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INA270, INA271
SBOS381E – FEBRUARY 2007 – REVISED JANUARY 2018
INA27x Voltage Output, Unidirectional Measurement Current-Shunt Monitor
1 Features
3 Description
•
•
•
The INA270 and INA271 family of voltage-output,
current-sense amplifiers can sense drops across
shunt resistors at common-mode voltages from –16 V
to +80 V, independent of the supply voltage. The
INA270 and INA271 pinouts readily enable filtering.
1
•
•
•
•
•
Wide Common-Mode Range: –16 V to +80 V
CMRR: 120 dB
Accuracy:
±0.5-mV Offset (typ)
±0.2% Gain Error (typ)
2.5 μV/°C Offset Drift (typ)
50 ppm/°C Gain Drift (max)
Bandwidth: Up to 130 kHz
Two Gain Options Available:
14 V/V (INA270)
20 V/V (INA271)
Quiescent Current: 700 μA (typ)
Power Supply: +2.7 V to +18 V
Provision for Filtering
The INA270 and INA271 are available with two gain
options: 14 V/V and 20 V/V. The 130-kHz bandwidth
simplifies use in current-control loops.
The INA270 and INA271 operate from a single +2.7-V
to +18-V supply, drawing 700 μA (typical) of supply
current. The devices are specified over the extended
operating temperature range of –40°C to +125°C and
are offered in an SOIC-8 package.
Device Information(1)
PART NUMBER
2 Applications
•
•
•
•
•
•
•
PACKAGE
INA27x
SOIC (8)
BODY SIZE (NOM)
4.90 mm × 3.91 mm
(1) For all available packages, see the orderable addendum at
the end of the datasheet.
Power Management
Automotive
Telecom Equipment
Notebook Computers
Battery Chargers
Cell Phones
Welding Equipment
Simplified Schematic
RS
-16V to +80V
Supply
Load
Single-Pole Filter
Capacitor
+2.7V to +18V
IN+
PRE OUT
IN5kW
BUF IN
V+
5kW
OUT
A1
96kW
A2
RL
INA270
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. PRODUCTION DATA.
INA270, INA271
SBOS381E – FEBRUARY 2007 – REVISED JANUARY 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
3
7.1
7.2
7.3
7.4
7.5
7.6
3
4
4
4
5
7
Absolute Maximum Ratings ......................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Typical Characteristics ..............................................
Detailed Description ............................................ 10
8.1 Overview ................................................................. 10
8.2 Functional Block Diagram ....................................... 10
8.3 Feature Description................................................. 11
8.4 Device Functional Modes........................................ 12
9
Application and Implementation ........................ 15
9.1 Application Information............................................ 15
9.2 Typical Application ................................................. 15
10 Power Supply Recommendations ..................... 17
10.1 Shutdown .............................................................. 17
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
Documentation Support ........................................
Related Links ........................................................
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
19
19
19
19
19
19
13 Mechanical, Packaging, and Orderable
Information ........................................................... 19
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision D (November 2014) to Revision E
Page
•
Added title to page 1 figure ................................................................................................................................................... 1
•
Updated ESD Ratings table to current standards ................................................................................................................. 4
•
Changed Figure 16: changed op amp input to BUF IN pin from negative to positive ......................................................... 12
•
Added Community Resources section ................................................................................................................................. 19
Changes from Revision C (May 2010) to Revision D
Page
•
Changed format to meet latest data sheet standards ............................................................................................................ 1
•
Added Handling Rating, Pin Descriptions, and Recommended Operating Conditions tables and Feature
Description, Device Functional Modes, Application and Implementation, Power Supply
Recommendations, Layout, Device and Documentation Support, and Mechanical, Packaging, and Orderable
Information sections................................................................................................................................................................ 1
•
Changed Accuracy and Quiescent Current Features bullets: changed from max specifications and values to typical......... 1
•
Changed wording in Two Gain Options Available Features bullet ........................................................................................ 1
•
Changed Description section for clarification ......................................................................................................................... 1
•
Added Device Information table ............................................................................................................................................. 1
•
Deleted Ordering Information table ........................................................................................................................................ 3
•
Changed Input, Full-Scale Input Voltage parameter conditions in Electrical Characteristics table........................................ 5
•
Changed title of First- or Second-Order Filtering section ..................................................................................................... 12
•
Changed title of Power Supply Recommendations section.................................................................................................. 17
Changes from Revision B (July 2008) to Revision C
Page
•
Corrected Figure 17 y-axis ................................................................................................................................................... 14
•
Corrected Figure 18 y-axis ................................................................................................................................................... 14
2
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SBOS381E – FEBRUARY 2007 – REVISED JANUARY 2018
5 Device Comparison Table
DEVICE
GAIN
INA270
14 V/V
INA271
20 V/V
6 Pin Configuration and Functions
D Package
SOIC-8
Top View
IN-
1
GND
2
8
IN+
7
NC
(1)
INA27x
PRE OUT
3
6
V+
BUF IN
4
5
OUT
NOTE (1): NC denotes no internal connection.
