TI1 INA2181A1QDGSRQ1 Automotive, bidirectional, low- and high-side voltage output, current-sense amplifier Datasheet

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INA181-Q1, INA2181-Q1, INA4181-Q1
SLYS018 – APRIL 2018
INAx181-Q1 Automotive, Bidirectional, Low- and High-Side Voltage Output,
Current-Sense Amplifiers
1 Features
3 Description
•
The INA181-Q1, INA2181-Q1, and INA4181-Q1
(INAx181-Q1) current sense amplifiers are designed
for cost-optimized applications. These devices are
part of a family of bidirectional, current-sense
amplifiers (also called current-shunt monitors) that
sense voltage drops across current-sense resistors at
common-mode voltages from –0.2 V to +26 V,
independent of the supply voltage. The INAx181-Q1
family integrates a matched resistor gain network in
four, fixed-gain device options: 20 V/V, 50 V/V, 100
V/V, or 200 V/V. This matched gain resistor network
minimizes gain error and reduces the temperature
drift.
1
•
•
•
•
•
•
•
•
AEC-Q100 Qualified for Automotive Applications
– Temperature Grade 1: –40°C ≤ TA ≤ +125°C
– HBM ESD Classification Level 2
– CDM ESD Classification Level C6
Common-Mode Range (VCM): –0.2 V to +26 V
High Bandwidth: 350 kHz (A1 Devices)
Offset Voltage:
– ±150 µV (Max) at VCM = 0 V
– ±500 µV (Max) at VCM = 12 V
Output Slew Rate: 2 V/µs
Bidirectional Current-Sensing Capability
Accuracy:
– ±1% Gain Error (Max)
– 1-µV/°C Offset Drift (Max)
Gain Options:
– 20 V/V (A1 Devices)
– 50 V/V (A2 Devices)
– 100 V/V (A3 Devices)
– 200 V/V (A4 Devices)
Quiescent Current: 260 µA Max (INA181)
These devices operate from a single 2.7-V to 5.5-V
power supply. The single-channel INA181-Q1 draws
a maximum supply current of 260 µA; whereas, the
dual-channel INA2181-Q1 draws a maximum supply
current of 500 µA, and the quad-channel INA4181-Q1
draws a maximum supply current of 900 µA.
The INA181-Q1 is available in a 6-pin, SOT-23
package. The INA2181-Q1 is available in an 10-pin,
VSSOP package. The INA4181-Q1 is available in a
20-pin, TSSOP package. All device options are
specified over the extended operating temperature
range of –40°C to +125°C.
Device Information(1)
2 Applications
•
•
•
•
•
PART NUMBER
Motor Control
Battery Monitoring
Power Management
Lighting Control
Overcurrent Detection
(2)
PACKAGE
BODY SIZE (NOM)
INA181-Q1
SOT-23 (6)
2.90 mm × 1.60 mm
INA2181-Q1
VSSOP (10)
3.00 mm × 3.00 mm
INA4181-Q1(2)
TSSOP (20)
6.50 mm × 4.40 mm
(1) For all available packages, see the package option addendum
at the end of the data sheet.
(2) INA181-Q1 and INA4181-Q1 are preview devices.
Typical Application Circuit
Bus Voltage, VCM
Up To 26 V
Power Supply, VS
2.7 V to 5.5 V
CBYPASS
0.1 µF
RSENSE
Load
INA4181-Q1 (quad-channel)
INA2181-Q1 (dual-channel)
INA181-Q1 (single-channel)
Microcontroller
IN±
±
OUT
ADC
+
IN+
REF
GND
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. UNLESS OTHERWISE NOTED, this document contains PRODUCTION
DATA.
INA181-Q1, INA2181-Q1, INA4181-Q1
SLYS018 – APRIL 2018
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
6
7.1
7.2
7.3
7.4
7.5
7.6
6
6
6
6
7
8
Absolute Maximum Ratings .....................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Typical Characteristics ..............................................
9
9.1 Application Information............................................ 22
9.2 Typical Application .................................................. 29
10 Power Supply Recommendations ..................... 31
10.1 Common-Mode Transients Greater Than 26 V .... 31
11 Layout................................................................... 32
11.1 Layout Guidelines ................................................. 32
11.2 Layout Example .................................................... 32
12 Device and Documentation Support ................. 35
12.1
12.2
12.3
12.4
12.5
12.6
12.7
12.8
Detailed Description ............................................ 15
8.1
8.2
8.3
8.4
Overview .................................................................
Functional Block Diagrams .....................................
Feature Description.................................................
Device Functional Modes........................................
Application and Implementation ........................ 22
15
15
17
19
Device Support......................................................
Documentation Support ........................................
Related Links ........................................................
Receiving Notification of Documentation Updates
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
35
35
35
35
35
35
35
36
13 Mechanical, Packaging, and Orderable
Information ........................................................... 36
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
2
DATE
REVISION
NOTES
April 2018
*
Initial release.
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SLYS018 – APRIL 2018
5 Device Comparison Table
PRODUCT
NUMBER OF CHANNELS
GAIN (V/V)
INA181A1-Q1
1
20
INA181A2-Q1
1
50
INA181A3-Q1
1
100
INA181A4-Q1
1
200
INA2181A1-Q1
2
20
INA2181A2-Q1
2
50
INA2181A3-Q1
2
100
INA2181A4-Q1
2
200
INA4181A1-Q1
4
20
INA4181A2-Q1
4
50
INA4181A3-Q1
4
100
INA4181A4-Q1
4
200
6 Pin Configuration and Functions
INA180-Q1: DBV Package(1)
6-Pin SOT-23
Top View
OUT
1
6
VS
GND
2
5
REF
IN+
3
4
IN±
Not to scale
(1)
INA181-Q1 is preview device. See the Package Option Addendum at the end of this data sheet for more information.
Pin Functions: INA181-Q1 (Single Channel)
PIN
TYPE
DESCRIPTION
NAME
NO.
GND
2
Analog
IN–
4
Analog input
Current-sense amplifier negative input. For high-side applications, connect to load
side of sense resistor. For low-side applications, connect to ground side of sense
resistor.
IN+
3
Analog input
Current-sense amplifier positive input. For high-side applications, connect to busvoltage side of sense resistor. For low-side applications, connect to load side of
sense resistor.
OUT
1
Analog output
Output voltage
REF
5
Analog input
Reference input
VS
6
Analog
Ground
Power supply, 2.7 V to 5.5 V
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INA4180-Q1: PW Package(1)
20-Pin TSSOP
Top View
INA2180-Q1: DGS Package
10-Pin VSSOP
Top View
VS
REF1
1
20
REF4
9
OUT2
OUT1
2
19
OUT4
3
8
IN±2
IN±1
3
18
IN±4
GND
4
7
IN+2
IN+1
4
17
IN+4
REF1
5
6
REF2
VS
5
16
GND
IN+2
6
15
IN+3
IN±2
7
14
IN±3
OUT2
8
13
OUT3
REF2
9
12
REF3
10
11
NC
OUT1
1
10
IN±1
2
IN+1
Not to scale
NC
Not to scale
(1)
INA4181-Q1 is preview device. See the Package Option Addendum at the end of this data sheet for more information.
Pin Functions: INA2181-Q1 (Dual Channel) and INA4181-Q1 (Quad Channel)
PIN
4
TYPE
DESCRIPTION
NAME
INA2181-Q1
INA4181-Q1
GND
4
16
Analog
IN–1
2
3
Analog input
Current-sense amplifier negative input for channel 1. For high-side
applications, connect to load side of channel-1 sense resistor. For lowside applications, connect to ground side of channel-1 sense resistor.
IN+1
3
4
Analog input
Current-sense amplifier positive input for channel 1. For high-side
applications, connect to bus-voltage side of channel-1 sense resistor. For
low-side applications, connect to load side of channel-1 sense resistor.
