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REF2912, REF2920, REF2925
REF2930, REF2933, REF2940
SBVS033C – JUNE 2002 – REVISED JUNE 2016
REF29xx 100 ppm/°C, 50 µA in 3-Pin SOT-23 CMOS Voltage Reference
1 Features
3 Description
•
•
•
•
•
•
The REF29xx is a precision, low-power, low-voltage
dropout voltage reference family available in a tiny
3‑pin SOT-23 package.
1
MicroSIZE Package: SOT-23
Low Dropout: 1 mV
High Output Current: 25 mA
Low Temperature Drift: Maximum of 100 ppm/°C
High Accuracy: 2%
Low IQ: Maximum of 50 µA
The small size and low power consumption (50 µA
maximum) of the REF29xx make it ideal for portable
and battery-powered applications. The REF29xx does
not require a load capacitor, but it is stable with any
capacitive load.
2 Applications
•
•
•
•
Unloaded, the REF29xx can be operated with
supplies within 1 mV of output voltage. All models are
specified for the wide temperature range, –40°C to
125°C.
Portable, Battery-Powered Equipment
Data Acquisition Systems
Medical Equipment
Hand-Held Test Equipment
Device Information(1)
PART NUMBER
REF29xx
PACKAGE
SOT-23 (3)
BODY SIZE (NOM)
2.92 mm × 1.30 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Dropout Voltage vs Load Current
350
Dropout Voltage (mV)
300
250
200
150
100
50
0
0
5
10
15
20
25
30
Load Current (mA)
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
REF2912, REF2920, REF2925
REF2930, REF2933, REF2940
SBVS033C – JUNE 2002 – REVISED JUNE 2016
www.ti.com
Table of Contents
1
2
3
4
5
6
7
8
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Device Comparison Table.....................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
3
4
7.1
7.2
7.3
7.4
7.5
7.6
4
4
4
4
5
7
Absolute Maximum Ratings ......................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Typical Characteristics ..............................................
Detailed Description ............................................ 11
8.1 Overview ................................................................. 11
8.2 Functional Block Diagram ....................................... 11
8.3 Feature Description................................................. 11
8.4 Device Functional Modes........................................ 13
9
Application and Implementation ........................ 15
9.1 Application Information............................................ 15
9.2 Typical Application .................................................. 15
10 Power Supply Recommendations ..................... 18
11 Layout................................................................... 18
11.1 Layout Guidelines ................................................. 18
11.2 Layout Example .................................................... 18
12 Device and Documentation Support ................. 19
12.1
12.2
12.3
12.4
12.5
12.6
Related Links ........................................................
Receiving Notification of Documentation Updates
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
19
19
19
19
19
19
13 Mechanical, Packaging, and Orderable
Information ........................................................... 19
4 Revision History
Changes from Revision B (February 2008) to Revision C
Page
•
Added ESD Ratings table, Thermal Information table, Feature Description section, Device Functional Modes,
Application and Implementation section, Power Supply Recommendations section, Layout section, Device and
Documentation Support section, and Mechanical, Packaging, and Orderable Information section....................................... 1
•
Deleted Ordering Information table; see POA at the end of the data sheet........................................................................... 1
2
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SBVS033C – JUNE 2002 – REVISED JUNE 2016
5 Device Comparison Table
PRODUCT
VOLTAGE (V)
REF2912
1.25
REF2920
2.048
REF2925
2.5
REF2930
3
REF2933
3.3
REF2940
4.096
6 Pin Configuration and Functions
DBZ Package
3-Pin SOT-23
Top View
IN
OUT
1
2
REF2912
REF2920
REF2925
REF2930
REF2933
REF2940
3
GND
Pin Functions
PIN
NO.
