Datasheet ADR1581 Datasheet (ANALOG DEVICES)

Page 1
1.25 V Micropower, Precision Shunt
V
V
www.BDTIC.com/ADI

FEATURES

Wide operating range: 60 μA to 10 mA Initial accuracy: ±0.12% maximum Temperature drift: ±50 ppm/°C maximum Output impedance: 0.5 Ω maximum Wideband noise (10 Hz to 10 kHz): 20 μV rms Operating temperature range: −40°C to +85°C High ESD rating
4 kV human body model 400 V machine model
Compact, surface-mount SOT-23 package

APPLICATIONS

Portable, battery-powered equipment
Cellular phones, notebook computers, PDAs, GPSs, and DMMs
Computer workstations
Suitable for use with a wide range of video RAMDACs Smart industrial transmitters PCMCIA cards Automotive 3 V/5 V, 8-bit to 12-bit data converters

GENERAL DESCRIPTION

The ADR15811 is a low cost, 2-terminal (shunt), precision band gap reference. It provides an accurate 1.250 V output for input currents between 60 A and 10 mA.
The superior accuracy and stability of the ADR1581 is made possible by the precise matching and thermal tracking of on­chip components. Proprietary curvature correction design techniques have been used to minimize the nonlinearities in the voltage output temperature characteristics. The ADR1581 is stable with any value of capacitive load.
The low minimum operating current makes the ADR1581 ideal fo
r use in battery-powered 3 V or 5 V systems. However, the wide operating current range means that the ADR1581 is extremely versatile and suitable for use in a wide variety of high current applications.
The ADR1581 is available in two grades, A and B, both of which
re provided in the SOT-23 package. Both grades are specified
a over the industrial temperature range of −40°C to +85°C.
1
Protected by U.S. Patent No. 5,969,657; other patents pending.
Voltage Reference
ADR1581

PIN CONFIGURATION

ADR1581
1
+
NC (OR V–)
3
2
TOP VIEW
NC = NO CONNECT
Figure 1. SOT-23
20
18
16
14
12
10
QUANTITY
8
6
4
2
0 –20 –10 0 10 20
Figure 2. Reverse Voltage Temperature Drift Distribution
100
90
80
70
60
50
QUANTITY
40
30
20
10
0
–5 –4 –3 –2 –1 0 1 2 3 4 5
TEMPERATURE DRIFT (ppm/°C)
OUTPUT ERROR (mV)
Figure 3. Reverse Voltage Error Distribution
06672-001
06672-002
06672-003
Rev. 0
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Anal og Devices for its use, nor for any infringements of patents or ot her 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: 781.329.4700 www.analog.com Fax: 781.461.3113 ©2007 Analog Devices, Inc. All rights reserved.
Page 2
ADR1581
www.BDTIC.com/ADI

TABLE OF CONTENTS

Features.............................................................................................. 1
Temperature Performance............................................................6
Applications....................................................................................... 1
General Description ......................................................................... 1
Pin Configuration............................................................................. 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Absolute Maximum Ratings............................................................ 4
ESD Caution.................................................................................. 4
Typical Performance Characteristics ............................................. 5
Theory of Operation ........................................................................ 6
Applying the ADR1581................................................................ 6

REVISION HISTORY

5/07—Revision 0: Initial Version
Voltage Output Nonlinearity vs. Temperature..........................7
Reverse Voltage Hysteresis...........................................................7
Output Impedance vs. Frequency ...............................................8
Noise Performance and Reduction .............................................8
Turn-On Time ...............................................................................8
Transient Response .......................................................................9
Precision Micropower Low Dropout Reference .......................9
Using the ADR1581 with 3 V Data Converters ..................... 10
Outline Dimensions....................................................................... 11
Ordering Guide .......................................................................... 12
Rev. 0 | Page 2 of 12
Page 3
ADR1581
www.BDTIC.com/ADI