Pin Functions
PIN
NAME
I/O
NO.
DESCRIPTION
BUF IN
4
Analog input
GND
2
Analog
Connect to output of filter from PRE OUT
IN–
1
Analog input
Connect to load side of shunt resistor
IN+
8
Analog input
Connect to supply side of shunt resistor
NC
7
—
OUT
5
Analog output
Output voltage
PRE OUT
3
Analog output
Connect to input of filter to BUF IN
V+
6
Analog input
Ground
Connect to ground
Power supply, +2.7 V to +18 V
7 Specifications
7.1 Absolute Maximum Ratings (1)
MIN
Supply voltage (VS)
Analog inputs, VIN+, VIN–:
UNIT
+18
V
Differential, (VIN+) – (VIN–)
–18
+18
V
Common-mode
–16
+80
V
GND – 0.3
(V+) + 0.3
V
5
mA
–55
+150
°C
+150
°C
+150
°C
Analog output: OUT and PRE OUT pins
Input current into any pin
Operating temperature
Junction temperature
Storage temperature, Tstg
(1)
MAX
–65
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.
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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)
±750
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)
MIN
NOM
MAX
UNIT
VCM
Common-mode input voltage
–16
12
80
VS
Operating supply voltage
2.7
5
18
V
V
TA
Operating free-air temperature
–40
125
°C
7.4 Thermal Information
INA27x
THERMAL METRIC (1)
D (SOIC)
UNIT
8 PINS
RθJA
Junction-to-ambient thermal resistance
78.8
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
71.6
°C/W
RθJB
Junction-to-board thermal resistance
68.2
°C/W
ψJT
Junction-to-top characterization parameter
22.0
°C/W
ψJB
Junction-to-board characterization parameter
67.6
°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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SBOS381E – FEBRUARY 2007 – REVISED JANUARY 2018
7.5 Electrical Characteristics
At TA = +25°C, VS = +5 V, VCM = +12 V, VSENSE = 100 mV, and PRE OUT connected to BUF IN, unless otherwise noted.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
INPUT
VSENSE
Full-scale input voltage
VSENSE = (VIN+) – (VIN–)
VCM
Common-mode input range
TA = –40°C to +125°C
–16
CMRR
Common-mode rejection ratio
VIN+ = –16 V to +80 V
80
120
dB
CMRR over temperature
VIN+ = +12 V to +80 V, TA = –40°C to
+125°C
100
120
dB
Offset voltage, RTI (1)
VOS
TA = –40°C to +125°C
dVOS/dT
VOS vs temperature
TA = –40°C to +125°C
PSR
VOS vs power-supply
VS = +2.7 V to +18 V, VCM = +18 V,
TA = –40°C to +125°C
IB
Input bias current, VIN– pin
TA = –40°C to +125°C
(2)
Buffer input bias current
Buffer input bias current temperature
coefficient
OUTPUT (VSENSE ≥ 20mV)
V
2.5
mV
±3
mV
2.5
20
μV/°C
5
100
μV/V
±8
±16
μA
96
kΩ
–50
nA
±0.03
nA/°C
(3)
G
Gain
GBUF
Output buffer gain
INA270 total gain
14
V/V
INA271 total gain
20
V/V
2
Total gain error
VSENSE = 20 mV to 100 mV
Total gain error Over temperature
TA = –40°C to +125°C
Total gain error vs temperature
TA = –40°C to +125°C
Total output error (4)
RO
V
+80
±0.5
VOS over temperature
