INA138-Q1 Datasheet, PDF (7/19 Pages) Texas Instruments – HIGH-SIDE MEASUREMENT CURRENT SHUNT MONITOR

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INA138-Q1, IN168-Q1
SGLS174D – SEPTEMBER 2003 – REVISED DECEMBER 2010
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Figure 9. Basic Circuit Connections
OUTPUT VOLTAGE RANGE
The output of the INA138 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 two equations below:
V_{out max} = (V₊) − 0.7 V − (_VIN+ − V_IN−)
or
V_{out max} = V_IN− − 0.5 V
(whichever is lower)
BANDWIDTH
Measurement bandwidth is affected by the value of the load resistor, R_L. High gain produced by high values of
R_L yields a narrower measurement bandwidth (see the Typical Characteristics section). 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 section.
If bandwidth limiting (filtering) is desired, a capacitor can be added to the output (see Figure 12). This will not
cause instability.
APPLICATIONS
The INA138 is designed for current shunt measurement circuits, as shown in Figure 9, but its basic function is
useful in a wide range of circuitry. An engineer may find many unforeseen uses in measurement and level
shifting circuits. A few ideas are illustrated in Figure 10 through Figure 15.
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