMPERATURE ( C)
40
15
10
35
60
85
0
LINE REGULATION (ppm/V)
1
2
4
5
3
TPC 9. ADR380 Line Regulation vs. Temperature
V
IN
= 2.8V TO 15V
TEMPERATURE ( C)
40
15
10
35
60
85
0
LINE REGULATION (ppm/V)
1
2
4
5
3
TPC 10. ADR381 Line Regulation vs. Temperature
40 C
LOAD CURRENT (mA)
0
1
2
3
4
5
0
DIFFERENTIAL VOLTAGE (V)
0.2
0.4
0.6
0.8
+85 C
+25 C
TPC 11. ADR380 Minimum Input/Output
Voltage Differential vs. Load Current
40 C
LOAD CURRENT (mA)
0
1
2
3
4
5
0
DIFFERENTIAL VOLTAGE (V)
0.2
0.4
0.6
0.8
+85 C
+25 C
TPC 12. ADR381 Minimum Input/Output Voltage
Differential vs. Load Current
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 +25 C 40 C
85 C +25 C
TPC 13. ADR381 V
OUT
Hysteresis
TIME (1s/DIV)
2 V/DIV
TPC 14. ADR381 Typical Noise Voltage 0.1 Hz to 10 Hz
REV. A
8
ADR380/ADR381
TIME (10ms/DIV)
100 V/DIV
TPC 15. ADR381 Typical Noise Voltage 10 Hz to 10 kHz
TIME (10 s/DIV)
1V/DIV
0.5V/DIV
C
BYPASS
= 0 F
V
OUT
LINE INTERRUPTION
0.5V/DIV
V
IN
TPC 16. ADR381 Line Transient Response
TIME (10 s/DIV)
1V/DIV
0.5V/DIV
C
BYPASS
= 0.1 F
V
OUT
LINE INTERRUPTION
0.5V/DIV
TPC 17. ADR381 Line Transient Response
C
L
= 0 F
TIME (200 s/DIV)
1V/DIV
V
OUT
V
LOAD
ON
LOAD OFF
LOAD = 1mA
2V/DIV
TPC 18. ADR381 Load Transient Response with
C
L
= 0
F
C
L
= 1nF
TIME (200 s/DIV)
1V/DIV
V
OUT
V
LOAD
ON
LOAD OFF
LOAD = 1mA
2V/DIV
TPC 19. ADR381 Load Transient Response with
C
L
= 1 nF
C
L
= 100nF
TIME (200 s/DIV)
1V/DIV
V
OUT
V
LOAD
ON
LOAD OFF
LOAD = 1mA
2V/DIV
TPC 20. ADR381 Load Transient Response with
C
L
= 100 nF
REV. A
ADR380/ADR381
9
R
L
= 500
TIME (200 s/DIV)
2V/DIV
V
OUT
V
IN
5V/DIV
TPC 21. ADR381 Turn-On/Turn-Off Response at 5 V
10
Z
OUT
(10
/DIV)
C
L
= 40pF
C
L
= 0.1 F
C
L
= 1 F
C
B
= 0.1 F
100
1k
10k
100k
1M
FREQUENCY (Hz)
TPC 22. ADR381 Output Impedance vs. Frequency
HOURS
0
150
0
100
DRIFT (ppm)
100
50
50
100
150
200
300
400
500
600
700
800
900
1000
CONDITIONS: V
IN
= 6V IN A CONTROLLED
ENVIRONMENT 50 C 1 C
TPC 23. ADR380 Long-Term Drift
HOURS
0
150
0
100
DRIFT (ppm)
100
50
50
100
150
200
300
400
500
600
700
800
900
1000
CONDITIONS: V
IN
= 6V IN A CONTROLLED
ENVIRONMENT 50 C 1 C
TPC 24. ADR381 Long-Term Drift
REV. A
10
ADR380/ADR381
THEORY OF OPERATION
Band gap references are the high performance solution for low
supply voltage and low power voltage reference applications,
and the ADR380/ADR381 are no exception. But the unique-
ness of this product lies in its architecture. By observing Figure
1, the ideal zero TC band gap voltage is referenced to the
output, not to ground. The band gap cell consists of the PNP
pair Q51 and Q52, running at unequal current densities. The
difference in V
BE
results in a voltage with a positive TC which is
amplified up by the ratio of 2
R58/R54. This PTAT voltage,
combined with V
BEs
of Q51 and Q52, produce the stable band
gap voltage. Reduction in the band gap 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.