PRE OUT output impedance
0.15 (VS – 0.2) / Gain
Total output error
TA = –40°C to +125°C
Nonlinearity error
VSENSE = 20 mV to 100 mV
Output impedance, pin 5
Maximum capacitive load
No sustained oscillation
±0.2%
V/V
±1%
±2%
50
±0.75%
±2.2%
±1.0%
±3.0%
ppm/°C
±0.002%
1.5
Ω
10
nF
VOLTAGE OUTPUT (5) (RL = 10 kΩ to GND)
Swing to V+ power-supply rail
TA = –40°C to +125°C
(V+) – 0.05
(V+) – 0.2
V
Swing to GND (6)
TA = –40°C to +125°C
VGND + 0.003
VGND + 0.05
V
FREQUENCY RESPONSE
BW
SR
tS
(1)
(2)
(3)
(4)
(5)
(6)
Bandwidth
CLOAD = 5 pF
130
kHz
Phase margin
CLOAD < 10 nF
40
Degrees
1
V/μs
2
μs
Slew rate
Settling time (1%)
VSENSE = 10 mV to 100 mVPP,
CLOAD = 5 pF
RTI means Referred-to-Input.
Initial resistor variation is ±30% with an additional –2200-ppm/°C temperature coefficient.
For output behavior when VSENSE < 20 mV, see the Accuracy Variations as a Result of VSENSE and Common-Mode Voltage section.
Total output error includes effects of gain error and VOS.
See typical characteristic curve Output Swing vs Output Current and the Accuracy Variations as a Result of VSENSE and Common-Mode
Voltage section.
Ensured by design; not production tested.
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Electrical Characteristics (continued)
At TA = +25°C, VS = +5 V, VCM = +12 V, VSENSE = 100 mV, and PRE OUT connected to BUF IN, unless otherwise noted.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
NOISE, RTI (1)
en
Voltage noise density
40
nV/√Hz
POWER SUPPLY
VS
Operating range
TA = –40°C to +125°C
+18
V
IQ
Quiescent current
VOUT = 2 V
+2.7
700
900
μA
IQ over temperature
VSENSE = 0 mV, TA = –40°C to +125°C
350
950
μA
+125
°C
TEMPERATURE RANGE
θJA
6
Specified temperature range
–40
Operating temperature range
–55
Thermal resistance, SO-8
+150
150
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°C
°C/W
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7.6 Typical Characteristics
At TA = +25°C, VS = +12 V, VCM = 12 V, and VSENSE = 100 mV, unless otherwise noted.
45
40
35
35
Gain (dB)
40
30
Gain (dB)
45
CLOAD = 1000pF
G = 20
25
G = 14
20
30
G = 20
25
G = 14
20
15
15
10
10
5
CLOAD = 0pF
5
10k
100k
10k
1M
100k
Frequency (Hz)
Figure 1. Gain vs Frequency
20
Figure 2. Gain vs Frequency
140
VS = 18V
18
Common-Mode and
Power-Supply Rejection (dB)
130
16
VOUT (V)
14
20V/V
12
10
8
14V/V
6
4
2
120
CMRR
110
100
90
PSR
80
70
60
50
1300
1200
1000
1100
800
900
700
500
600
300
400
200
0
100
0
40
10
100
1k
VSENSE (mV)
10k
100k
Frequency (Hz)
Figure 3. Gain Plot
Figure 4. Common-Mode and Power-Supply Rejection vs
Frequency
4.0
0.10
3.5
0.09
0.08
3.0
Output Error (%)
Total Output Error
(% error of the ideal output value)
1M
Frequency (Hz)
2.5
2.0
1.5
1.0
0.07
0.06
0.05
0.04
0.03
0.02
0.5
0.01
0
0
50
100 150
200
250 300
350 400 450 500
0
-16 -12 -8 -4
VSENSE (mV)
0
4
8
12 16 20
...
