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LP8556: A boost LED driver with individual segment control

matt meerian
Prodigy 30 points
Part Number: LP8556
Other Parts Discussed in Thread: LP8551, , TLC5940, LP55231

Hi, I’m looking for a boost type IC that can individually control which LED outputs are on through I2C. There are several backlight drivers that are close to the requirements: TPS61199PWPR, LP8556, LP8551, etc. (but, they do not have individual segment control) The end usage will be a point of sale product that will have individual 5mm LED segments turn off and on.

Here are my ideal requirements:

- Step up boost LED driver

- 4 to 16 LED outputs per IC

- The Vin = 12V to 24V

- 10mA to 20mA per segment output

- Would like a I2C or SPI control (the individual outputs should be able to be turned off, individual PWM control for each channel is not necessary)

Matt M.

  • 0
    TI__Intellectual 1985 points

    Hi Matt,

    Need a few more details from you on your requirement.

    1. How many LEDs are there in each segment? Are connected in series or parallel? this will determine the output voltage require.

    2. Is Vin fixed or it can fluctuate from 12V to 24V?

    3. When you mentioned 4 to 16 LEDs per IC, can you elaborate a little more on arrangement of these LEDs?

    Typical backlight drivers does not support control of individual channels. We do have other products that can support 16 LEDs and each LED can be individually control. Check out TLC5940.

    Regards
    H L

  • 0 in reply to Hak-Leong Ng
    Prodigy 30 points
    One application for the IC would be used on various sizes of scoreboard digits. (7-segment displays) The individual segments on the digits would be made up of 5mm LED’s (red, green, amber, or white) There could be up to 220, 5mm LED’s on a through hole board.

    The main goal would be to put the driver IC(s) and MCU on a surface mount daughter board. The daughter board would then be attached to the main through hole LED board. (we are looking at getting away from using solder pallets to combine surface mount and plated through hole on the same board) We are looking at minimizing the number of connections between the daughter board and through hole board, which is why having more LED’s in a string by boosting the voltage seems to be the way to go. (multiplexing the LED’s is not an option)

    Answers:
    1) There is a variable number, depending on the digit board. Connected in series.
    2) The input voltage would be fixed at 12V or 24V. (depends on the application)
    3) The LED’s will be arranged in a 7-segment configuration

    If it helps, the ST part LED7708 is almost an ideal solution, except for the long lead times.

    We use an IC very similar to the TLC5940 in our existing design.

    Matt M.
  • 0 in reply to matt meerian
    TI__Intellectual 1985 points
    Hi Matt,

    Is there a reason why TLC5940 is not an option now?

    For most backlight drivers, you can control the brightness level for all, but not individually. For indicator driver, you can control individually, but typically it only supports 1 LED per channel, like LP55231.

    Do you need to control the brightness individually or just need to be ON and OFF individually and the brightness can stay the same for all those that are on?

    24V input can be a problem, most of our backlight driver can only go up to 20V,

    Regards
    H L
  • 0 in reply to Hak-Leong Ng
    TI__Intellectual 1985 points
    Hi Matt,

    Do you have more questions related to LP8556?

    Regards
    H L
  • 0 in reply to Hak-Leong Ng
    Prodigy 30 points

    I do not.  Thanks for your time.

    Matt M.