SPECIFICATIONS

TA = 25°C, IIN = 100 µA, unless otherwise noted.
Table 1.
ADR1581A ADR1581B
Parameter Min Typ Max Min Typ Max Unit
REVERSE VOLTAGE OUTPUT (SOT-23) 1.240 1.250 1.260 1.2485 1.250 1.2515 V REVERSE VOLTAGE TEMPERATURE DRIFT
−40°C to +85°C 100 50 ppm/°C
MINIMUM OPERATING CURRENT, T
MIN
to T
60 60 A
MAX
REVERSE VOLTAGE CHANGE WITH REVERSE CURRENT
60 A < IIN < 10 mA, T 60 A < IIN < 1 mA, T
MIN
MIN
to T
2.5 6 2.5 6 mV
MAX
to T
0.8 0.8 mV
MAX
DYNAMIC OUTPUT IMPEDANCE (VR/∆IR)
IIN = 1 mA ± 100 A (f = 120 Hz) 0.4 1 0.4 0.5
OUTPUT NOISE
RMS Noise Voltage: 10 Hz to 10 kHz 20 20 V rms
Low Frequency Noise Voltage: 0.1 Hz to 10 Hz 4.5 4.5 V p-p TURN-ON SETTLING TIME TO 0.1% OUTPUT VOLTAGE HYSTERESIS
1
2
5 5 µs 80 80 µV
TEMPERATURE RANGE
Specified Performance, T
Operating Range
1
Measured with a no load capacitor.
2
Output hysteresis is defined as the change in the +25°C output voltage after a temperature excursion to −40°C, then to +85°C, and back to +25°C.
3
The operating temperature range is defined as the temperature extremes at which the device continues to function. Parts may deviate from their specified
performance.
3
MIN
to T
−40 +85 −40 +85 °C
MAX
−55 +125 −55 +125 °C
Rev. 0 | Page 3 of 12
Page 4
ADR1581
www.BDTIC.com/ADI

ABSOLUTE MAXIMUM RATINGS

Table 2.
Parameter Rating
Reverse Current 25 mA Forward Current 20 mA Internal Power Dissipation
SOT-23 (RT) 0.3 W Storage Temperature Range −65°C to +150°C Operating Temperature Range
ADR1581/RT −55°C to +125°C Lead Temperature, Soldering
Vapor Phase (60 sec) 215°C
Infrared (15 sec) 220°C ESD Susceptibility2
Human Body Model 4 kV
Machine Model 400 V
1
Specification is for device (SOT-23 package) in free air at 25°C: θJA = 300°C/W.
2
The human body model is a 100 pF capacitor discharged through 1.5 kΩ. For
the machine model, a 200 pF capacitor is discharged directly into the device.
1
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.

ESD CAUTION

Rev. 0 | Page 4 of 12
Page 5
ADR1581
www.BDTIC.com/ADI

TYPICAL PERFORMANCE CHARACTERISTICS

2000
100
1500
1000
500
0
–500
REVERSE VOLTAGE CHANGE (pp m)
–1000
–1500
–55 –35 –15 5 25 45 65 85 105 125
TEMPERATURE (°C)
20ppm/° C
5ppm/° C
Figure 4. Output Drift for Different Temperature Characteristics
7
6
5
4
3
2
1
REVERSE VOLTAGE CHANGE (mV)
0
+25°C
+85°C
–40°C
80
60
40
REVERSE CURRENT (µA)
20
0
06672-004
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
REVERSE VOLTAGE (V)
+25°C
+125°C
–40°C
06672-007
Figure 7. Reverse Current vs. Reverse Voltage
1
0.8
0.6
0.4
FORWARD VOLTAGE (µA)
0.2
+25°C
–40°C
+85°C
–1
0.01 0.10 1.00 10 REVERSE CURRENT (mA)
Figure 5. Output Voltage Error vs. Reverse Current
06672-005
0
0.01 0.1 1 10 100 FORWARD CURRENT (mA)
Figure 8. Forward Voltage vs. Forward Current
06672-008
600
400
200
NOISE VOLTAGE (nV/ Hz)
1.0 10 100 1k 10k 100k 1M
FREQUENCY (Hz)
Figure 6. Noise Spectral Density
06672-006
Rev. 0 | Page 5 of 12
Page 6
ADR1581
V
V
V
www.BDTIC.com/ADI

