PT4115 LED-Square

Status: RETIRED
Availability: design files

IMGP9025

A small 50x50mm board with 6 high-efficiency Nichia LEDs driven by a PT4115 buck regulator. Total light output was about 180lm for the first version (see below), the upgraded version is essentially twice the brightness. It runs with 24V and consumes about 100mA (first version) / 200mA (upgraded version).

Some images from older versions:

8 Responses to PT4115 LED-Square

  1. Arun says:

    Do I need a zener diode and 1k resistor for DIM pin when using arduino pwm ? or 1k resistor enough ?

    • robert says:

      From personal experience I recommend using a Zener diode plus resistor.

      • Arun says:

        My PT4115 worked well for around 24 hours doesn’t get hot. Now it gets too hot, turns off and on the LEDs alternatively. What would be the reason bad caps or inductor spiking?

        • robert says:

          It’s dead. I had a few die like this before I used the Zener protection. You can measure the dim pin input resistance once you’ve taken out the chip. Should be high when chip OK.

          What supply voltage & LED current were you using?

          • Arun says:

            it is around 37.1 Kilo-ohms . I left DIM pin float . it gets hot even with no load .
            my 2nd chip faced this same problem after 2 weeks.

            • robert says:

              The chips I killed had about 6 Ohm to GND. Symptons: LEDs always ON (no switching, very high current) or always OFF.

              Still, 37.1k is rather low for an input pin. All my boards died by touching them with my fingers while they were on. I guess either ESD or I somehow bridged VCC to DIM. Once I had the Zener-Diode protection on the layout, not a single one has died so far.

          • Arun says:

            which type of decoupling capacitor do you recommend for this IC ?

            • robert says:

              I used 1x 4.7µF ceramic X5R next to the chip and 4x on the bus connectors. This works for my board (200mA, 24V from a clean DC power supply). I don’t remember if I ever measured ripple voltage, it worked in this case. YMMV. There are some hints in the datasheet on page 12.

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