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LM36011: IR mode ramp rate

Austin Allen
Intellectual 1560 points
Part Number: LM36011

Hi team,

I have a question on the ramp rate in IR mode on the LM36011. 

The datasheet specifies that "In IR mode, the current source does not control the ramp rate of the LED output. The current transitions immediately from off to on and then on to off."

Do you have any more details or any test data on what constitutes "immediately" here? Is this just dictated by the parasitics of the specific LED used?

Thanks!

Austin Allen

  • 0
    TI__Expert 6440 points

    Hi Austin,

    Nice to hear you!

    When configure the LM36011 to IR mode, it will be controlled by STROBE pin, and it is level sensitive. So, it may be affected by the STROBE signal ramp up time.

    It is very fast after the STORBE pin is pulled high, you can take below waveform as reference:

    And I can help you test the detailed ramp up time if necessary.

    Thanks!

    BRs,

    Ives Li

  • 0 in reply to Ives Li
    TI__Intellectual 1560 points

    Thanks Ives!

    My one follow-on question would be - does the team think that STROBE ramp-up time would be the limiting factor in IR mode (other than the component’s LED ramp-up time)? Is there anything in the IC design that would limit it as well?

    Thank you!

    Austin Allen

  • 0 in reply to Austin Allen
    TI__Expert 6440 points

    Hi Austin,

    I captured the STROBE pin and ILED waveforms for you, please provide below picture to customer:

    Test condition: VIN=5V, IR mode, ILED=1.5A

    1) Overview:

    2) Ramp up detail 1:

    The delay between STROBE pin turn high and IL start to ramp up is around 4.3us.

    3) Ramp up detail 2:

    The ramp up time between 0-1.5A is around 6us.

    Thanks!

    BRs,

    Ives Li