I've got a small 4-string LED driver board made using AD5211.
It's schematic is basically the 'application circuit' from current datasheet and from Eval_ADD5211_Calculation.xlsx
Rfreq = 49.9K (default)
Rc/Cc = 100R, 2.2uF (default)
Rset = 12.5k (120mA string)
Rramp, Rcs are 6.8/0.1R
Coil, NFet and diode are from 5211 EVAL BOM:
IRLR120NTRPBF + Wurth 744771133 + SK310B-LTP. Sense resistor is WSL2010R1000FEA18
The board is powered by 14-15V, with the following spec for leds;
My R/OVP is 220K/10K @ 57.5V
Anything else not mentioned is per datasheet.
Dimming freq is 20kHz.
At 50% duty, the setup is drawing aroudn 1A from 14V supply.
Rsense (and eventually the FET) are running at around 90C.
I think the AD5211-EVAL was made for 100mA strings, but still going from 100 to 120 shouldn't matter that much, right?
What is the normal operating condition of the components in 5211-EVAL? My board's layout is basically what's shown in Eval_ADD5211_Bill_Of_Materials.xlsx page (the coil + fet + input/output cap + diode section. Going to 95% duty heats it up even more, so that's not really acceptable.
When running, I don't expect this to be completely cold, but I don't expect 90C either.
The AD5211 itself is warm, but I can't tell if that's heat radiated by the Rsense or comes from the driver itself. Anyway, its significantly less than what fet + rsense are running. Components sourced from Digikey and checked for correct values (R + C, anyway, I've had them swap in different parts before).
Any ideas? What's the rated wattage 5211-EVAL runs at, while staying reasonably not-hot?
Do I need to change these two components for something with higher ratings, or could I be doing something else wrong?