INA181 datasheet(28/62 Pages) TI2

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An example output response of a summing configuration is shown in Figure 8-4. The reference pin of the first

circuit is connected to ground, and sine waves at different frequencies are applied to the two circuits to produce

a summed output as shown. The sine wave voltage input for the first circuit is offset so that the whole wave is

above GND.

Time (4 ms/div)

Output

Inputs

VREF = 0 V

Figure 8-4. Current Summing Application Output Response (A2 Devices)

8.1.5 Detecting Leakage Currents

Occasionally, the need arises to confirm that the current going into a load is identical to the current coming

out of a load; typically, as part of diagnostic testing or fault detection. This situation requires precision current

differencing, which is the same as summing, except that the two amplifiers have the inputs connected opposite

of each other. To correctly detect leakage currents, the values for the current sense resistor RSENSE must be the

same for all channels. Provide an external reference voltage to the REF1 input to allow bidirectional leakage

current detection.

If the current into a load is equal to the current out of the load, then the voltage at OUT2 is the same as the

applied voltage to REF1. To enable accurate differences between the two currents, a reference voltage must be

applied. The reference voltage prevents the output of the device from being driven to ground, and also enables

detection if the current into the load is either greater than or less than the current coming out of the load.

For current differencing, the dual-channel INA2181 must have the inputs connected opposite to each other, as

shown in Figure 8-5. The reference input of the first channel sets the output quiescent level for all the devices

in the string. Connect the output of the first channel to the reference input of the second channel. The reference

input of the first channel sets the reference at the output. This circuit example is identical to the current summing

example, except that the two shunt inputs are reversed in polarity. Under normal operating conditions, the final

output is very close to the reference value and proportional to any current difference. This current differencing

circuit is useful in detecting when current into and out of a load do not match.

INA181, INA2181, INA4181

SBOS793H – APRIL 2017 – REVISED NOVEMBER 2023

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INA181 Datasheet(PDF) 28 Page - Texas Instruments