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LM36274: questions on LED current ramp function

Given Ding
Expert 8025 points
Part Number: LM36274

Hi Team, 

there is a questions on LED current ramp function. 

we change ramp through REG0x03 bit [6-3] to adjust current ramp but we found that it only affects when led current change from low to high. But if led current change from high to low, it doesn't have effect. 

we test on EVM and it's same situation. Please kindly help check and explain on the reason. thanks. 

BRs

Given 

  • 0
    TI__Mastermind 22980 points

    Hi Given,

    I'll try repeating this symptom on our EVM first. Reply will be sent tomorrow.

    Best Regards,

    Patrick Yao

  • +1
    TI__Mastermind 22980 points

    Hi Given,

    I can't repeat this symptom on our EVM. The current ramp is working normally when current changes from low to high and high to low.

    I set the ramp time as 20ms (REG0x03 is set as 0xBD). The current changes from 15mA to 30mA (low to high) and 30mA to 15mA (high to low).

             

    A 10Ω resistor is used to acquire the LED current so the waveform is measured as voltage. ILED=V/10

    Could you please send us more details about your working conditions? Such as Vin, Vout and registers' settings.

    This will be very helpful for deeper analysis.

    Best Regards,

    Patrick Yao

  • 0 in reply to Patrick Yao
    TI__Expert 8025 points

    Hi Patrick, 

    Thanks for your reply.

    we'll double check. Thanks. 

    BRs

    Given