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LM3644: how to use Flash mode?

Jesse Lee
Expert 1985 points
Part Number: LM3644

hello

we want to set LM3644 in Flash mode, how do i to set the hardware and Registers?

Now out setting is:

1. TX pin was pulled down to Ground with 300K Resistor.

2. HWEN pin was pulled up to VDD.

3. STROBE pin connect with GPIO

After we write the register 0x01 to 0x8D,  is it turn on the flash mode ?  and do we need to send a high level interrupt to active Flash?

Now we write the register 0x01 to value of 0x8D, then read it, the value is 0x81; while we write to 0x8C, and read the value ,it become to 0x80.LM3644--SMV135A PC BOARD-A.pdf

  • 0
    TI__Mastermind 22745 points
    Hi Jesse,
    I think the phenomenon is a little strange, yes, it shoud write 0x8C to reg 0x01 to enter flash mode.
    1.when you write 0x8D to reg0x01, it will enbale LED1 and LED2 ,but you only connect LED1 load, so it will report falut OVP, you can try to read on reg 0x0C, and it will returen to defalut 0x81 standby mode.
    2. When you write 0x8C to reg 0x8D, but you read 0x80, this is a little strange. I suggest you connect the LED load and test again.
    I suggest you test again with LED load again.
    Regards
    Sean
  • 0 in reply to Sean Zhou
    Expert 1985 points
    thanks
    If we don't control the TX pin(no input on TX), and just write 0x8C to reg0x01, whether the LED1 can flash?
  • 0 in reply to Jesse Lee
    TI__Mastermind 22745 points
    Hi Jesse,
    yes, TX pin has two function, one is for Torch mode, another is for interuption. You can get detail description from the datasheet.
    Regards
    Sean
  • 0 in reply to Sean Zhou
    Expert 1985 points

    I don't think the description is elaborate.

    we find that the torch mode is normal.  why just the flash mode can not work?
    we set the regiters value as :  0x8C， 0x01, 0xBF, 0x00, 0xBF, 0x00,  0x09, 0x1A, 0x08, 0x00, 0x04, 0x02, 0x00

  • 0 in reply to Jesse Lee
    TI__Mastermind 22745 points
    Hi Jesse,

    Can you give me some wavefroms when you use the flash mode? When the device is enabled in Flash Mode through the Enable Register, all mode bits in the Enable Register are cleared after a flash time-out event.
    Your need to write 0x8D to reg0x01 to enable LED1 and enter flash mode. Other regs are ok.

    Regards
    Sean