TI1 INA138NA/250 High-side measurement current shunt monitor Datasheet

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INA138, INA168
SBOS122D – DECEMBER 1999 – REVISED DECEMBER 2014
INA1x8 High-Side Measurement Current Shunt Monitor
1 Features
3 Description
•
The INA138 and INA168 are high-side, unipolar,
current shunt monitors. Wide input common-mode
voltage range, low quiescent current, and tiny SOT23 packaging enable use in a variety of applications.
1
•
•
•
•
•
•
•
•
Complete Unipolar High-Side Current
Measurement Circuit
Wide Supply and Common-Mode Range
INA138: 2.7 V to 36 V
INA168: 2.7 V to 60 V
Independent Supply and Input Common-Mode
Voltages
Single Resistor Gain Set
Low Quiescent Current (25 µA Typical)
Wide Temperature Range: –40°C to +125°C
5-Pin SOT-23 Package
Input common-mode and power-supply voltages are
independent and can range from 2.7 V to 36 V for the
INA138 and 2.7 V to 60 V for the INA168. Quiescent
current is only 25 µA, which permits connecting the
power supply to either side of the current
measurement shunt with minimal error.
The device converts a differential input voltage to a
current output. This current is converted back to a
voltage with an external load resistor that sets any
gain from 1 to over 100. Although designed for
current shunt measurement, the circuit invites
creative applications in measurement and level
shifting.
2 Applications
•
•
•
•
•
•
Current Shunt Measurement:
– Automotive, Telephone, Computers
Portable and Battery-Backup Systems
Battery Chargers
Power Management
Cell Phones
Precision Current Source
Both the INA138 and INA168 are available in SOT235 and are specified for the –40°C to 125°C
temperature range.
Device Information(1)
PART NUMBER
PACKAGE
BODY SIZE (NOM)
INA138
SOT-23 (5)
18.00 mm × 18.00 mm
INA168
SOT-23 (5)
18.00 mm × 18.00 mm
(1) For all available packages, see the orderable addendum at
the end of the datasheet.
Typical Application Circuit
IS
RS
VIN+
Up To 60V
3
4
VIN–
VIN+
5kΩ
Load
5kΩ
V+
5
OUT
GND
2
VO = ISRSRL/5kΩ
1
RL
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.
INA138, INA168
SBOS122D – DECEMBER 1999 – REVISED DECEMBER 2014
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Table of Contents
1
2
3
4
5
6
7
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
4
6.1
6.2
6.3
6.4
6.5
6.6
4
4
4
4
5
6
Absolute Maximum Ratings ......................................
ESD Ratings ............................................................
Recommended Operating Conditions.......................
Thermal Information .................................................
Electrical Characteristics...........................................
Typical Characteristics ..............................................
Detailed Description .............................................. 8
7.1 Overview ................................................................... 8
7.2 Functional Block Diagram ......................................... 8
7.3 Feature Description................................................... 8
7.4 Device Functional Modes.......................................... 9
8
Application and Implementation ........................ 10
8.1 Application Information............................................ 10
8.2 Typical Applications ............................................... 11
9 Power Supply Recommendations...................... 17
10 Layout................................................................... 18
10.1 Layout Guidelines ................................................. 18
10.2 Layout Example .................................................... 18
11 Device and Documentation Support ................. 19
11.1
11.2
11.3
11.4
11.5
Documentation Support .......................................
Related Links ........................................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
19
19
19
19
19
12 Mechanical, Packaging, and Orderable
Information ........................................................... 20
4 Revision History
Changes from Revision C (November 2005) to Revision D
•
2
Page
Added ESD Ratings table, Feature Description section, Device Functional Modes, Application and Implementation
section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and
Mechanical, Packaging, and Orderable Information section. ................................................................................................ 1
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5 Pin Configuration and Functions
DBV Package
5-Pin SOT-23
Top View
OUT 1
5
V+
4
VIN–
GND 2
VIN+ 3
Pin Functions
PIN
NO.
