INA170

7

SBOS193B

www.ti.com

currents by minimizing the effects of offset, while low values

that provides a full-scale shunt voltage of 50mV to 100mV.

Maximum input voltage for accurate measurements is 500mV.

The output impedance of the INA170 Out terminal is very

excellent accuracy. The input impedance of any additional

circuitry at the output should be much higher than the value

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

resistor to ground. Alternatively, an op-amp can be used to

buffer the A/D converter input, as shown in Figure 2. See

OUTPUT VOLTAGE RANGE

The output of the INA170 is a current, which is converted to

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:

IN

(5)

or

(6)

(whichever is lower)

BANDWIDTH

Measurement bandwidth is affected by the value of the load

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.

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.

FIGURE 4. Offsetting the Output Voltage.

FIGURE 2. Buffering Output to Drive A/D Converter.

FIGURE 3. Output Filter.

I

S

OPA340

INA170

2

1

4

6

Z

IN

R

L

Buffer of amp drives A/D converter

without affecting gain.

INA170

f

1

2

πR

V

O

f

–3dB

R

L

C

L

2

1

4

6

V

0

V

REF

R

L

6

Gain Set by R

L

Output Offset Current =

V

REF

R

OS

Output Offset Voltage =

• R

L

V

REF

R

OS

INA170

2

1

4

5

3

I

S

R

OS