INA170EA250 Burr-Brown Corporation, INA170EA250 Datasheet - Page 7

• Manufacturer Part Number: INA170EA250
• Description: High-Side/ Bidirectional CURRENT SHUNT MONITOR
• Manufacturer: Burr-Brown Corporation

currents by minimizing the effects of offset, while low values
of R
applications, best performance is attained with an R
that provides a full-scale shunt voltage of 50mV to 100mV.
Maximum input voltage for accurate measurements is 500mV.
R
The output impedance of the INA170 Out terminal is very
high which permits using values of R
excellent accuracy. The input impedance of any additional
circuitry at the output should be much higher than the value
of R
Some Analog-to-Digital (A/D) converters have input imped-
ances that will significantly affect measurement gain. The
input impedance of the A/D converter can be included as
part of the effective R
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 R
OUTPUT VOLTAGE RANGE
The output of the INA170 is a current, which is converted to
a voltage by the load resistor, R
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
INA170
FIGURE 2. Buffering Output to Drive A/D Converter.
FIGURE 4. Offsetting the Output Voltage.
SBOS193B
L
is chosen to provide the desired full-scale output voltage.
L
S
to avoid degrading accuracy.
minimize voltage loss in the supply line. For most
INA170
2
I
S
4
1
6
L
R
if its input can be modeled as a
L
OPA340
V
Buffer of amp drives A/D converter
without affecting gain.
L
REF
. The output current remains
3
L
L
.
up to 100k
2
5
INA170
R
OS
I
S
4
1
S
6
Z
IN
value
with
www.ti.com
R
L
V
0
output swing. The maximum output voltage compliance is
limited by the lower of the two equations below:
BANDWIDTH
Measurement bandwidth is affected by the value of the load
resistor, R
yield a narrower measurement bandwidth (see Typical Per-
formance 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.
FIGURE 3. Output Filter.
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.
Output Offset Current =
Output Offset Voltage =
Gain Set by R
L
V
. High gain produced by high values of R
out max
INA170
2
V
L
= (V+) – 0.7V – (V
(whichever is lower)
4
out max
V
V
R
R
REF
REF
OS
OS
1
6
• R
= V
L
or
f
–3dB
IN
R
–
L
– 0.5V
=
2 R
1
L
IN
+
C
C
L
f
L
–3dB
– V
IN
V
–
O
)
L
will
(5)
(6)
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