AD ADR512

1.2 V Precision Low Noise
Shunt Voltage Reference
ADR512
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: –40C to +85C
PIN CONFIGURATION
3-Lead SOT-23
V+ 1
ADR512
3 TRIM/NC
V– 2
ADR512
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
Output
Voltage
(VO)
Model
ADR512ART-REEL7 1.200
Initial
Accuracy
(mV) (%)
Temperature
Coefficient
(ppm/C)
3.5
60
0.3
GENERAL DESCRIPTION
A TRIM terminal is available on the ADR512 to provide adjustment 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.
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.
VS
IL + IQ
ADR512
RBIAS
IL
VOUT = 1.2V
IQ
COUT
(OPTIONAL)
RBIAS =
VS – VOUT
IL + IQ
Figure 1. Typical Operating Circuit
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 that
may result from its use. 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 companies.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
www.analog.com
Fax: 781/326-8703
© 2003 Analog Devices, Inc. All rights reserved.
ADR512–SPECIFICATIONS
ELECTRICAL CHARACTERISTICS (I
Parameter
IN
= 100 A to 10 mA @ TA = 25C, unless otherwise noted.)
Symbol
1
Output Voltage
Initial Accuracy
VO
VOERR
VOERR%
TCVO
∆VR
(∆VR/∆IR)
IIN
eN p-p
tR
VO_HYS
Temperature Coefficient A Grade
Output Voltage Change vs. IIN
Dynamic Output Impedence
Minimum Operating Current
Voltage Noise
Turn-On Settling Time2
Output Voltage Hysteresis
Conditions
Min
Typ
1.1965 1.2
–3.5
–0.3
–40°C < TA < +85°C
IIN = 0.1 mA to 10 mA
IIN = 1 mA ± 100 µA
–40°C < TA < +85°C
f = 0.1 Hz to 10 Hz
To within 0.1% of Output
Max
Unit
1.2035
+3.5
+0.3
60
3
0.3
V
mV
%
ppm/°C
mV
Ω
µA
µV p-p
µs
ppm
100
4
10
50
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.
ABSOLUTE MAXIMUM RATINGS*
Reverse Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 mA
Forward Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 mA
Storage Temperature Range
RT Package . . . . . . . . . . . . . . . . . . . . . . . . –65°C to +150°C
Operating Temperature Range . . . . . . . . . . . . –40°C to +85°C
Junction Temperature Range
RT Package . . . . . . . . . . . . . . . . . . . . . . . . –65°C to +150°C
Lead Temperature Range (Soldering, 60 Sec) . . . . . . . . 300°C
Package Type1
JA2
JC
Unit
3-SOT-23 (RT)
230
146
°C/W
NOTES
1
Package power dissipation = (T JMAX – TA)/θJA.
2
θJA is specified for worst-case conditions, i.e., θJA is specified for
device soldered.
*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.
ORDERING GUIDE
Model
Output
Voltage
(VO)
ADR512ART-REEL7 1.2
ADR512ART-R2
1.2
Initial
Accuracy
(mV) (%)
Temperature
Number
Coefficient
Package
Package
of Parts
(ppm/C)
Description Option Branding per Reel
Temperature
Range
3.5
3.5
60
60
–40°C to +85°C
–40°C to +85°C
0.3
0.3
SOT-23
SOT-23
RT-3
RT-3
RGA
RGA
3,000
250
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.
–2–
REV. 0
Typical Performance Characteristics–ADR512
1.204
1.203
1.202
VIN = 2V/DIV
VOUT (V)
1.201
1.200
1.199
VOUT = 1V/DIV
1.198
1.197
1.196
–40
–15
10
35
TEMPERATURE (C)
60
TIME (400s/DIV)
85
TPC 1. Typical VOUT vs. Temperature
TPC 4. Turn Off Time
VIN = 2V/DIV
VIN = 2V/DIV
VOUT = 1V/DIV
VOUT = 1V/DIV
TIME (100s/DIV)
TIME (200s/DIV)
TPC 2. Turn On Time
TPC 5. Turn Off Time with 1 µ F Input Capacitor
∆IIN = 100A
VIN = 2V/DIV
VOUT = 20mV/DIV
VOUT = 1V/DIV
TIME (2s/DIV)
TIME (100s/DIV)
TPC 6. Output Response to 100 µ A Input Current Change
TPC 3. Turn On Time with 1 µ F Input Capacitor
REV. 0
–3–
ADR512
∆IIN = 100A
2V/DIV
VOUT = 20mV/DIV
TIME (2s/DIV)
TIME (400ms/DIV)
TPC 7. Output Response to 100 µ A Input Current
Change With 1 µ F Capacitor
TPC 8. 1 Hz to 10 Hz Noise
PARAMETER DEFINITIONS
Temperature Coefficient
APPLICATIONS SECTION
The ADR512 is a 1.2 V precision shunt voltage reference. It
is designed to operate without an external output capacitor between the positive and negative terminals for stability. An external
capacitor can be used for additional filtering of the supply.