76 80
Common-Mode Voltage (V)
Figure 5. Total Output Error vs VSENSE
Figure 6. Output Error vs Common-Mode Voltage
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Typical Characteristics (continued)
At TA = +25°C, VS = +12 V, VCM = 12 V, and VSENSE = 100 mV, unless otherwise noted.
1000
12
11
10
800
Sourcing Current
9
+25°C
8
700
-40°C
+125°C
7
6
VS = 3V
5
Sourcing Current
+25°C
4
-40°C
2
+125°C
0
0
500
400
300
Output stage is designed
to source current. Current
sinking capability is
approximately 400mA.
3
1
600
IQ (mA)
Output Voltage (V)
900
VS = 12V
200
100
0
5
10
20
15
25
30
0
2
1
3
4
Output Current (mA)
Figure 7. Positive Output Voltage Swing vs Output Current
34
VSENSE = 100mV:
VS = 12V
VS = 2.7V
775
IQ (mA)
675
575
475
VS = 12V
375
7
6
VSENSE = 0mV:
8
9
10
Figure 8. Quiescent Current vs Output Voltage
VS = 2.7V
275
Output Short-Circuit Current (mA)
875
5
Output Voltage (V)
175
-40°C
30
+25°C
26
+125°C
22
18
14
10
6
-16 -12 -8 -4
0
4
8
12 16
20
...
76 80
2.5 3.5
4.5
5.5 6.5
7.5
8.5
9.5 10.5 11.5 17
18
VCM (V)
Supply Voltage (V)
Figure 9. Quiescent Current vs Common-Mode Voltage
Figure 10. Output Short-Circuit Current vs Supply Voltage
200
150
Gain (dB)
Population
Phase
100
50
Gain
80
82
84
86
88
90
92
94
96
98
100
102
104
106
108
110
112
114
116
118
120
0
-50
10
100
10k
100k
1M
10M
Frequency (Hz)
RPREOUT (kW)
Figure 11. PRE OUT Output Resistance Production
Distribution
8
1k
Figure 12. Buffer Gain vs Frequency
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Typical Characteristics (continued)
50mV/div
500mV/div
At TA = +25°C, VS = +12 V, VCM = 12 V, and VSENSE = 100 mV, unless otherwise noted.
10ms/div
10ms/div
Figure 13. Small-Signal Step Response
(10-mV to 20-mV Input)
Figure 14. Large-Signal Step Response
(10-mV to 100-mV Input)
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8 Detailed Description
8.1 Overview
The INA270 and INA271 family of current-shunt monitors with voltage output can sense drops across current
shunts at common-mode voltages from –16 V to +80 V, independent of the supply voltage. The INA270 and
INA271 pinouts readily enable filtering.
The INA270 and INA271 are available with two output voltage scales: 14 V/V and 20 V/V. The 130-kHz
bandwidth simplifies use in current-control loops.
The INA270 and INA271 operate from a single +2.7-V to +18-V supply, drawing a maximum of 900 μA of supply
current. The devices are specified over the extended operating temperature range of –40°C to +125°C and are
offered in an SOIC-8 package.
8.2 Functional Block Diagram
IN+
IN
PRE OUT
BUF IN
A1
V+
OUT
A2
GND
10
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8.3 Feature Description
8.3.1 Basic Connection
Figure 15 shows the basic connection of the INA270 and INA271. Connect the input pins (IN+ and IN–) as
closely as possible to the shunt resistor to minimize any resistance in series with the shunt resistance.
