NC

V+

NC

OUT

VIN-

VIN+

GND

NC

Via to Ground Plane

Via to Power Plane

RL

INA138-Q1

INA168-Q1

Sense/Shunt

Resistor

To Load

To Bus Voltage

Supply

Bypass

Capacitor

19

INA138-Q1, INA168-Q1

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SGLS174J – SEPTEMBER 2003 – REVISED AUGUST 2018

Product Folder Links: INA138-Q1 INA168-Q1

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Copyright © 2003–2018, Texas Instruments Incorporated

9 Power Supply Recommendations

The input circuitry of the INA1x8-Q1 can accurately measure beyond the power-supply voltage, V+. For example,

the V+ power supply can be 5 V, whereas the load power-supply voltage goes up to 36 V with the INA138-Q1, or

60 V with the INA168-Q1. However, the output voltage range of the OUT pin is limited by the lesser of the two

voltages (see the Output Voltage Range section). Place a 0.1-µF capacitor near the power-supply pin on the

INA1x8-Q1. Additional capacitance may be required for applications with noisy power-supply voltages.

10 Layout

10.1 Layout Guidelines

Figure 19 shows the basic connection of the INA1x8-Q1 in the TSSOP-8 package. Connect input pins VIN+ and

VIN− as closely as possible to the shunt resistor to minimize any resistance in series with the shunt resistance.

Output resistor RL is shown connected between the OUT pin and ground. Best accuracy is achieved with the

output voltage measured directly across RL. Measuring directly across RL is especially important in high-current

systems where load current could flow in the ground connections and affect measurement accuracy.

No power-supply bypass capacitors are required for stability of the INA1x8-Q1. However, applications with noisy

or high-impedance power supplies may require decoupling capacitors to reject power-supply noise. Connect

bypass capacitors close to the device pins.

10.2 Layout Example

Figure 19. Typical Layout Example