NAME
I/O
DESCRIPTION
1
IN
I
Input supply voltage
2
OUT
O
Reference output voltage
3
GND
—
Ground
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7 Specifications
7.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1)
MIN
MAX
UNIT
7
V
Supply voltage, V+ to V–
Output short circuit
(2)
Continuous
Lead temperature (soldering, 10 s)
Operating temperature
–40
Junction temperature
Storage temperature, Tstg
(1)
(2)
–65
°C
300
°C
125
°C
150
°C
150
°C
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
Short-circuit to ground.
7.2 ESD Ratings
VALUE
V(ESD)
(1)
(2)
Electrostatic discharge
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1)
±4000
Charged-device model (CDM), per JEDEC specification JESD22-C101 (2)
±1500
UNIT
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
7.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted)
VIN
Input voltage
ILOAD
Load current
TA
Operating temperature
(1)
MIN
MAX
VREF + 0.05 (1)
5.5
V
25
mA
125
°C
–40
UNIT
Minimum supply voltage for the REF2912 is 1.8 V.
7.4 Thermal Information
REF29xx
THERMAL METRIC (1)
DBZ (SOT-23)
UNIT
3 PINS
RθJA
Junction-to-ambient thermal resistance
297.3
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
128.5
°C/W
RθJB
Junction-to-board thermal resistance
91.7
°C/W
ψJT
Junction-to-top characterization parameter
12.8
°C/W
ψJB
Junction-to-board characterization parameter
90.3
°C/W
RθJC(bot)
Junction-to-case (bottom) thermal resistance
N/A
°C/W
(1)
4
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report.
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SBVS033C – JUNE 2002 – REVISED JUNE 2016
7.5 Electrical Characteristics
Boldface limits apply over the specified temperature range, TA = –40°C to 125°C. At TA = 25°C, ILOAD = 0 mA, VIN = 5 V,
unless otherwise noted.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
1.225
1.25
1.275
V
REF2912 – 1.25 V
VOUT
Output voltage
Initial accuracy
2%
Output voltage noise
f = 0.1 Hz to 10 Hz,
14
µVPP
Voltage noise
f = 10 Hz to 10 kHz
42
µVrms
Line regulation
1.8 V ≤ VIN ≤ 5.5 V
60
190
2.048
2.089
µV/V
REF2920
VOUT
Output voltage
2.007
Initial accuracy
V
2%
Output voltage noise
f = 0.1 Hz to 10 Hz,
23
µVPP
Voltage noise
f = 10 Hz to 10 kHz
65
µVrms
Line regulation
VREF + 50 mV ≤ VIN ≤ 5.5 V
110
290
µV/V
2.5
2.55
V
REF2925
VOUT
Output voltage
2.45
Initial accuracy
2%
Output voltage noise
f = 0.1 Hz to 10 Hz
28
µVPP
Voltage noise
f = 10 Hz to 10 kHz
80
µVrms
Line regulation
VREF + 50 mV ≤ VIN ≤ 5.5 V
120
325
µV/V
3
3.06
V
REF2930
VOUT
Output voltage
2.94
Initial accuracy
2%
Output voltage noise
f = 0.1 Hz to 10 Hz,
33
µVPP
Voltage noise
f = 10 Hz to 10 kHz
94
µVrms
Line regulation
VREF + 50 mV ≤ VIN ≤ 5.5 V
120
375
3.3
3.366
µV/V
REF2933
VOUT
Output voltage
3.234
Initial accuracy
V
2%
Output voltage noise
f = 0.1 Hz to 10 Hz,
36
µVPP
Voltage noise
f = 10 Hz to 10 kHz
105
Line regulation
VREF + 50 mV ≤ VIN ≤ 5.5 V
130
400
4.096
4.178
µVrms
µV/V
REF2940
VOUT
Output voltage
4.014
Initial accuracy
V
2%
Output voltage noise
f = 0.1 Hz to 10 Hz,
45
µVPP
Voltage noise
f = 10 Hz to 10 kHz
128
µVrms
VREF + 50 mV ≤ VIN ≤ 5.5 V
160
410
µV/V
–40°C ≤ TA ≤ 125°C
35
100
ppm/°C
25
mA
0 to 1000H
24
1000 to 2000H
15
REF2912, REF2920, REF2925, REF2930, REF2933, REF2940
dVOUT/dT
Output voltage temperature drift (1)
ILOAD
Output current
Long-term stability
dVOUT/dILOAD
(1)
(2)
(3)
Load regulation (2)
0 mA < ILOAD < 25 mA,
VIN = VREF + 500 mV (3)
3
ppm
100
µV/mA
Box Method used to determine overtemperature drift.
