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LP5562: Can use the LP5562 LED driver for analog based frequency modulation

Alistair Newcombe
Prodigy 60 points
Part Number: LP5562

As the title says, I want to modulate a RGB LED at different frequencies so I can use a tone search algorithm (FFT etc) in order to distinguish between the signals. I will want to modulating these LEDs at 800 Hz+. Will I be able to send these signals at a fast enough rate over I2C in order to achieve this. From what I have read I believe this is achievable. nut i just want to double check before purchasing this product. Additional can I load the analog current values into the internal memory, there are only examples of loading PMW values into that.

Thankyou for your help.

  • 0
    TI__Genius 14295 points
    Hi, Alistair,

    Do you want to refresh the data at 800Hz or switch the LED at 800Hz?

    LP5562 can just support as high as 558Hz for LED PWM switching frequency.

    Thanks.
    Regards,
    Kenneth
  • 0 in reply to Kenneth Du
    Prodigy 60 points
    Hi Kenneth,

    I want to switch the LED channels at around 800 Hz, so flash them on and off at around 800 Hz. I will be wanting to be flashing each LED channel at a different frequency as I want to be obtaining frequency information from the different channels. Because of this I cant use PWM control, rather I need to use analog current control.

    Cheers
  • 0 in reply to Alistair Newcombe
    TI__Intellectual 950 points
    Hi,
    Based on datasheet, PWM frequency is maximum 558Hz and it can't meet your requirements. However, as you said, you don't use PWM but analog current control. Please attach a diagram or any table to help us understand your idea so that we can better support you.
    Thanks,
    BRs,
    Rosley
  • 0 in reply to Rosley Ge
    Prodigy 60 points
    Hi,

    I want to flash my LEDS on and off at 800 Hz (or any frequency), should that I can flash two leds at difference frequencies and then preform a tone search to differentiate between them. So essential I want to have the LED on for say 0.1 ms, off for 0.1 ms, then on again, and repeat (this would be around 10 Hz - but I want much faster than this). Because I will be doing a tone search for the specific frequency that im modulating the LEDs at i can't use PWM because that will give me a frequency of 558 Hz no matter what actual frequency i want to modulate the LEDs at.

    So is it possible to communicate via I2C fast enough to achieve high frequency current control? In that case, what would be the maximum time require to send a command to the device?

    Additional can i store analog current control values within the internal memory, so i dont have to repeatably sent commands to the device?

    Many thanks,
    Alistair
  • 0 in reply to Alistair Newcombe
    TI__Intellectual 950 points
    Hi,
    Internal memory can't refresh at 800Hz so you can't use internal memory to do it.
    If you want to refresh data at 800Hz, it highly depends on your I2C speed.
    Thanks,
    BRs,
    Rosley
  • 0 in reply to Rosley Ge
    Prodigy 60 points
    Hi,

    Thanks for your reply.



    Are you aware of any TI products that will allow for me have to have current control over the LED and can support switching the current at high frequencies. I don't mind the communication method, or the number of outputs the driver has. Or do you think the best bet would be to use a LED driver with a constant current and then control the blinking pattern of the LEDs with a transistor.



    Cheers.