Power-supply bypass capacitors are required for stability. Applications with noisy or high-impedance power
supplies may require additional decoupling capacitors to reject power-supply noise. Place minimum bypass
capacitors of 0.01 μF and 0.1 μF in value close to the supply pins. Although not mandatory, an additional 10-mF
electrolytic capacitor placed in parallel with the other bypass capacitors may be useful in applications with
particularly noisy supplies.
RS
-16V to +80V
Supply
Load
Single-Pole Filter
Capacitor
+2.7V to +18V
IN+
PRE OUT
IN5kW
BUF IN
0.01mF
V+
0.1mF
5kW
OUT
A1
96kW
A2
RL
INA270
GND
Figure 15. INA270 Basic Connections
8.3.2 Selecting RS
The value chosen for the shunt resistor, RS, depends on the application and is a compromise between smallsignal accuracy and maximum permissible voltage loss in the measurement line. High values of RS provide better
accuracy at lower currents by minimizing the effects of offset, while low values of RS minimize voltage loss in the
supply line. For most applications, best performance is attained with an RS value that provides a full-scale shunt
voltage range of 50 mV to 100 mV. Maximum input voltage for accurate measurements is (VS – 0.2) / Gain.
8.3.3 Transient Protection
The –16-V to +80-V common-mode range of the INA270 and INA271 is ideal for withstanding automotive fault
conditions ranging from 12-V battery reversal up to +80-V transients because no additional protective
components are needed up to those levels. In the event that the INA270 and INA271 are exposed to transients
on the inputs in excess of their ratings, external transient absorption with semiconductor transient absorbers
(zeners or Transzorbs) are necessary.
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Feature Description (continued)
Use of MOVs or VDRs is not recommended except when they are used in addition to a semiconductor transient
absorber. Select the transient absorber such that it never allows the INA270 and INA271 to be exposed to
transients greater than 80 V (that is, allow for transient absorber tolerance, as well as additional voltage because
of transient absorber dynamic impedance). Despite the use of internal zener-type ESD protection, the INA270
and INA271 are not suited to using external resistors in series with the inputs because the internal gain resistors
can vary up to ±30%, but are tightly matched (if gain accuracy is not important, then resistors can be added in
series with the INA270 and INA271 inputs with two equal resistors on each input).
8.4 Device Functional Modes
8.4.1 First- or Second-Order Filtering
The output of the INA270 and INA271 is accurate within the output voltage swing range set by the power-supply
pin, V+.
The INA270 and INA271 readily enable the inclusion of filtering between the preamp output and buffer input.
Single-pole filtering can be accomplished with a single capacitor because of the 96-kΩ output impedance at PRE
OUT on pin 3, as shown in Figure 16a.
The INA270 and INA271 readily lend themselves to second-order Sallen-Key configurations, as shown in
Figure 16b. When designing these configurations consider that the PRE OUT 96-kΩ output impedance exhibits
an initial variation of ±30% with the addition of a –2200-ppm/°C temperature coefficient.
RS
Load
Supply
RS
Load
Supply
Second-Order, Sallen-Key Filter Connection
CFILT
Single-Pole Filter
Capacitor
CFILT
RS
+2.7V to +18V
IN+
PRE OUT
IN5kW
BUF IN
+2.7V to +18V
V+
IN+
5kW
5kW
Output
A1
BUF IN
V+
5kW
A1
96kW
A2
PRE OUT
IN-
Output
96kW
A2
RL
RL
INA270
INA270
GND
a) Single-Pole Filter
GND
b) Second-Order, Sallen-Key Filter
NOTE: Remember to use the appropriate buffer gain (INA270 = 1.4, INA271 = 2) when designing Sallen-Key configurations.
Figure 16. The INA270–INA271 can be Easily Connected for First- or Second-Order Filtering
12
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Device Functional Modes (continued)
8.4.2 Accuracy Variations as a Result of VSENSE and Common-Mode Voltage
The accuracy of the INA270 and INA271 current shunt monitors is a function of two main variables: VSENSE
(VIN+ – VIN–) and common-mode voltage (VCM) relative to the supply voltage, VS. VCM is expressed as (VIN+ +
VIN–) / 2; however, in practice, VCM is used as the voltage at VIN+ because the voltage drop across VSENSE is
usually small.