Typical value of load regulation reflects measurements using a force and sense contacts, see Load Regulation.
Minimum supply voltage for REF2912 is 1.8 V.
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Electrical Characteristics (continued)
Boldface limits apply over the specified temperature range, TA = –40°C to 125°C. At TA = 25°C, ILOAD = 0 mA, VIN = 5 V,
unless otherwise noted.
PARAMETER
dT
Thermal Hysteresis (4)
VIN – VOUT
Dropout voltage
ISC
Short-circuit current
Turnon settling time
TEST CONDITIONS
MIN
to 0.1% at VIN = 5 V with CL = 0
TYP
MAX
UNIT
25
100
ppm
1
50
mV
45
mA
120
µs
POWER SUPPLY
VS
Voltage
IL = 0
Voltage over temperature
–40°C ≤ TA ≤ 125°C
VREF + 0.001 (5)
5.5
VREF + 0.05
5.5
Quiescent current
IQ
Quiescent current over temperature
42
–40°C ≤ TA ≤ 125°C
50
59
V
µA
TEMPERATURE RANGE
RθJC
RθJA
(4)
(5)
6
Specified range
–40
125
°C
Operating range
–40
125
°C
Storage range
–65
150
Thermal resistance for SOT-23
surface-mount
°C
110
°C/W
336
°C/W
Thermal hysteresis procedure is explained in more detail in Thermal Hysteresis.
For IL > 0, see Typical Characteristics.
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SBVS033C – JUNE 2002 – REVISED JUNE 2016
50
100
45
90
40
80
35
70
Number of Units
Number of Units
7.6 Typical Characteristics
30
25
20
15
60
50
40
30
10
20
5
10
0
0
5
10 15 20 25 30 35 40 45 50 55 60 65
5
10 15 20 25 30 35 40 45 50 55 60 65
Drift (ppm/°C)
Drift (ppm/°C)
Figure 1. Temperature Drift (0°C to 70°C)
Figure 2. Temperature Drift (–40°C to 125°C)
35
Maximum Load Current (mA)
2.502
Output Voltage (V)
2.500
2.498
2.496
2.494
2.492
2.490
30
25
20
15
10
5
–40
–20
0
20
40
60
80
100
120
140
–40
–20
0
Temperature ( °C)
40
60
80
100
120
140
Temperature ( °C)
Figure 3. Output Voltage vs Temperature
Figure 4. Maximum Load Current vs Temperature
6
60
5
50
4
40
IQ (µA)
Load Regulation (µV/mA)
20
3
30
2
20
1
10
0
0
–40
–20
0
20
40
60
80
100
120
Temperature ( °C)
Figure 5. Load Regulation vs Temperature
Copyright © 2002–2016, Texas Instruments Incorporated
140
–40
–20
0
20
40
60
80
100
120
140
Temperature (° C)
Figure 6. Quiescent Current vs Temperature
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Typical Characteristics (continued)
100
150
Output Impedance (dB)
Line Regulation (µV/V)
200
100
50
0
10
1
0.1
0.01
–50
–40
–20
0
20
40
60
80
100
120
1
140
10
2.50138
80
2.50000
70
2.49862
Output Voltage (V)
90
60
50
40
30
100k
2.49586
2.49448
2.49310
2.49172
10
2.49034
2.48896
1
10
100
1k
10k
2.5
100k
3
3.5
4
4.5
5
5.5
6
Supply (V)
Frequency (Hz)
Figure 9. Power-Supply Rejection Ratio vs Frequency
Figure 10. Output Voltage vs Supply Voltage (No Load)
2.5008
2.50152
2.5000
2.50000
Output Voltage (V)
2.4992
Output Voltage (V)
10k
2.49724
20
0
2.4984
2.4976
2.4968
2.4967
2.49848
2.49696
2.49544
2.49392
2.4952
2.49824
2.4944
2.49088
2.4936
2.48936
2.5
3
3.5
4
4.5
5
5.5
6
Supply (V)
Figure 11. Output Voltage vs Supply Voltage (ILOAD = 25 mA)
8
1k
Figure 8. Output Impedance vs Frequency
