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LM3644: LM3644 Torch mode Setting

Zeno Lee
Prodigy 40 points
Part Number: LM3644

Tool/software:

Hi All,

We used the LM3644 to drive LED in Torch mode.

But we find the torch mode can't be set at some devices.

We have checked the schematic, the Torch pin and Strobe pin are floating.

Do those two pins need to be connect to "High"? 

Or have any idea for this problem?

Thank you.

Zeno

  • 0
    TI__Intellectual 1840 points

    Hi Zeno, 

    Could you please share the register value of both the good torch device and the not torch one? I can help you debug. 

    Thank you! 

    Best, 

    John. 

  • 0 in reply to John Shen
    Prodigy 40 points

    Hi John,

    Thank you for your reply.

    The Enable registor value : 

    Set Enable Register => 0b10001011 (0x88) ,

    but read the Enable registor value is :

    Read Enable Register => 0b10000011 (0x83)

    And we read the Fault flag (0x0A &0B), the flag value :

    Read Flag1: 0x80 (0x0A)

    Read Flag2: 0x02 (0x0B)

    Thank you.

    Zeno

  • 0 in reply to Zeno Lee
    TI__Intellectual 1840 points

    Hi Zeno, 

    In torch mode you used, you could leave Torch pin and Strobe pin floating. It should work. 

    It is very weird that the OVP fault bit is 1 in 0x0B register. There might be LED open happening when turn on the current, or the LED VF is too large. Could please show me the LED you are using? Could you please capture a waveform at that moment? 

    Thanks! 

    Best, 

    John.