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bikeron

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bikeron

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  • 01.24.2013
  • The voice
  • "The Voice" was Frank (Sinatra). I eagerly clicked the link seeing that phase and was dissappointed to see a rendering of Ernie Kovacs voice.
  • 08.06.2013
  • Tackling efficiency and thermal behavior of SMPS with SPICE
  • Very nice! A slow diode that exhibits lots of junction capacitance can replace the the cap also. This use of C to take the base charge both into and out of the BE junction was used extensively in the 70"s and early 80s in off line PSU's. Some of the best info on exactly how to do this (including the use of an inductor to optimally sweep out the charge just as the collector voltage starts to fall) was from work done by Philips, the predecessor of NXP. Why was the base resistor chosen to be 470 ohms? Did you use the sweep feature in Multisim to determine the optimal value these beforehand? Ron
  • 05.22.2013
  • Many digital power functions moving to state machine-based control
  • Exar has the 77XX series that has the regulators and logic integrated together. It is a system IC that has four regulators and the programmable logic.. These devices can be daisy chained to form systems with more rails. GPIOs are available so that the 77XX can put other, external regulators in the sequencing system with Power goods and enables.
  • 07.08.2013
  • Polyphase rectification
  • Used GE 86F series caps in the 70's. Did a check on a McIntosh Amplifier with these caps (9300uF 50V) that had not been used since the 70's. It was in a storage locker. The date codes on the caps indicate that they were made in 1971. I can't post graphics on here but the ESR was 25 milliohms at 54KHz... leakage was low.. My memory from that time says that they were rated for 2Khrs at 85C. So assuming 25C as the average temp they should have gone bad in 128Khrs or about 14.6 years. Many of the axial leaded caps had gone bad (Philips and ERO) but the multi-section 87Fs and the 86Fs were all in excellent shape. We did weight tests on a lot of these "computer grade" caps back in the day to determine operational life. They were way better than their spec life. All bets are off if the ripple current is too high though (internal heating). Vapor cycling can occur if the delta T is too great inside the can. The core can then dry out leading to higher ESR and more heat which leads to more of the electrolyte migrating to the can walls.. etc. etc. Bottom line was that even in the old days you could do government contract 7 year specs with electrolytics which were way less money than multiphase xformers. Now if the spec was for 15 years (yes, the government does ask for such things) then the transformers might be better. But then again I have radios from the 1930's that still have good electrolytic caps.... Ron
  • 01.31.2013
  • Do Engineers Still Use Breadboards?
  • OK so no one answered so I will. Yes, I still build breadboards. It is not generally accepted by customers however as "proof of concept" however. Thus I wind up designing and building a PCB as proof of concept in most instances. I'd love to post a few pictures... This box won't let me...
  • 04.15.2013
  • A new 21st-century shootout at the O-K Corral?
  • No, I don't see a shoot out. I see software getting around the issues of drift and inaccuracy in the analog front ends of SOC's. I think smart meters are good examples of this. The analog art does not have to be that good. All of this is at the cost of calibration however. Many analog systems are inherently accurate and do not need to be "softwared around" to meet spec. COmponents like resistors are incredibly good now, in the 1PPM region, have very predictable shift with time temperature etc. No need for adjustment pots to calibrate. Which is more cost effective? Probably the SOC with software if you're doing millions of products, probably analog if you're doing tens of products.
  • 03.18.2013
  • Dual '4424 drivers
  • Fairchild has some "compound drive" output topologies in many of their drivers which helps with larger MOSFET input C. I was on the team at Teledyne that did the first drivers (TC426). The "442X" series solved a lot of the issues related to latch up in the drivers. Some vendors drivers are much more robust (not that this is reflected in their datasheets) than others, in which case the external diodes may not be needed. This same circuit was used with the IR2110 high voltage driver with a TSC4426 back in the early 90's. It worked very well. I would suggest a resistor from the input to the 4424 to it's ground pin and from gate to source of the MOSFET, in the region of 1K. This would be to prevent noise triggers turning on the MOSFET during high dv/dt events like ESD discharge (machine model, not human body), lightening and substation switching events.