Figure 7. Line Regulation vs Temperature
PSRR (dB)
100
Frequency (Hz)
Temperature ( °C)
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0
5
10
15
20
25
30
Load Current (mA)
Figure 12. Output Voltage vs Load Current
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SBVS033C – JUNE 2002 – REVISED JUNE 2016
5V/div
VOUT
VIN
1V/div
3V/div
VIN
1V/div
Typical Characteristics (continued)
VOUT
40µs/div
10µs/div
Figure 13. Step Response, CL = 0, 3-V Start-Up
Figure 14. Step Response, CL = 0, 5-V Start-Up
VIN
IL = 0mA
20mV/div
50mV/div
500mV/div
IL = 1mA
VOUT
VOUT
10µs/div
10µs/div
Figure 15. Line Transient Response
Figure 16. 0 to 1-mA Load Transient (CL = 0)
IL = 5mA
IL = 6mA
20mV/div
20mV/div
IL = 0mA
VOUT
10µs/div
Figure 17. 0 to 5-mA Load Transient (CL = 0)
Copyright © 2002–2016, Texas Instruments Incorporated
IL = 0mA
VOUT
40µs/div
Figure 18. 1 to 6-mA Load Transient (CL = 1 µF)
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Typical Characteristics (continued)
IL = 25mA
10 µV/div
20mV/div
IL = 1mA
VOUT
100µs/div
1.0s/div
Figure 19. 1 to 25-mA Load Transient (CL = 1 µF)
Figure 20. 0.1 to 10-Hz Noise
80
Absolute Output Voltage Drift (ppm)
Absolute Output Voltage Drift (ppm)
80
70
60
50
40
30
20
10
100
200
300
400
500
600
700
800
60
50
40
30
20
10
0
1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000
0
0
70
900 1000
Time (hours)
Time (hours)
Figure 22. Long-Term Stability 1000 to 2000 Hours
Figure 21. Long-Term Stability 0 to 1000 Hours
Absolute Output Voltage Drift (ppm)
80
70
60
50
40
30
20
10
0
0
200
400
600
800 1000 1200 1400 1600 1800 2000
Time (hours)
Figure 23. Long-Term Stability 0 to 2000 Hours
10
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8 Detailed Description
8.1 Overview
The REF29xx is a series, CMOS, precision band-gap voltage reference. Its basic topology is shown in Functional
Block Diagram. The transistors Q1 and Q2 are biased such that the current density of Q1 is greater than that of
Q2. The difference of the two base-emitter voltages, Vbe1 – Vbe2, has a positive temperature coefficient and is
forced across resistor R1. This voltage is gained up and added to the base-emitter voltage of Q2, which has a
negative coefficient. The resulting output voltage is virtually independent of temperature. The curvature of the
band-gap voltage, as seen in Figure 3, is due to the slightly nonlinear temperature coefficient of the base-emitter
voltage of Q2.
8.2 Functional Block Diagram
R1
+
+
Vbe1 Vbe2
–
–
Q1
Q2
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Figure 24. Simplified Schematic of Band-Gap Reference
8.3 Feature Description
8.3.1 Supply Voltage
The REF29xx family of references features an extremely low dropout voltage. With the exception of the
REF2912, which has a minimum supply requirement of 1.8 V, the REF29xx can be operated with a supply of
only 1 mV above the output voltage in an unloaded condition. For loaded conditions, see Dropout Voltage vs
Load Current.