IN–2
8
7
Analog input
Current-sense amplifier negative input for channel 2. For high-side
applications, connect to load side of channel-2 sense resistor. For lowside applications, connect to ground side of channel-2 sense resistor.
IN+2
7
6
Analog input
Current-sense amplifier positive input for channel 2. For high-side
applications, connect to bus-voltage side of channel-2 sense resistor. For
low-side applications, connect to load side of channel-2 sense resistor.
IN–3
—
14
Analog input
Current-sense amplifier negative input for channel 3. For high-side
applications, connect to load side of channel-3 sense resistor. For lowside applications, connect to ground side of channel-3 sense resistor.
IN+3
—
15
Analog input
Current-sense amplifier positive input for channel 3. For high-side
applications, connect to bus-voltage side of channel-3 sense resistor. For
low-side applications, connect to load side of channel-3 sense resistor.
IN–4
—
18
Analog input
Current-sense amplifier negative input for channel 4. For high-side
applications, connect to load side of channel-4 sense resistor. For lowside applications, connect to ground side of channel-4 sense resistor.
IN+4
—
17
Analog input
Current-sense amplifier positive input for channel 4. For high-side
applications, connect to bus-voltage side of channel-4 sense resistor. For
low-side applications, connect to load side of channel-4 sense resistor.
NC
—
10, 11
—
OUT1
1
2
Analog output
Channel 1 output voltage
Ground
NC denotes no internal connection. These pins can be left floating or
connected to any voltage between VS and ground.
OUT2
9
8
Analog output
Channel 2 output voltage
OUT3
—
13
Analog output
Channel 3 output voltage
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Pin Functions: INA2181-Q1 (Dual Channel) and INA4181-Q1 (Quad Channel) (continued)
PIN
TYPE
DESCRIPTION
NAME
INA2181-Q1
INA4181-Q1
OUT4
—
19
Analog output
REF1
5
1
Analog input
Channel 1 reference voltage, 0 to VS
REF2
6
9
Analog input
Channel 2 reference voltage, 0 to VS
REF3
—
12
Analog input
Channel 3 reference voltage, 0 to VS
REF4
—
20
Analog input
Channel 4 reference voltage, 0 to VS
VS
10
5
Analog
Channel 4 output voltage
Power supply pin, 2.7 V to 5.5 V
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7 Specifications
7.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1)
MIN
MAX
UNIT
6
V
Supply voltage, VS
Differential (VIN+) – (VIN–)
Analog inputs, IN+, IN– (2) (3)
Input voltage range
–28
28
Common-mode (4)
GND – 0.3
28
at REF pin
GND – 0.3
VS + 0.3
GND – 0.3
VS + 0.3
V
8
mA
150
°C
150
°C
150
°C
Output voltage
Maximum output current, IOUT
Operating free-air temperature, TA
–55
Junction temperature, TJ
Storage temperature, Tstg
(1)
(2)
(3)
(4)
–65
V
V
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.
VIN+ and VIN– are the voltages at the IN+ and IN– pins, respectively.
Sustained operation between 26 V and 28 V for more than a few minutes may cause permanent damage to the device.
Input voltage at any pin can exceed the voltage shown if the current at that pin is limited to 5 mA.
7.2 ESD Ratings
VALUE
V(ESD)
(1)
(2)
Electrostatic discharge
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1)
±3000
Charged-device model (CDM), per JEDEC specification JESD22-C101 (2)
±1000
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
MIN
NOM
MAX
UNIT
VCM
Common-mode input voltage (IN+ and IN–)
–0.2
12
26
VS
Operating supply voltage
2.7
5
5.5
V
V
TA
Operating free-air temperature
–40
125
°C
7.4 Thermal Information
THERMAL METRIC
(1)
INA181-Q1
(PREVIEW)
INA2181-Q1
INA4181-Q1
(PREVIEW)
DBV (SOT-23)
DGS (VSSOP)
PW (TSSOP)
UNIT
6 PINS
10 PINS
20 PINS
RθJA
Junction-to-ambient thermal resistance
198.7
177.3
97.0
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
120.9
68.7
37.7
°C/W
RθJB
Junction-to-board thermal resistance
52.3
98.4
48.3
°C/W
ψJT
Junction-to-top characterization parameter
30.3
12.6
3.6
°C/W
ψJB
Junction-to-board characterization parameter
52.0
96.9
47.9
°C/W
RθJC(bot)
Junction-to-case (bottom) thermal resistance
N/A
N/A
N/A
°C/W
(1)
6
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report.
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7.5 Electrical Characteristics
at TA = 25°C, VS = 5 V, VREF = VS / 2, VIN+ = 12 V, and VSENSE = VIN+ – VIN– (unless otherwise noted)
PARAMETER
CONDITIONS
MIN
TYP
VIN+ = 0 V to 26 V, VSENSE = 0 mV,
TA = –40°C to +125°C
84
100
MAX
UNIT
INPUT
CMRR
Common-mode rejection ratio,
RTI (1)
VOS
Offset voltage, RTI
dVOS/dT
VSENSE = 0 mV
dB
±100
±500
VSENSE = 0 mV, VIN+ = 0 V
±25
±150
Offset drift, RTI
VSENSE = 0 mV, TA = –40°C to +125°C
0.2
1
μV/°C
PSRR
Power-supply rejection ratio, RTI
VS = 2.7 V to 5.5 V, VIN+ = 12 V,
VSENSE = 0 mV
±8
±40
μV/V
IIB
Input bias current
IIO
Input offset current
μV
μV
VSENSE = 0 mV, VIN+ = 0 V
-6
µA
VSENSE = 0 mV
75
µA
VSENSE = 0 mV
±0.05
µA
A1 devices
20
V/V
A2 devices
50
V/V
A3 devices
100
V/V
A4 devices
200
V/V
OUTPUT
G
EG
Gain
Gain error
VOUT = 0.5 V to VS – 0.5 V,
TA = –40°C to +125°C
Gain error vs temperature
TA = –40°C to +125°C
Nonlinearity error
VOUT = 0.5 V to VS – 0.5 V
Maximum capacitive load
No sustained oscillation
VOLTAGE OUTPUT
±0.1%
±1%
1.5
20
ppm/°C
±0.01%
1
nF
(2)
VSP
Swing to VS power-supply rail (3)
VSN
(3)
Swing to GND
RL = 10 kΩ to GND, TA = –40°C to +125°C
(VS) – 0.02
(VS) – 0.03
V
RL = 10 kΩ to GND, TA = –40°C to +125°C
(VGND) +
0.0005
(VGND) +
0.005
V
FREQUENCY RESPONSE
BW
SR
Bandwidth
A1 devices, CLOAD = 10 pF
350
kHz
A2 devices, CLOAD = 10 pF
210
kHz
A3 devices, CLOAD = 10 pF
150
kHz
A4 devices, CLOAD = 10 pF
105
kHz
2
V/µs
40
nV/√Hz
Slew rate
NOISE, RTI (1)
Voltage noise density
POWER SUPPLY
INA181-Q1
(preview)
IQ
Quiescent current
INA2181-Q1
INA4181-Q1
(preview)
(1)
(2)
(3)
VSENSE = 0 mV
195
VSENSE = 0 mV, TA = –40°C to +125°C
VSENSE = 0 mV
356
VSENSE = 0 mV, TA = –40°C to +125°C
VSENSE = 0 mV
VSENSE = 0 mV, TA = –40°C to +125°C
690
260
µA
300
µA
500
µA
520
µA
900
µA
1000
µA
RTI = referred-to-input.
See Figure 19.
Swing specifications are tested with an overdriven input condition.