This section addresses the accuracy of these specific operating regions:
Normal Case 1: VSENSE ≥ 20 mV, VCM ≥ VS
Normal Case 2: VSENSE ≥ 20 mV, VCM < VS
Low VSENSE Case 1:
VSENSE < 20 mV, –16 V ≤ VCM < 0
Low VSENSE Case 2:
VSENSE < 20 mV, 0 V ≤ VCM ≤ VS
Low VSENSE Case 3:
VSENSE < 20 mV, VS < VCM ≤ 80 V
8.4.2.1 Normal Case 1: VSENSE ≥ 20 mV, VCM ≥ VS
This region of operation provides the highest accuracy. Here, the input offset voltage is characterized and
measured using a two-step method. First, the gain is determined by Equation 1.
VOUT1 - VOUT2
G=
100mV - 20mV
where
•
•
VOUT1 = Output voltage with VSENSE = 100 mV and
VOUT2 = Output voltage with VSENSE = 20 mV.
(1)
Then the offset voltage is measured at VSENSE = 100 mV and referred to the input (RTI) of the current shunt
monitor, as shown in Equation 2.
VOUT1
VOSRTI (Referred-To-Input) =
- 100mV
G
(2)
In the Typical Characteristics, the Output Error vs Common-Mode Voltage curve (Figure 6) shows the highest
accuracy for the this region of operation. In this plot, VS = 12 V; for VCM ≥ 12 V, the output error is at its
minimum. This case is also used to create the VSENSE ≥ 20 mV output specifications in the Electrical
Characteristics table.
8.4.2.2 Normal Case 2: VSENSE ≥ 20 mV, VCM < VS
This region of operation has slightly less accuracy than Normal Case 1 as a result of the common-mode
operating area in which the device functions, as illustrated in the Output Error vs Common-Mode Voltage curve
(Figure 6). As noted, for this graph VS = 12 V; for VCM < 12 V, the output error increases when VCM becomes less
than 12 V, with a typical maximum error of 0.005% at the most negative VCM = –16 V.
8.4.2.3 Low VSENSE Case 1: VSENSE < 20 mV, –16 V ≤ VCM < 0; and Low VSENSE Case 3: VSENSE < 20 mV,
VS < VCM ≤ 80 V
Although the INA270 family of devices are not designed for accurate operation in either of these regions, some
applications are exposed to these conditions. For example, when monitoring power supplies that are switched on
and off while VS is still applied to the INA270 or INA271, knowing what the behavior of the devices is in these
regions is important.
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Device Functional Modes (continued)
When VSENSE approaches 0 mV, in these VCM regions, the device output accuracy degrades. A larger-thannormal offset can appear at the current shunt monitor output with a typical maximum value of VOUT = 60 mV for
VSENSE = 0 mV. When VSENSE approaches 20 mV, VOUT returns to the expected output value with accuracy as
specified in the Electrical Characteristics. Figure 17 shows this effect using the INA271 (gain = 20).
0.40
0.36
0.32
VOUT (V)
0.28
0.24
Actual
0.20
0.16
Ideal
0.12
0.08
0.04
0
0
2
4
6
8
10
12
14
16
18
20
VSENSE (mV)
Figure 17. Example For Low VSENSE Cases 1 and 3 (INA271, Gain = 20)
8.4.2.4 Low VSENSE Case 2: VSENSE < 20 mV, 0 V ≤ VCM ≤ VS
This region of operation is the least accurate for the INA270 family. To achieve the wide input common-mode
voltage range, these devices use two op amp front ends in parallel. One op amp front end operates in the
positive input common-mode voltage range, and the other in the negative input region. For this case, neither of
these two internal amplifiers dominates and overall loop gain is very low. Within this region, VOUT approaches
voltages close to linear operation levels for Normal Case 2.
