LED drivers have unusual components...what are they for?

[treez]

Hello,
Page 26 (PMP4026 Schematic) of the following features the output sense resistor voltage being divided down by R5 & R3. This seems like a bad idea..do you agree?
Also, why are they using a 2Ohm sense resistor with 700mA of current?..surely too much dissipation, considering that the error amp ref voltage is just 200mV in the TPS40211..

**broken link removed**

..also, what is Q11 for...its just a nfet turned off?
Also, on page 28 of the above (schem PMP3943) surely R5 should be 49.9k and not 49.9?

 

[godfreyl]

Sorry, I don't have the answers, but here are the circuits to save others a 6.6MB download.