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LM5118 EN pin threshold

Arnauld Guiheneuf
Prodigy 100 points
Other Parts Discussed in Thread: LM5118

Hi,

The LM5118 datasheet states the following: If the EN pin is below 0.5V, the regulator will be in a low power state drawing less than 10 µA from VIN. EN must be raised above 3V for normal operation.

The exact same data can be found in the Electrical Characteristics (EN INPUT)

However, it appears that the EN Input High Threshold is much lower in my circuit (around 1.7V). Can it be specific to the chip I am using or is there an error in the datasheet?

FYI, I use a resistor voltage divider on the EN pin in combination with another resistor voltage divider on the UVLO pin to provide a wide input voltage turn-on/turn-off window. E.g. Turns on @ Vin=20V, and locks on till Vin drops below 12V.

  • 0
    TI__Guru 58241 points

    Hi

    There is no error about EN threshold on the datasheet. 0.5V and  3.0V thresholds are guaranteed value over temperature.

    Regards,

    Eric

  • 0 in reply to EricLee
    Prodigy 100 points

    Hi Eric,

    I have done some more measurements today and results are consistent on the five boards I have tested. I am not getting the specified thresholds for the EN Input:

    VIH=1.7V, VIL=1.1V (+/- 0.05V across different boards)

    For this test above, I directly connected my adjustable bench power supply to the EN pin.

    Part marking FYI: LM5118Q1MH ; batch code: JM07AB and JM22AC

    Please advise.

    Thanks and regards,

    Arnauld

  • 0 in reply to Arnauld Guiheneuf
    TI__Guru 58241 points

    Hi Arnauld

    Your measurements are right. Nothing wrong on your measurement results. You just measured only 5 units at room temperature while the 0.5V and 3V thresholdsin the datasheet are guaranteed maximum/mimimum thresholds over the operating temperature range including part-to-part variation.  

    Regards,

    Eric

     

  • 0 in reply to EricLee
    Prodigy 100 points

    Right I get it now. The way the EN pin operation is detailed (Pages 2,4,9) is a bit confusing to me. Threshold is a misleading term in the electrical characteristics table; it somehow got me to think that the EN pin was some sort of Schmitt trigger input. VIL and VHL are actually guaranteed levels rather than thresholds.

    Thank you.

    Arnauld