This deviation from linear operation becomes greatest the closer VSENSE approaches 0 V. Within this region,
when VSENSE approaches 20 mV, device operation is closer to that described by Normal Case 2. Figure 18
shows this behavior for the INA271. The VOUT maximum peak for this case is determined by maintaining a
constant VS, setting VSENSE = 0 mV, and sweeping VCM from 0 V to VS. The exact VCM at which VOUT peaks
during this case varies from device to device. The maximum peak voltage for the INA270 is 0.28 V; for the
INA271, the maximum peak voltage is 0.4 V.
0.48
0.44 INA271 VOUT Limit
(1)
VCM1
0.40
Ideal
0.36
VCM2
VOUT (V)
0.32
0.28
VCM3
0.24
0.20
0.16
VOUT limit at VSENSE = 0mV,
0 £ VCM1 £ VS
VCM4
0.12
VCM2, VCM3, and VCM4 illustrate the variance
from part to part of the VCM that can cause
maximum VOUT with VSENSE < 20mV.
0.08
0.04
0
0
2
4
6
8
10
12
14
16
18
20
22
24
VSENSE (mV)
NOTE: (1) INA271 VOUT Limit = 0.4V. INA270 VOUT Limit = 0.28V.
Figure 18. Example for Low VSENSE Case 2 (INA271, Gain = 20)
14
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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 INA270 and INA271 measures the voltage developed across a current-sensing resistor when current passes
through it. The ability to drive the reference terminal to adjust the functionality of the output signal offers multiple
configurations discussed throughout this section. There is also a filtering feature to remove unwanted transients
and smooth the output voltage.
9.2 Typical Application
RS
-16V to +80V
Supply
Load
Single-Pole Filter
Capacitor
+2.7V to +18V
IN+
PRE OUT
IN5kW
BUF IN
0.01mF
V+
0.1mF
5kW
OUT
A1
96kW
A2
RL
INA270
GND
Figure 19. Filtering Configuration
9.2.1 Design Requirements
In this application, the device is configured to measure a triangular periodic current at 10 kHz with filtering. The
average current through the shunt is the information that is desired. This current can be either solenoid current or
inductor current where current is being pulsed through.
Selecting the capacitor size is based on the lowest frequency component to be filtered out. The amount of signal
that is filtered out is dependant on this cutoff frequency. From the cutoff frequency, the attention is 20 dB per
decade.
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Typical Application (continued)
9.2.2 Detailed Design Procedure
Without this filtering capability, an input filter must be used. When series resistance is added to the input, large
errors also come into play because the resistance must be large to create a low cutoff frequency. By using a
10-nF capacitor for the single-pole filter capacitor, the 10-kHz signal is averaged. The cutoff frequency made by
the capacitor is set at 166 Hz frequency. This frequency is well below the periodic frequency and reduces the
ripple on the output and the average current can easily be measured.
9.2.3 Application Curves
Figure 20 shows the output waveform without filtering. The output signal tracks the input signal with a large
ripple. If this current is sampled by an ADC, many samples must be taken to average the current digitally. This
process takes additional time to sample and average and is very time consuming, thus is unwanted for this
application.
Figure 21 shows the output waveform with filtering. The output signal is filtered and the average can easily be
measured with a small ripple. If this current is sampled by an ADC, only a few samples must be taken to
average. Digital averaging is now not required and the time required is significantly reduced.
4.5
4
4
3.5
Output Voltage
Shunt and Output (V)
Shunt and Output (V)
5
4.5
3.5
Output Voltage
3
2.5
2
1.5
3
2.5
2
1.5
1
1
Shunt Voltage
Shunt Voltage
0.5
0.5
0
0
0
0.0002
0.0004
0.0006
100Ps/div
0.0008
0.001
0
0.0002
D001
Figure 20. Without Filtering
16
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0.0004
0.0006
100Ps/div
0.0008
0.001
D002
Figure 21. With Filtering
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10 Power Supply Recommendations
The input circuitry of the INA270 and INA271 can accurately measure beyond its power-supply voltage, V+. For
example, the V+ power supply can be 5 V, whereas the load power-supply voltage is up to +80 V. The output
voltage range of the OUT terminal, however, is limited by the voltages on the power-supply pin.