THEORY OF OPERATION

The ADR1581 uses the band gap concept to produce a stable, low temperature coefficient voltage reference suitable for high accuracy data acquisition components and systems. The device makes use of the underlying physical nature of a silicon transistor base emitter voltage in the forward-biased operating region. All such transistors have an approximately −2 mV/°C temperature coefficient, which is unsuitable for use directly as a low TC reference; however, extrapolation of the temperature characteristic of any one of these devices to absolute zero (with collector current proportional to absolute temperature) reveals that its V
goes
BE
to approximately the silicon band gap voltage. Therefore, if a voltage could be developed with an opposing temperature coefficient to sum with V The ADR1581 circuit in
, a zero TC reference would result.
BE
Figure 9 provides such a compensating voltage, V1, by driving two transistors at different current densities and amplifying the resultant V positive TC. The sum of V
difference (∆VBE), which has a
BE
and V1 provides a stable voltage
BE
reference.
+
Figure 11 shows a typical connection of the ADR1581BRT o
perating at a minimum of 100 µA. This connection can provide ±1 mA to the load while accommodating ±10% power supply variations.
S
IR + I
R
S
V
R
I
R
Figure 10. Typical Connection Diagram
+5V(+3V) ±10%
R
V
Figure 11. Typical Connection Diagram
S
R
I
L
2.94k (1.30kΩ)
L
V
OUT
6672-010
V
OUT
6672-011
V1
ΔV
BE
BE
Figure 9. Schema
tic Diagram
V–

APPLYING THE ADR1581

The ADR1581 is simple to use in virtually all applications. To operate the ADR1581 as a conventional shunt regulator (see Figure 10), an external series resistor is connected between the supply
voltage and the ADR1581. For a given supply voltage, the series resistor, R the ADR1581. The value of R the expected variations of the supply voltage (V (I
), and the ADR1581 reverse voltage (VR) while maintaining an
L
acceptable reverse current (I
The minimum value for R minimum and I the minimum acceptable reverse current.
The value of R when V
S
The equation for selecting R
= (VS − VR)/(IR + IL)
R
S
, determines the reverse current flowing through
S
must be chosen to accommodate
S
), load current
S
) through the ADR1581.
R
should be chosen when VS is at its
S
and VR are at their maximum while maintaining
L
should be large enough to limit IR to 10 mA
S
is at its maximum and IL and VR are at their minimum.
is as follows:
S

TEMPERATURE PERFORMANCE

The ADR1581 is designed for reference applications where stable temperature performance is important. Extensive temperature testing and characterization ensure that the device’s performance is maintained over the specified temperature range.
Some confusion exists in the area of defining and specifying refer­e
nce voltage error over temperature. Historically, references have
06672-009
been characterized using a maximum deviation per degree Celsius, for example, 50 ppm/°C. However, because of nonlinearities in temperature characteristics that originated in standard Zener references (such as S type characteristics), most manufacturers now use a maximum limit error band approach to specify devices. This technique involves the measurement of the output at three or more temperatures to guarantee that the voltage falls within the given error band. The proprietary curvature correction design techniques used to minimize the ADR1581 nonlinearities allow the temperature performance to be guaranteed using the maximum deviation method. This method is more useful to a designer than one that simply guarantees the maximum error band over the entire temperature change.
Figure 12 shows a typical output voltage drift for the ADR1581
nd illustrates the methodology. The maximum slope of the two
a diagonals drawn from the initial output value at +25°C to the output values at +85°C and −40°C determines the performance grade of the device. For a given grade of the ADR1581, the designer can easily determine the maximum total error from the initial tolerance plus the temperature variation.
Rev. 0 | Page 6 of 12
Page 7
ADR1581
www.BDTIC.com/ADI
1.2508
SLOPE = TC =
1.2506
1.2504
1.2502
1.2500
1.2498
1.2496
1.2494
OUTPUT VOLTAGE (V)
1.2492
1.2490
1.2488 –55 –35 –15 5 25 45 65 85 105 125
(+85°C – +25° C) × 1.250V × 10
SLOPE = TC =
V
MIN
TEMPERATURE ( °C)
Figure 12. Output Voltag
– VO)
(V
MAX
V
V
O
– VO)
(V
(–40°C – +25°C) × 1.250V × 10
MIN
e vs. Temperature
–6
MAX
–6
06672-012
600
500
400
300
200
RESIDUAL DRIFT ERROR (ppm)
100
0
–55 –35 –15 5 25 45 65 85 105 125
TEMPERATURE ( °C)
Figure 13. Residual Drift Error
06672-013
For example, the ADR1581BRT initial tolerance is ±1.5 mV; a ±50 ppm/°C temperature coefficient corresponds to an error band of ±4.1 mV (50 × 10
−6
× 1.250 V × 65°C). Therefore, the unit is guaranteed to be 1.250 V ± 5.6 mV over the operating temperature range.
Duplication of these results requires a combination of high
curacy and stable temperature control in a test system. Evaluation
ac of the ADR1581 produces curves similar to those in
nd Figure 12.
a
Figure 4

