I've disconnected JP2 on this eval board, and soldered a wire across J4 so I can connect my own LED array across J3 and J4. My array consists of twenty-four OSRAM 4240 in series.
I'm seeing two different unexpected occurrences:
1. With a signal generator, I'm able to give a PWM signal to the CTRL pin and the device scales my current quite nicely when viewed on a scope. When I use the EasyScale function, I can also dim using the GUI controls, but the output is a little noisy and not like what I see when PWM'ing the CTRL pin. I aslo never seem to get an Acknowledge from the IC when using this mode.
2. Using either PWM or EasyScale, my maximum current draw through my LED array is fixed around 127 mA. This should be 100 mA, and I understand that I should have a value of 2 ohms for R2 to achieve this. Since I don't have a 2-ohm resistor handy, I'm using a 2.2-ohm resistor and I still see 127 mA, where I expect to see less than 100 mA. Using EasyScale, I reach this 127 mA at a feedback voltage of 0.152V, which is also concerning since all voltages above this value also show a current maximum.
Is there something I'm missing to cause the issues I'm experiencing?