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7.6 Typical Characteristics
-440
-400
-360
-320
-280
-240
-200
-160
-120
-80
-40
0
40
80
120
160
200
240
280
320
360
400
-170
-155
-140
-125
-110
-95
-80
-65
-50
-35
-20
-5
10
25
40
55
70
85
100
115
130
145
Population
Population
at TA = 25°C, VS = 5 V, VREF = VS / 2, and VIN+ = 12 V (unless otherwise noted)
D001
Input Offset Voltage (PV)
Input Offset Voltage (PV)
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
10
20
30
40
50
60
70
80
Population
Figure 2. Input Offset Voltage Production Distribution A2
-195
-180
-165
-150
-135
-120
-105
-90
-75
-60
-45
-30
-15
0
15
30
45
60
75
90
105
120
Population
Figure 1. Input Offset Voltage Production Distribution A1
D002
D003
Input Offset Voltage (PV)
Input Offset Voltage (PV)
Figure 3. Input Offset Voltage Production Distribution A3
D004
Figure 4. Input Offset Voltage Production Distribution A4
A1
A2
A3
A4
50
Population
Offset Voltage ( PV)
100
0
-100
-50
-25
0
25
50
75
Temperature (qC)
100
125
150
D005
-55
-50
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
5
10
15
20
25
30
35
40
45
50
-50
Common-Mode Rejection Ratio (PV/V)
D006
Figure 5. Offset Voltage vs Temperature
Figure 6. Common-Mode Rejection Production Distribution
A1
8
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Typical Characteristics (continued)
-11
-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
7
8
9
10
Population
-20
-18
-16
-14
-12
-10
-8
-6
-4
-2
0
2
4
6
8
10
12
14
16
18
20
22
Population
at TA = 25°C, VS = 5 V, VREF = VS / 2, and VIN+ = 12 V (unless otherwise noted)
D007
Common-Mode Rejection Ratio (PV/V)
D008
Common-Mode Rejection Ratio (PV/V)
Figure 7. Common-Mode Rejection Production Distribution
A2
Figure 8. Common-Mode Rejection Production Distribution
A3
Population
Common-Mode Rejection Ratio (PV/V)
10
A1
A2
A3
A4
8
6
4
2
0
-2
-4
-6
-8
-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
7
8
9
10
11
-10
-50
-25
0
25
50
75
Temperature (qC)
100
125
150
D010
D009
Common-Mode Rejection Ratio (PV/V)
Figure 10. Common-Mode Rejection Ratio vs Temperature
Gain Error (%)
D011
Figure 11. Gain Error Production Distribution A1
-0.16
-0.145
-0.13
-0.115
-0.1
-0.085
-0.07
-0.055
-0.04
-0.025
-0.01
0.005
0.02
0.035
0.05
0.065
0.08
0.095
0.11
0.125
0.14
0.155
-0.14
-0.13
-0.12
-0.11
-0.1
-0.09
-0.08
-0.07
-0.06
-0.05
-0.04
-0.03
-0.02
-0.01
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
Population
Population
Figure 9. Common-Mode Rejection Production Distribution
A4
Gain Error (%)
D012
Figure 12. Gain Error Production Distribution A2
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Typical Characteristics (continued)
-0.29
-0.265
-0.24
-0.215
-0.19
-0.165
-0.14
-0.115
-0.09
-0.065
-0.04
-0.015
0.01
0.035
0.06
0.085
0.11
0.135
0.16
0.185
0.21
0.235
Population
-0.17
-0.155
-0.14
-0.125
-0.11
-0.095
-0.08
-0.065
-0.05
-0.035
-0.02
-0.005
0.01
0.025
0.04
0.055
0.07
0.085
0.1
0.115
0.13
0.145
Population
at TA = 25°C, VS = 5 V, VREF = VS / 2, and VIN+ = 12 V (unless otherwise noted)
D013
Gain Error (%)
Figure 13. Gain Error Production Distribution A3
Figure 14. Gain Error Production Distribution A4
50
0.4
A1
A2
A3
A4
0.3
0.2
A1
A2
A3
A4
40
30
0.1
Gain (dB)
Gain Error (%)
D014
Gain Error (%)
0
-0.1
20
10
-0.2
0
-0.3
-0.4
-50
-25
0
25
50
75
Temperature (qC)
100
125
-10
10
150
100
Figure 15. Gain Error vs Temperature
Common-Mode Rejection Ratio (dB)
Power-Supply Rejection Ratio (dB)
1M
10M
D016
140
100
80
60
40
20
100
1k
10k
Frequency (Hz)
100k
1M
D017
Figure 17. Power-Supply Rejection Ratio vs Frequency
10
10k
100k
Frequency (Hz)
Figure 16. Gain vs Frequency
120
0
10
1k
D015
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A1
A2
A3
A4
120
100
80
60
40
20
0
10
100
1k
10k
100k
Frequency (Hz)
1M
10M
D018
Figure 18. Common-Mode Rejection Ratio vs Frequency
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Typical Characteristics (continued)
at TA = 25°C, VS = 5 V, VREF = VS / 2, and VIN+ = 12 V (unless otherwise noted)
VS
120
–40°C
25°C
125°C
100
Input Bias Current (PA)
Output Swing (V)
VS – 1
VS – 2
GND + 2
80
60
40
20
GND + 1
0
GND
0
5
10
15
20 25 30 35 40
Output Current (mA)
45
50
55
-20
-5
60
0
5
10
15
20
Common-Mode Voltage (V)
D019
25
30
D020
Supply voltage = 5 V
Figure 19. Output Voltage Swing vs Output Current
Figure 20. Input Bias Current vs Common-Mode Voltage
120
80
79
100
Input Bias Current (PA)
Input Bias Current (PA)
78
80
60
40
20
77
76
75
74
73
72
0
-20
-5
71
0
5
10
15
20
Common-Mode Voltage (V)
25
70
-50
30
-25
0
D021
25
50
75
Temperature (qC)
100
125
150
D022
Supply voltage = 0 V
Figure 21. Input Bias Current vs Common-Mode Voltage
(Both Inputs, Shutdown)
Figure 22. Input Bias Current vs Temperature
380
210
375
370
Quiescent Current (PA)
Quiescent Current (PA)
205
200
195
190
365
360
355
350
185
180
-50
345
-25
0
25
50
75
Temperature (qC)
100
125
340
-50
150
D023
Figure 23. Quiescent Current vs Temperature (INA181-Q1)
-25
0
25
50
75
Temperature (qC)
100
125
150
D023
Figure 24. Quiescent Current vs Temperature (INA2181-Q1)
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Typical Characteristics (continued)
at TA = 25°C, VS = 5 V, VREF = VS / 2, and VIN+ = 12 V (unless otherwise noted)
710
400
705
350
695
Quiescent Current (PA)
Quiescent Current (PA)
700
690
685
680
675
670
665
300
250
200
660
655
650
-50
-25
0
25
50
75
Temperature (qC)
100
125
150
-5
150
1450
700
1350
650
1250
600
550
500
450
400
5
10
15
20
Common-Mode Voltage (V)
25
30
D031
Figure 26. IQ vs Common-Mode Voltage (INA181-Q1)
750
Quiescent Current (PA)
Quiescent Current (PA)
Figure 25. Quiescent Current vs Temperature (INA4181-Q1)
1150
1050
950
850
750
650
350
300
-5
0
D038
0
5
10
15
20
Common-Mode Voltage (V)
25
550
-5
30
D031
Figure 27. IQ vs Common-Mode Voltage (INA2181-Q1)
0
5
10
15
20
Common-Mode Voltage (V)
25
30
D039
Figure 28. IQ vs Common-Mode Voltage (INA4181-Q1)
80
70
60
Referred-to-Input
Voltage Noise (200 nV/div)
Input-Referred Voltage Noise (nV/—Hz)
100
50
40
30
20
10
10
100
1k
10k
Frequency (Hz)
100k
D025
D024
Figure 29. Input-Referred Voltage Noise vs Frequency
(A3 Devices)
12
Time (1 s/div)
1M
Figure 30. 0.1-Hz to 10-Hz Voltage Noise (Referred-to-Input)
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Typical Characteristics (continued)
VCM
VOUT
VOUT (100 mV/div)
Input Voltage
40 mV/div
Common-Mode Voltage (5 V/div)
Output Voltage
2 V/div
at TA = 25°C, VS = 5 V, VREF = VS / 2, and VIN+ = 12 V (unless otherwise noted)
Time (25 Ps/div)
Time (10 Ps/div)
D027
D026
80-mVPP input step
Figure 31. Step Response
Figure 32. Common-Mode Voltage Transient Response
Voltage (2 V/div)
Noninverting Input
Output
Voltage (2 V/div)
Inverting Input
Output
0V
0V
Time (250 Ps/div)
Time (250 Ps/div)
D028
D029
Figure 33. Inverting Differential Input Overload
Figure 34. Noninverting Differential Input Overload
Supply Voltage
Output Voltage
Voltage (1 V/div)
Voltage (1 V/div)
Supply Voltage
Output Voltage
0V
0V
Time (100 Ps/div)
Time (10 Ps/div)
D032
D030
Figure 35. Start-Up Response
Figure 36. Brownout Recovery
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Typical Characteristics (continued)