The REF29xx features a low quiescent current, which is extremely stable over changes in both temperature and
supply. The typical room temperature quiescent current is 42 µA, and the maximum quiescent current over
temperature is just 59 µA. Additionally, the quiescent current typically changes less than 2.5 µA over the entire
supply range, as shown in Figure 25.
42.5
IQ (µA)
42.0
41.5
41.0
40.5
40.0
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
VIN (V)
Figure 25. Supply Current vs Supply Voltage
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Feature Description (continued)
Supply voltages below the specified levels can cause the REF29xx to momentarily draw currents greater than
the typical quiescent current. Using a power supply with a fast rising edge and low output impedance easily
prevents this.
8.3.2 Thermal Hysteresis
Thermal hysteresis for the REF29xx is defined as the change in output voltage after operating the device at
25°C, cycling the device through the specified temperature range, and returning to 25°C, and can be expressed
as shown in Equation 1.
æ abs VPRE - VPOST ö
6
VHYST = ç
÷ ´ 10 (ppm )
V
NOM
è
ø
where
•
•
•
VHYST = calculated hysteresis
VPRE = output voltage measured at 25°C pretemperature cycling
VPOST = output voltage measured when device has been operated at 25°C, cycled through specified range
–40°C to 125°C and returned to operation at 25°C
(1)
8.3.3 Temperature Drift
The REF29xx is designed to exhibit minimal drift error, defined as the change in output voltage over varying
temperature. Using the box method of drift measurement, the REF29xx features a typical drift coefficient of 20
ppm from 0°C to 70°C— the primary temperature range of use for many applications. For industrial temperature
ranges of –40°C to 125°C, the REF29xx family drift increases to a typical value of 50 ppm.
8.3.4 Noise Performance
The REF29xx generates noise less than 50 µVPP between frequencies of 0.1 Hz to 10 Hz, and can be seen in
Figure 20. The noise voltage of the REF29xx increases with output voltage and operating temperature. Additional
filtering may be used to improve output noise levels, however, take care ensuring the output impedance does not
degrade AC performance.
8.3.5 Long-Term Stability
Long-term stability refers to the change of the output voltage of a reference over a period of months or years.
This effect lessens as time progresses as is apparent by the long-term stability curves. The typical drift value for
the REF29xx is 24 ppm from 0 to 1000 hours, and 15 ppm from 1000 to 2000 hours. This parameter is
characterized by measuring 30 units at regular intervals for a period of 2000 hours.
8.3.6 Load Regulation
Load regulation is defined as the change in output voltage due to changes in load current. Load regulation for the
REF29xx is measured using force and sense contacts as pictured in Figure 26. The force and sense lines tied to
the contact area of the output pin reduce the impact of contact and trace resistance, resulting in accurate
measurement of the load regulation contributed solely by the REF29xx. For applications requiring improved load
regulation, force and sense lines must be used.
12
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SBVS033C – JUNE 2002 – REVISED JUNE 2016
Feature Description (continued)
Output Pin
+
Contact and
Trace Resistance
VOUT
–
IL
Sense Line
Force Line
Load
Meter
Copyright © 2016, Texas Instruments Incorporated
Figure 26. Accurate Load Regulation of REF29xx
8.4 Device Functional Modes
8.4.1 Negative Reference Voltage
For applications requiring a negative and positive reference voltage, the OPA703 and REF29xx can be used to
provide a dual-supply reference from a ±5-V supply. Figure 27 shows the REF2925 used to provide a ±2.5-V
supply reference voltage. The low offset voltage and low drift of the OPA703 complement the low drift
performance of the REF29xx to provide an accurate solution for split-supply applications.
