ETC INA170EA/250

INA170
SBOS193 – MARCH 2001
High-Side, Bidirectional
CURRENT SHUNT MONITOR
FEATURES
DESCRIPTION
● COMPLETE BIDIRECTIONAL CURRENT
MEASUREMENT CIRCUIT
● WIDE SUPPLY RANGE: 2.7V to 40V
● SUPPLY-INDEPENDENT COMMON-MODE
VOLTAGE: 2.7V TO 60V
● RESISTOR PROGRAMMABLE GAIN SET
● LOW QUIESCENT CURRENT: 75µA (typ)
● MSOP-8 PACKAGE
The INA170 is a high-side, bidirectional current shunt
monitor featuring a wide input common-mode voltage range,
low quiescent current, and a tiny MSOP-8 package.
Bidirectional current measurement is accomplished by output offsetting. The offset voltage level is set with an external
resistor and voltage reference. This permits measurement of
a bidirectional shunt current while using a single supply for
the INA170.
Input common-mode and power-supply voltages are independent. Input voltage can range from +2.7V to +60V on
any supply voltage from +2.7V to +40V. Low 10µA input
bias current adds minimal error to the shunt current.
The INA170 converts a differential input voltage to a
current output. This current develops a voltage across an
external load resistor, setting any gain from 1 to over 100.
The INA170 is available in an MSOP-8 package, and is
specified over the extended industrial temperature range,
–40°C to +85°C with operation from –55°C to +125°C.
APPLICATIONS
● CURRENT SHUNT MEASUREMENT:
Automotive, Telephone, Computers, Power
Systems, Test, General Instrumentation
● PORTABLE & BATTERY-BACKUP
SYSTEMS
● BATTERY CHARGERS
● POWER MANAGEMENT
● CELL PHONES
V+
VSUPPLY
8
+
VIN
IS
RS
RG1
1kΩ
2
–
VIN
RG2
1kΩ
1
VREF
Q1
6
OUT
3
Load
A2
ROS
A1
Q2
RL
INA170
5
GND
ROS
4
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
Copyright © 2001, Texas Instruments Incorporated
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
www.ti.com
PACKAGE/ORDERING INFORMATION
PRODUCT
PACKAGE
PACKAGE
DRAWING
NUMBER
INA170EA
MSOP-8
337
–40°C to +85°C
INA170EA
"
"
"
"
"
SPECIFIED
TEMPERATURE
RANGE
PACKAGE
MARKING
ORDERING
NUMBER(1)
TRANSPORT
MEDIA
INA170EA/250
INA170EA/2K5
Tape and Reel
Tape and Reel
NOTE: (1) Models with a slash (/) are available only in Tape and Reel in the quantities indicated (e.g., /2K5 indicates 2500 devices per reel). Ordering 2500 pieces
of “INA170NA/2K5” will get a single 2500-piece Tape and Reel.
ABSOLUTE MAXIMUM RATINGS(1)
Supply Voltage, V+ to GND ................................................. –0.3V to 40V
Analog Inputs, Common Mode ............................................ –0.3V to 60V
+
– ) .................................. –40V to 2V
Differential (VIN
) – (VIN
Analog Output, Out .............................................................. –0.3V to 40V
Operating Temperature .................................................. –55°C to +125°C
Storage Temperature ..................................................... –65°C to +150°C
Junction Temperature .................................................................... +150°C
Lead Temperature (soldering, 10s) ............................................... +300°C
NOTE: (1) Stresses above these ratings may cause permanent damage.
Exposure to absolute maximum conditions for extended periods may degrade
device reliability. These are stress ratings only, and functional operation of the
device at these or any other conditions beyond those specified is not implied.
2
ELECTROSTATIC
DISCHARGE SENSITIVITY
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.
INA170
SBOS193
ELECTRICAL CHARACTERISTICS
+ = 12V, R
At TA = –40°C to +85°C, VS = 5V, VIN
OUT = 25kΩ, unless otherwise noted.
