INA300-Q1: Overcurrent not detected

Hi Priya,

can you show us your schematic? How is the shunt chosen?

Kai

Hello Priya,

There are various sources of error that may make the actual trip point higher.  Below are some calculations I did on the possible error you may see in your detection.  As I did not know what your system common mode voltage and power supply were, I assumed they were the same as the conditions used in the datasheet for the listed specifications.  As for your resistors (shunt and limit), I assumed a tolerance of 1%.  After accounting for the possible error, if your device still does not detect, please let me know.

Hello Simmons,

Thanks for your reply.

I have seen your calculation, which is same as i calculated. but yet, circuit is not detecting the overcurrent.

I am sharing the schematic herewith for your reference.

Thanks & Regards,

Priya Bagal

Hello Priya,

I setup a INA300EVM like in the figure below and was able to get the device to trigger.  My setup mimics the voltage conditions your shunt resistor and limit resistor would impose on the INA300-Q1.  At this point I would suspect that either your part is broken or not all of the pins are properly soldered.  So I would inspect your device under a microscope or I would replace the part and assess if a new device will not work.  If you still have issues there may be a layout issue with parasitics or a system issue involving transients destroying your device.

Hello Kai,

Yes I have read your post. I have attached schematic on simmons comment. please check and suggest if you have any solution.

Thanks & regards,

Priya Bagal

Hello Kai,

If we pass 2A current from INA300-Q1, then the voltage at limit resistor is 18mV. We have generated 3.3V by using LDO and the voltage at pin IN+ is 8.4V.

Could you explain the basic work of INA300-Q1. because still i am not got tje solution.

Thanks & Regards,

Priya

Hello Priya,

Presuming you are not overlooking a transient that is damaging your part from connecting the battery or your start up sequence, current passes through your shunt resistor creating a voltage that is compared with the Vlimit voltage, which then triggers the alert to to pull low after 50 μs (since DELAY is tied to ground).  Thereupon, if the alert triggers, the sensed voltage will need to drop 4mV lower than Vlimit, before the Alert will be restored to high.

Hello Priya,

My hardware setup in the lab mimics your conditions and works. Therefore, I suspect there is either a connection issue or your part is damaged. During the overcurrent condition, I need you to probe directly on the INA300 pins to find the voltage differential between device ground and HYS Pin, device ground and LIMIT pin, device ground and ENABLE pin, device ground and LATCH pin, device ground and Supply pin, device ground and DELAY PIN. I also need you to measure the differential between the IN+ and IN- pins. I would like to emphasize that these need be directly on the device pins, which will require fine tipped multimeter probes. In the figure below, I show an example of proper and improper probe placement for measuring the differential between the Limit pin and device ground. Be sure to use the proper placement for all measurements.  Please let me know what voltages you measure.

Hello Kai,

If 2A current flow through the shunt then the voltage at the limit pin is 18mV. the voltage at pin IN+ is 8.4V . we are producing the voltage 3.3V by using LDO UA78M33QDCYRG4Q1. We are not using any cable at that time.

Hello Kai,

Yes, i have managed probe directly on the pins of device & i have checked it at test point end also.

both way overcurrent is not detected.

Hello Javier,

The issue of INA300-Q1  is solved, now the alert signal goes low when i applied 2A load.

 I have added RC filter circuit of capacitor 100nF and Resistor 22ohm value.

But now the new problem is arises  that when i have added switch & control circuit before the load connection and then I have applied 2A load, then alert signal does not go low, it remains high after overcurrent limit exceed.

in short, INA300-Q1 is worked individually, but when it interface with switch and control circuit then alert signal does not go low.

I have used switch & control circuit as like your reference design of Automotive Precision eFuse Reference Design.

so please help us.

Regards,

Priya