Recent content by geologic

Well, i do't know IgorT but i hope he gets better... And good news, i found the problem of my unstable boost... HEAT! I read on the datasheet that the LM3410 has a temperature protection that shuts down de IC when the junction temperature reachs 165ºC. I'm in the middle of the summer, with air...

Hi I'm building a LED driver based on the LM3410, but i'm having some trouble getting more than 520mA output current. Setting R1=0,33ohm i got as stable output @ 520mA, but setting R1=0,22ohm the output fluctuates and the LED starts flashing. I read on the forum that you build one with this...

Hum... Do you know what inductor IgorT used? I'm using Coilcraft 4,7microH, 3A. Should i use a bigger one (maybe around 10microH) or one with bigger Isat (maybe 6A or 7A)? Or maybe both?

Ok, i did some more tests to (try) reach 800mA (R1=0,24ohm): 1) add a tantalum 30microF to the LED - didn't work, same instable output; 2) replace the LED by a dummy load (6 1N4007 + 1ohm) - didn't work, same instable output; The last stable output was around 560mA (R1=0,33ohm), so i think i...

Go to national website, do a search by "LM3410", it will show you 2 entries (LM3410 and LM341). On the first grid, 5th column: Output current 1500mA. But you're right, it says nothing on the datasheet (pretty strange...)

I went to http://webench.national.com, they have a simulator where you can play with the ICs. I entered desired values for Vin (2,7V to 5,5V) and Vout (6V@700mA) hoping that i could suggest the LM3410. Strangely, the simulator showed a empty list... I went back, choosed Iout=600mA, and now it...

Ok, i quit from the SEPIC design and now i'm using the boost design. Set Cin and Cout to 10microF and powered the circuit with 4,5V. I started with 190mA output current and raised it putting several 1ohm resistors in paralell. Up to 0,33ohm everything was fine, i was getting 520mA @ 5,66V output...

So, to get 750mA from it, what values for C1 and C2 did you use?

Was in SEPIC mode or in boost mode?

Well, i used all my 10microF in parallel but it didn't work... Set C1 (input) to 20microF, C2 (output) to 40microF and C3 (coupling) to 30microF... The LED turns on for about 5 seconds and then starts flashing... I'm using R1=0,22omh so i was expecting around 800mA at output, but only reached...

I was trying to get a new value for C3 as close as the LM3410 datasheet (original value is 2,2microF), but i'll try your suggestion first, since i have lots of 10microF, i can parallel them to make 20microF or 30microF... I'll be back...

Well, i changed C3 for a new one 10microF (the only value i had in SMD) and the SEPIC is working!!! VFB is around 190mV and output 3.4V @ 190mA (R1=1ohm). Nice! Next step, i changed R1 to 0,22ohm to get the output up to 860ma. Powered on and... the led starts flashing... (i build my first...

Yes, in boost mode FB voltage always around 190mV, so the IC is alive. I found a apps note at http://www.national.com/an/AN/AN-1484.pdf about SEPIC design. They say something about the coupling capacitor: "The SEPIC capacitor must be rated for a large RMS current relative to the output power"...

I read somewhere that it can delivery up to 1,5A continuous, and little more pulsed, i'll do some tests if i can put it to work in SEPIC... :undecided: I realize that you build several LM3410 circuits, any in SEPIC mode? What components did you use?

Yes, i'm using 2.2uf as coupling capacitor. About the drawing, just L1 is connected to SW (pin1). L2 is connected to GND (pin2). After "downgrading" the circuit, i soldered C3 and L2 again and the circuit stoped working. I removed L2 and shorted C3 and it worked again... (so f****...