at TA = 25°C, VS = 5 V, VREF = VS / 2, and VIN+ = 12 V (unless otherwise noted)
200
100
50
140
A1
A2
A3
A4
20
10
5
2
1
0.5
0.2
0.1
10
120
110
100
90
80
100
1k
10k
100k
Frequency (Hz)
1M
10M
D033
70
100
1k
10k
Frequency (Hz)
100k
1M
D034
Figure 38. Channel Separation vs Frequency (INA2181-Q1)
Figure 37. Output Impedance vs Frequency
14
Ch1 onto Ch2
Ch2 onto Ch1
130
Channel Separation (dB)
Output Impedance (:)
1000
500
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8 Detailed Description
8.1 Overview
The INA181-Q1, INA2181-Q1, and INA4181-Q1 (INAx181-Q1) are automotive-grade, 26-V common-mode,
current-sensing amplifiers used in both low-side and high-side configurations. These specially-designed, currentsensing amplifiers accurately measure voltages developed across current-sensing resistors on common-mode
voltages that far exceed the supply voltage powering the device. Current can be measured on input voltage rails
as high as 26 V, and the devices can be powered from supply voltages as low as 2.7 V.
8.2 Functional Block Diagrams
VS
Single-Channel
TI Device
IN±
±
OUT
+
IN+
REF
GND
Figure 39. INA181-Q1 Functional Block Diagram
VS
Dual-Channel
TI Device
IN±1
±
OUT1
+
REF1
IN+1
IN±2
±
OUT2
+
REF2
IN+2
GND
Figure 40. INA2181-Q1 Functional Block Diagram
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Functional Block Diagrams (continued)
VS
Quad-Channel
TI Device
IN±1
±
OUT1
+
REF1
IN+1
IN±2
±
OUT2
+
REF2
IN+2
IN±3
±
OUT3
+
REF3
IN+3
IN±4
±
OUT4
+
REF4
IN+4
GND
Figure 41. INA4181-Q1 Functional Block Diagram
16
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8.3 Feature Description
8.3.1 High Bandwidth and Slew Rate
The INAx181-Q1 support small-signal bandwidths as high as 350 kHz, and large-signal slew rates of 2 V/µs. The
ability to detect rapid changes in the sensed current, as well as the ability to quickly slew the output, make the
INAx181-Q1 a good choice for applications that require a quick response to input current changes. One
application that requires high bandwidth and slew rate is low-side motor control, where the ability to follow rapid
changing current in the motor allows for more accurate control over a wider operating range. Another application
that requires higher bandwidth and slew rates is system fault detection, where the INAx181-Q1 are used with an
external comparator and a reference to quickly detect when the sensed current is out of range.
8.3.2 Bidirectional Current Monitoring
The INA181-Q1 senses current flow through a sense resistor in both directions. The bidirectional current-sensing
capability is achieved by applying a voltage at the REF pin to offset the output voltage. A positive differential
voltage sensed at the inputs results in an output voltage that is greater than the applied reference voltage;
likewise, a negative differential voltage at the inputs results in output voltage that is less than the applied
reference voltage. The output voltage of the current-sense amplifier is shown in Equation 1.
VOUT
I LOAD u RSENSE u GAIN
VREF
where
•
•
•
•
ILOAD is the load current to be monitored.
RSENSE is the current-sense resistor.
GAIN is the gain option of the selected device.
VREF is the voltage applied to the REF pin.
(1)
8.3.3 Wide Input Common-Mode Voltage Range
The INAx181-Q1 support input common-mode voltages from –0.2 V to +26 V. Because of the internal topology,
the common-mode range is not restricted by the power-supply voltage (VS) as long as VS stays within the
operational range of 2.7 V to 5.5 V. The ability to operate with common-mode voltages greater or less than VS
allow the INAx181-Q1 to be used in high-side, as well as low-side, current-sensing applications, as shown in
Figure 42.
Bus Supply
±0.2 V to +26 V
Direction of Positive
Current Flow
IN+
High-Side Sensing
Common-mode voltage (VCM)
is bus-voltage dependent.
RSENSE
IN±
LOAD
Direction of Positive
Current Flow
IN+
RSENSE
Low-Side Sensing
Common-mode voltage (VCM)
is always near ground and is
isolated from bus-voltage spikes.
IN±
Figure 42. High-Side and Low-Side Sensing Connections
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Feature Description (continued)
8.3.4 Precise Low-Side Current Sensing
When used in low-side current sensing applications the offset voltage of the INAx181-Q1 is within ±150 µV. The
low offset performance of the INAx181-Q1 has several benefits. First, the low offset allows these devices to be
used in applications that must measure current over a wide dynamic range. In this case, the low offset improves
the accuracy when the sensed currents are on the low end of the measurement range. Another advantage of low
offset is the ability to sense lower voltage drop across the sense resistor accurately, thus allowing a lower-value
shunt resistor. Lower-value shunt resistors reduce power loss in the current sense circuit, and help improve the
power efficiency of the end application.
The gain error of the INAx181-Q1 is specified to be within 1% of the actual value. As the sensed voltage
becomes much larger than the offset voltage, this voltage becomes the dominant source of error in the current
sense measurement.
8.3.5 Rail-to-Rail Output Swing
The INAx181-Q1 allow linear current sensing operation with the output close to the supply rail and GND. The
maximum specified output swing to the positive rail is 30 mV, and the maximum specified output swing to GND is
only 5 mV. In order to compare the output swing of the INAx181-Q1 to an equivalent operational amplifier (op
amp), the inputs are overdriven to approximate the open-loop condition specified in op amp data sheets. The
current-sense amplifier is a closed-loop system; therefore, the output swing to GND can be limited by the product
of the offset voltage and amplifier gain during unidirectional operation (VREF = 0 V).
For devices that have positive offset voltages, the swing to GND is limited by the larger of either the offset
voltage multiplied by the gain or the swing to GND specified in the Electrical Characteristics table.
For example, in an application where the INA181A4-Q1 (gain = 200 V/V) is used for low-side current sensing and
the device has an offset of 40 µV, the product of the device offset and gain results in a value of 8 mV, greater
than the specified negative swing value. Therefore, the swing to GND for this example is 8 mV. If the same
device has an offset of –40 µV, then the calculated zero differential signal is –8 mV. In this case, the offset helps
overdrive the swing in the negative direction, and swing performance is consistent with the value specified in the
Electrical Characteristics table.
The offset voltage is a function of the common-mode voltage as determined by the CMRR specification;
therefore, the offset voltage increases when higher common-mode voltages are present. The increase in offset
voltage limits how low the output voltage can go during a zero-current condition when operating at higher
common-mode voltages with VREF = 0 V . The typical limitation of the zero-current output voltage vs commonmode voltage for each gain option is shown in Figure 43.
