INA302 Current Monitor: 7 Checks for Warning and Critical Alerts
INA302 Current Monitor: 7 Checks for Warning and Critical Alerts
INA302 checks for two overcurrent thresholds, REF-aware scaling, delayed warning qualification and independently latched alerts. This is a documentation-based planning guide, not a report of independent hands-on testing.
1. Distinguish two overlimits from a window comparator
The INA302 combines a bidirectional current-sense amplifier with two overlimit comparators. Its sibling INA303 implements a different window-comparator arrangement; the shared datasheet does not make the two alert functions interchangeable. The INA302 operates from 2.7 V to 5.5 V and supports the documented input common-mode range from minus 0.1 V to 36 V. Define supply, monitored bus, current direction and transient exposure separately before choosing warning and critical thresholds for a protected low-voltage test fixture. Manufacturer documentation.
2. Include REF in the output and trip equations
The amplifier output equals sensed current multiplied by shunt resistance and gain, plus the applied REF voltage. Available fixed gains are 20, 50 and 100 according to the ordering suffix. A nonzero reference supports signed current interpretation, but also shifts the comparator threshold calculation. Check reference-source behavior and output headroom over the whole current range. A formula copied from a ground-referenced unidirectional circuit can place both alerts at the wrong currents even if the resistor arithmetic itself is correct. Manufacturer documentation.
3. Set each threshold in amplifier-output volts
Each LIMIT pin is compared with amplifier output, not directly with shunt voltage. With the typical 80 microamp limit-setting source, the nominal resistor is the desired amplifier trip voltage divided by 80 microamps. For example, a 1 V reference, gain 20, 0.01 ohm shunt and 1 A positive trip imply 1.2 V and approximately 15 kilohms. Apply the specified limit-source, comparator, reference, shunt and amplifier errors, and ensure the limit voltage satisfies its documented range at the chosen supply. Manufacturer documentation.
4. Assign fast and delayed alerts intentionally
Comparator 1 provides the fast alert path, while comparator 2 supports an externally programmed delay. A useful arrangement is a delayed lower warning threshold and a higher critical threshold on the fast path, but that assignment remains an application decision. The ALERT2 delay follows the manufacturer capacitor relation, including its fixed timing contribution; it is not just an arbitrary RC filter. An overlimit event must persist through the qualification interval to produce the delayed alert. Test pulse duration as well as amplitude. Manufacturer documentation.
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5. Select latch behavior independently for each output
LATCH1 and LATCH2 control their respective alert modes: low selects transparent operation and high selects latching. The two outputs need not use the same recovery policy. A latched alert remains active after the current returns to normal; clear it by pulling the corresponding latch control low for at least 100 ns when the overlimit condition has ended. Return the pin high to rearm latching. A reset request cannot clear a real continuing fault into a healthy state. Manufacturer documentation.
6. Treat open-drain alerts as observations not disconnectors
Both alerts are active-low open-drain outputs and need suitable pull-ups. Check receiver compatibility, pull-up voltage limits and rise time, especially when the host supply differs from the monitor supply. Response-time specifications depend on overdrive and conditions and do not include software or actuator latency. The INA302 does not itself interrupt the power path. A switch, fuse or other independent protection requires its own design review; two comparator outputs do not make the monitor a complete certified safety system. Manufacturer documentation.
7. Test warning timing and critical recovery separately
Record actual current, shunt temperature, REF, OUT, both LIMIT voltages, delay components, latch controls and alert states. Apply bounded current steps and short pulses to verify which path responds and whether the warning qualification rejects the intended transients. Repeat the clear-and-rearm procedure after removing the event. Compare results with tolerance bands rather than a single ideal calculation. The final record should distinguish measured current direction, warning persistence, a critical crossing and a stored historical fault. Manufacturer documentation.
Related reading: INA301 Current Monitor: 7 Checks for a Meaningful Overcurrent Alert.
Catalog note: The exact-part search did not return a matching Epro listing during preparation. Check the current catalog; this guide makes no price, availability or included-accessory claim.