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2003 Analog Devices, Inc. All rights reserved.
ADR512
1.2 V Precision Low Noise
Shunt Voltage Reference
FEATURES
Precision 1.200 V Voltage Reference
Ultracompact 3 mm 3 mm SOT-23 Package
No External Capacitor Required
Low Output Noise: 4 V p-p (0.1 Hz to 10 Hz)
Initial Accuracy: 0.3% Max
Temperature Coefficient: 60 ppm/ C Max
Operating Current Range: 100 A to 10 mA
Output Impedance: 0.3
Max
Temperature Range: 40 C to +85 C
APPLICATIONS
Precision Data Acquisition Systems
Battery-Powered Equipment:
Cellular Phone, Notebook Computer, PDA,
and GPS
3 V/5 V, 8-/12-Bit Data Converters
Portable Medical Instruments
Industrial Process Control Systems
Precision Instruments
GENERAL DESCRIPTION
Designed for space critical applications, the ADR512 is a low
voltage (1.200 V), precision shunt-mode voltage reference in the
ultracompact (3 mm 3 mm) SOT-23 package. The ADR512
features low temperature drift (60 ppm/ C), high accuracy
( 0.30%), and ultralow noise (4 V p-p) performance.
The ADR512's advanced design eliminates the need for an
external capacitor, yet it is stable with any capacitive load. The
minimum operating current increases from a scant 100 A to a
maximum of 10 mA. This low operating current and ease of use
make the ADR512 ideally suited for handheld battery-powered
applications.
PIN CONFIGURATION
3-Lead SOT-23
1
3
2
V
+
V
ADR512
TRIM/NC
A TRIM terminal is available on the ADR512 to provide adjust-
ment of the output voltage over 0.5% without affecting the
temperature coefficient of the device. This feature provides
users with the flexibility to trim out any system errors.
V
S
R
BIAS
I
Q
I
L
V
OUT
= 1.2V
C
OUT
(OPTIONAL)
I
L
+ I
Q
V
S
V
OUT
I
L
+ I
Q
R
BIAS
=
ADR512
Figure 1. Typical Operating Circuit
ADR512
Output
Initial
Temperature
Voltage
Accuracy
Coefficient
Model
(V
O
)
(mV)
(%)
(ppm/ C)
ADR512ART-REEL7 1.200
3.5
0.3
60
REV. 0
2
ADR512SPECIFICATIONS
ELECTRICAL CHARACTERISTICS
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
Output Voltage
1
V
O
1.1965 1.2
1.2035
V
Initial Accuracy
V
OERR
3.5
+3.5
mV
V
OERR%
0.3
+0.3
%
Temperature Coefficient A Grade
TCV
O
40
C < T
A
< +85
C
60
ppm/
C
Output Voltage Change vs. I
IN
V
R
I
IN
= 0.1 mA to 10 mA
3
mV
Dynamic Output Impedence
(
V
R
/
I
R
)
I
IN
= 1 mA
100 A
0.3
Minimum Operating Current
I
IN
40
C < T
A
< +85
C
100
A
Voltage Noise
e
N
p-p
f = 0.1 Hz to 10 Hz
4
V p-p
Turn-On Settling Time
2
t
R
To within 0.1% of Output
10
s
Output Voltage Hysteresis
V
O_HYS
50
ppm
NOTES
1
The forward diode voltage characteristic at 1 mA is typically 0.65 V.
2
Measured without a load capacitor.
Specifications subject to change without notice.
(I
IN
= 100 A to 10 mA @ T
A
= 25 C, unless otherwise noted.)
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
ADR512 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
*
Reverse Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 mA
Forward Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 mA
Storage Temperature Range
RT Package . . . . . . . . . . . . . . . . . . . . . . . . 65
C to +150C
Operating Temperature Range . . . . . . . . . . . . 40
C to +85C
Junction Temperature Range
RT Package . . . . . . . . . . . . . . . . . . . . . . . . 65
C to +150C
Lead Temperature Range (Soldering, 60 Sec) . . . . . . . . 300
C
*Absolute maximum ratings apply at 25
C, unless otherwise noted. 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.