VOLTAGE OUTPUT NONLINEARITY VS. TEMPERATURE

When a reference is used with data converters, it is important to understand how temperature drift affects the overall converter performance. The nonlinearity of the reference output drift represents additional error that is not easily calibrated out of the system. The usual way of showing the reference output drift is to plot the reference voltage vs. temperature (see al
ternative method is to draw a straight line between the temperature endpoints and measure the deviation of the output from the straight line. This shows the same data in a different format. This characteristic (see n
ormalizing the measured drift characteristic to the endpoint
Figure 13) is generated by
average drift. The residual drift error of approximately 500 ppm shows that the ADR1581 is compatible with systems that require 10-bit accurate temperature performance.
Figure 12). An

REVERSE VOLTAGE HYSTERESIS

A major requirement for high performance industrial
uipment manufacturers is a consistent output voltage at
eq nominal temperature following operation over the operating temperature range. This characteristic is generated by measuring the difference between the output voltage at +25°C after operating at +85°C and the output voltage at +25°C after operating at −40°C. Figure 14 displays the hysteresis associated with the ADR1581. This ch
aracteristic exists in all references and has been minimized
in the ADR1581.
40
35
30
25
20
QUANTITY
15
10
5
0
–400 –300 –200 –100 0 100 200 300 400
Figure 14. Reverse Voltage Hyster
HYSTERESIS VOLTAGE (µV)
esis Distribution
06672-014
Rev. 0 | Page 7 of 12
Page 8
ADR1581
V
www.BDTIC.com/ADI

OUTPUT IMPEDANCE VS. FREQUENCY

Understanding the effect of the reverse dynamic output impedance in a practical application is important to successfully applying the ADR1581. A voltage divider is formed by the ADR1581 output impedance and the external source impedance. When an external source resistor of about 30 k (I noise from a 100 kHz switching power supply is developed at the output of the ADR1581.
pacitor connected directly across the ADR1581 reduces the
ca effect of power supply noise to less than 0.01%.
1k
= 100 A) is used, 1% of the
R
Figure 15 shows how a 1 µF load
40µV/DIV 21µV rms
20µV/DIV
10µV/DIV
10ms/DIV
Figure 17. Total RMS Noise
6.5µV rms, t = 0.2ms
2.90µV rms, t = 960ms
(a)
(b)
(c)
06672-017
100
10
= 0.1I
ΔI
R
R
IR = 100µA
OUTPUT IMPEDANCE (Ω)
1
I
= 1mA
R
0.1 10 100 1k 10k 100k 1M
Figure 15. Output Imped
FREQUENCY (Hz)
ance vs. Frequency
CL = 0
C
= 1µF
L
06672-015

NOISE PERFORMANCE AND REDUCTION

The noise generated by the ADR1581 is typically less than 5 µV p-p over the 0.1 Hz to 10 Hz band.
0.1 H
z to 10 Hz noise of a typical ADR1581. Noise in a 10 Hz to 10 kHz bandwidth is approximately 20 V rms (see Figure 17a). I
f further noise reduction is desired, a one-pole low-pass filter can be added between the output pin and ground. A time constant of 0.2 ms has a −3 dB point at about 800 Hz and reduces the high frequency noise to about 6.5 V rms (see constant of 960 ms has a −3 dB point at 165 Hz and reduces the high frequency noise to about 2.9 V rms (see
Figure 16 shows the
Figure 17b). A time
Figure 17c).
4.48µV p-p