0.06
A1
A2
A3
A4
Zero Current Output Voltage (V)
0.054
0.048
0.042
0.036
0.03
0.024
0.018
0.012
0.006
0
0
2
4
6
8 10 12 14 16 18 20 22 24 26
Common Mode Voltage (V)
D033
Figure 43. Zero-Current Output Voltage vs Common-Mode Voltage
18
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8.4 Device Functional Modes
8.4.1 Normal Mode
The INAx181-Q1 are in normal operation when the following conditions are met:
• The power supply voltage (VS) is between 2.7 V and 5.5 V.
• The common-mode voltage (VCM) is within the specified range of –0.2 V to +26 V.
• The maximum differential input signal times gain plus VREF is less than VS minus the output voltage swing to
VS.
• The minimum differential input signal times gain plus VREF is greater than the swing to GND (see the Rail-toRail Output Swing section).
During normal operation, these devices produce an output voltage that is the gained-up representation of the
difference voltage from IN+ to IN– plus the reference voltage at VREF.
8.4.2 Unidirectional Mode
These devices can be configured to monitor current flowing in one direction (unidirectional) or in both directions
(bidirectional) depending on how the REF pin is configured. The most common case is unidirectional where the
output is set to ground when no current is flowing by connecting the REF pin to ground, as shown in Figure 44.
When the current flows from the bus supply to the load, the input signal across IN+ to IN– increases, and causes
the output voltage at the OUT pin to increase.
Bus Voltage
±0.2 V to +26 V
Power Supply, VS
2.7 V to 5.5 V
CBYPASS
0.1 µF
RSENSE
Load
Single-Channel
TI Device
VS
IN±
OUT
±
Output
+
IN+
REF
GND
Figure 44. Unidirectional Application
The linear range of the output stage is limited by how close the output voltage can approach ground under zero
input conditions. In unidirectional applications where measuring very low input currents is desirable, bias the REF
pin to a convenient value above 50 mV to get the output into the linear range of the device. To limit commonmode rejection errors, buffer the reference voltage connected to the REF pin.
A less-frequently used output biasing method is to connect the REF pin to the power-supply voltage, VS. This
method results in the output voltage saturating at 200 mV less than the supply voltage when no differential input
signal is present. This method is similar to the output saturated low condition with no input signal when the REF
pin is connected to ground. The output voltage in this configuration only responds to negative currents that
develop negative differential input voltage relative to the device IN– pin. Under these conditions, when the
differential input signal increases negatively, the output voltage moves downward from the saturated supply
voltage. The voltage applied to the REF pin must not exceed VS.
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Device Functional Modes (continued)
8.4.3 Bidirectional Mode
The INAx181-Q1 are bidirectional, current-sense amplifiers capable of measuring currents through a resistive
shunt in two directions. This bidirectional monitoring is common in applications that include charging and
discharging operations where the current flowing through the resistor can change directions.
Bus Voltage
±0.2 V to +26 V
Power Supply, VS
2.7 V to 5.5 V
CBYPASS
0.1 µF
RSENSE
Load
Single-Channel
TI Device
VS
Reference
Voltage
IN±
±
OUT
Output
+
IN+
REF
+
GND
±
Figure 45. Bidirectional Application
The ability to measure this current flowing in both directions is enabled by applying a voltage to the REF pin, as
shown in Figure 45. The voltage applied to REF (VREF) sets the output state that corresponds to the zero-input
level state. The output then responds by increasing above VREF for positive differential signals (relative to the IN–
pin) and responds by decreasing below VREF for negative differential signals. This reference voltage applied to
the REF pin can be set anywhere between 0 V to VS. For bidirectional applications, VREF is typically set at midscale for equal signal range in both current directions. In some cases, however, VREF is set at a voltage other
than mid-scale when the bidirectional current and corresponding output signal do not need to be symmetrical.
8.4.4 Input Differential Overload
If the differential input voltage (VIN+ – VIN–) times gain exceeds the voltage swing specification, the INAx181-Q1
drive the output as close as possible to the positive supply or ground, and does not provide accurate
measurement of the differential input voltage. If this input overload occurs during normal circuit operation, then
reduce the value of the shunt resistor or use a lower-gain version with the chosen sense resistor to avoid this
mode of operation. If a differential overload occurs in a fault event, then the output of the INAx181-Q1 returns to
the expected value approximately 20 µs after the fault condition is removed.
20
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Device Functional Modes (continued)
8.4.5 Shutdown Mode
Although the INAx181-Q1 do not have a shutdown pin, the low power consumption of these devices allows the
output of a logic gate or transistor switch to power the INAx181-Q1. This gate or switch turns on and off the
INAx181-Q1 power-supply quiescent current.
However, in current shunt monitoring applications, there is also a concern for how much current is drained from
the shunt circuit in shutdown conditions. Evaluating this current drain involves considering the simplified
schematic of the INAx181-Q1 in shutdown mode, as shown in Figure 46.
VS
2.7 V to 5.5 V
RPULL-UP
10 k
Bus Voltage
±0.2 V to +26 V
Shutdown
RSENSE
Load
CBYPASS
0.1 µF
VS
Single-Channel
TI Device
IN±
OUT
Output
±
+
IN+
REF
GND
Figure 46. Basic Circuit to Shut Down the INA181-Q1 With a Grounded Reference
There is typically more than 500 kΩ of impedance (from the combination of 500-kΩ feedback and
input gain set resistors) from each input of the INAx181-Q1 to the OUT pin and to the REF pin. The amount of
current flowing through these pins depends on the voltage at the connection. For example, if the REF pin is
grounded, the calculation of the effect of the 500 kΩ impedance from the shunt to ground is straightforward.
However, if the reference is powered while the INAx181-Q1 is in shutdown mode, instead of assuming 500 kΩ to
ground, assume 500 kΩ to the reference voltage.
Regarding the 500-kΩ path to the output pin, the output stage of a disabled INAx181-Q1 does constitute a good
path to ground. Consequently, this current is directly proportional to a shunt common-mode voltage present
across a 500-kΩ resistor.
As a final note, as long as the shunt common-mode voltage is greater than VS when the device is powered up,
there is an additional and well-matched 55-µA typical current that flows in each of the inputs. If less than VS, the
common-mode input currents are negligible, and the only current effects are the result of the 500-kΩ resistors.
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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
The INAx181-Q1 amplify the voltage developed across a current-sensing resistor as current flows through the
resistor to the load or ground. The ability to drive the reference pin to adjust the functionality of the output signal
offers multiple configurations, as discussed in previous sections.
9.1.1 Basic Connections
Figure 47 shows the basic connections of the INA181-Q1. Connect the input pins (IN+ and IN–) as closely as
possible to the shunt resistor to minimize any resistance in series with the shunt resistor.
Bus Voltage
±0.2 V to +26 V
Power Supply, VS
2.7 V to 5.5 V
CBYPASS
0.1 µF
RSENSE
Load
VS
Single-Channel
TI Device
IN±
Microcontroller
OUT
±
ADC
+
IN+
REF
GND
NOTE: To help eliminate ground offset errors between the device and the analog-to-digital converter (ADC), connect
the REF pin to the ADC reference input and then to ground. For best performance, use an RC filter between the
output of the INAx181-Q1 and the ADC. See Closed-Loop Analysis of Load-Induced Amplifier Stability Issues Using
ZOUT for more details.
Figure 47. Basic Connections for the INA181-Q1
A power-supply bypass capacitor of at least 0.1 µF is required for proper operation. Applications with noisy or
high-impedance power supplies may require additional decoupling capacitors to reject power-supply noise.
Connect bypass capacitors close to the device pins.
