Table 8-4. Register Values (continued)

Register Name

Contents

Right Shifted 12 -

bit Value

LSB Value

Calculated Value

Power (3h)

450d (1C2h)

—

Current LSB x 32 = 160 mW/LSB

450 × 160 mW = 72 W

Shunt Voltage and Current return values in two's complement format. In two's complement format a negative

value in binary is represented by having a 1 in the most significant bit of the returned value. These values can

be converted to decimal by first inverting all the bits and adding 1 to obtain the unsigned binary value. This value

should then be converted to decimal with the negative sign applied.

9 Power Supply Recommendations

Figure 8-2 shows that the device input circuitry can accurately measure signals on common-mode voltages

whereas the bus power-supply voltage being monitored (the common-mode voltage) can be as high as 28 V.

The device can also withstand the full -0.3 V to 28 V range at the input pins, regardless of whether the device

has power applied or not.

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

device to ensure stability. A typical value for this supply bypass capacitor is 0.1 µF. Applications with noisy or

high-impedance power supplies can 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.

These connection techniques ensure that only the current-sensing resistor impedance is detected 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.

INA234

SBOS844A – MAY 2021 – REVISED AUGUST 2021

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