INA170EA
PARAMETER
CONDITION
INPUT
Full-Scale Sense (Input) Voltage
Common-Mode Input Range
Common-Mode Rejection
Offset Voltage(1) RTI
vs Temperature
vs Power Supply
Input Bias Current
MIN
+ – V–
VSENSE = VIN
IN
+2.7
100
+ = +2.7V to +60V, V
VIN
SENSE = 50mV
TMIN to TMAX
V+ = +2.7V to +60V, VSENSE = 50mV
+ , V–
VIN
IN
OFFSETTING AMPLIFIER
Offsetting Equation
Input Voltage
Input Offset Voltage
vs Temperature
Programming Current through ROS
Input Impedance
Input Bias Current
TYP
MAX
UNITS
100
500
+60
mV
V
dB
mV
µV/°C
µV/V
uA
120
±0.2
1
0.1
10
±1
10
VOS = (RL/ROS) VREF
1
±0.2
10
TMIN to TMAX
0
VSENSE = 10mV to 150mV
VSENSE = 100mV
VSENSE = 10mV to 150mV
VSENSE = 100mV
FREQUENCY RESPONSE
Bandwidth
Settling Time (0.1%)
1
1010 || 4
+10
+ , V–
VIN
IN
OUTPUT
Transconductance
vs Temperature
Nonlinearity Error
Total Output Error
Output Impedance
Voltage Output
Swing to Power Supply, V+
Swing to Common Mode, VCM
VS – 1
±1
0.990
1
50
±0.01
±0.5
1 || 5
1.01
(V+) – 0.9
VCM – 0.6
(V+) – 1.2
VCM – 1.0
±0.1
±2
V
mV
µV/°C
mA
Ω || pF
nA
mA/V
nA/°C
%
%
GΩ || pF
V
V
ROUT = 10kΩ
5V Step, ROUT = 10kΩ
400
3
kHz
µs
BW = 100kHz
20
7
pA/√Hz
nA RMS
NOISE
Output-Current Noise Density
Total Output-Current Noise
POWER SUPPLY
Operating Range
Quiescent Current
V+
VSENSE = 0, IO = 0
+2.7
75
TEMPERATURE RANGE
Specification, TMIN to TMAX
Operating
Storage
Thermal Resistance, θJA
–40
–55
–65
+60
125
V
µA
85
125
150
°C
°C
°C
°C/W
150
NOTE: (1) Defined as the amount of input voltage, VSENSE, to drive the output to zero.
PIN CONFIGURATION
PIN DESCRIPTION
TOP VIEW
INA170
SBOS193
MSOP
–
VIN
1
8
V+
+
VIN
2
7
NC
VREF
3
6
OUT
GND
4
5
ROS
PIN
DESIGNATOR
1
2
3
4
5
6
7
8
+
VIN
–
VIN
VREF
GND
ROS
OUT
NC
V+
DESCRIPTION
Noninverting Input
Inverting Input
Reference Voltage Input
Ground
Offset Resistor
Output
No Connection
Supply Voltage
3
TYPICAL CHARACTERISTICS
+ = 12V, R = 25kΩ, unless otherwise noted.
At TA = +25°C, V+ = 5V, VIN
L
COMMON-MODE REJECTION vs FREQUENCY
GAIN vs FREQUENCY
40
120
Common-Mode Rejection (dB)
RL = 100kΩ
30
RL = 10kΩ
Gain (dB)
20
10
RL = 1kΩ
0
–10
–20
G = 100
100
80
G = 10
60
G=1
40
20
0
100
10k
1k
100k
10M
1M
0.1
10
1
Frequency (Hz)
100
5
+ – V– )
VIN = (VIN
IN
120
Total Output Error (%)
Power-Supply Rejection (dB)
–55°C
G = 100
100
G = 10
80
G=1
60
0
+150°C
–5
+25°C
–10
40
–15
20
1
100
1k
Frequency (Hz)
10
10k
0
100k
25
50
75
100
125
150
200
VIN (mV)
TOTAL OUTPUT ERROR
vs POWER-SUPPLY VOLTAGE
QUIESCENT CURRENT
vs POWER-SUPPLY VOLTAGE
2
100
Output error is essentially
independent of both
V+ supply voltage and
input common-mode voltage.
1
+150°
Quiescent Current (µA)
Total Output Error (%)
100k
TOTAL OUTPUT ERROR vs VIN
POWER-SUPPLY REJECTION vs FREQUENCY
140
G=1
0
G = 10
G = 25
–1
–2
+125°
80
60
+25°
–55°
40
20
0
0
10
20
Power-Supply Voltage (V)
4
10k
1k
Frequency (Hz)
30
40
0
10
20
30
40
Power-Supply Voltage (V)
INA170
SBOS193
TYPICAL CHARACTERISTICS (Cont.)
+ = 12V, R = 25kΩ, unless otherwise noted.
At TA = +25°C, V+ = 5V, VIN
L
STEP RESPONSE
STEP RESPONSE
1.5V
1V
G = 100
G = 50
0.5V
0V
1V
2V
G = 100
G = 10
0V
0V
20µs/div
INA170
SBOS193
10µs/div
5
OPERATION
Figure 1 shows the basic circuit diagram for the INA170.
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.
