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LM3645EVM: Unable to detect LED open detection when strobe frequency is higher than 1.4Khz

Sarthak Mutreja
Prodigy 30 points
Part Number: LM3645EVM

Tool/software:

Hi,

I hope this thread finds you well! In the IR mode we are unable to detect led open detection. We have some below observations.

1) In case of IR mode If the strobe frequency is above 1.4Khz, it is not able to detect the led open in led drive mode priority with voltage mode disable.
2) Below 1.4khz if we remove one of the led and check the 15 flag it is able to detect the led open.

We are giving strobes from the Arduino Uno board with on time-> 100uS, off time-> 100uS.

Regards

  • 0
    TI__Mastermind 34875 points

    Hi John,

    There should be flag delay time if LED open is detected.

    You  can check it as below:

    1. set strobe freq = fixed 1KHz

    2, decrease ON time from 400us to 100us.

    3. check the flag data if LED open reported.

  • 0 in reply to Andy Chen
    Prodigy 30 points

    Hi Andy,

    We set the strobe frequency fixed 1 KHZ 
    time on: 100uS and time off 900uS 
    Its not reporting in the LED drive priority mode with voltage mode disable.

    Just for your information i am using 4 led and i removed one to check the open flag detection, also i am using arduino uno for driving strobe signal.
    The register setting is 
    0x00 -> 52
    0x01-> 1F
    0x02-> 55
    0x03-> 0F
    0x5,6,7,8-> 10

    Please let us know if the config above is correct or not

    For My use case, i want 6KHZ to be the strobe frequency and want if any led is open it should be detected as open.

    Regards

  • 0 in reply to Sarthak Mutreja
    TI__Mastermind 23190 points

    Hi Sarthak,

    Our expert is currently out of office and will reply to you later. Thanks for your understanding.

    Best Regards,

    Steven

  • 0 in reply to Steven Li
    TI__Mastermind 34875 points

    Hi Sarthak

    Did you check OVP by bit6 of reg 0x15?

    How do you set bit 5&6 of reg 0X12----can you try IR ramp disable or 32us?

    Did you check actual waveform applied on STROBE1 pin?

  • 0 in reply to Steven Li
    TI__Mastermind 34875 points

    Hi,

    Besides Strobe1 waveform, did you also check waveform on OUT pin?  the OUT voltage should be >5.7V to report OVP even though only 1 LED is open.