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:
VO (T2 ) − VO (T1 )
 ppm 
TCVO 
× 106
=
C
°
V
C
T
T
25
°
×
−
) ( 2 1)
O(


where:
As with all shunt voltage references, an external bias resistor
(RBIAS) is required between the supply voltage and the ADR512
(see Figure 1). RBIAS sets the current that is required to pass
through the load (IL) and the ADR512 (IQ). The load and the
supply voltage can vary, thus RBIAS is chosen based on
(1)
VO(25°C) = VO at 25°C
•
RBIAS must be small enough to supply the minimum IQ current to the ADR512 even when the supply voltage is at its
minimum and the load current is at its maximum value.
•
RBIAS also needs to be large enough so that IQ does not
exceed 10 mA when the supply voltage is at its maximum
and the load current is at its minimum.
VO(T1 ) = VO at Temperature 1
VO(T2) = VO 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 +85°C and back to +25°C. This is a typical value from
a sample of parts put through such a cycle.
Given these conditions, RBIAS is determined by the supply
voltage (Vs), the load and operating current (IL and IQ) of the
ADR512, and the ADR512’s output voltage.
VO _ HYS = VO (25°C ) −VO _ TC
VO _ HYS [ ppm ] =
VO (25°C ) −VO _ TC
where:
VO (25°C )
× 106
RBIAS = (VS – VOUT ) / (IL + IQ )
(2)
(3)
VO(25°C) = VO at 25°C
VO_TC = VO at 25°C after temperature cycle at +25°C
to –40°C to +85°C and back to +25°C
–4–
REV. 0
ADR512
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.
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, VOUT, is determined by the gain of the
circuit, which is completely dependent on resistors R2 and R1.
VOUT = 1 +
R2
R1
0
MSB
ADR512
(4)
9
LSB
1
VDD
AD7533
1
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.
R2
GN
3
2
1
15
–VDD
VOUT = 0V TO 1.2V
VCC
RBIAS
1.2V
AD8610
Figure 4. ADR512 as a Reference for a 10-Bit
CMOS DAC (AD7533)
VOUT = 1.2(1 + R2/R1)
Precise Negative Voltage Reference
ADR512
The ADR512 is suitable for use in applications where a precise
negative voltage reference is desired, including the application
detailed in Figure 4.
R2
C2 (OPTIONAL)
R1
Figure 5 shows the ADR512 configured to provide a –1.2 V output.
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 kΩ
potentiometer.
ADR512
–
–1.2V
R1
VCC
–VDD
RBIAS
Figure 5. Precise –1.2 V Reference Configuration
VOUT
ADR512
R1
100k
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.
POT
50k
R1 in Figure 5 should be chosen so that 100 µA to 10 mA is
provided to properly bias the ADR512.
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 batterypowered portable instruments, such as the AD7533 CMOS
multiplying DAC, that use precision data converters.
REV. 0
VDD
(5)
I
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.
R1 =
–5–
ADR512
OUTLINE DIMENSIONS
3-Lead Small Outline Transistor Package [SOT-23]
(RT-3)
Dimensions shown in millimeters
3.04
2.90
2.80
1.40
1.30
1.20
3
1
2.64
2.10
2
PIN 1
0.95 BSC
1.90 BSC
1.12
0.89
0.10
0.01
SEATING
PLANE
0.50
0.30
0.60
0.50
0.40
0.20
0.08
COMPLIANT TO JEDEC STANDARDS TO-236AB
–6–
REV. 0
–7–
–8–
C03700–0–7/03(0)