10.1 Shutdown
The INA270 and INA271 do not provide a shutdown pin; however, because these devices consume a quiescent
current less than 1 mA, they can be powered by either the output of logic gates or by transistor switches to
supply power. Driving the gate low shuts down the INA270 and INA271. Use a totem-pole output buffer or gate
that can provide sufficient drive along with a 0.1-μF bypass capacitor, preferably ceramic with good highfrequency characteristics. This gate must have a supply voltage of 3 V or greater because the INA270 and
INA271 require a minimum supply greater than 2.7 V. In addition to eliminating quiescent current, this gate also
turns off the 10-μA bias current present at each of the inputs. Note that the IN+ and IN– inputs are able to
withstand full common-mode voltage under all powered and under-powered conditions. An example shutdown
circuit is shown in Figure 22.
IL
RS
-16V to +80V
Supply
Single-Pole Filter
Capacitor
IN+
Negative
and
Positive
Common-Mode
Voltage
PRE OUT
IN5kW
Load
BUF IN
V+
5kW
V+ > 3V
OUT
A1
74HC04
0.1mF
96kW
A2
RL
INA270, INA271
GND
Figure 22. INA270–INA271 Example Shutdown Circuit
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11 Layout
11.1 Layout Guidelines
•
•
Connect the input pins to the sensing resistor using a Kelvin or 4-wire connection. This connection technique
ensures 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 closely as possible to the 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.
11.1.1 RFI and EMI
Attention to good layout practices is always recommended. Keep traces short and, when possible, use a printed
circuit board (PCB) ground plane with surface-mount components placed as close to the device pins as possible.
Small ceramic capacitors placed directly across amplifier inputs can reduce RFI and EMI sensitivity. PCB layout
must locate the amplifier as far away as possible from RFI sources. Sources can include other components in
the same system as the amplifier itself, such as inductors (particularly switched inductors handling a lot of current
and at high frequencies). RFI can generally be identified as a variation in offset voltage or dc signal levels with
changes in the interfering RF signal. If the amplifier cannot be located away from sources of radiation, shielding
may be needed. Twisting wire input leads makes them more resistant to RF fields. The difference in input pin
location of the INA270 and INA271 versus the INA193 to INA198 may provide different EMI performance.
11.2 Layout Example
Shunt Resistor
IN-
Single-Pole Filter
Capacitor
IN+
GND
NC
PRE
OUT
V+
BUF IN
Supply Bypass
Capacitor
Supply Voltage
OUT
Analog Output
Via to Power or Ground Plane
Via to Internal Layer
Figure 23. Example Layout
18
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12 Device and Documentation Support
12.1 Documentation Support
12.1.1 Related Documentation
For related documentation see the following:
INA270 TINA-TI Spice Model, SBOM306
INA270 PSpice Model, SBOM485
INA270 TINA-TI Reference Design, SBOC246
12.2 Related Links
The table below lists quick access links. Categories include technical documents, support and community
resources, tools and software, and quick access to order now.
Table 1. Related Links
PARTS
PRODUCT FOLDER
ORDER NOW
TECHNICAL
DOCUMENTS
TOOLS &
SOFTWARE
SUPPORT &
COMMUNITY
INA270
Click here
Click here
Click here
Click here
Click here
INA271
Click here
Click here
Click here
Click here
Click here
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.
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PACKAGE OPTION ADDENDUM
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20-Aug-2021
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)
(4/5)
(6)
INA270AID
ACTIVE
SOIC
D
8
75
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 125
I270A
INA270AIDR
ACTIVE
SOIC
D
8
2500
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 125
I270A
INA271AID
ACTIVE
SOIC
D
8
75
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 125
I271A
INA271AIDG4
ACTIVE
SOIC
D
8
75
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 125
I271A
INA271AIDR
ACTIVE
SOIC
D
8
2500
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 125
I271A
(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
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