Overload conditions are another consideration for the device inputs. The device inputs are specified to tolerate

±40 V differential across the IN+ and IN– pins. A large differential scenario might be a short to ground on the

load side of the shunt. This type of event can result in full power-supply voltage across the shunt (as long the

power supply or energy storage capacitors support it). Removing a short to ground can result in inductive

kickbacks that could exceed the 40-V differential or 85-V common-mode absolute maximum rating of the device.

Inductive kickback voltages are best controlled by Zener-type transient-absorbing devices (commonly called

transzorbs) combined with sufficient energy storage capacitance. See the Transient Robustness for Current

Shunt Monitors reference design which describes a high-side current shunt monitor used to measure the voltage

developed across a current-sensing resistor when current passes through it.

In applications that do not have large energy storage, electrolytic capacitors on one or both sides of the shunt,

an input overstress condition may result from an excessive dV/dt of the voltage applied to the input. A hard

physical short is the most likely cause of this event. This problem occurs because an excessive dV/dt can

activate the ESD protection in the device in systems where large currents are available. Testing demonstrates

that the addition of 10-Ω resistors in series with each input of the device sufficiently protects the inputs against

this dV/dt failure up to the 40-V maximum differential voltage rating of the device. Selecting these resistors in the

range noted has minimal effect on accuracy.

<100

<100

IN+

IN-

VBUS

GND

100 nF

Load

Load

Supply

0.1µF to 1µF

Figure 8-1. Input Filtering

linearity.

8.2 Typical Application

The low offset voltage and low input bias current of the INA229 allow accurate monitoring of a wide range of

currents. To accurately monitor currents with high resolution, select the value of the shunt resistor so that the

resulting sense voltage is close to the maximum allowable differential input voltage range (either ±163.84 mV or

±40.96 mV, depending on register settings). The circuit for monitoring currents in a high-side configuration is

shown in Figure 8-2.

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INA229

SLYS023 – DECEMBER 2020

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