Package Type
1
JA
2
JC
Unit
3-SOT-23 (RT)
230
146
C/W
NOTES
1
Package power dissipation = (T
JMAX
T
A
)/
JA
.
2
JA
is specified for worst-case conditions, i.e.,
JA
is specified for
device soldered.
ORDERING GUIDE
Output
Initial
Temperature
Number
Voltage
Accuracy
Coefficient
Package
Package
of Parts
Temperature
Model
(V
O
)
(mV) (%)
(ppm/ C)
Description
Option
Branding per Reel
Range
ADR512ART-REEL7 1.2
3.5
0.3
60
SOT-23
RT-3
RGA
3,000
40
C to +85C
ADR512ART-R2
1.2
3.5
0.3
60
SOT-23
RT-3
RGA
250
40
C to +85C
REV. 0
Typical Performance CharacteristicsADR512
3
TEMPERATURE ( C)
V
OUT
(V)
1.204
1.203
1.202
1.201
1.200
1.199
1.198
1.197
1.196
15
40
10
35
60
85
TPC 1. Typical V
OUT
vs. Temperature
TIME (100 s/DIV)
V
IN
= 2V/DIV
V
OUT
= 1V/DIV
TPC 2. Turn On Time
TIME (100 s/DIV)
V
IN
= 2V/DIV
V
OUT
= 1V/DIV
TPC 3. Turn On Time with 1
F Input Capacitor
TIME (400 s/DIV)
V
IN
= 2V/DIV
V
OUT
= 1V/DIV
TPC 4. Turn Off Time
TIME (200 s/DIV)
V
IN
= 2V/DIV
V
OUT
= 1V/DIV
TPC 5. Turn Off Time with 1
F Input Capacitor
I
IN
= 100 A
V
OUT
= 20mV/DIV
TIME (2 s/DIV)
TPC 6. Output Response to 100
A Input Current Change
REV. 0
4
ADR512
PARAMETER DEFINITIONS
Temperature Coefficient
This is the change of output voltage with respect to operating
temperature changes, normalized by the output voltage at 25
C.
This parameter is expressed in ppm/
C and can be determined
with the following equation:
TCV
ppm
C
V T
V T
V
C
T
T
O
O
O
O
=
( )
-
( )
(
)
-
(
)
2
1
2
1
6
25
10
(1)
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
Thermal Hysteresis
Thermal hysteresis is defined as the change of output voltage
after the device is cycled through the temperature from +25
C to
40
C 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
(2)
where:
V
O
(25
C) = V
O
at 25
C
V
O_TC
= V
O
at 25
C after temperature cycle at +25C
to 40
C to +85C and back to +25C
APPLICATIONS SECTION
The ADR512 is a 1.2 V precision shunt voltage reference. It
is designed to operate without an external output capacitor be-
tween the positive and negative terminals for stability. An external
capacitor can be used for additional filtering of the supply.
As with all shunt voltage references, an external bias resistor
(R
BIAS
) is required between the supply voltage and the ADR512
(see Figure 1). R
BIAS
sets the current that is required to pass
through the load (I
L
) and the ADR512 (I
Q
). The load and the
supply voltage can vary, thus R
BIAS
is chosen based on
R
BIAS
must be small enough to supply the minimum I
Q
cur-
rent to the ADR512 even when the supply voltage is at its
minimum and the load current is at its maximum value.
R
BIAS
also needs to be large enough so that I
Q
does not
exceed 10 mA when the supply voltage is at its maximum
and the load current is at its minimum.
Given these conditions, R
BIAS
is determined by the supply
voltage (Vs), the load and operating current (I
L
and I
Q
) of the
ADR512, and the ADR512's output voltage.
