Hi,
I still have problem with my design.
I also contacted maxim’s support and got the following answer:
_I tested on the EVKIT and changed 2 serial LEDs about 5V. When VIN is in the range 5V~20V, the LED current is basically stable and won’t go too high.
For the inductance, the formula V=L(di/dt). The inductance must be higher than the calculated value.
And also for the di, 1A LED current has about 0.3A di, 4.8A LED current has about 1.4A~1.5A di. But the EVKIT assembled 56uH inductor, so for sliding scale, 4.8A LED current also need a inductor bigger than 10uH._
I made a new driver with a 10uH inductor that was suggested by the support, but it did not work properly. The current is still not stable:
I also made some measuremets at the point indicated on the last picture of the link below:
https://imgur.com/a/hYBgiya
1. measurement at D2 at 25%pwm dimming signal
2. measurement at D2 at 50%pwm dimming signal
3. 4. and 5. measurement at D2 at 100%pwm dimming signal
My measurement (if it is correct) shows 3 MHz switching frequency?
Of course the driver is still to hot.
Shall I change to LM3409? Can it be better for my configuration (xhp 50 , xhp 70; 2 and 3 cell drivers)