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INA300: INA300 connection check

Part Number: INA300

hi Team,

customer using INA300 to detect an overcurrent and give an alert

the voltage across the Rsense will have charge current and discharge current. the INA300 is only required to detect the discharge over current event.

apparently from the current schematic it will not work,

I've asked to make the following changes, but still not able to trigger output 

please help double check on the connection and any comments are apprecaited, 

Pin 1 : connect to the high voltage side of the Rsense voltage

Pin 2 : connect to the low voltage side of the Rsense voltage

Pin 3 : setting the alert threshold limit

Pin 4: should connect to Vs

Pin 5: Alert output with pull high from Vs

Pin 6: connect to gnd for transparent output mode

Pin 7: connect to gnd for 50us

Pin 8:GND

Pin 9: connect to 2.7 to 5.5V

Pin 10: floating

  • John,

    A few things stand out here, and it looks like you've addressed most of them in your recommendations to the customer. I agree that they need to address Enable by attaching it to Vs, and ensuring that they ground pin 6 if they do not need the device to be in latch mode. Can you share what sense resistor is being used for each of these devices?

    I think the largest issue here that might be causing them problem is more than likely the customer's choice of pull-up resistor. If you look at at section 10.1 of the datasheet, we recommend using a 10k resistor to pull up for this device, and your customer has used a 10M resistor, 3 complete orders of magnitude larger than recommended. When you get up into impedances this large, in addition to potentially restricting current beyond an ability to properly drive the device, you can also potentially run into loading effects from the resistor, essentially creating a voltage divider through the device. We have a great resource here that discusses the pro's and con's of resistor selection for open drain. 

    In summary, here's a few things I would recommend trying:

    - Have your customer probe the 10Mohm resistors and see how much of Vs is being absorbed by them against the high impedance of the pin. They can also probe at pin 5 to see how much voltage is actually being realized by the device as a result of my comment above.

    - Have your customer replace the 10Mohm resistor with 10kohm ones. If this solves the issue, and they wish to use a larger value, they can play around with the value empirically to optimize their system, or use the equations in the above linked documentation for power optimization purposes.

    - Have them remove the signal chain leading to RTC, T, P, etc., and see if they can get the output to pull low in this state. It would be helpful to decouple this and isolate the devices to see if there is any undesired activity from this circuitry.

    Try these above and let me know if this alleviates the issue.