22
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Application Information (continued)
9.1.2 RSENSE and Device Gain Selection
The accuracy of the INAx181-Q1 is maximized by choosing the current-sense resistor to be as large as possible.
A large sense resistor maximizes the differential input signal for a given amount of current flow and reduces the
error contribution of the offset voltage. However, there are practical limits as to how large the current-sense
resistor can be in a given application. The INAx181-Q1 have typical input bias currents of 75 µA for each input
when operated at a 12-V common-mode voltage input. When large current-sense resistors are used, these bias
currents cause increased offset error and reduced common-mode rejection. Therefore, using current-sense
resistors larger than a few ohms is generally not recommended for applications that require current-monitoring
accuracy. A second common restriction on the value of the current-sense resistor is the maximum allowable
power dissipation that is budgeted for the resistor. Equation 2 gives the maximum value for the current sense
resistor for a given power dissipation budget:
PDMAX
RSENSE
IMAX2
where:
•
•
PDMAX is the maximum allowable power dissipation in RSENSE.
IMAX is the maximum current that will flow through RSENSE.
(2)
An additional limitation on the size of the current-sense resistor and device gain is due to the power-supply
voltage, VS, and device swing to rail limitations. In order to make sure that the current-sense signal is properly
passed to the output, both positive and negative output swing limitations must be examined. Equation 3 provides
the maximum values of RSENSE and GAIN to keep the device from hitting the positive swing limitation.
IMAX u RSENSE u GAIN VSP VREF
where:
•
•
•
•
IMAX is the maximum current that will flow through RSENSE.
GAIN is the gain of the current sense-amplifier.
VSP is the positive output swing as specified in the data sheet.
VREF is the externally applied voltage on the REF pin.
(3)
To avoid positive output swing limitations when selecting the value of RSENSE, there is always a trade-off between
the value of the sense resistor and the gain of the device under consideration. If the sense resistor selected for
the maximum power dissipation is too large, then it is possible to select a lower-gain device in order to avoid
positive swing limitations.
The negative swing limitation places a limit on how small of a sense resistor can be used in a given application.
Equation 4 provides the limit on the minimum size of the sense resistor.
IMIN u RSENSE u GAIN > VSN VREF
where:
•
•
•
•
IMIN is the minimum current that will flow through RSENSE.
GAIN is the gain of the current sense amplifier.
VSN is the negative output swing of the device (see Rail-to-Rail Output Swing).
VREF is the externally applied voltage on the REF pin.
(4)
In addition to adjusting the offset and gain, the voltage applied to the REF pin can be slightly increased to avoid
negative swing limitations.
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Application Information (continued)
9.1.3 Signal Filtering
Provided that the INAx181-Q1 output is connected to a high impedance input, the best location to filter is at the
device output using a simple RC network from OUT to GND. Filtering at the output attenuates high-frequency
disturbances in the common-mode voltage, differential input signal, and INAx181-Q1 power-supply voltage. If
filtering at the output is not possible, or filtering of only the differential input signal is required, it is possible to
apply a filter at the input pins of the device. Figure 48 provides an example of how a filter can be used on the
input pins of the device.
Bus Voltage
±0.2 V to +26 V
RSENSE
Load
f
VS
2.7 V to 5.5 V
1
3dB
2S(RF
RF )CF
VS
Single-Channel
TI Device
RINT
IN±
RF < 10
f±3dB
CF
±
OUT
VOUT
REF
VREF
Bias
+
RF < 10
IN+
RINT
Figure 48. Filter at Input Pins
The addition of external series resistance creates an additional error in the measurement; therefore, the value of
these series resistors must be kept to 10 Ω (or less, if possible) to reduce impact to accuracy. The internal bias
network shown in Figure 48 present at the input pins creates a mismatch in input bias currents when a
differential voltage is applied between the input pins. If additional external series filter resistors are added to the
circuit, the mismatch in bias currents results in a mismatch of voltage drops across the filter resistors. This
mismatch creates a differential error voltage that subtracts from the voltage developed across the shunt resistor.
This error results in a voltage at the device input pins that is different than the voltage developed across the
shunt resistor. Without the additional series resistance, the mismatch in input bias currents has little effect on
device operation. The amount of error these external filter resistors add to the measurement can be calculated
using Equation 6, where the gain error factor is calculated using Equation 5.
The amount of variance in the differential voltage present at the device input relative to the voltage developed at
the shunt resistor is based both on the external series resistance (RF) value as well as internal input resistor RINT,
as shown in Figure 48. The reduction of the shunt voltage reaching the device input pins appears as a gain error
when comparing the output voltage relative to the voltage across the shunt resistor. A factor can be calculated to
determine the amount of gain error that is introduced by the addition of external series resistance. Calculate the
expected deviation from the shunt voltage to what is measured at the device input pins is given using Equation 5:
1250 u RINT
Gain Error Factor
(1250 u RF ) (1250 u RINT ) (RF u RINT )
where:
•
•
24
RINT is the internal input resistor.
RF is the external series resistance.
(5)
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Application Information (continued)
With the adjustment factor from Equation 5, including the device internal input resistance, this factor varies with
each gain version, as shown in Table 1. Each individual device gain error factor is shown in Table 2.
Table 1. Input Resistance
PRODUCT
GAIN
RINT (kΩ)
INAx181A1-Q1
20
25
INAx181A2-Q1
50
10
INAx181A3-Q1
100
5
INAx181A4-Q1
200
2.5
Table 2. Device Gain Error Factor
PRODUCT
SIMPLIFIED GAIN ERROR FACTOR
INAx181A1-Q1
25000
(21u RF ) 25000
INAx181A2-Q1
10000
(9 u RF ) 10000
INAx181A3-Q1
1000
RF 1000
INAx181A4-Q1
2500
(3 u RF ) 2500
The gain error that can be expected from the addition of the external series resistors can then be calculated
based on Equation 6:
Gain Error (%) = 100 - (100 ´ Gain Error Factor)
(6)
For example, using an INA181A2-Q1 and the corresponding gain error equation from Table 2, a series
resistance
of
10 Ω results in a gain error factor of 0.991. The corresponding gain error is then calculated using Equation 6,
resulting in an additional gain error of approximately 0.89% solely because of the external 10-Ω series resistors.
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9.1.4 Summing Multiple Currents
The outputs of the INA2181-Q1 are easily summed by connecting the output of one channel to the reference
input of a second channel. The circuit configuration shown in Figure 49 is an easy way to achieve current
summing. To correctly sum multiple output currents the values for the current sense resistor RSENSE must be the
same for all channels.
Power
Supply
Dual-Channel
TI Device
REF1
IN+1
+
RSENSE
OUT1
±
IN±1
LOAD1
REF2
IN+2
+
OUT2
ADC
RSENSE
±
VOUT2 = (ILOAD1 + ILOAD2) × RSENSE × GAIN
IN±2
LOAD2
GND
Figure 49. Summing Multiple Currents
Connect the output of one channel of the INA2181-Q1 to the reference input of the other channel. Use the
reference input of the first circuit to set the reference of the final summed output operating point. The currents
sensed at each circuit in the chain are summed at the output of the last device in the chain.
26
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An example output response of a summing configuration is shown in Figure 50. The reference pin of the first
circuit is connected to ground, and sine waves at different frequencies are applied to the two circuits to produce a
summed output as shown. The sine wave voltage input for the first circuit is offset so that the whole wave is
above GND.
20 mV/div
1 V/div
Output
Inputs
Time (4 ms/div)
VREF = 0 V
Figure 50. Current Summing Application Output Response (A2 Devices)
9.1.5 Detecting Leakage Currents
Occasionally, the need arises to confirm that the current going into a load is identical to the current coming out of
a load; usually, as part of diagnostic testing or fault detection. This situation requires precision current
differencing, which is the same as summing, except that the two amplifiers have the inputs connected opposite of
each other. To correctly detect leakage currents, the values for the current sense resistor RSENSE must be the
same for all channels. Also an external reference voltage must be provided to the REF1 input to allow
bidirectional leakage current detection.