NAME
I/O
DESCRIPTION
1
OUT
O
Output current
2
GND
—
Ground
3
VIN+
I
Positive input voltage
4
V+
I
Power supply voltage
5
VIN-
I
Negative input voltage
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6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted)
V+
Supply voltage
Analog inputs, INA138
VIN+, VIN–
MIN
MAX
UNIT
INA138
–0.3
60
V
INA168
–0.3
75
V
Common mode (2)
–0.3
60
V
Differential (VIN+) – (VIN–)
–40
2
V
–0.3
75
V
–40
2
V
–0.3
40
V
10
mA
–55
150
°C
150
°C
150
°C
Common mode
Analog inputs, INA138
(1)
(2)
Differential (VIN+) – (VIN–)
Analog output, Out (2)
Input current into any pin
Operating temperature
Junction temperature
Storage temperature, Tstg
(1)
(2)
–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.
The input voltage at any pin may exceed the voltage shown if the current at that pin is limited to 10mA.
6.2 ESD Ratings
VALUE
Human body model (HBM), per ANSI/ESDA/JEDEC JS-001, all pins
V(ESD)
(1)
(2)
Electrostatic discharge
(1)
UNIT
±1000
Charged device model (CDM), per JEDEC specification JESD22-C101, all
pins (2)
V
±500
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.
6.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted)
MIN
NOM
MAX
UNIT
INA138
V+
2.7
5
36
V
Common Mode Voltage
2.7
12
36
V
INA168
V+
2.7
5
60
V
Common Mode Voltage
2.7
12
60
V
6.4 Thermal Information
INA1x8
THERMAL METRIC (1)
DBV
UNIT
5 PINS
RθJA
Junction-to-ambient thermal resistance
209.6
RθJC(top)
Junction-to-case (top) thermal resistance
196.8
RθJB
Junction-to-board thermal resistance
107.5
ψJT
Junction-to-top characterization parameter
36.2
ψJB
Junction-to-board characterization parameter
104.5
(1)
4
°C/W
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
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6.5 Electrical Characteristics
All other characteristics at TA = +25°C, VS = 5V, VIN+ = 12V, and ROUT = 125kΩ, unless otherwise noted.
PARAMETER
TEST CONDITIONS
INA138
MIN
INA168
TYP
MAX
100
500
MIN
TYP
MAX
100
500
UNIT
INPUT
Full-Scale Sense Voltage
VSENSE = VIN+ – VIN–
Common-Mode Input Range
2.7
Common-Mode Rejection
VIN+ = 2.7V to 40V, VSENSE = 50mV
36
100
Offset Voltage vs Temperature
(1)
TA = –40°C to +125°C
V– = 2.7V to 40V, VSENSE = 50mV
Offset Voltage vs Power Supply, V+
V– = 2.7V to 60V, VSENSE = 50mV
120
±0.2
mV
1
10
µV/°C
1
0.1
2
TA = –40°C to +125°C
dB
±1
±2
1
0.1
Input Bias Current
Input Bias Current vs Temperature
±1
±2
TA = –40°C to +125°C
Offset Voltage
V
dB
100
±0.2
(1)
mV
60
120
Offset Voltage
Offset Voltage Over Temperature
2.7
µV/V
10
2
µA
10
OUTPUT
Transconductance
TA = +25°C,
VSENSE = 10mV – 150mV
198
Transconductance vs Temperature
VSENSE = 100mV,
TA = –40°C to +125°C
196
Transconductance Over Temperature
TA = –40°C to +125°C
Nonlinearity Error
VSENSE = 10mV to 150mV
Total Output Error
Total Output Error Over Temperature
200
202
198
204
196
10
200
202
µA/V
204
µA/V
10
nA/°C
±0.01%
±0.1%
±0.0%
±0.1%
VSENSE = 100mV
±0.5%
±2%
±0.5%
±2%
TA = –40°C to +125°C
±2.5%
±2.5%
1 || 5
1 || 5
Output Impedance
GΩ || pF
Voltage Output Swing to Power
Supply, V+
(V+) – 0.8
(V+) – 1.0
(V+) – 0.8
(V+) – 1.0
V
Voltage Output Swing to Common
Mode, VCM
VCM – 0.5
VCM – 0.8
VCM – 0.5
VCM – 0.8
V
FREQUENCY RESPONSE
Bandwidth
Settling Time (0.1%)
ROUT = 5kΩ
800
800
kHz
ROUT = 125kΩ
32
32
kHz
5V Step, ROUT = 5kΩ
1.8
1.8
µs
5V Step, ROUT = 125kΩ
30
30
µs
9
9
pA/√Hz
3
3
nA RMS
NOISE
Output-Current Noise Density
Total Output-Current Noise
BW = 100kHz
POWER SUPPLY
Operating Range, V+
2.7
Quiescent Current
TA = +25°C, VSENSE = 0, IO = 0
Quiescent Current Over Temperature
TA = –40°C to +125°C
36
25
2.7
45
25
60
60
V
45
µA
60
µA
TEMPERATURE RANGE
Specification, TMIN to TMAX
–40
125
–40
125
°C
Operating
–55
150
–55
150
°C
Storage
–65
150
–65
150
Thermal Resistance, θJA
(1)
200
200
°C
°C/W
Defined as the amount of input voltage, VSENSE, to drive the output to zero.
