LM3409HV LED driver board - Page 1
Forum section: electronics / projects

author: TeraHz
author_rank: Contributor
timestamp: July 05, 2011, 03:13:42 am
content: Hi there guys,First project from start to finish by a non-ee person, so please be gentleI've been using LEDs on my reef tank for a while now and decided to try the National LM3409 IC as a driver because I wanted to be able to use analog dimming.What I've done is to follow the schematics in the datasheet and the app note from the evaluation board that National offers and ended up with this:It is basically the circuit from the schematic, combining analog and pwm dimming (jumper selectable), with a simple resistor divider to bring down 5V to 1.24V for analog dimming. As per the datasheet, the load is very low, so no need for regulator ?I'm guessing the schematic is OK, as it is basically the schematic in the data sheet. However I'd like to get some feedback on the PCB:Anyway, I'll be building a prototype soon to verify it actually works and wanted to get some feedback before I send the gerbers off to seeedstudio/iteadstudio to get a batch of PCBs.I've put together a spreadsheet that computes the various values of the few components as per the datasheet:http://joro.geodar.com/code/lm3409/lm3409.xls<- Excelhttp://joro.geodar.com/code/lm3409/lm3409.zip<- NumbersSo thanks very much and again, please be gentle

author: ivan747
author_rank: Super Contributor
timestamp: July 06, 2011, 05:19:08 am
content: Looks ok at a first glance. The only thing I can point out for now is the position of R3, between the IC and the DPAK package. It looks like it will be tricky to solder and desolder. Also, don't trust the silkscreen for dimensions, you may end up not being able to fit the components on the board. Trust me, if you manage to fit them they won't look very nice.

author: TeraHz
author_rank: Contributor
timestamp: July 11, 2011, 04:56:51 am
content: Thanks ivan747. I've updated all small packages to 0603 to give me some extra room with the silkscreen. Also made some more adjustments. After actually checking the packages of the various components, it turns out that quite a few of them are larger.Anyway, here is second revision. I've used pours on various areas (following the demo board design again) instead of thick signals. Also renamed the components top left to bottom right for easy assembly.

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 11, 2011, 08:59:06 am
content: what software you used?

author: Psi
author_rank: Super Contributor
timestamp: July 11, 2011, 10:31:42 am
content: (Assuming you plan to solder them yourself)0603 can be tricky to solder, especially if you don't have much experience soldering smt.It's easy to be fooled about their size when designing a pcb because the pcb design software gives you a view many times larger than real life. 0604 are 1.6mm by 0.8mm, so pretty tiny. Though i guess, if you can solder that 10pin mini soic then a 0604 should be fine.Most people doing hand soldering tend to stick to 0805 components unless they have a good reason to need something smaller.0604 and even 0402 are perfectly doable but they do require some practice/skill.

author: TeraHz
author_rank: Contributor
timestamp: July 11, 2011, 02:10:54 pm
content: @Mechatrommer: I'm using eagle.@Psi: I've worked with SSOP28 before, so I'm familiar with that pitch. It isn't that bad. Also, I'm hoping that Dave will have the SMT tutorial up by time the board is ready

author: TeraHz
author_rank: Contributor
timestamp: August 28, 2011, 09:51:39 pm
content: I have a question for the ones that know more than me.The LM3409(HV) shown above supports a few methods of dimming. One of them is to pass 0-1.24V on the Iadj pin. Another is to do PWM on the EN pin, and a third is to just place a resistor between Iadj and GND so that an internal power source can set the current.I was thinking that grounding Iadj would result in OFF state, however hat doesn't seem to be the case. Even when Iadj is grounded (by 2" wire) the IC still outputs ~8mA which still causes the LEDs to emit light. So I want to be able to kill the power if the voltage on Iadj is lower than, say, 100mV. To do that, all I should need is a transistor to open the EN pin based on the voltage on Iadj, however I can't find one that will have such a low cut off voltage. Also the C-E voltage on said transistor can be as high as 75V but the current is typ 10nA.So does such transistor even exist or am I just dreaming?What else can I do to achieve this result?

author: ivan747
author_rank: Super Contributor
timestamp: August 28, 2011, 09:58:23 pm
content: Transistor like th probably exists, but the odds are it won't be quite practical and may leak more current when the temperature changes.

author: TeraHz
author_rank: Contributor
timestamp: October 23, 2011, 04:26:24 am
content: Ok I'm at the 4th revision of the board and I'm a little stuck. I ended up adding a comparator circuit to turn off the IC when the voltage goes under 0.1V. This is what the latest board looks like:source:http://joro.geodar.com/code/LM3409%20v0.4/So, the comparator works just fine, until I plug in the LED power supply. The 0.1V now becomes about 1.2V in order to turn on the IC, and it never shuts off. I have to short VIN+ to GND so that it shuts off.The opamp is powered by 5V, and 0-5V are used on VIN+.LED PSU I use is 15V.Any help will be very much appreciated.

