Tag Archives: Engineering

Office Tomfoolery

So Monday at work I successfully pulled a prank on the designer for the part that is currently occupying the majority of my time. Concept, planning, and execution took about two weeks or so as I had to fit this little side project in around my real work obviously. Ever since the part’s inception this designer had been claiming it was perfectly designed and any errors were clearly the fault of me, the Applications Engineer. He wasn’t being mean or anything, this sort of good-natured rivalry is pretty common between the Apps and Design departments at work, but being that this is my first part as lead apps since starting a year ago meant I got some extra abuse. I figured it would be a good idea to go on the offensive and show everyone I wasn’t such an easy target. My boss, who’s been good friends with the designer for a long time now, thought it would be pretty funny and approved the gag, eager to see how it would play out.

The part is a single phase buck regulator meant for Vcore applications in laptops and ultrabooks. Vcore means that the regulator provides the main voltage rail to the processor, specifically an Intel one in this case as AMD and other processors have different power requirements. My goal was to somehow screw with the regulator, cause the output voltage to glitch and go out of spec, and convince the designer this was a silicon bug and not a board issue. After a little brain storming I came up with the following circuit which could be cobbled together out of various parts in the lab:

Prank Circuit

My Prank Circuit

Without diving down the rabbit hole that is regulator compensation, the comp pin of any buck converter is the output of an error amplifier which connects to a networks of passives going back to its negative terminal (the Feedback pin) and is part of the control loop used to keep the output voltage stable and well-regulated. My circuit would periodically drive this pin away from its steady state operating point. This disturbance would propagate through the chip and result in a noticeable glitch on the output voltage until the compensation loop could regain control and bring the output voltage back into spec.

As phase switches merrily along at the frequency and duty cycle set by the controller it gets divided down by R1 and R2. When phase is high the output of this voltage divider is enough to forward bias the diode and cause current to flow into C1 for a brief period before going low again. C1, which also connects to the positive input comparator U1, charges over time and when the voltage across the cap gets to be higher than the reference voltage present on the comparator’s negative input the comparator’s output swings to 5V. When U1’s output goes high two things happen. One, comp is driven away from steady state through R5 and two, the gate of M1 goes high which discharges C1 below the reference voltage starting the cycle over again.

Prank Sims

Prank Circuit Sim Results (Click to view properly)

There really wasn’t much thought process behind the component values in my circuit; they were determined through trial and error in simulation. I didn’t care how often the circuit would trigger, only that it did and the disturbances it caused would appear on Vout. One of my only goals was to ensure that the resistor dividers wouldn’t draw enough current to interfere with the normal operation of the regulator and cause it not to start up. My second goal was to “break” the regulator just enough to cause concern but not enough to trigger any of various over voltage, current, or temperature protections built into the chip. This is why R5 had to be added; without it comp was driven too hard and the part simply shutdown (there’s no fun in that).

With the circuit idea solidified I headed into the lab to jury rig it into place underneath one of the eval boards. It was a messy hour after work one day, but I successfully placed each component and wired in the various signals and voltages from all across the board. Once things got going, there would be so many cables and probes attached to the board I knew it wouldn’t get turned over until I was ready to reveal what I’d done.

 

Holding my breath I powered up the board after making all the necessary modifications. Surprisingly enough it worked! I hadn’t made any disastrous mistakes when wiring it all up and the resulting waveforms basically match with my sims. All that was needed was some tweaking of R5 to find the right value and I was ready for action.

Cutting to Monday morning, I spent a little time taking scope captures of a good board and my doctored eval board. These were placed in a quick report which I shot off to my boss and the designer right after lunch. To add to the joke I took my clean scope caps using a part from an old rev of silicon and explained how the “bug” was only seen in the latest version of the chip. This caused the initial spark of concern in the designer as we’re currently waiting on a new rev of the chip to arrive from the fab and it was too late to make any changes. After getting some tests to run and tweaks to try, I actually went into the lab and did them! For one I was curious to see if any of them could actually fix the error (they didn’t) and secondly, this designer is pretty hands on and likes to come out to Apps Lab quite often. I knew that if he came out to see the glitch on the bench and none of his changes were made he would get suspicious. Fortunately, or unfortunately, other obligations kept him away for the day and he never came out to see the problem until the end of the day.

