VOUT

ALERT

CMPREF

-1

0

1

2

3

4

5

6

Time (2ms/div)

9

INA381

www.ti.com

SBOS848 – DECEMBER 2017

Product Folder Links: INA381

Submit Documentation Feedback

Copyright © 2017, Texas Instruments Incorporated

Feature Description (continued)

7.3.3 High Bandwidth and Slew Rate

The INA381 supports small-signal bandwidths as high as 350 kHz, and large-signal slew rates of 2 V/µs. The

ability to detect rapid changes in the sensed current, as well as the ability to quickly slew the output, makes the

INA381 a good choice for applications that require a quick response to input current changes. One application

that requires high bandwidth and slew rate is low-side motor control, where the ability to follow rapid changing

current in the motor allows for more accurate control over a wider operating range. Another application that

requires higher bandwidth and slew rates is system fault detection. The integrated comparator within the INA381

is designed to quickly detect when the sense current is out of range and provides a digital output on the ALERT

pin for quicker and faster responses.

7.3.4 Alert Output

The device ALERT pin is an active-low, open-drain output that is designed to be pulled low when the input

conditions are detected to be out-of-range. This open-drain output pin is recommended to include a 10-kΩ pullup

but must not exceed 5.5 V.

Figure 2 shows the alert output response of the internal comparator. When the output voltage of the amplifier is

lower than the set reference voltage on CMPREF, the comparator output is in the default high state. When the

amplifier output voltage exceeds the reference voltage set at the CMPREF pin, the comparator output becomes

active and pulls low. This active low output indicates that the measured signal at the amplifier input has

exceeded the programmed threshold level, indicating an overcurrent or out-of-range condition has occurred.

Figure 2. Overcurrent Alert Response

7.3.5 Alert Mode

The device has two output operating modes, transparent and latched, that are selected based on the RESET pin

setting. These modes change how the ALERT pin responds following an alert when the overcurrent condition is

removed.

7.3.5.1 Transparent Output Mode

The device is set to transparent mode when the RESET pin is pulled low, allowing the output alert state to

change and follow the input signal with respect to the programmed alert threshold. For example, when the

differential input signal rises above the alert threshold, the alert output pin is pulled low. When the differential

input signal drops below the alert threshold, the output returns to the default high output state. A common

implementation using the device in transparent mode is connecting the ALERT pin to a hardware interrupt input

on a microcontroller. When an overcurrent condition is detected and the ALERT pin is pulled low, the controller

interrupt pin detects the output state change and begins making changes to the system operation required to

address the overcurrent condition. Under this configuration, the ALERT pin high-to-low transition is captured by

the microcontroller so the output returns to the default high state when the overcurrent event is removed.