Playing with ICs
This Cisco Router quit on us. We bought a new router since the kids didn’t want to wait and see if I could fix it. I decided to salvage all of the SMD components that I could use. Finding out that the SOP-8 IC is an 18V, 2A, 340 KHz Synchronous Step-Down DC/DC Converter, I decided to play with it on my Breadboard (BB). I soldered some BB wires onto the leads. Please click on the below to visit the datasheet website:
I re-wrapped the SMD 10uH inductor to make a through-hole inductor out of it with 22cm of 28 gauge magnet wire.
The white 10uH inductor that I have is just too big for my small BB, as you can see in one of the pictures.
My circuit is set up like the top schematic on page 2 in the Datasheet. My new 1/4w 1% resistors came in today, so I changed the resistors in the circuit with the 1% resistors, except for the two that are in parallel in front of the inductor. I don’t have a 26.1K 1% resistor, so I’m using one each of 82K & 39K 5% resistors in parallel which measure a tad over 26K – which is within tolerance. I ordered some 26.1K 1% resistors but they may not get here before I publish this article.
It is supposed to output 3.3V according to the schematic with 4.5V input, but it is outputting around 4V. I started changing the resistor values and it didn’t make any difference.
The DC voltage trace looks pretty clean. The bottom trace is from the power supply, and the top trace is the IC output. I believe that this IC is what caused the router to quit. The CPU shut down because it wasn’t getting the proper voltage. I put the circuit back according to the schematic and raised the voltage up to 12V. According to the schematic in the datasheet, it should handle 18V. Pop! Whatever was bad in the IC gave up the ghost when I raised the voltage up.
When I heard the pop and saw the LED go out, I saw the amps max out at 0.5A on my power supply that it was set to, and the volts went to zero. I touched the top of the IC and it was getting hot. So I shut the power supply off.
I guess play time is over! I wanted to get a new IC to check against this one on my BB, but I couldn’t find one. I checked Mouser, Digikey, and a couple others but none of them even had a listing for this IC. Oh well – on to the next project.
This article was written by Robert Calk Jr. He is an Electronics Hobbyist and loves learning electronics and device repair.
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February 12, 2015 at 9:07 pm
C'est la vie - that's how we learn!!
February 13, 2015 at 2:25 am
Thanks Dave - I'm glad you liked my article.
February 12, 2015 at 9:55 pm
Thank you, it's good to know that..
February 13, 2015 at 2:26 am
Thanks Carlos. It is a lot of fun playing with IC's.
February 12, 2015 at 10:36 pm
it is cool article and thanks.
February 13, 2015 at 8:00 am
Thanks Beh. I'm glad you like it.
February 12, 2015 at 10:46 pm
Thank you,very nice,these is for my remember all time.
February 13, 2015 at 8:02 am
Hi Vasile, you are very welcome.
February 12, 2015 at 10:52 pm
Good experiment thanks for sharing.
February 13, 2015 at 8:03 am
You are welcome Yogesh. I'm glad you liked it.
February 13, 2015 at 12:00 am
You win some/you lose some but I always enjoy reading your articles. You have a wonderfully logical approach, the guts to think outside the box and the moxie to "go for it".
Keep up the articles - you're wonderfully articulate and your presentation is always clear, precise and just a joy to read.
If you ever find yourself in Fort Lauderdale, drop me a line.
February 13, 2015 at 8:05 am
Thanks Evan. You are very kind. I wish I could have found a good IC so I would be able to make a better article.
February 13, 2015 at 1:22 am
Hi Robert, good experiment. Congratulations.
February 13, 2015 at 8:06 am
February 13, 2015 at 2:18 am
enjoyable experiment. enjoy
February 13, 2015 at 8:07 am
Thanks Waleed. Good to hear from you.
February 13, 2015 at 4:50 am
Hi mr.robert i enjoyment of your research
February 13, 2015 at 8:08 am
Thanks Mahmoud, I'm glad you liked it.
February 13, 2015 at 5:02 am
I missed the purpose of winding a new inductor?
Surely a DC-DC converter of equivalent current capacity can be located & adjusted to output the desired voltage?
Is it possible that the suspect IC was damaged during the removal from CB process?
February 13, 2015 at 8:17 am
Hi Peter. I rewound the inductor because the leads were too short. It is easier to use in my BB with longer leads. Plus now it has new wire; less chance of it becoming a problem.
I didn't want to compare it with anything other than an identical IC.
I used my Hot Air rework station to remove the IC so no, I did not damage it. The router had already quit working.
February 13, 2015 at 8:04 am
Hi Robert, It a great I dear to test these IC's according to the Data sheet Recommendations, because you can never be sure If an IC is good or bad until you test them. Sometimes when I cannot get IC's (Hard to find) I send out a requisition on Alibaba.com and I get feedback from China who supplies me with the IC that I need. Maybe you can try that. Anyway nice article... Keep up the good work.
February 13, 2015 at 8:20 am
Thanks Andre. I'm glad you liked it. And thanks for the tips.
February 13, 2015 at 12:10 pm
Hi Mr. Calk,
Another good job with clear explanation.
I wait to see your article when it is replaced with a new IC.
February 14, 2015 at 3:23 am
February 13, 2015 at 2:23 pm
Very nice. Thanks for sharing.
February 14, 2015 at 3:26 am
You are welcome, Memo.
February 13, 2015 at 3:11 pm
Very informative post jestine. I am now starting to put things together from the time I bought your book Switched mode power supplies. This article about the Ic FOR THE routr is great, thanks, I hope I WILL get to your level, Because its still hard for me to build circuit from scratch.
February 14, 2015 at 3:28 am
Thanks Last, I'm glad you liked it. Just keep learning and experimenting and you'll do fine. Just remember to not get in a hurry and be safe!
February 13, 2015 at 8:22 pm
i like all you have been sending to my mail.
keep it up and thanks.
February 14, 2015 at 3:30 am
You are very welcome, Emeka. I'm glad that you like my article.
February 15, 2015 at 2:57 pm
what a nice experiment.thanx robert
February 15, 2015 at 5:33 pm
You are welcome, Dicksy. I'm glad you liked it.
February 16, 2015 at 10:49 am
this is fun and learnt something from it.
you can find the FR9882 in this link ...
February 16, 2015 at 11:19 am
Thanks Steven, I appreciate that. I'll order some and check them
February 17, 2015 at 3:35 am
You can save yourself some additional money buy using a different link on the aliexpress.com than the one S. NEO provided -- and you WON'T have to buy a minimum lot of 10 pieces. Currently $0.31 each plus $2.63 shipping from this vendor (via aliexpress) at:
February 17, 2015 at 4:25 pm
March 11, 2015 at 6:08 pm
I ordered 10 of them. The shipping was more than that when I got to checkout. But at least I found some - thanks guys. They still haven't arrived yet.
February 16, 2015 at 9:54 pm
Now I realize that I am not the only one who had the same kind of problem on of.
Thank you ,Robert Calk.
February 17, 2015 at 4:27 pm
Thanks Tana. It's fun to experiment and play with IC's!
February 17, 2015 at 1:12 am
February 17, 2015 at 4:28 pm
February 24, 2015 at 12:19 pm
your article has some good information and your research make sure that IC is a defective component.very nice experiment
February 24, 2015 at 11:15 pm
RICKY D. SCOTT
April 5, 2015 at 12:20 pm
Thanks for your article.Very intersting . RICK SCOTT/TN
April 6, 2015 at 12:25 am
You are welcome Ricky. I'm glad you liked it.
May 20, 2015 at 8:09 pm