INA229 datasheet(39/48 Pages) TI

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9 Power Supply Recommendations

The input circuitry of the device can accurately measure signals on common-mode voltages beyond its power-

supply voltage, VS. For example, the voltage applied to the VS power supply terminal can be 5 V, whereas the

load power-supply voltage being monitored (the common-mode voltage) can be as high as 85 V. Note that the

device can also withstand the full 0 V to 85 V range at the input terminals, regardless of whether the device has

power applied or not. Avoid applications where the GND pin is disconnected while device is actively powered.

Place the required power-supply bypass capacitors as close as possible to the supply and ground terminals of

the device. A typical value for this supply bypass capacitor is 0.1 µF. Applications with noisy or high-impedance

power supplies may require additional decoupling capacitors to reject power-supply noise.

10 Layout

10.1 Layout Guidelines

Connect the input pins (IN+ and IN–) to the sensing resistor using a Kelvin connection or a 4-wire connection.

This connection technique ensures that only the current-sensing resistor impedance is sensed between the input

pins. Poor routing of the current-sensing resistor commonly results in additional resistance present between

the input pins. Given the very low ohmic value of the current-sensing resistor, any additional high-current

carrying impedance causes significant measurement errors. Place the power-supply bypass capacitor as close

as possible to the supply and ground pins.

10.2 Layout Example

Supply bypass

capacitor

MOSI

MISO

ALERT

IN+

INt

GND

VBUS

SCLK

(1)

SPI

interface

Via to Ground Plane

Via to Power Plane

Alert output

Sense/Shunt

resistor

(2)

(1) Connect the VBUS pin to the voltage powering the load for load power calculations..

(2) Can be left floating if unused.

Figure 10-1. INA229-Q1 Layout Example

www.ti.com

INA229-Q1

SLYS024A – MAY 2020 – REVISED JUNE 2021

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