Datasheet

A1
A2
Single-PoleFilter
Capacitor
+2.7Vto+18V
5kW5kW
96kW
R
L
PREOUT BUFIN
GND
OUT
IN-IN+ V+
Load
-16Vto+80V
Supply
R
S
INA270
0.01 Fm 0.1 Fm
INA270
INA271
SBOS381C –FEBRUARY 2007–REVISED MAY 2010 www.ti.com
APPLICATIONS INFORMATION
BASIC CONNECTION POWER SUPPLY
Figure 15 shows the basic connection of the INA270 The input circuitry of the INA270 and INA271 can
and INA271. The input pins, IN+ and IN–, should be accurately measure beyond its power-supply voltage,
connected as closely as possible to the shunt resistor V+. For example, the V+ power supply can be 5V,
to minimize any resistance in series with the shunt whereas the load power-supply voltage is up to +80V.
resistance. The output voltage range of the OUT terminal,
however, is limited by the voltages on the
Power-supply bypass capacitors are required for
power-supply pin.
stability. Applications with noisy or high-impedance
power supplies may require additional decoupling
SELECTING R
S
capacitors to reject power-supply noise. Minimum
bypass capacitors of 0.01mF and 0.1mF in value
The value chosen for the shunt resistor, R
S
, depends
should be placed close to the supply pins. Although
on the application and is a compromise between
not mandatory, an additional 10mF electrolytic
small-signal accuracy and maximum permissible
capacitor placed in parallel with the other bypass
voltage loss in the measurement line. High values of
capacitors may be useful in applications with
R
S
provide better accuracy at lower currents by
particularly noisy supplies.
minimizing the effects of offset, while low values of
R
S
minimize voltage loss in the supply line. For most
applications, best performance is attained with an R
S
value that provides a full-scale shunt voltage range of
50mV to 100mV. Maximum input voltage for accurate
measurements is (V
S
– 0.2)/Gain.
Figure 15. INA270 Basic Connections
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