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LMV331: LMV331 application questions

Part Number: LMV331


Our customer used LMV331 as the comparator, when the input voltage is lower than some voltage, output is high level and hold it high. When MCU detected it, the IO port output low level and unlocked. But sometimes the supply current of LMV331 could get to 10mA, while normal operation is less than 1mA. Below is the schematic, the purpose of the diode and 1kohm resistor is to make the output high level feedback to the IN+, if the IN+ is higher than IN-, OUT is always high and hold it high until the output is pulled low by MCU. Please help to analyze why the supply current is so high.


Best regards


  • Hi Kailyn,

    at "MCU" an output pin of microcontroller is connected? What when the output of LMV331 is low level but the microcontroller is emitting high level? Then a short circuit current into the output of LMV331 will flow :-(

    Another issue is that the common mode input voltage range could be exceeded at both input pins. The voltage at the input of LMV331 could even become negative, depending on "Vin".

    Also, remove C3. A filtering cap at the +input of any comparator is counterproductive. As if you sit in a car and step on the accelerator pedal and the break pedal at the same time :-(


  • Hello Kailyn,

    As Kai pointed out, there is a possibility of the LMV331's output shorting the MCU output if the MCU is high and the LMV331 output goes low.

    Is the comparator itself drawing 10mA? Or the entire circuit? The comparator is open collector and should not draw that much current from the supply pin. 10mA for the entire circuit is more like it when the output is shorted.

    Consider driving the top of the R1 pull-up resistor from the MCU instead of VCC. When the MCU is "HIGH", that will place 3.3V on top of the pullup, and when it is "low" then the comparator output will be low.

    You can also place a (Schottky) diode in series with the MCU line so that when it goes "low" it will pull-down, but block current when the MCU is high (preventing a short). But this will increase the output low voltage to around 250mV (assuming schottky diode, or 600mV with a regular diode).