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6.6 Typical Characteristics
At TA = +25°C, V+ = 5V, VIN+ = 12V, and RL = 125kΩ, unless otherwise noted.
40
120
Common-Mode Rejection (dB)
RL = 500kΩ
30
RL = 50kΩ
Gain (dB)
20
10
RL = 5kΩ
0
–10
CL = 10nF
–20
100
1k
CL = 1nF
10k
CL = 100pF
100k
1M
G = 100
100
80
G = 10
60
G=1
40
20
0
10M
0.1
Frequency (Hz)
1
10
100
1k
10k
100k
Frequency (Hz)
Figure 1. Gain vs Frequency
Figure 2. Common-Mode Rejection vs Frequency
140
5
VIN = (VIN+ – VIN–)
0 –5 –
G = 100
100
G = 10
80
G=1
60
Total Output Error (%)
Power-Supply Rejection (dB)
–55°C
120
+150°C
+25°C
10
40
–15
20
1
10
100
1k
Frequency (Hz)
10k
0
100k
25
100
125
150
200
Figure 4. Total Output Error vs VIN
2
50
Output error is essentially
independent of both
V+ supply voltage and
input common-mode voltage.
1
G=1
0
G = 10
G = 25
–1
+150°
40
Quiescent Current (µA)
Total Output Error (%)
75
VIN (mV)
Figure 3. Power-Supply Rejection vs Frequency
–2
+125°
30
+25°
–55°
20
Use INA168 with
(V+) > 36V
10
0
0
10
20
30
40
50
60
70
0
10
Power-Supply Voltage (V)
20
30
40
50
60
70
Power-Supply Voltage (V)
Figure 5. Total Output Error vs Power-Supply Voltage
6
50
Figure 6. Quiescent Current vs Power-Supply Voltage
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Typical Characteristics (continued)
At TA = +25°C, V+ = 5V, VIN+ = 12V, and RL = 125kΩ, unless otherwise noted.
200mV
G=1
G = 25
100mV
1V/div
0V
50mV/div
100mV
G=1
G = 10
0mV
0V
10µs/div
500mV/div
10µs/div
Figure 7. Step Response
Figure 8. Step Response
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7 Detailed Description
7.1 Overview
The INA138 and INA168 devices are comprised of a high voltage, precision operational amplifier, precision thin
film resistors trimmed in production to an absolute tolerance and a low noise output transistor. The INA138 and
INA168 devices can be powered from a single power supply and their input voltages can exceed the power
supply voltage. The INA138 and INA168 devices are ideal for measuring small differential voltages, such as
those generated across a shunt resistor, in the presence of large common-mode voltages. Refer to Functional
Block Diagram which illustrates the functional components within both INA138 and INA168 devices.
7.2 Functional Block Diagram
VIN+
VIN-
V+
+
OUT
GND
7.3 Feature Description
7.3.1 Output Voltage Range
The output of the INA138 device is a current, which is converted to a voltage by the load resistor, RL. The output
current remains accurate within the compliance voltage range of the output circuitry. The shunt voltage and the
input common-mode and power-supply voltages limit the maximum possible output swing. The maximum output
voltage compliance is limited by the lower of the following two equations:
Vout max = (V+) – 0.7 V – (VIN+ – VIN–)
(1)
Vout max = VIN– – 0.5 V
(2)
or
(whichever is lower)
8
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Feature Description (continued)
7.3.2 Bandwidth
Measurement bandwidth is affected by the value of the load resistor, RL. High gain produced by high values of
RL will yield a narrower measurement bandwidth (see Typical Characteristics). For widest possible bandwidth,
keep the capacitive load on the output to a minimum. Reduction in bandwidth due to capacitive load is shown in
the Typical Characteristics.