+5 V
+2.5V
REF2925
10 kΩ
10 kΩ
+5 V
OPA703
–2.5 V
–5 V
Copyright © 2016, Texas Instruments Incorporated
Figure 27. REF2925 Combined With OPA703 to Create Positive and Negative Reference Voltages
8.4.2 Data Acquisition
Often data acquisition systems require stable voltage references to maintain necessary accuracy. The REF29xx
family features stability and a wide range of voltages suitable for most micro-controllers and data converters. See
Figure 28 for a basic data acquisition system.
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Product Folder Links: REF2912 REF2920 REF2925 REF2930 REF2933 REF2940
13
REF2912, REF2920, REF2925
REF2930, REF2933, REF2940
SBVS033C – JUNE 2002 – REVISED JUNE 2016
www.ti.com
Device Functional Modes (continued)
3.3 V
REF2933
V+
GND
5Ω
+ 1µF to
10 µF
ADS7822
VREF
VCC
0.1 µF
VIN
+In
CS
–In
DOUT
GND
VS
+
1 µF to 10 µF
Microcontroller
DCLOCK
Copyright © 2016, Texas Instruments Incorporated
Figure 28. Basic Data Acquisition System 1
14
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Product Folder Links: REF2912 REF2920 REF2925 REF2930 REF2933 REF2940
REF2912, REF2920, REF2925
REF2930, REF2933, REF2940
www.ti.com
SBVS033C – JUNE 2002 – REVISED JUNE 2016
9 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
For normal operation, the REF29xx does not require a capacitor on the output. If a capacitive load is connected,
take special care when using low equivalent series resistance (ESR) capacitors and high capacitance. This
precaution is especially true for low-output voltage devices; therefore, for the REF2912 use a low-ESR
capacitance of 10 µF or less. Figure 29 shows the typical connections required for operation of the REF29xx. TI
always recommends a supply bypass capacitor of 0.47 µF.
VIN
1
0.47µF
VOUT
REF29xx
3
2
Figure 29. Typical Connections for Operating REF29xx
9.2 Typical Application
Figure 30 shows a low-power reference and conditioning circuit. This circuit attenuates and level-shifts a bipolar
input voltage within the proper input range of a single-supply low-power 16-bit ΔΣ ADC, such as the one inside
the MSP430 or other similar single-supply ADCs. Precision reference circuits are used to level-shift the input
signal, provide the ADC reference voltage and to create a well-regulated supply voltage for the low-power analog
circuitry. A low-power, zero-drift, operational amplifier circuit is used to attenuate and level-shift the input signal.
Copyright © 2002–2016, Texas Instruments Incorporated
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REF2912, REF2920, REF2925
REF2930, REF2933, REF2940
SBVS033C – JUNE 2002 – REVISED JUNE 2016
www.ti.com
Typical Application (continued)
3.3 V
REF2930
IN
3.0 V
OUT
1.25 V
R2
20 k
R3
100 k
20 k
3.0 V
MSP430F2013
Launchpad
3.3 V
VOUT
+
VIN
±5 V
J1.2/A1+
OPA317
+
±
IN+
J1.3/A1±
R4
±
REF2912
A-ADC
R5
10 k
100 k
3.0 V
IN±
SD_16
VREF
+
R1
1.25 V
J1.5/VREF
IN OUT
R6
47 k
R7
47 k
0.625 V
C2
47 µF
Copyright © 2016, Texas Instruments Incorporated
Figure 30. Low-Power Reference and Bipolar Voltage Conditioning Circuit for Low-Power ADCs
16
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REF2912, REF2920, REF2925
REF2930, REF2933, REF2940
www.ti.com
SBVS033C – JUNE 2002 – REVISED JUNE 2016
Typical Application (continued)
9.2.1 Design Requirements
• Supply Voltage: 3.3 V
• Maximum Input Voltage: ±6 V
• Specified Input Voltage: ±5 V
• ADC Reference Voltage: 1.25 V
The goal for this design is to accurately condition a ±5-V bipolar input voltage into a voltage suitable for
conversion by a low-voltage ADC with a 1.25-V reference voltage, VREF, and an input voltage range of VREF / 2.
