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[LP8501/LP55231] Max switching frequency

Florian Engesser
Prodigy 30 points
Other Parts Discussed in Thread: LP55231, LP8501, LP5523

Hello,

we want to use the LP8501 or the LP55231 to drive some white µLEDs. The LEDs should be switched On/Off with a frequency around 2kHz. If I understand the datasheet correctly the PWM frequency is 312Hz. Is there a way to change that value manually? If not is the driver still capable to drive the LED, disregard the PWM function, with the desired settings?

Regards,

Florian E.
  • 0
    TI__Intellectual 2510 points

    Hi Florian,

    There is not bit to change the PWM frequency for these devices.

    Can you tell me more about the application or the LEDs? Is the 2kHz requirement coming from the application? How much are you needing the programmablity of the device (the LED engines)?

    You could also set the PWM to 100% and set the brightness with current. There is 8-bit current control for each LED output, but this is not available with the LED engines.

    Also I would like to note that the LP8501 is a DSBGA device and LP55231 is a WQFN. There is LP5523 also, which is DSBGA device.

    Thank you,

    Sami

  • 0 in reply to Sami Kotijarvi
    Prodigy 30 points

    Hi Sami,

    we want to drive up to 24 GaInN-µLEDs. They are located on flexible a PI substrate and they are designed with a common cathode so we need to switch their anodes. In addition we want to control the current of each µLED separately. The above mentioned drivers offer all these features.

    Each channel needs to be adressed independently. And yes the 2kHz are comming from the application. We don't need to go faster than that.

    I don't think we need the LED engine feature.


    Those drivers are the only ones I found that have a programmable current source. Most drivers only allow sinking current.

    Regards,

    Florian E.

  • 0 in reply to Florian Engesser
    TI__Intellectual 2510 points

    Hi Florian,

    I want to clarify this for myself still a little so please bear with me.

    In these devices we have current control and PWM duty cycle control for each LED output (both eight bits). The PWM frequency is 312 Hz (typically).

    You would like to control the current for each channel individually, which works fine. Do you need to change the PWM frequency for each channel as well? These devices do not support external PWM control possibility.

    In case you want to talk more details, you can contact me also via email directly.

    Regards,

    Sami

  • 0 in reply to Sami Kotijarvi
    Prodigy 30 points

    Hi Sami,

    I wrote you an Email.

    Regards, 

    Florian E.