INA2227 datasheet(32/43 Pages) TI2

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8.2 Typical Application

Ch1 VBUS

Load 1

Load 2

Ch2 VBUS

IN+1

GND

IN-1

IN+2

IN-2

ALERT

SDA

SCL

CBYPASS

0.1 µF

Supply Voltage

(1.7 V to 5.5 V)

INA2227

VBUS1

VBUS2

Figure 8-3. Typical Low-Side Sensing Circuit Configuration, INA2227

8.2.1 Design Requirements

The INA2227 features 2 channels that measure the voltage developed across a current-sensing resistor

(RSHUNT) when current passes through the resistor. The device also measures the bus supply voltage and

calculates power and energy for each channel. The device also comes with alert capability, where the alert pin

can be programmed to respond to a user-defined event or a conversion ready notification.

Table 8-3 lists the design requirements for a single channel of the circuit shown in Figure 8-3.

Table 8-3. Design Parameters for Channel 1

DESIGN PARAMETER

EXAMPLE VALUE

Power-supply voltage (VS)

3.3V

Bus supply rail (VCM)

12V

Average Current

Overcurrent fault threshold

Maximum current monitored (IMAX)

10A

ADC Range Selection (VSENSE_MAX)

±81.92mV

Energy Accumulation Period

1 hour

8.2.2 Detailed Design Procedure

This design example walks through the process of selecting the shunt resistor, programming the calibration

channel 1 of the device. The configuration of additional channels is similar with calculated values programmed

into the registers corresponding to the appropriate channel.

8.2.2.1 Select the Shunt Resistor

Using values from Table 8-3, the maximum value of the shunt resistor is calculated based on the value of

the maximum current to be sensed (IMAX) and the maximum allowable sense voltage (VSENSE_MAX) for the

chosen ADC range. When operating at the maximum current, the differential input voltage must not exceed the

maximum full scale range of the device, VSENSE_MAX. Using Equation 6 for the given design parameters, the

maximum value for RSHUNT is calculated to be 8.192mΩ. The closest standard resistor value that is smaller than

the maximum calculated value is 8.0mΩ. Smaller resistors can be used to minimize power loss at the expense

INA2227

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