LED driver with RL filter

Discussion in 'The Projects Forum' started by kaznov, Feb 26, 2013.

  1. kaznov

    Thread Starter Member

    Mar 10, 2012
    Hi guys
    I was looking over DD311 chip which is a high constant current driver and I foun in its datasheet sayin that " the longer rise time and fall time of the EN dimming signal, adjustable by RC filter, produce the smooth transient response of output current "
    how can I know if they mean RC low pass filter or high filter , also how would I know which value of R and C that would fit the best please

    here is their datasheet

    any help will be appreciated
  2. crutschow


    Mar 14, 2008
    The diagram shows an RC low-pass filter at the input. From the scope diagrams of the output with the filter, I would estimate the filter has a time-constant of around 200ns. This can be achieved with a 1kΩ resistor and a 200pF capacitor.