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Playing with ICs

By on February 12, 2015
playing with ic7








playing with ic

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:


playing with ic9


playing with ic1

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.

playing with ic2

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.

playing with ic3

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.

playing with ic4

 playing with ic5

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.

playing with ic6

robert calk











This article was written by Robert Calk Jr. He is an Electronics Hobbyist and loves learning electronics and device repair.

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  1. Dave

    February 12, 2015 at 9:07 pm

    C'est la vie - that's how we learn!!

    • Robert Calk

      February 13, 2015 at 2:25 am

      Thanks Dave - I'm glad you liked my article.

  2. Carlos

    February 12, 2015 at 9:55 pm

    Thank you, it's good to know that..

    • Robert Calk

      February 13, 2015 at 2:26 am

      Thanks Carlos. It is a lot of fun playing with IC's.

  3. beh

    February 12, 2015 at 10:36 pm

    Hi Robert
    it is cool article and thanks.

    • Robert Calk

      February 13, 2015 at 8:00 am

      Thanks Beh. I'm glad you like it.

  4. Vasile Petrica

    February 12, 2015 at 10:46 pm

    Thank you,very nice,these is for my remember all time.

    • Robert Calk

      February 13, 2015 at 8:02 am

      Hi Vasile, you are very welcome.

  5. Yogesh Panchal

    February 12, 2015 at 10:52 pm

    Good experiment thanks for sharing.

    • Robert Calk

      February 13, 2015 at 8:03 am

      You are welcome Yogesh. I'm glad you liked it.

  6. Evan Evans

    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.

    • Robert Calk

      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.

  7. Humberto

    February 13, 2015 at 1:22 am

    Hi Robert, good experiment. Congratulations.

    • Robert Calk

      February 13, 2015 at 8:06 am

      Thanks Humberto.

  8. Waleed Rishmawi

    February 13, 2015 at 2:18 am

    enjoyable experiment. enjoy

    • Robert Calk

      February 13, 2015 at 8:07 am

      Thanks Waleed. Good to hear from you.

  9. mahmoud

    February 13, 2015 at 4:50 am

    Hi mr.robert i enjoyment of your research

    • Robert Calk

      February 13, 2015 at 8:08 am

      Thanks Mahmoud, I'm glad you liked it.

  10. peter

    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?

    • Robert Calk

      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.

  11. Andre Gopee

    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 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.

    • Robert Calk

      February 13, 2015 at 8:20 am

      Thanks Andre. I'm glad you liked it. And thanks for the tips.

  12. Amendar

    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.

    • Robert Calk

      February 14, 2015 at 3:23 am

      Thanks Amendar.

  13. Memo

    February 13, 2015 at 2:23 pm

    Very nice. Thanks for sharing.

    • Robert Calk

      February 14, 2015 at 3:26 am

      You are welcome, Memo.

  14. last

    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.

    • Robert Calk

      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.

    • Robert Calk

      February 14, 2015 at 3:30 am

      You are very welcome, Emeka. I'm glad that you like my article.

  16. dicksy

    February 15, 2015 at 2:57 pm

    what a nice experiment.thanx robert

    • Robert Calk

      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 ...

    • Robert Calk

      February 16, 2015 at 11:19 am

      Thanks Steven, I appreciate that. I'll order some and check them

      • Becker

        February 17, 2015 at 3:35 am

        You can save yourself some additional money buy using a different link on the 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:

        • Robert Calk

          February 17, 2015 at 4:25 pm

          Thanks Becker.

        • Robert Calk

          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.

  18. tana

    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.


    • Robert Calk

      February 17, 2015 at 4:27 pm

      Thanks Tana. It's fun to experiment and play with IC's!

  19. shahid ahmad

    February 17, 2015 at 1:12 am


    • Robert Calk

      February 17, 2015 at 4:28 pm

      Thanks Shahid.

  20. zacy

    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

    • Robert Calk

      February 24, 2015 at 11:15 pm

      Thanks Zacy.


    April 5, 2015 at 12:20 pm

    Thanks for your article.Very intersting . RICK SCOTT/TN

    • Robert Calk

      April 6, 2015 at 12:25 am

      You are welcome Ricky. I'm glad you liked it.

  22. yaghob

    May 20, 2015 at 8:09 pm

    very good
    thanks master


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