What is that IC? (K403) - Page 1
Forum section: electronics / projects

author: xuio
author_rank: Contributor
timestamp: January 27, 2014, 12:39:59 pm
content: Hi everyone,I'm reverse-engeneering a bicycle lamp and want to drive it with PWM. There is a chip on the PCB that I suppose to be the CC LED-driver. It has K403 and Y107 written on it. I couldn't find any information about it. So if you can identify it please let me know!Moritz

author: amyk
author_rank: Super Contributor
timestamp: January 27, 2014, 12:42:50 pm
content: Pictures, package, pinout...?

author: xuio
author_rank: Contributor
timestamp: January 27, 2014, 12:43:21 pm
content: It is in an 8 pin SMD package (I'll post pictures later when I'm at home)Moritz

author: xuio
author_rank: Contributor
timestamp: January 27, 2014, 04:08:34 pm
content: Okay, here are the pictures of the PCB. I checked the pins and most of them are just noise. (I'll test them again)Moritz

author: BiOzZ
author_rank: Regular Contributor
timestamp: January 27, 2014, 04:30:07 pm
content: im not sure there is a real chance its just a Chinese part thats nearly impossible for you or me to find and chances on a datasheet are lowwhat you can do is find a drop in replacement by tracing out the pinout and spend some time on digikey looking up LED drivers of the same package and find the one with the same pinoutif its not an LED driver than you might be stuck with a generic Chinese microcontroller than i say good luck!

author: Electr0nicus
author_rank: Regular Contributor
timestamp: April 07, 2014, 05:20:31 pm
content: Ok I know that the topic is old, but I'll post my findings here anyway.I came across this topic, because I myself currently repairing my LED Bicycle- Lamp. It's from a company called "Lumotec IQ" and the Lamp is called "LED Pro Senso Plus". My lamp suddenly stopped working, as I was cycling down a mountain with high speed (approx. 60km/h). As I opened the lamp, I saw a tiny 5 pin SMD Chip has released the magic smoke. Because this chip was completely charred, I was unable to read the marking code. So I had to figure out, what chip that was, by reverse engineering the PCB (which I haven't quite finished yet). I came to the conclusion that it's a single Logic gate. Either a inverting Schmitt- Trigger or a normal inverter. In the reverse engineering process, I also came across that 8 pin TSSOP chip with the K403 marking on it. In the second line of the marking I had Y436 written on it, but that was clearly some sort if manufacturing location, year and week marking. I searched a few hours and then found a chip, where I'm pretty sure that it is the right one, judging from the exernal circuitry. It's a LM2904 dual opamp.www.st.com/web/en/resource/technical/document/datasheet/CD00000535.pdf.The power supply pins matchThe OPAMP outputs go to the gates of some MOSFETs which makes senseThe LDR (for automatic switchon of the light in darkness) goes to the non inverting Input of the second OPAMPThere are a few resistors around the chip, most likely FB- resistorsOn page 21 of the datasheet under "Ordering Information" you can see that a marking of "K403" corresponds to a LM2904ST in a MiniSO-8 package, which it is exactly (measured the dimensions of the package).

author: 128er
author_rank: Regular Contributor
timestamp: April 07, 2014, 06:06:41 pm
content: LM2904 is my guess too. At a CC-LED-Driver, you would possibly see more thick traces.These two sites helped me a lot in the past:http://chip.tomsk.ru/chip/chipdoc.nsf/vc1?readform&start=1&view=smd&cat=A&count=500http://www.s-manuals.com/smd