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VOUT

VLIMIT

ALERT

C001

14

INA301

SBOS713A – SEPTEMBER 2015 – REVISED FEBRUARY 2016

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Copyright © 2015–2016, Texas Instruments Incorporated

7.3 Feature Description

7.3.1 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-k

Ω, pullup

resistor to the supply voltage. This open-drain pin can be pulled up to a voltage beyond the supply voltage, VS,

but must not exceed 5.5 V.

Figure 36 shows the alert output response of the internal comparator. When the output voltage of the amplifier is

lower than the voltage developed at the LIMIT pin, the comparator output is in the default high state. When the

amplifier output voltage exceeds the threshold voltage set at the LIMIT 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 36. Overcurrent Alert Response

7.3.2 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.

7.3.2.1 Transparent Output Mode

The device is set to transparent mode when the RESET pin is pulled low, thus 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. As soon as 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 to connect the ALERT pin to a hardware

interrupt input on a microcontroller. As soon as an overcurrent condition is detected and the ALERT pin is pulled

low, the controller interrupt pin detects the output state change and can begin making changes to the system

operation required to address the overcurrent condition. Under this configuration, the ALERT pin transition from

high to low is captured by the microcontroller so the output can return to the default high state when the

overcurrent event is removed.

7.3.2.2 Latch Output Mode

Some applications do not have the functionality available to continuously monitor the state of the output ALERT

pin to detect an overcurrent condition as described in the Transparent Output Mode section. A typical example of

this application is a system that is only able to poll the ALERT pin state periodically to determine if the system is

functioning correctly. If the device is set to transparent mode in this type of application, the state change of the

ALERT pin can be missed when ALERT is pulled low to indicate an out-of-range event if the out-of-range

condition does not appear during one of these periodic polling events. Latch mode is specifically intended to

accommodate these applications.