If bandwidth limiting (filtering) is desired, a capacitor can be added to the output (see Figure 12). This will not
cause instability.
7.4 Device Functional Modes
For proper operation the INA138 and INA168 devices must operate within their specified limits. Operating either
device outside of their specified power supply voltage range or their specified common-mode range will result in
unexpected behavior and is not recommended. Additionally operating the output beyond their specified limits with
respect to power supply voltage and input common-mode voltage will also produce unexpected results. Refer to
Electrical Characteristics for the device specifications.
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8 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.
8.1 Application Information
8.1.1 Operation
Figure 9 illustrates the basic circuit diagram for both the INA138 and INA168 devices. Load current IS is drawn
from supply VS through shunt resistor RS. The voltage drop in shunt resistor VS is forced across RG1 by the
internal op amp, causing current to flow into the collector of Q1. External resistor RL converts the output current
to a voltage, VOUT, at the OUT pin. The transfer function for the INA138 device is:
IO = gm(VIN+ – VIN–)
(3)
where gm = 200 µA/V.
In the circuit of Figure 9, the input voltage, (VIN+ – VIN–), is equal to IS × RS and the output voltage, VOUT, is equal
to IO × RL. The transconductance, gm, of the INA138 device is 200 µA/V. The complete transfer function for the
current measurement amplifier in this application is:
VOUT = (IS) (RS) (200µA/V) (RL)
(4)
The maximum differential input voltage for accurate measurements is 0.5 V, which produces a 100-µA output
current. A differential input voltage of up to 2 V will not cause damage. Differential measurements (pins 3 and 4)
must be unipolar with a more-positive voltage applied to pin 3. If a more-negative voltage is applied to pin 3, the
output current, IO, will be zero, but it will not cause damage.
VP
Load Power Supply
+2.7 to 36V(1)
Shunt
RS
VIN–
VIN+
3
V+ power can be common or
V+
independent of load supply.
IS
4
RG1
5kΩ
Load
RG2
5kΩ
2.7 ≤(V+) ≤36V(1)
5
Q1
VOLTAGE GAIN
EXACT RL (&)
NEAREST 1% RL (&)
1
5k
4.99k
2
10k
10k
5
25k
24.9k
10
50k
49.9k
20
100k
100k
50
250k
249k
100
500k
499k
INA138
2
OUT
1
+
I0
RL
VO
–
NOTE: (1) Maximum VP and V+ voltage is 60V with INA168.
Figure 9. Basic Circuit Connections
10
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8.2 Typical Applications
The INA138 device is designed for current shunt measurement circuits, as shown in Figure 9, but its basic
function is useful in a wide range of circuitry. A creative engineer will find many unforeseen uses in measurement
and level shifting circuits. A few ideas are illustrated in Figure 10 through Figure 18.
8.2.1 Buffering Output to Drive an ADC
IS
VIN+
VIN-
OPA340
+
INA138
or
INA168
RS
ADC
RL
Buffer amplifier
drives ADC without
affecting gain
C
Figure 10. Buffering Output to Drive an A/D Converter
8.2.1.1 Design Requirements
Digitize the output of the INA138 or INA168 devices using a 1-MSPS analog-to-digital converter (ADC).
8.2.1.2 Detailed Design Procedure
8.2.1.2.1 Selecting the Shunt Resistor and RL
In Figure 9 the value chosen for the shunt resistor depends on the application and is a compromise between
small-signal accuracy and maximum permissible voltage loss in the measurement line. High values of shunt
resistor provide better accuracy at lower currents by minimizing the effects of offset, while low values of shunt
resistor minimize voltage loss in the supply line. For most applications, best performance is attained with a shunt
resistor value that provides a full-scale shunt voltage range of 50 mV to 100 mV. Maximum input voltage for
accurate measurements is 500 mV.
The load resistor, RL, is chosen to provide the desired full-scale output voltage. The output impedance of the
INA138 and INA168 OUT terminal is very high which permits using values of RL up to 500 kΩ with excellent
accuracy. The input impedance of any additional circuitry at the output should be much higher than the value of
RL to avoid degrading accuracy.
Some Analog-to-Digital (A/D) converters have input impedances that will significantly affect measurement gain.