TURN-ON TIME

Many low power instrument manufacturers are becoming increasingly concerned with the turn-on characteristics of the components in their systems. Fast turn-on components often enable the end user to keep power off when not needed, and yet those components respond quickly when the power is turned on for operation. o
f the ADR1581.
Upon application of power (cold start), the time required for the
utput voltage to reach its final value within a specified error is
o the turn-on settling time. Two components normally associated with this are time for active circuits to settle and time for thermal gradients on the chip to stabilize. This characteristic is generated from cold start operation and represents the true turn-on wave­form after power-up. t
urn-on settling characteristics of the device; the total settling time to within 1.0 mV is about 6 µs, and there is no long thermal tail when the horizontal scale is expanded to 2 ms/div.
0V
Figure 18 displays the turn-on characteristics
Figure 20 shows both the coarse and fine
2.4V
V
IN
CL = 200pF
1µV/DIV
TIME (1s/DIV)
06672-016
Figure 16. 0.1 Hz to 10 Hz Voltage Noise
Rev. 0 | Page 8 of 12
250mV/DIV 5µs/DIV
Figure 18. Turn-On Response Time
RS= 11.5k
+
IN
V
R
Figure 19. Turn-On, Settling, and Tra
R
L
CLV
nsient Test Circuit
OUT
06672-018
006672-010
Page 9
ADR1581
3
www.BDTIC.com/ADI
Output turn-on time is modified when an external noise-reduction filter is used. When present, the time constant of the filter dom­inates the overall settling.
2.4V
V
0V
IN
OUTPUT ERROR 1mV/DIV, 2µs/DIV
Attempts to drive a large capacitive load (in excess of 1000 pF) may r
esult in ringing, as shown in the step response (see Figure 22). This
ue to the additional poles formed by the load capacitance and
is d the output impedance of the reference. A recommended method of driving capacitive loads of this magnitude is shown in
Figure 19. A resistor isolates the capacitive load from the output stage, whereas the capacitor provides a single-pole low-pass filter and lowers the output noise.
2.0V
OUTPUT
0.5mV/DIV, 2ms/DIV
Figure 20. Turn-On Settling
6672-020

TRANSIENT RESPONSE

Many ADCs and DACs present transient current loads to the reference. Poor reference response can degrade the converter’s performance.
Figure 21 displays both the coarse and fine settling characteristics of the device to load transients of ±50 A.
20mV/DIV
20mV/DIV
1mV/DIV
IR = 150µA + 50µA STEP
IR = 150µA – 50µA ST EP
1µs/DIV1mV/DIV
Figure 21. Transient Settling
(a)
(b)
06672-021
1.8V
Figure 22. Transient Response with Capacitive Load
V
IN
CL = 0.01µF
50µs/DIV10mV/DIV
06672-022

PRECISION MICROPOWER LOW DROPOUT REFERENCE

The circuit in Figure 23 provides an ideal solution for creating a stable voltage reference with low standby power consumption, low input/output dropout capability, and minimum noise output. The amplifier both buffers and optionally scales up the ADR1581 output voltage. Output voltages as high as 2.1 V can supply 1 mA of load current. A one-pole filter connected between the ADR1581 and the OP193 input can be used to achieve low output noise. The nominal quiescent power consumption is 250 µW.
V
28.7k 205
4.7µF
OP193
V
= 1.250V
OUT
OR
= 1.250 (1 + R2/ R3)
V
OUT
Figure 21a shows the settling characteristics of the device for an increased reverse current of 50 A. Figure 21b shows the response w
hen the reverse current is decreased by 50 µA. The transients
settle to 1 mV in about 3 µs.
Rev. 0 | Page 9 of 12
ADR1581
R2
R3
Figure 23. Micropower Buffered Reference
06672-023
Page 10
ADR1581
V
V
A
V
www.BDTIC.com/ADI