Without offset, the transfer function for the INA170 is:
+ – V–)
IO = gm (VIN
IN
(1)
where gm = 1000µA/V
(2)
+ – V – ), is
In the circuit of Figure 1, the input voltage, (VIN
IN
equal to IS • RS and the output voltage, VOUT, is equal to
IO • RL. The transconductance, gm, of the INA170 is
1000µA/V. The complete transfer function for the current
measurement amplifier in this application is:
VOUT = (IS) (RS) (1000µA/V) (RL)
(3)
Applying a positive reference voltage to pin 3 causes a
current to flow through ROS, forcing output current IO to be
offset from zero. The transfer function then becomes:
 V • R L   IS • RS • R L 
VOUT =  REF
±

1kΩ
 R OS  
(4)
The maximum differential input voltage for accurate measurements is 0.5V, which produces a 500µA output current.
A differential input voltage of up to 2V will not cause
damage. Differential measurements (pins 1 and 2) can be
bipolar with a more-positive voltage applied to pin 2. If a
more-negative voltage is applied to pin 1, output current IO
will decrease towards zero.
BASIC CONNECTION
Figure 1 shows the basic connection of the INA170. The
+ and V – , should be connected as closely as
input pins, VIN
IN
possible to the shunt resistor to minimize any resistance in
series with the shunt resistance. The output resistor, RL, is
shown connected between pin 6 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 INA170. However, applications with noisy or high
impedance power supplies may require de-coupling capacitors to reject power-supply noise. Connect bypass capacitors
close to the device pins.
POWER SUPPLIES
The input circuitry of the INA170 can accurately measure
beyond its power-supply voltage, V+. For example, the V+
power supply can be 5V, while the load power-supply
voltage (INA170 input voltage) is up to +60V. However, the
output-voltage range of the OUT terminal (pin 6) is limited
by the supply.
SELECTING RS AND RL
The value chosen for the shunt resistor, RS, depends on the
application and is a compromise between small-signal accuracy and maximum permissible voltage loss in the measurement line. High values of RS provide better accuracy at lower
VP
Load Power Supply
+2.7 to 60V
V+ power can be
common or
indepedent of
load supply.
Shunt
RS
+
VIN
IS
–
VIN
1
2
Load
V+
INA170
RG1
1kΩ
2.7 ≤ (V+) ≤ 40V
RG2
1kΩ
8
VOLTAGE GAIN
EXACT RL (Ω)
NEAREST 1% RL (Ω)
1
1k
1k
2
2k
2k
5
5k
4.99k
10
10k
10k
20
20k
20k
50
50k
49k
100
100k
100k
VREF
3
Q2
5
Q1
4
ROS
OUT
6
+
I0
RL
VO
–
FIGURE 1. Basic Circuit Connections.
6
INA170
SBOS193
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 of 50mV to 100mV.
Maximum input voltage for accurate measurements is 500mV.
RL is chosen to provide the desired full-scale output voltage.
The output impedance of the INA170 Out terminal is very
high which permits using values of RL up to 100kΩ 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.
output swing. The maximum output voltage compliance is
limited by the lower of the two equations below:
Vout
+ – V–)
= (V+) – 0.7V – (VIN
IN
max
(5)
or
Vout
max
– – 0.5V
= VIN
(6)
(whichever is lower)
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 Performance Curves). For widest possible bandwidth, keep the
capacitive load on the output to a minimum.
If bandwidth limiting (filtering) is desired, a capacitor can be
added to the output, as shown in Figure 3. This will not
cause instability.
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, as shown in Figure 2. See
Figure 1 for recommended values of RL.
IS
2
1
1
2
f–3dB
INA170
INA170
ZIN
OPA340
6
4
1
f–3dB =
2πRLCL
6
4
RL
VO
RL
CL
Buffer of amp drives A/D converter
without affecting gain.
FIGURE 2. Buffering Output to Drive A/D Converter.
FIGURE 3. Output Filter.
OUTPUT VOLTAGE RANGE
APPLICATIONS
The INA170 is designed for current shunt measurement
circuits as shown in Figure 1, 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.
The output of the INA170 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
IS
1
2
Gain Set by RL
INA170
VREF
6
3
5
4
ROS
V0
Output Offset Current =
VREF
ROS
Output Offset Voltage =
VREF
• RL
ROS
RL
FIGURE 4. Offsetting the Output Voltage.
INA170
SBOS193
7
IS = ±10A
0.0125Ω
+5V
Load
28V
0.1µF
∆V =
±125mV
Full-Scale
8
1
2
V+
–
VIN
IO = 125µA ± 125µA
+
VIN
6
INA170
IOS = 125µA
OUT
3
+2.5V
RL
10kΩ
VREF
ROS
VOUT = 0 to +2.5V Full-Scale
GND
5
4
20kΩ
FIGURE 5. Bipolar Current Measurement.
8
INA170
SBOS193
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TI’s standard warranty. Testing and other quality control techniques are utilized to the extent TI deems necessary
to support this warranty. Specific testing of all parameters of each device is not necessarily performed, except
those mandated by government requirements.
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safeguards must be provided by the customer to minimize inherent or procedural hazards.
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