The input impedance of the A/D converter can be included as part of the effective RL if its input can be modeled
as a resistor to ground. Alternatively, an op amp can be used to buffer the A/D converter input. The INA138 and
INA168 are current output devices, and as such have an inherently large output impedance. The output currents
from the amplifier are converted to an output voltage via the load resistor, RL, connected from the amplifier
output to ground. The ratio of the load resistor value to that of the internal resistor value determines the voltage
gain of the system.
In many applications digitizing the output of the INA138 or INA168 devices is required. This can be accomplished
by connecting the output of the amplifier to an ADC. It is very common for an ADC to have a dynamic input
impedance. If the INA138 or INA168 output is connected directly to an ADC input, the input impedance of the
ADC is effectively connected in parallel with the gain setting resistor RL. This parallel impedance combination will
affect the gain of the system and the impact on the gain is difficult to estimate accurately. A simple solution that
eliminates the paralleling of impedances, simplifying the gain of the circuit is to place a buffer amplifier, such as
the OPA340, between the output of the INA138 or INA168 devices and the input to the ADC.
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Typical Applications (continued)
Figure 10 illustrates this concept. Notice that a low pass filter is placed between the OPA340 output and the input
to the ADC. The filter capacitor is required to provide any instantaneous demand for current required by the input
stage of the ADC. The filter resistor is required to isolate the OPA340 output from the filter capacitor to maintain
circuit stability. The values for the filter components will vary according to the operational amplifier used for the
buffer and the particular ADC selected. More information can be found regarding the design of the low pass filter
in the TI Precision Design 16 bit 1MSPS Data Acquisition Reference Design for Single-Ended Multiplexed
Applications, TIPD173.
Figure 10 shows the expected results when driving an analog-to-digital converter at 1MSPS with and without
buffering the INA138 or INA168 output. Without the buffer, the high impedance of the INA138 or INA168 will
react with the input capacitance and sample and hold (S/H) capacitance of the analog-to-digital converter and will
not allow the S/H to reach the correct final value before it is reset and the next conversion starts. Adding the
buffer amplifier significantly reduces the output impedance driving the S/H and allows for higher conversion rates
than can be achieved without adding the buffer.
8.2.1.3 Application Curve
Input to ADC (0.25 V/div)
with buffer
without Buffer
Time
Figure 11. Driving an A/D with and without a Buffer
8.2.2 Output Filter
3
4
f–3dB
INA138
1
f–3dB =
2 πR L C L
VO
RL
CL
Figure 12. Output Filter
8.2.2.1 Design Requirements
Filter the output of the INA138 or INA168 devices.
12
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Typical Applications (continued)
8.2.2.2 Detailed Design Procedure
A low-pass filter can be formed at the output of the INA138 or INA168 devices simply by placing a capacitor of
the desired value in parallel with the load resistor. First determine the value of the load resistor needed to
achieve the desired gain. Refer to the table in Figure 9. Next, determine the capacitor value that will result in the
desired cutoff frequency according to the equation shown in Figure 12. Figure 13 illustrates various combinations
of gain settings (determined by RL) and filter capacitors.
8.2.2.3 Application Curve
40
RL = 500kΩ
30
RL = 50kΩ
Gain (dB)
20
10
0
RL = 5kΩ
–10
CL = 10nF
–20
100
1k
10k
CL = 1nF
100k
CL = 100pF
1M
10M
Frequency (Hz)
Figure 13. Gain vs Frequency
8.2.3 Offsetting the Output Voltage
For many applications using only a single power supply it may be required to level shift the output voltage away
from ground when there is no load current flowing in the shunt resistor. Level shifting the output of the INA138 or
INA168 devices is easily accomplished by one of two simple methods shown in Figure 14. The method on the
left hand side of Figure 14 illustrates a simple voltage divider method. This method is useful for applications that
require the output of the INA138 or INA168 devices to remain centered with respect to the power supply at zero
load current through the shunt resistor. Using this method the gain is determine by the parallel combination of R1
and R2 while the output offset is determined by the voltage divider ratio R1 and R2. For applications that may
require a fixed value of output offset, independent of the power supply voltage, the current source method shown
on the right-hand side of Figure 14 is recommended. With this method a REF200 constant current source is used
to generate a constant output offset. Using his method the gain is determined by RL and the offset is determined
by the product of the value of the current source and RL.
