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INA300: Start-up mode

Cobus Hoffmann
Prodigy 20 points
Part Number: INA300

It looks like the INA300 IC starts-up in transparent mode. 

Is there a way that you can start-up in Latch mode?

CH1 - Output current

CH2 - Alert signal

CH3 - Enable signal

CH4 - Latch signal

 

A) U10 starts-up in transparent mode even when forcing LATCH pin high with external power supply

B) MCU boots up and toggles enable line

C) Over current event occurs and latches alert low turning off U9

  • 0
    TI__Mastermind 31815 points

    Hello,

    Welcome to the forum. I am looking this over and will respond shortly.

    Best,

    Peter

  • 0
    TI__Mastermind 31815 points

    Hello valued engineer,

    Could you please send a schematic of the device and MCU?

    Also, why is the device toggling the enable pin? This seems to also be toggling the ALERT pin. Is there any example where the ALERT does not go and stay low on power up with an over current condition?

    Thank you.

    Best,

    Peter

  • 0 in reply to Peter Iliya
    Prodigy 20 points

    Hi Peter, 

    Thanks for the quick response. 
    Here is a snippet of the relevant part of the circuit. 


    The diode D20 is used to pull ALERT low when the micro toggles ENABLE.

    The ALERT line is used to drive a high side smart FET, via some additional circuitry. 

    I am not the designer of the circuit, but I am doing some testing and found that the current sense IC starts up in transparent mode even when LATCH is kept high on start up. 

    I know this IC has a 1ms start-up time so I am wondering if this is playing a role, since it behaves as intended once the micro wakes up and toggles the ENABLE line.

  • 0 in reply to Cobus Hoffmann
    TI__Mastermind 31815 points

    Hello Cobus,

    I assume R74 and R77 are not populated. Please confirm.

    I also assume there is a pull-up resistor for the ALERT pin. Please confirm this value.

    I am confused with the diode connecting ENABLE and ALERT. What is the point of this? Maybe D20 should be removed to check to see if this is what is causing the unexpected behavior.

    It is not clear to me that the device is starting up in transparent mode. Could you please send a scope shot of the following:

    • The over current condition is present (sense current > 1.815 mA) with INA300 turned off.
    • The LATCH pin is pulled up to 3.3V with external source (LATCH mode)
    • The INA300 is turned on and ALERT pin goes LOW because sensed current exceeds threshold
      • This should cause the load current to open up via some feedback loop in system
    • Once load current goes to 0A, the ALERT pin incorrectly goes back to high, when it should just remain low because device is in latch mode

    Thank you,

    Peter