R
(V
V
) (I
I )
BIAS
S
OUT
L
Q
=
+
/
(3)
I
IN
= 100 A
V
OUT
= 20mV/DIV
TIME (2 s/DIV)
TPC 7. Output Response to 100
A Input Current
Change With 1
F Capacitor
2 V/DIV
TIME (400ms/DIV)
TPC 8. 1 Hz to 10 Hz Noise
REV. 0
ADR512
5
Adjustable Precision Voltage Source
The ADR512, combined with a precision low input bias op amp
such as the AD8610, can be used to output a precise adjustable
voltage. Figure 2 illustrates the implementation of this application
using the ADR512.
The output of the op amp, V
OUT
, is determined by the gain of the
circuit, which is completely dependent on resistors R2 and R1.
V
R
R
OUT
= +
1
2
1
(4)
An additional capacitor in parallel with R2 can be added to filter
out high frequency noise. The value of C2 is dependent on the
value of R2.
V
OUT
= 1.2(1 + R2/R1)
R
BIAS
R1
V
CC
R2
AD8610
ADR512
1.2V
C2 (OPTIONAL)
Figure 2. Adjustable Precision Voltage Source
Output Voltage Trim
Using a mechanical or digital potentiometer, the output voltage
of the ADR512 can be trimmed
0.5%. The circuit in Figure 3
illustrates how the output voltage can be trimmed, using a 10 k
potentiometer.
R
BIAS
V
CC
R1
100k
POT
50k
ADR512
V
OUT
Figure 3. Output Voltage Trim
Using the ADR512 with Precision Data Converters
The compact ADR512 package and the device's low minimum
operating current requirement make it ideal for use in battery-
powered portable instruments, such as the AD7533 CMOS
multiplying DAC, that use precision data converters.
Figure 4 shows the ADR512 serving as an external reference to
the AD7533, a CMOS multiplying DAC. Such a DAC requires
a negative voltage input in order to provide a positive output
range. In this application, the ADR512 is supplying a 1.2 V
reference to the REF input of the AD7533.
MSB
V
DD
V
OUT
= 0V TO 1.2V
V
DD
G
N
LSB
1
2
3
1
1
15
0
9
R2
ADR512
AD7533
Figure 4. ADR512 as a Reference for a 10-Bit
CMOS DAC (AD7533)
Precise Negative Voltage Reference
The ADR512 is suitable for use in applications where a precise
negative voltage reference is desired, including the application
detailed in Figure 4.
Figure 5 shows the ADR512 configured to provide a 1.2 V output.
1.2V
V
DD
R1
ADR512
Figure 5. Precise 1.2 V Reference Configuration
Since the ADR512 characteristics resemble those of a Zener diode,
the cathode shown in Figure 5 will be 1.2 V higher with respect
to the anode (V+ with respect to V on the ADR512 package).
Since the cathode of the ADR512 is tied to ground, the anode
must be 1.2 V.
R1 in Figure 5 should be chosen so that 100
A to 10 mA is
provided to properly bias the ADR512.
R
V
I
DD
1
=
(5)
The resistor R1 should be chosen so that power dissipation is at
a minimum. An ideal resistor value can be determined through
manipulation of Equation 5.
REV. 0
6
ADR512
OUTLINE DIMENSIONS
3-Lead Small Outline Transistor Package [SOT-23]
(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
7
C0370007/03(0)
8
Document Outline
- FEATURES
- APPLICATIONS
- PIN CONFIGURATION
- GENERAL DESCRIPTION
- SPECIFICATIONS
- ABSOLUTE MAXIMUM RATINGS
- ORDERING GUIDE
- Typical Performance Characteristics
- PARAMETER DEFINITIONS
- Temperature Coefficient
- Thermal Hysteresis
- APPLICATIONS SECTION
- Adjustable Precision Voltage Source
- Output Voltage Trim
- Using the ADR512 with Precision Data Converters
- Precise Negative Voltage Reference
- OUTLINE DIMENSIONS
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