author: marcelo.correia
author_rank: Newbie
timestamp: November 01, 2011, 11:07:48 am
content: Check this one outhttp://www.reefcentral.com/forums/showthread.php?t=1983302

author: TeraHz
author_rank: Contributor
timestamp: November 01, 2011, 01:53:37 pm
content: Thanks Marcelo. I've seen that thread.The problem is now solved, actually. Turns out that I had used too high valued for R6 and R7. When I changed the values to 91 and 30 ohms, things started working like a charm.

author: TeraHz
author_rank: Contributor
timestamp: January 24, 2012, 03:24:17 am
content: I figured I'd update this thread if someone ever found it.5+ months later I think I have a final version for this board and I'm quite happy with it so far. I've learned so much while working on this board...Quite a few changes have gone in.I've added a 12bit i2c DAC on the board. I've also changed the PFET to a TO-220 package and added space for a nice heatsink.The DAC allows for up to 8 drivers per i2c bus and is gives nice fine control for the LED current.http://joro.geodar.com/code/code/LM3409%20v0.6/<- BOM, Schematic and other filesEnjoy

author: mobbarley
author_rank: Regular Contributor
timestamp: January 24, 2012, 05:41:35 am
content: Your switching loops could probably be reduced by moving C1/R1 closer to the rest of the switching parts, but if it is working well then that is probably not a big deal.Also the trace from R1 to Q1 is thick on the underside but tiny on the top side - similarly for Q1's gate connection (which seems a bit oversized on the underside anyway)

author: TeraHz
author_rank: Contributor
timestamp: January 24, 2012, 04:20:34 pm
content: mobbarley, In the first few revisions of the board I had the fet right next to r1/c1 and the IC, but I t was a pain to put the heatsink, that's why I moved it to the outside of the board. I haven't checked how stable everything is with a scope, but just measuring the current on the LED side, things seem to be good. The switching frequency is not very high - around 300khz.I really know close to nothing about proper trace size, other than trying to be within the current rating. Is there any harm in having partially wider trace and a much wider trace for the job? I always assumed bigger is better:).

author: Blue
author_rank: Regular Contributor
timestamp: January 24, 2012, 06:22:13 pm
content: Very nice!Do you know Meanwell makes: LDD-1000H ?If you're interested I have 5 to sell. Pb me.

author: vhrch1
author_rank: Newbie
timestamp: April 04, 2017, 06:32:20 pm
content: I have a doubt, I have an arduino who is controlling my cree led lamp by PWM with a GND and i have a power supply for my leds lamp with a GND too, question for 1 to 5 version of this dimmer, Do I have to conect both GND (Arduino and led's power supply) to conect ADJ or just it doesn't need to be conected?Have a nice day

author: BrianHG
author_rank: Super Contributor
timestamp: April 04, 2017, 06:50:09 pm
content: Add more vias, at least 2 (I would add 6 along the side of the resistor), to the Source of the mosfet & R1 + on the top of the PCB, make R1's trace to these additional vias at least as thick as the bottom trace. The trace to the IC pin doesn't need to be any thicker than it is as it has no real current load.This is the annoyance of feeding all your power through vias, 1 is not enough to supply what all your LED's will be consuming.

author: james_s
author_rank: Super Contributor
timestamp: April 04, 2017, 07:11:04 pm
content: This is a 5 year old thread, I doubt the OP is even working on this project anymore.

author: TeraHz
author_rank: Contributor
timestamp: April 05, 2017, 12:45:42 am
content: Quote from: vhrch1 on April 04, 2017, 06:32:20 pmYou need to connect all 4 pins for analog dimming. For PWM you connect VIN, GND and ADJ(pwm).Quote from: james_s on April 04, 2017, 07:11:04 pmYou're correct!

author: vhrch1
author_rank: Newbie
timestamp: April 06, 2017, 05:54:31 am
content: Hi TeraHzYes I saw that post has 5 yearI'm confused about connecting my arduino and the dimmer the way you tell meYou need to connect all 4 pins for analog dimming. For PWM you connect VIN, GND and ADJ(pwm).Ok, you have Vin, GND, ADJ and 5V. Well, what I think is, Vin and GND thas from my power supply (12V), ang 5V it could be from a power supply too or from arduino?. and the last one ADJ- Arduino.I'm working with the same circuit as OP did it, Iaquahttp://www.plantedtank.net/forums/20-diy/677265-iaqua-my-touch-interface-aquarium-controller-arduino-114.htmlThanks.

author: vhrch1
author_rank: Newbie
timestamp: April 07, 2017, 02:15:53 am
content: Hi TeraHzToday I check connections, and I connected allmost all as you have in your circuit dimmer and i 'm not sure if the connection with 5v is correc, I connect GND instead of 5V and all configured in PWM it was working right.I post some picture

author: TeraHz
author_rank: Contributor
timestamp: April 07, 2017, 02:57:31 am
content: Good job vhrch1! Yes, for PWM you do not need 5V, that's just reference for the comparator. With PWM you're just pulsing the EN pin on the LM3409. I'm glad it's working for you!