If the current into a load is equal to the current out of the load, then the voltage at OUT2 is the same as the
applied voltage to REF1. To enable accurate differences between the two currents, a reference voltage must be
applied. The reference voltage prevents the output of the device from being driven to ground, and also enables
detection if the current into the load is either greater than or less than the current coming out of the load.
For current differencing, the dual-channel INA2181-Q1 must have the inputs connected opposite to each other,
as shown in Figure 51. The reference input of the first channel sets the output quiescent level for all the devices
in the string. Connect the output of the first channel to the reference input of the second channel. The reference
input of the first channel sets the reference at the output. This circuit example is identical to the current summing
example, except that the two shunt inputs are reversed in polarity. Under normal operating conditions, the final
output is very close to the reference value and proportional to any current difference. This current differencing
circuit is useful in detecting when current in to and out of a load do not match.
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Power
Supply
Dual-Channel
TI Device
REF1
IN+1
+
RSENSE
VREF1
OUT1
±
IN±1
LOAD
REF2
IN+2
+
OUT2
ADC
RSENSE
±
VOUT2 = VREF1 if there is no leakage current
IN±2
Figure 51. Detecting Leakage Currents
20 mV/div
1 V/div
An example output response of a difference configuration is shown in Figure 52. The reference pin of the first
channel is connected to a reference voltage of 2.048 V. The inputs to each circuit is a 100-Hz sine wave, 180°
out-of-phase with each other, resulting in a zero output as shown. The sine wave input to the first circuit is offset
so that the input wave is completely above GND.
Output
Inputs
Time (4 ms/div)
VREF = 2.048 V
Figure 52. Current Differencing Application Output Response (A2 Devices)
28
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9.2 Typical Application
One application for the INAx181-Q1 is to monitor bidirectional currents. Bidirectional currents are present in
systems that have to monitor currents in both directions; common examples are monitoring the charging and
discharging of batteries and bidirectional current monitoring in motor control. The device configuration for
bidirectional current monitoring is shown in Figure 53. Applying stable REF pin voltage closer to the middle of
device supply voltage allows both positive- and negative-current monitoring, as shown in this configuration.
Configure the INAx181-Q1 to monitor unidirectional currents by grounding the REF pin.
Bus Voltage
±0.2 V to +26 V
Power Supply, VS
2.7 V to 5.5 V
CBYPASS
0.1 µF
RSENSE
Load
Single-Channel
TI Device
VS
Reference
Voltage
IN±
±
OUT
Output
+
IN+
REF
+
±
GND
Figure 53. Measuring Bidirectional Current
9.2.1 Design Requirements
The design requirements for the circuit shown in Figure 53, are listed in Table 3
Table 3. Design Parameters
DESIGN PARAMETER
EXAMPLE VALUE
Power-supply voltage, VS
5V
Bus supply rail, VCM
12 V
RSENSE power loss
< 450 mW
Maximum sense current, IMAX
±20 A
Current sensing error
Less than 3.5% at maximum current, TJ = 25°C
Small-signal bandwidth
> 100 kHz
9.2.2 Detailed Design Procedure
The maximum value of the current sense resistor is calculated based on the maximum power loss requirement.
By applying Equation 2, the maximum value of the current-sense resistor is calculated to be 1.125 mΩ. This is
the maximum value for sense resistor RSENSE; therefore, select RSENSE to be 1 mΩ because it is the closest
standard resistor value that meets the power-loss requirement.
The next step is to select the appropriate gain and reduce RSENSE, if needed, to keep the output signal swing
within the VS range. The design requirements call for bidirectional current monitoring; therefore, a voltage
between 0 and VS must be applied to the REF pin. The bidirectional currents monitored are symmetric around 0
(that is, ±20 A); therefore, the ideal voltage to apply to VREF is VS / 2 or 2.5 V. If the positive current is greater
than the negative current, using a lower voltage on VREF has the benefit of maximizing the output swing for the
given range of expected currents. Using Equation 3, and given that IMAX = 20 A , RSENSE = 1 mΩ, and VREF = 2.5
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V, the maximum current-sense gain calculated to avoid the positive swing-to-rail limitations on the output is
122.5. Likewise, using Equation 4 for the negative-swing limitation results in a maximum gain of 124.75.
Selecting the gain-of-100 device maximizes the output range while staying within the output swing range. If the
maximum calculated gains are slightly less than 100, the value of the current-sense resistor can be reduced to
keep the output from hitting the output-swing limitations.
To calculate the accuracy at peak current, the two factors that must be determined are the gain error and the
offset error. The gain error of the INAx181-Q1 is specified to be a maximum of 1%. The error due to the offset is
constant, and is specified to be 500 µV (maximum) for the conditions where VCM = 12 V and VS = 5 V. Using
Equation 7, the percentage error contribution of the offset voltage is calculated to be 2.5%, with total offset error
= 500 µV, RSENSE = 1 mΩ, and ISENSE = 20 A.
Total Offset Error (V)
Total Offset Error (%) =
u 100%
ISENSE u RSENSE
(7)
One method of calculating the total error is to add the gain error to the percentage contribution of the offset error.
However, in this case, the gain error and the offset error do not have an influence or correlation to each other. A
more statistically accurate method of calculating the total error is to use the RSS sum of the errors, as shown in
Equation 8:
Total Error (%) = Total Gain Error (%)2 + Total Offset Error (%)2
(8)
After applying Equation 8, the total current sense error at maximum current is calculated to be 2.7%, and that is
less than the design example requirement of 3.5%.
The INA181A3-Q1 (gain = 100) also has a bandwidth of 150 kHz that meets the small-signal bandwidth
requirement of 100 kHz. If higher bandwidth is required, lower-gain devices can be used at the expense of either
reduced output voltage range or an increased value of RSENSE.
9.2.3 Application Curve
Output Voltage
(1 V/div)
An example output response of a bidirectional configuration is shown in Figure 54. With the REF pin connected
to a reference voltage (2.5 V in this case), the output voltage is biased upwards by this reference level. The
output rises above the reference voltage for positive differential input signals, and falls below the reference
voltage for negative differential input signals.
VOUT
VREF
0V
Time (500 µs/div)
C002
Figure 54. Bidirectional Application Output Response
30
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10 Power Supply Recommendations
The input circuitry of the INAx181-Q1 accurately measures beyond the power-supply voltage, VS. For example,
VS can be 5 V, whereas the bus supply voltage at IN+ and IN– can be as high as 26 V. However, the output
voltage range of the OUT pin is limited by the voltages on the VS pin. The INAx181-Q1 also withstand the full
differential input signal range up to 26 V at the IN+ and IN– input pins, regardless of whether or not the device
has power applied at the VS pin.
10.1 Common-Mode Transients Greater Than 26 V
With a small amount of additional circuitry, the INAx181-Q1 can be used in circuits subject to transients higher
than 26 V, such as automotive applications. Use only Zener diodes or Zener-type transient absorbers
(sometimes referred to as transzorbs)—any other type of transient absorber has an unacceptable time delay.
Start by adding a pair of resistors as a working impedance for the Zener diode; see Figure 55. Keep these
resistors as small as possible; most often, around 10 Ω. Larger values can be used with an effect on gain that is
discussed in the Signal Filtering section. This circuit limits only short-term transients; therefore, many applications
are satisfied with a 10-Ω resistor along with conventional Zener diodes of the lowest acceptable power rating.
This combination uses the least amount of board space. These diodes can be found in packages as small as
SOT-523 or SOD-523.
