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INA302, INA303

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SBOS775C – SEPTEMBER 2016 – REVISED MARCH 2019

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7.4 Device Functional Modes

7.4.1 Alert Operating Modes

Each comparator has two output operating modes: transparent and latched. These modes determine how the

ALERTx pins respond when an out-of-range condition is removed. The device is placed into either transparent or

latched state based on the voltage applied to the corresponding LATCHx pin, as shown in Table 1.

Table 1. Output Mode Settings

OUTPUT MODE

LATCHx PINS SETTINGS

ALERTx transparent mode

LATCHx = low

ALERTx latch mode

LATCHx = high

7.4.1.1 Transparent Output Mode

The comparators are set to transparent output mode when the corresponding LATCHx pin is pulled low. When

set to transparent mode, the output of the comparators changes and follows the input signal with respect to the

programmed alert threshold. For example, when the amplifier output violates the set limit value, the ALERTx

output pin is pulled low. As soon as the differential input signal drops to less than 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 ALERTx pins to a hardware interrupt input on a microcontroller. The ALERTx pin is pulled low as

soon as an out-of-range condition is detected, thus notifying the microcontroller. The microcontroller immediately

reacts to the alert and takes action to address the overcurrent condition. In transparent output mode, there is no

need to latch the state of the alert output because the microcontroller responds as soon as the out-of-range

condition occurs.

7.4.1.2 Latch Output Mode

The comparators are set to latch output mode when the corresponding LATCHx pin is pulled high. Some

applications do not continuously monitor the state of the ALERTx pins as described in the Transparent Output

Mode section. For example, if the device is set to transparent output mode in an application that only polls the

state of the ALERTx pins periodically, then the transition of the ALERTx pins can be missed when the out-of-

range condition is not present during one of these periodic polling events. Latch output mode allows the output of

the comparators to latch the output of the range condition so that the transition of the ALERTx pins is not missed

when the status of the comparator ALERTx pins is polled.

The difference between latch mode and transparent mode is how the alert output responds when an overcurrent

condition is removed. In transparent mode (LATCH1, LATCH2 = low), when the differential input signal drops to

within normal operating range, the ALERTx pin returns to the default high setting to indicate that the overcurrent

event has ended.

In latch mode (LATCHx = high), when an out-of-range condition is detected and the corresponding ALERTx pin

is pulled low; the ALERTx pin does not return to the default high state when the out-of-range condition is

removed. In order to clear the alert, the corresponding LATCHx pin must be pulled low for at least 100 ns. Pulling

the LATCHx pins low allows the corresponding ALERTx pin to return to the default high level, provided the out-

of-range condition is no longer present. If the out-of-range condition is still present when the LATCHx pins are

pulled low, then the corresponding ALERTx pin remains low. The ALERTx pins can be cleared (reset to high) by

toggling the corresponding LATCHx pin when the alert condition is detected by the system controller.