USING THE ADR1581 WITH 3 V DATA CONVERTERS

The ADR1581 low output drift (50 ppm/°C) and compact sub
miniature SOT-23 package make it ideally suited for today’s
high performance converters in space-critical applications.
One family of ADCs for which the ADR1581 is well suited is the
AD7714-3 and AD7715-3. The AD7714/AD7715 are charge-
ncing (∑-∆) ADCs with on-chip digital filtering intended for
bala the measurement of wide dynamic range, low frequency signals, such as those representing chemical, physical, or biological processes. AD7714/AD7715 for 3 V operation.
Figure 24 shows the ADR1581 connected to the
3
28.7k
REF IN(+)
DR1581
REF IN(–)
SWITCHING FREQUENCY DEPENDS ON
f
CLKIN
Figure 24. Reference Circuit for the AD7714-3/AD7715-3
AD7714-3/AD7715-3
R
SW
5k (TYP)
C
REF
(3pF TO 8pF)
HIGH
IMPEDANCE
>1G
06672-024
The ADR1581 is ideal for creating the reference level to use with 12-bit multiplying DACs, such as the AD7943, AD7945, and AD7948. In the single-supply bias mode (see Figure 25), the im
pedance seen looking into the I
DAC code. If the ADR1581 drives I
terminal changes with
OUT2
and AGND directly, less
OUT2
than 0.2 LSBs of additional linearity error results. The buffer amp eliminates linearity degradation resulting from variations in the reference level.
3.3
R
DD
DGND
FB
DAC
3.3V
A1
SIGNAL G ROUND
I
OUT1
I
OUT2
AGND
C1
A1
Figure 25. Single-Supply System
A1: OP295 AD822 OP2283
V
OUT
06672-025
IN
V
REF
ADR1581
V
AD7943
29.4k
Rev. 0 | Page 10 of 12
Page 11
ADR1581
www.BDTIC.com/ADI

OUTLINE DIMENSIONS

3.04
2.90
1.40
1.30
1.20
PIN 1
0.10
0.01
Figure 26. 3-Lead Small Outline Transistor Package [SOT-23-3]
4.10
3.20
3.10
2.90
4.00
3.90
2.05
2.00
1.95
1.00 MIN
1.10
1.00
0.90
3.55
3.50
3.45
0.75 MIN
8.30
8.00
7.70
1.55
1.50
1.45
DIRECTION O F UNREELI NG
2.80
3
1
1.90 BSC
SEATING PLANE
COMPLIANT TO JEDEC STANDARDS TO-236-AB
2
0.95 BSC
2.64
2.10
0.50
0.30
1.12
0.89
0.60
0.50
0.40
(RT-3)
Dim
ensions shown in millimeters
1.10
1.00
0.90
2.80
2.70
2.60
0.35
0.30
0.25
Figure 27. Tape and Reel Dime
7” REEL 100.00
13” REEL 330.00
20.20 MIN
nsions
(RT-3)
Dimensions shown in millimeters
OR
1.50 MIN
0.20
0.08
14.40 MIN
13.20
13.00
12.80
7” REEL 50.00 MIN OR 13” REEL 100.00 MIN
9.90
8.40
6.90
053006-0
Rev. 0 | Page 11 of 12
Page 12
ADR1581
www.BDTIC.com/ADI

ORDERING GUIDE

Temperature Range
ADR1581ARTZ-REEL7 −40°C to +85°C 10 mV 100 ppm/°C 3-Lead SOT-23-3 RT-3 R2M ADR1581ARTZ-R2 −40°C to +85°C 10 mV 100 ppm/°C 3-Lead SOT-23-3 RT-3 R2M ADR1581BRTZ-REEL7 −40°C to +85°C 1 mV 50 ppm/°C 3-Lead SOT-23-3 RT-3 R2K ADR1581BRTZ-R2 −40°C to +85°C 1 mV 50 ppm/°C 3-Lead SOT-23-3 RT-3 R2K
1
Z = RoHS Compliant Part.
1
1
1
1
Initial Output Error
Temperature Coefficient
Package Option Model Package Description Branding
©2007 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D06672-0-5/07(0)
Rev. 0 | Page 12 of 12
Loading...