VS
2.7 V to 5.5 V
Bus Supply
±0.2 V to +26 V
CBYPASS
0.1 µF
RSENSE
Load
Single-Channel
TI Device
VS
IN±
±
RPROTECT
< 10
OUT
Output
+
REF
IN+
GND
Figure 55. Transient Protection Using Dual Zener Diodes
In the event that low-power Zener diodes do not have sufficient transient absorption capability, a higher-power
transzorb must be used. The most package-efficient solution involves using a single transzorb and back-to-back
diodes between the device inputs, as shown in Figure 56. The most space-efficient solutions are dual, seriesconnected diodes in a single SOT-523 or SOD-523 package. In either of the examples shown in Figure 55 and
Figure 56, the total board area required by the INAx181-Q1 with all protective components is less than that of an
SO-8 package, and only slightly greater than that of an MSOP-8 package.
VS
2.7 V to 5.5 V
Bus Supply
±0.2 V to +26 V
CBYPASS
0.1 µF
RSENSE
Load
Single-Channel
TI Device
< 10
VS
IN±
±
Transorb
OUT
Output
+
< 10
REF
IN+
GND
Figure 56. Transient Protection Using a Single Transzorb and Input Clamps
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Common-Mode Transients Greater Than 26 V (continued)
For more information, see Current Shunt Monitor With Transient Robustness Reference Design.
11 Layout
11.1 Layout Guidelines
•
•
•
Connect the input pins to the sensing resistor using a Kelvin or 4-wire connection. This connection technique
makes sure that only the current-sensing resistor impedance is detected between the input pins. Poor routing
of the current-sensing resistor commonly results in additional resistance present between the input pins.
Given the very low ohmic value of the current resistor, any additional high-current carrying impedance can
cause significant measurement errors.
Place the power-supply bypass capacitor as close as possible to the device power supply and ground pins.
The recommended value of this bypass capacitor is 0.1 µF. Additional decoupling capacitance can be added
to compensate for noisy or high-impedance power supplies.
When routing the connections from the current sense resistor to the device, keep the trace lengths as close
as possible in order to minimize any impedance mismatch..
11.2 Layout Example
Direction of Positive
Current Flow
RSHUNT
Bus Voltage
±0.2 V to 26 V
Connect REF to low
impedance voltage reference
or to GND pin if not used.
IN± 4
3 IN+
REF 4
2 GND
VS 5
1 OUT
Current
Sense
VIA to Ground
Plane
Power-Supply, VS
2.7 V to 5.5 V
CBYPASS
Figure 57. Single-Channel Recommended Layout
32
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Layout Example (continued)
Bus Voltage:
-0.2 V to 26 V
VIA to connect REF pins to low
impeda nce voltage referen ce or
to G ND pin if not use d.
VIA to
Gro und
Plan e
RSHU NT2
REF2 6
5 REF1
IN+2 5
4 GND
IN-2 6
3 IN+1
OUT2 7
2 IN-1
VS 8
1 OUT
Curren t Sense
Output 2
RSHU NT1
CBYPASS
Curren t Sense
Output 1
VS: 2.7 V to 5.5 V
Loa d2
Loa d1
Figure 58. Dual-Channel Recommended Layout
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Layout Example (continued)
Loa d2
Loa d3
Curren t Sense
Output 3
Curren t Sense
Output 2
Conne ct to GND or
Exte rnal Refe rence
NC 11
R SHU NT3
VIA to
Gro und
Plan e
Bus Voltage3:
-0.2 V to 26 V
10 NC
REF3 12
9 REF2
OUT3 13
8 OUT2
IN-3 14
7 IN-2
IN+3 15
6 IN+2
GND 16
5 VS
IN+4 17
4 IN+1
IN-4 18
3 IN-1
RSHU NT2
C BYPASS
Bus Voltage2:
-0.2 V to 26 V
OUT4 19
2 OUT1
REF4 20
1 REF1
Curren t Sense
Output 4
VIA to
Gro und
Plan e
VS: 2.7 V to 5.5 V
Curren t Sense
Output 1
Loa d1
Bus Voltage4:
-0.2 V to 26 V
RSHU NT4
Bus Voltage1:
-0.2 V to 26 V
RSHU NT1
Loa d4
Loa d1
Figure 59. Quad-Channel Recommended Layout
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12 Device and Documentation Support
12.1 Device Support
12.1.1 Development Support
Current Shunt Monitor With Transient Robustness Reference Design
12.2 Documentation Support
12.2.1 Related Documentation
For related documentation see the following:
• INA180-181EVM User's Guide
• INA2180-2181EVM User's Guide
• INA4180-4181EVM User's Guide
12.3 Related Links
Table 4 lists quick access links. Categories include technical documents, support and community resources,
tools and software, and quick access to order now.
Table 4. Related Links
PARTS
PRODUCT FOLDER
ORDER NOW
TECHNICAL
DOCUMENTS
TOOLS &
SOFTWARE
SUPPORT &
COMMUNITY
INA181-Q1 (preview)
N/A
N/A
N/A
N/A
N/A
INA2181-Q1
Click here
Click here
Click here
Click here
Click here
INA4181-Q1 (preview)
N/A
N/A
N/A
N/A
N/A
12.4 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.
12.5 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.
12.6 Trademarks
E2E is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
12.7 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.
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12.8 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.
36
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PACKAGE OPTION ADDENDUM
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PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
MSL Peak Temp
(2)
(6)
(3)
Op Temp (°C)
Device Marking
(4/5)
INA2181A1QDGSRQ1
ACTIVE
VSSOP
DGS
10
2500
Green (RoHS
& no Sb/Br)
CU NIPDAUAG
Level-2-260C-1 YEAR
-40 to 125
1O56
INA2181A2QDGSRQ1
ACTIVE
VSSOP
DGS
10
2500
Green (RoHS
& no Sb/Br)
CU NIPDAUAG
Level-2-260C-1 YEAR
-40 to 125
1O66
INA2181A3QDGSRQ1
ACTIVE
VSSOP
DGS
10
2500
Green (RoHS
& no Sb/Br)
CU NIPDAUAG
Level-2-260C-1 YEAR
-40 to 125
1O76
INA2181A4QDGSRQ1
ACTIVE
VSSOP
DGS
10
2500
Green (RoHS
& no Sb/Br)
CU NIPDAUAG
Level-2-260C-1 YEAR
-40 to 125
1O86
(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.
(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 <=1000ppm threshold. Antimony trioxide based
flame retardants must also meet the <=1000ppm threshold requirement.
(3)
MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4)
There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5)
Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
(6)
Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish
value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
19-May-2018
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
OTHER QUALIFIED VERSIONS OF INA2181-Q1 :
• Catalog: INA2181
NOTE: Qualified Version Definitions:
• Catalog - TI's standard catalog product
Addendum-Page 2
PACKAGE MATERIALS INFORMATION
www.ti.com
18-May-2018
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
B0
(mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
INA2181A1QDGSRQ1
VSSOP
DGS
10
2500
330.0
12.4
5.3
3.4
1.4
8.0
12.0
Q1
INA2181A2QDGSRQ1
VSSOP
DGS
10
2500
330.0
12.4
5.3
3.4
1.4
8.0
12.0
Q1
INA2181A3QDGSRQ1
VSSOP
DGS
10
2500
330.0
12.4
5.3
3.4
1.4
8.0
12.0
Q1
INA2181A4QDGSRQ1
VSSOP
DGS
10
2500
330.0
12.4
5.3
3.4
1.4
8.0
12.0
Q1
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
18-May-2018
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
INA2181A1QDGSRQ1
VSSOP
DGS
10
2500
366.0
364.0
50.0
INA2181A2QDGSRQ1
VSSOP
DGS
10
2500
366.0
364.0
50.0
INA2181A3QDGSRQ1
VSSOP
DGS
10
2500
366.0
364.0
50.0
INA2181A4QDGSRQ1
VSSOP
DGS
10
2500
366.0
364.0
50.0
Pack Materials-Page 2
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