GND
V
OUT
V
IN
Q1
R59
R54
Q51
R60
R61
R48
R49
R44
R58
R53
Q52
+
Figure 1. Simplified Schematic
Device Power Dissipation Considerations
The ADR380/ADR381 are 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 junc-
tion temperature or dissipation:
P
T
T
D
A
A
=
J
J
where:
P
D
is the device power dissipation,
T
J
and T
A
are junction and ambient temperatures,
respectively, and
JA
is the device package thermal resistance.
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 appli-
cations where the load current suddenly increases.
Output Capacitor
The ADR380/ADR381 do not need an output capacitor for
stability under any load condition. An output capacitor, typically
0.1
F, 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 in-
crease 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 imple-
mented:
GND
V
OUT
V
IN
C1
0.1 F
U2
ADR380/
ADR381
3
GND
V
OUT
V
IN
U1
ADR380/
ADR381
C3
0.1 F
C2
1 F
C4
1 F
3
R1
3.9k
V
OUT2
V
OUT1
2
2
1
1
V
IN
Figure 2. Stacking Voltage References with the
ADR380/ADR381
Two ADR380s or ADR381s are used; the outputs of the indi-
vidual references are simply cascaded to reduce the supply
current. Such configuration provides two output voltages--
V
OUT1
and V
OUT2
. V
OUT1
is the terminal voltage of U1, while
V
OUT2
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
A of current with the applicable V
OUT1
across it. Note
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
S
,
is determined by the sum of the outputs, V
OUT2
, plus the
300 mV 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 refer-
ence 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 an additional operational
amplifier at the output to reinvert the signal. A negative voltage
REV. A
ADR380/ADR381
11
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 output voltage. In general, any positive
voltage reference can be converted into a negative voltage refer-
ence through the use of an operational amplifier and a pair of
matched resistors in an inverting configuration. The disadvan-
tage 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
OUT
and GND. Thus, any negative output
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.
GND
V
OUT
V
IN
U1
ADR380
C2
0.1 F
3
+5V
V
REF
V
IN
R4
1k
C1
1 F
C3
1 F
2
R3
100k
A1
1
C4
1 F
U2
5V
OP195
R5
100
V
+V
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 pre-
cision 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
SET
(R1 + P1), 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 90
A to approximately 5 mA.
GND
V
OUT
V
IN
U1
ADR380
C2
0.1 F
3
V
IN
C1
1 F
C3
1 F
2
R1
1
R
L
P1
I
OUT
I
SY
ADJUST
Figure 4. A Precision Current Source
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 compro-
mising the accuracy of the ADR380/ADR381. By op amp action,
V
O
follows V
REF
with very low drop in R1. To maintain circuit
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, hun-
dreds of milliamps of load current can be achieved and the current
is limited by the thermal limitation of Q1. V
IN
= V
O
+ 300 mV.
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
Figure 5. ADR380/ADR381 for Precision High
Current Voltage Source
REV. A
C0217507/04(A)
12
ADR380/ADR381
OUTLINE DIMENSIONS
3-Lead Small Outline Transistor Package [SOT-23-3]
(RT-3)
Dimensions shown in millimeters
3.04
2.90
2.80
PIN 1
1.40
1.30
1.20
2.64
2.10
1.90 BSC
1
2
3
SEATING
PLANE
1.12
0.89
0.10
0.01
0.50
0.30
0.20
0.08
0.60
0.50
0.40
0.95 BSC
COMPLIANT TO JEDEC STANDARDS TO-236AB
Tape and Reel Dimensions
Dimensions shown in millimeters
4.10
4.00
3.90
1.55
1.50
1.50
8.30
8.00
7.70
3.20
3.10
2.90
2.05
2.00
1.95
1.85
1.75
1.65
3.55
3.50
3.45
2.80
2.70
2.60
1.10
1.00
0.90
0.35
0.30
0.25
13.20
13.00
12.80
9.90
8.40
8.40
20.20
MIN
1.50 MIN
7" REEL 100.00
OR
13" REEL 330.00
7" REEL 50.00 MIN
OR
13" REEL 100.00 MIN
14.40 MAX
0.75 MIN
DIRECTION OF UNREELING
1.00 MIN
Revision History
Location
Page
7/04--Data Sheet Changed from Rev. 0 to Rev. A.
Updated format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Universal
Changes to ORDERING GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Updated OUTLINE DIMENSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12