The circuit should function with reduced performance over a wider input range of at least ±6 V to allow for easier
protection of overvoltage conditions.
9.2.2 Detailed Design Procedure
Figure 30 depicts a simplified schematic for this design showing the MSP430 ADC inputs and full inputconditioning circuitry. The ADC is configured for a bipolar measurement where final conversion result is the
differential voltage between the voltage at the positive and negative ADC inputs. The bipolar, GND referenced
input signal must be level-shifted and attenuated by the operational amplifier so that the output is biased to VREF /
2 and has a differential voltage that is within the ±VREF / 2 input range of the ADC.
9.2.3 Application Curves
-0.0004
2000
Output Code Error (# Codes)
-0.00042
Error Voltage (V)
-0.00044
-0.00046
-0.00048
-0.0005
-0.00052
-0.00054
-0.00056
±6
±5
±4
±3
±2
±1
0
1
2
3
4
5
Input Voltage (V)
1000
0
±1000
±2000
±3000
±4000
6
±6
±5
±4
±3
±2
±1
0
1
2
3
4
5
Input Voltage (V)
C001
Figure 31. OPA317 Output Voltage vs Input Voltage
6
C002
Figure 32. OPA317 Output Voltage Error vs Input Voltage
1.25
Output Voltage (V)
1.00
0.75
0.50
0.25
0.00
±6
±5
±4
±3
±2
±1
0
1
2
3
4
5
Input Voltage (V)
6
C003
Figure 33. Output Code Error vs Input Voltage
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REF2912, REF2920, REF2925
REF2930, REF2933, REF2940
SBVS033C – JUNE 2002 – REVISED JUNE 2016
www.ti.com
10 Power Supply Recommendations
The REF29xx family of references feature an extremely low-dropout voltage. These references can be operated
with a supply of only 50 mV above the output voltage. For loaded reference conditions, see Dropout Voltage vs
Load Current. Use a supply bypass capacitor greater than 0.47 µF.
11 Layout
11.1 Layout Guidelines
Figure 34 illustrates an example of a printed-circuit board (PCB) layout using the REF29xx. Some key
considerations are:
• Connect low-ESR, 0.1-µF ceramic bypass capacitors at VIN of the REF29xx
• Decouple other active devices in the system per the device specifications
• Use a solid ground plane to help distribute heat and reduces electromagnetic interference (EMI) noise pickup
• Place the external components as close to the device as possible. This configuration prevents parasitic errors
(such as the Seebeck effect) from occurring
• Minimize trace length between the reference and bias connections to the INA and ADC to reduce noise
pickup
• Do not run sensitive analog traces in parallel with digital traces. Avoid crossing digital and analog traces if
possible, and only make perpendicular crossings when absolutely necessary
11.2 Layout Example
To ADC
To Input Power Supply
IN
OUT
C
C
REF29xx
GND
Via to Ground Plane
Figure 34. REF29xx Layout Example
18
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Product Folder Links: REF2912 REF2920 REF2925 REF2930 REF2933 REF2940
REF2912, REF2920, REF2925
REF2930, REF2933, REF2940
www.ti.com
SBVS033C – JUNE 2002 – REVISED JUNE 2016
12 Device and Documentation Support
12.1 Related Links
The table below lists quick access links. Categories include technical documents, support and community
resources, tools and software, and quick access to sample or buy.
Table 1. Related Links
PARTS
PRODUCT FOLDER
SAMPLE & BUY
TECHNICAL
DOCUMENTS
TOOLS &
SOFTWARE
SUPPORT &
COMMUNITY
REF2912
Click here
Click here
Click here
Click here
Click here
REF2920
Click here
Click here
Click here
Click here
Click here
REF2925
Click here
Click here
Click here
Click here
Click here
REF2930
Click here
Click here
Click here
Click here
Click here
REF2933
Click here
Click here
Click here
Click here
Click here
REF2940
Click here
Click here
Click here
Click here
Click here
12.2 Receiving Notification of Documentation Updates
To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper
right corner, click on Alert me to register and receive a weekly digest of any product information that has
changed. For change details, review the revision history included in any revised document.
