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Original question:

LM3492: Input voltage overshoot output

LM3492: working with overvoltage

Andreas Leibig
Prodigy 90 points
Part Number: LM3492

Hello,

from 8.5.1 of the data sheet, I can see that overvoltage will be indicated , but what else will happen?

The following I tried with my evaluation board:

LED string with 43V forward voltage

ILED1=100mA

dimming over PWM

Vin 10VDC-50VDC

The LM3492 didn't get hot or any other problem with the dimming.

Is it possible to use the LM3492 permanently under overvoltage conditions?

The chalange is, that I can not use a buck, because we are working with long cables. So at low current over the cable, we have 48VDC at the Vin but if current increases, we have a 25VDC voltage drop. The LED string can not be changed at the moment.

Regards

Andreas

  • 0
    TI__Mastermind 28655 points

    Hello Andreas,

    From 8.5.1 of the datasheet:  "The device does not latch off and continues to operate in the presence of the IOUT overvoltage indication."

    The LM3492 will continue to operate however there will be more voltage across the internal linear regulating MOSFETs which will create internal heat.  The fault will be present and can be read.  This operating is okay depending on how much power dissipation there is.  I would look at worst case to see how much dissipation there is.  Since this uses a boost converter Vout cannot be lower than Vin.

    Best Regards,