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LMP8278Q-Q1: taking intermediate output of LMP8278Q to indicate over-current .

Vasu Poojary
Intellectual 440 points
Part Number: LMP8278Q-Q1
Other Parts Discussed in Thread: INA310A

Tool/software:

Hello ,

In our application we want to sense load over-current which is higher than normal current measurement range.

We have plan of taking current sense output at A1 of LMP8278Q and comparing it with reference to give interrupt if over-current scenario .

Will adding this circuit have any impact of normal current monitoring at A2 out which will be connected to ADC ?  Will there be any impedance mismatch or noise issues ?

Please comeback.

  • 0
    TI__Mastermind 32240 points

    Hello Vasu,

    The datasheet goes through multiple scenarios when connecting to the A1 to A2 and 

    Vasu Poojary said:
    Will adding this circuit have any impact of normal current monitoring at A2 out which will be connected to ADC ?

    This depends on the ADC you are driving and the sampling rate.  This is an older device and I am not sure if we have the output impedance for this device.  If you are sampling at a slow rate or with something like a delta sigma it is normally not an issue.   https://www.ti.com/lit/an/sboa443/sboa443.pdf  Please understand with the image above you are filtering the output and reducing the bandwidth.  Also the datasheet has information on A1 and A2 separately to isolate specifications for each input/output

    Vasu Poojary said:
    Will there be any impedance mismatch or noise issues ?

    I would be more concerned with driving the ADC or the comparator.  For ADC I mentioned my concerns above.  For the comparator I have would worry about capacitor on the A1 node as there is a 100kΩ output resistor and any capacitance will slow down the output.  

    We have other devices that may meet your needs like the https://www.ti.com/product/INA310B The B version is more cost effective than the INA310A with specifications like offset being worse.  The biggest difference I see is power for the INA310 requires 4 times as much.

    Regards,

    Javier