Hello,
We've bought the TL4242 evaluation board to test with Wurth power leds (datasheet - code 158353027) . Vf is 3.2V, If is 350mA, (can handle max 1A)
Testing the board with 6 leds in series mounted on a heat sink, the leds begin to flicker after about 1-2 minutes. Then it stops for a few minutes and start again. Sometimes it works for a longer (ca. 5mins) period of time, but it always begins to flicker again. The off state of the leds is no longer than 0.1s
If I put the board in 'dim' modus or use only 3 leds, the problem goes away.
Power supplier is 24V - 4.5A
We test with 6 leds in series, witch makes 6x3.2V = 19.2V + 0.7 tl4242 drop = 19.8V, so my guess is that 24V is high enough.
I measure 17.33V over the leds, using 360mA (since the TL can handle 500mA, and the leds 1A I don't see a problem with that).
If the board goes in 'error' I measure spikes up to +20V over the leds.
I put a little heat sink on the bottom of the evaluation board, under the tl4242, thinking it got too hot. But it doesn't help.
Can someone explain what goes wrong, or what we are doing wrong ?
thank you.