Time (5 ms/div)

Positive Limit

Negative Limit

0 V

30

INA302, INA303

SBOS775C – SEPTEMBER 2016 – REVISED MARCH 2019

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Typical Application (continued)

8.2.1 Design Requirements

To allow for bidirectional monitoring, the INA303 requires a voltage applied to the REF pin. A voltage that is half

of the supply voltage is usually preferred to allow for maximum output swing in both the positive and negative

current direction. To reduce the errors in the reference voltage, drive the REF pin with a low-impedance source

(such as an op amp or external reference). A low-value resistor divider can be used at the expense of quiescent

current and accuracy. For this design, a single alert output is preferred, so both ALERT1 and ALERT2 are

connected together and use a single pullup resistor.

8.2.2 Detailed Design Procedure

To achieve bidirectional monitoring, drive the reference pin halfway between the supply with a resistor divider

buffered by an op amp, as shown in Table 5. To reduce the current draw from the supply, use 100-kΩ resistors

to create the divide-by-two voltage divider. The TLV313-Q1 is selected to buffer the voltage divider because this

device can operate from a single-supply rail with low IQ and offset voltage. To minimize the response time of the

ALERT2 output, a 100-kΩ pullup resistor was added from the DELAY pin to the VS pin. Select values for RSENSE,

RLIMIT2, and RLIMIT1 based on the desired current-sense levels and trip thresholds using the information in the

Resistor-Controlled Current Limit and Selecting a Current-Sensing Resistor (RSENSE) sections. For this example,

the values of RLIMIT1 and RLIMIT2 were selected so that the positive and negative overcurrent thresholds are the

same. Table 5 shows the alert output of the INA303 application circuit with the capability to detect both positive

and negative overcurrent conditions.

Table 5. Bidirectional Overcurrent Output Status

OVERCURRENT PROTECTION (OCP) STATUS

OUTPUT

Positive overcurrent detection (OCP+)

0

Negative overcurrent detection (OCP–)

0

Normal operation (no OCP)

1

8.2.3 Application Curve

Figure 53 shows the INA303 device being used in a bidirectional configuration to detect both negative and

positive overcurrent events.

Figure 53. Bidirectional Application Curve