After running the initial list of tests the designer gave me I had a flash of brilliance that really threw him for a loop. I took a series of scope shots at each of the four switching frequencies our part could run at and varied the value of R5 at each one. Now I had created a problem that went away as switching frequency increased and could explain why we hadn’t seen this issue before as the majority of our testing had taken place at high frequency up until this point! Bingo.

By the end of the day, the designer was pretty much stumped. He’d done an initial check of his schematics, couldn’t spot an obviously fault he made, but thought it was a mistake somewhere in the core of the modulator. He told me that at this point he essentially resigned himself to hoping the new version of the chip came out okay and whatever changes he made would happen to fix this (remember it’s too late to make changes now as the part’s being fabricated).

Right afterwards I called him into the lab saying I’d found something interesting and he should come take a look. When I showed him the circuit on back of the board he didn’t get it at first. He asked why all this crap was added and what did it fix? I couldn’t hold back anymore and broke out in a smile and said that I just wanted to mess with him. Slowly realization dawned on him and he started laughing as did my boss and a few other guys in the lab who were in on the joke.

In the end the designer took it really well and thought it was pretty funny. He told my boss to give me more work as clearly I didn’t have enough to do since I could pull these elaborate pranks but mostly he just laughed. I now owe him a round or two the next time a bunch of us go out after work but that’s a price I’m more than willing to pay all things considered. In the end I caused him just enough trouble so he started to sweat but not enough to take him away from any real tasks he had to get done. A well executed prank overall in my opinion. Surely, there’s no way this will every come back to haunt me right?


How to Stand Out & Other Career Fair Tips

A few weeks ago I traveled back to my alma mater to recruit some students for co-op and full-time positions available at various locations throughout my company. For the first time I was going to experience what it was like to stand on the employer side of the booth at a Career Fair. Chris Gammell, the good guy that he is, gave me some tips on getting through the day in one piece which came in quite handy. Fast forward to today and I can tell you that working a Career Fair is exhausting. I had fun and definitely plan on doing it again but I would almost say it’s easier to be the one looking for a job.

Regardless of how I feel personally about working Career Fairs, standing in that Field House all day I did see a few pitfalls that students fell into. Bearing in mine I’m not even close to a recruitment expert, read on for my take on what you the student can do to improve your game, standout, and sell yourself better to employers while attending a Career Fair. In no particular order they are:

  • Check out these tips from Chris Gammell. Go ahead, I’ll wait…
    • His post gives a lot of good advice and I pretty much agree with what he has to say (except for #4 when it comes to candy, that’s fair game) . Following his tips will definitely take you a long way when it comes it impressing potential employers.
  • Format your resume so it’s easy to read.
    • I looked at a lot of resumes during the 5 hours I was the Career Fair, a lot. There were long ones, short ones, pretty ones, and ugly ones. Some with one font, two fonts, red fonts, blue fonts. Okay, maybe that last part was a little bit of an exaggeration but I liked the Dr. Suess rhythm I had going. You’re only talking to an employer for a few minutes at most and those couple of minutes should be a discussion between you two rather than awkward fumbling and pointing as you try to locate and point out some portion of your resume after it’s come up in conversation.
    • Try and keep it to one page with only the most relevant information about yourself on it. Instead of listing every single course you’ve taken in school focus on work experience, skills, and projects you’ve done.
  • Highlight your big accomplishments that make you unique.
    • This goes along with my above point about relevant info on your resume. If you’re an upper level EE an employer should be able to assume you’re familiar with basic circuit theory. Showcasing the EE101 Resistor Divider Lab that everyone in 3 departments has to take is not making you stand out.
    • Have you taken a difficult elective not many others do? Were you also passionate about the work you did in that class? Talk about that instead.
      • VLSI and IC design course tend to really make you jump out to semiconductor companies. I know from both working the Career Fair and from my own job hunting experience. A hard copy of your layout will make even the toughest recruiter take you more seriously.
    • Did you solve a particularly interesting problem on an old internship or co-op? Be sure to mention that if it doesn’t come up on its own.
    •  Work on projects or study topics on your own or as part of a club? Those are both worth their weight in gold when it comes to standing out as it shows you’re passionate about the work you do and are self motivated. There’s also the possibility that a strong interest in your field outside of your required course work can make up for a less than stellar GPA or lack of on the job experience.
  • Be honest about what you like.
    • Our table was cluttered with all sorts of circuit boards and demo projects. Some were eval boards showcasing parts in our catalog and others were customer boards that had parts from our company designed in. Telling me one minute you like to design and work with electronics is one thing. However, if the next minute you’re not so much as batting an eye when I dig out an old intern project that has you doing just that doesn’t bode well for you. If you’re not thrilled about working with hardware (or software, or embedded systems, or MEMs, or whatever) don’t lead the recruiter on. It just wastes everyone’s time and it’s easy to see through.
  • Introductions are important.
    • You may not be the most outgoing person in existence and that’s okay. What’s not however is looking at the ground and mumbling your name during an introduction. The venue is going to be noisy to begin with and if the recruiter can’t catch your name after the first or second try it’s going to be tough not to put your resume in the pass pile. It’s sad but it’s true. 
    • Speak up, speak clearly, make eye contact, and have a firm handshake. It’s  simple things like that which can make you stand out after a recruiter has been on their feet all day dealing with Low-Talkers.
  • Come across as someone who is fun to work with. 
    • There was a second year student looking for their first co-op who whipped out a plate of homemade cookies and offered  them to all of us at the booth after we were done talking to him. That’s good stuff. We laughed, thanked him for offering, and once he was gone bumped his resume up a few spots on our list. Do you have to do something that extreme? No, but giving the impression working with you isn’t going to be hell counts for a lot.
  • Do at least some research as to who is looking to hire someone with your skills.
    • I work for an analog IC company. If you didn’t know that going into the Fair it was printed on our gigantic sign and the table was cluttered with all manner of circuit boards. The Co-op Office website had the list of majors we were interested in and so did the packets of info each student got upon entering the Fair. Odds are good we aren’t going to have openings for astronomers if all our material screams EE’s Wanted (yes, I was actually asked that).
    • If a company catches your eye you didn’t know existed until right that moment it’s okay to approach them and ask for more information, that’s why they’re at the Career Fair. There is however, a right and a wrong way to go about doing it.
      • Student A: “Hey, I’m an EE. What positions are available?” Isn’t going to cut it when there are people out there who are actually interested whatever the company does.
      • Student B: “Hi, my name is … I don’t know much about your company but I see your booth is covered in circuit boards. I really like working with electronics and would like to learn more about possibly getting a job with you guys.” This is almost word for word how a student introduced themselves to me at the Fair  and it’s a great example of how to approach a previously unheard of company.
      • Needless to say Student B got much more of my time than Student A did.
  • Don’t let employers push you around.
    • This tip is just something I encountered back when I was a student and want to pass along. On two occasions I had recruiters telling me how I was going to change my whole co-op schedule around and what courses to take to work  for them, after we had already established they stretched the truth about having hardware positions available. In these cases I politely interrupted the recruiter, said I wasn’t interested, and asked for my resume back if they hadn’t written on it (yes, it’s okay to do that once in a while).
    • Just as you shouldn’t waste an employers time they should be wasting yours. It’s better to spend your time  with companies that might actually have something for you (see also point #1 from Chris’ post).

Well there you have it, my take on Career Fairs and how you can avoid some of the mistakes that I witnessed during my first recruiting assignment. As I go out to other colleges and spend more time evaluating potential full-time and co-op candidates I’ll come back and revise and add to the list.

 Got any other tips for student job hunters? Did I miss the mark on any of my points? Just have a humorous Career Fair story from either side of the booth? Sound off in the comments.


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