12.3 Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective
contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of
Use.
TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration
among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help
solve problems with fellow engineers.
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
12.4 Trademarks
E2E is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
12.5 Electrostatic Discharge Caution
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.
12.6 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
13 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
Copyright © 2002–2016, Texas Instruments Incorporated
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19
PACKAGE OPTION ADDENDUM
www.ti.com
14-Oct-2022
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
Samples
(4/5)
(6)
REF2912AIDBZR
ACTIVE
SOT-23
DBZ
3
3000
RoHS & Green
NIPDAUAG
Level-1-260C-UNLIM
-40 to 125
R29A
Samples
REF2912AIDBZT
ACTIVE
SOT-23
DBZ
3
250
RoHS & Green
NIPDAUAG
Level-1-260C-UNLIM
-40 to 125
R29A
Samples
REF2920AIDBZR
ACTIVE
SOT-23
DBZ
3
3000
RoHS & Green
NIPDAUAG
Level-1-260C-UNLIM
-40 to 125
R29B
Samples
REF2920AIDBZT
ACTIVE
SOT-23
DBZ
3
250
RoHS & Green
NIPDAUAG
Level-1-260C-UNLIM
-40 to 125
R29B
Samples
REF2925AIDBZR
ACTIVE
SOT-23
DBZ
3
3000
RoHS & Green
NIPDAUAG
Level-1-260C-UNLIM
-40 to 125
R29C
Samples
REF2925AIDBZRG4
ACTIVE
SOT-23
DBZ
3
3000
RoHS & Green
NIPDAUAG
Level-1-260C-UNLIM
-40 to 125
R29C
Samples
REF2925AIDBZT
ACTIVE
SOT-23
DBZ
3
250
RoHS & Green
NIPDAUAG
Level-1-260C-UNLIM
-40 to 125
R29C
Samples
REF2925AIDBZTG4
ACTIVE
SOT-23
DBZ
3
250
RoHS & Green
NIPDAUAG
Level-1-260C-UNLIM
-40 to 125
R29C
Samples
REF2930AIDBZR
ACTIVE
SOT-23
DBZ
3
3000
RoHS & Green
NIPDAUAG
Level-1-260C-UNLIM
-40 to 125
R29D
Samples
REF2930AIDBZRG4
ACTIVE
SOT-23
DBZ
3
3000
RoHS & Green
NIPDAUAG
Level-1-260C-UNLIM
-40 to 125
R29D
Samples
REF2930AIDBZT
ACTIVE
SOT-23
DBZ
3
250
RoHS & Green
NIPDAUAG
Level-1-260C-UNLIM
-40 to 125
R29D
Samples
REF2930AIDBZTG4
ACTIVE
SOT-23
DBZ
3
250
RoHS & Green
NIPDAUAG
Level-1-260C-UNLIM
-40 to 125
R29D
Samples
REF2933AIDBZR
ACTIVE
SOT-23
DBZ
3
3000
RoHS & Green
NIPDAUAG
Level-1-260C-UNLIM
-40 to 125
R29E
Samples
REF2933AIDBZT
ACTIVE
SOT-23
DBZ
3
250
RoHS & Green
NIPDAUAG
Level-1-260C-UNLIM
-40 to 125
R29E
Samples
REF2940AIDBZR
ACTIVE
SOT-23
DBZ
3
3000
RoHS & Green
NIPDAUAG
Level-1-260C-UNLIM
-40 to 125
R29F
Samples
REF2940AIDBZT
ACTIVE
SOT-23
DBZ
3
250
RoHS & Green
NIPDAUAG
Level-1-260C-UNLIM
-40 to 125
R29F
Samples
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
Addendum-Page 1
PACKAGE OPTION ADDENDUM
www.ti.com
14-Oct-2022
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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