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Typical Applications (continued)
Figure 14. Offsetting the Output Voltage
8.2.4 Bipolar Current Measurement
The INA138 or INA168 devices can be configured as shown in Figure 15 in applications where measuring current
bi-directionally is required. Two INA devices are required connecting their inputs across the shunt resistor as
shown in Figure 15. A comparator, such as the TLV3201, is used to detect the polarity of the load current. The
magnitude of the load current is monitored across the resistor connected between ground and the connection
labeled Output. In this example the 100-kΩ resistor results in a gain of 20 V/V. The 10-kΩ resistors connected in
series with the INA138 or INA168 output current are used to develop a voltage across the comparator inputs.
Two diodes are required to prevent current flow into the INA138 or INA168 output, as only one device at a time is
providing current to the Output connection of the circuit. The circuit functionality is illustrated in Figure 16.
14
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Typical Applications (continued)
+/-1 A
Load Curent
RSH
100 m
VIN+
VIN-
VIN-
VIN+
Bus
Voltage
Load
Current
5k
5k
5k
V+
+5 V
V+
+
INA138
or
INA168
+
+5 V
5k
OUT
OUT
GND
GND
1N4148
INA138
or
INA168
1N4148
+
Sign
TLV3201
10 k 10 k Output
100 k Figure 15. Bipolar Current Measurement
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Typical Applications (continued)
Voltage
Load Current
Output
Sign
Time
Figure 16. Bipolar Current Measurements Results (arbitrary scale)
8.2.5 Bipolar Current Measurement Using Differential Input of A/D Converter
The INA138 or INA168 devices can be used with an A/D Converter such as the ADS7870 programmed for
differential mode operation. Figure 17 illustrates this configuration. In this configuration the use of two INA's
allows for bi-directional current measurement. Depending upon the polarity of the current, one of the INA's will
provide an output voltage while the other output is zero. In this way the A/D converter will read the polarity of
current directly, without the need for additional circuitry.
RS
V+
4
3
4
3
+5V
+5V
+5V
5
REFOUT BUFIN
BUFOUT
5
Digital
I/O
INA138
2
1
RL
25kΩ
REF
BUF
INA138
2
1
MUX
PGIA
12-Bit A/D
Converter
RL
25kΩ
A/D converter programmed for differential input.
Depending on polarity of current, one INA138 provides
an output voltage, the output of the other is zero.
Clock
Divider
Oscillator
ADS7870
Serial
I/O
Figure 17. Bipolar Current Measurement Using Differential Input of A/D Converter
16
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Typical Applications (continued)
8.2.6 Multiplexed Measurement Using Logic Signal for Power
Multiple loads can be measured as illustrated in Figure 18. In this configuration each INA138 or INA168 device is
powered by the Digital I/O from the ADS7870. Multiplexing is achieved by switching on or off each the desired
I/O.
Other INA168s
Digital I/O on the ADS7870 provides power to select
the desired INA168. Diodes prevent output current of
the on INA168 from flowing into the off INA168.
INA168
V+
+5V
––
REFOUT BUFIN
Digital
I/O
REF
BUFOUT
BUF
INA168
V+
––
MUX
12-Bit A/D
Converter
PGIA
IN4148
RL
Clock
Divider
Oscillator
Serial
I/O
ADS7870
Figure 18. Multiplexed Measurement Using Logic Signal for Power
9 Power Supply Recommendations
The input circuitry of the INA138 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 36 V (or 60 V with the INA168).
The output voltage range of the OUT terminal, however, is limited by the lesser of the two voltages (see Output
Voltage Range). A 0.1-µF capacitor is recommenced to be placed near the power supply pin on the INA138 or
INA168. Additional capacitance may be required for applications with noisy power supply voltages.
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10 Layout
10.1 Layout Guidelines
Figure 19 shows the basic connection of the INA138 device. The input pins, VIN+ and VIN– , should be connected
as closely as possible to the shunt resistor to minimize any resistance in series with the shunt resistance. The
output resistor, RL, is shown connected between pin 1 and ground. Best accuracy is achieved with the output
voltage measured directly across RL. This is especially important in high-current systems where load current
could flow in the ground connections, affecting the measurement accuracy.
No power-supply bypass capacitors are required for stability of the INA138. However, applications with noisy or
high-impedance power supplies may require decoupling capacitors to reject power-supply noise. Connect bypass
capacitors close to the device pins.
10.2 Layout Example
VIA to Ground Plane
INA138
INA168
Output
OUT
Supply Voltage
V+
0.1 µF
GND
RL
To Bus
Voltage
VIN+
VIN-
PCB pad
To Load
PCB pad
RSHUNT
Figure 19. Typical Layout Example
18
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SBOS122D – DECEMBER 1999 – REVISED DECEMBER 2014
11 Device and Documentation Support
11.1 Documentation Support
11.1.1 Related Documentation
For related documentation see the following:
• 16 bit 1MSPS Data Acquisition Reference Design for Single-Ended Multiplexed Applications, TIDU504
• ADS7870 12-Bit ADC, MUX, PGA and Internal Reference Data Acquisition System, SBAS124
• TLV3201, TLV3202 40-ns, microPOWER, Push-Pull Output Comparators, SBOS561
• REF200 Dual Current Source/Current Sink, SBVS020
11.2 Related Links
The table below lists quick access links. Categories include technical documents, support and community
resources, tools and software, and quick access to sample or buy.
Table 1. Related Links
PARTS
PRODUCT FOLDER
SAMPLE & BUY
TECHNICAL
DOCUMENTS
TOOLS &
SOFTWARE
SUPPORT &
COMMUNITY
INA138
Click here
Click here
Click here
Click here
Click here
INA168
Click here
Click here
Click here
Click here
Click here
11.3 Trademarks
All trademarks are the property of their respective owners.
11.4 Electrostatic Discharge Caution
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
11.5 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
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12 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.
20
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PACKAGE OPTION ADDENDUM
www.ti.com
11-Apr-2013
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
(2)
MSL Peak Temp
Op Temp (°C)
Top-Side Markings
(3)
(4)
INA138NA/250
ACTIVE
SOT-23
DBV
5
250
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
-40 to 125
B38
INA138NA/250G4
ACTIVE
SOT-23
DBV
5
250
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
-40 to 125
B38
INA138NA/3K
ACTIVE
SOT-23
DBV
5
3000
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
-40 to 125
B38
INA138NA/3KG4
ACTIVE
SOT-23
DBV
5
3000
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
-40 to 125
B38
INA168NA/250
ACTIVE
SOT-23
DBV
5
250
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
A68
INA168NA/250G4
ACTIVE
SOT-23
DBV
5
250
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
A68
INA168NA/3K
ACTIVE
SOT-23
DBV
5
3000
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
-40 to 125
A68
INA168NA/3KG4
ACTIVE
SOT-23
DBV
5
3000
Green (RoHS
& no Sb/Br)
CU NIPDAU
Level-2-260C-1 YEAR
-40 to 125
A68
(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)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
11-Apr-2013
(4)
Multiple Top-Side Markings will be inside parentheses. Only one Top-Side 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 Top-Side Marking for that device.
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
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 INA138, INA168 :
• Automotive: INA138-Q1, INA168-Q1
NOTE: Qualified Version Definitions:
• Automotive - Q100 devices qualified for high-reliability automotive applications targeting zero defects
Addendum-Page 2
PACKAGE MATERIALS INFORMATION
www.ti.com
31-Dec-2013
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
INA138NA/250
SOT-23
DBV
5
250
178.0
9.0
3.3
B0
(mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
3.2
1.4
4.0
8.0
Q3
INA138NA/3K
SOT-23
DBV
5
3000
178.0
9.0
3.3
3.2
1.4
4.0
8.0
Q3
INA168NA/250
SOT-23
DBV
5
250
178.0
9.0
3.23
3.17
1.37
4.0
8.0
Q3
INA168NA/3K
SOT-23
DBV
5
3000
178.0
9.0
3.23
3.17
1.37
4.0
8.0
Q3
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
31-Dec-2013
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
INA138NA/250
SOT-23
DBV
INA138NA/3K
SOT-23
DBV
5
250
180.0
180.0
18.0
5
3000
180.0
180.0
18.0
INA168NA/250
SOT-23
DBV
INA168NA/3K
SOT-23
DBV
5
250
180.0
180.0
18.0
5
3000
180.0
180.0
18.0
Pack Materials-Page 2
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