Gene Heskett wrote: > > > Very true Peter, but would not this sort of problem be better treated with > some logic to use the gate delay to delay the on swing? I'm thinking cmos, > old style 4000 series because I personally used some of that sort of > trickery to put colored outlines around a character in a character > generator that didn't have that capability originally. Running on 28 > volts, that 4028 ran detectably warm, but in 2 years, never failed. Of > coarse in those days we thought 200 ns was a short time. Now, 25ns is > economy grade utility stuff. But the idea should be just as valid. > > 4000-series can't handle large currents at the output. I had an earlier servo amp where I used a 4069 inverter, with 3 sections driving each side of a little charge pump transformer. It would blow up, run hot or just not work. I finally figured out inter-winding capacitance was driving a lot of current into the inverter output pins. I had to split the windings on the bobbin to make it work.
Anyway, the IR2113 and similar drivers can source or sink 2A to the FET gates. Can't do that with 4000 CMOS. My first version of the brushless servo amp used a triple half-bridge driver chip that was supposed to deliver 600 mA. Turns out if you read the datasheet more closely, you really only get 200 mA. And, that caused the transistors to run hot due to slow turn-on/turn-off. The only fix was to go to 3 separate half-bridge driver chips instead of the all--in-one part. But, now it runs much faster, without the partial shoot-through. My brush servo amp is really old-school, uses 4000-series logic and RC-diode delays to control dead-time on the inputs to the IR FET driver chips. Jon ------------------------------------------------------------------------------ Try New Relic Now & We'll Send You this Cool Shirt New Relic is the only SaaS-based application performance monitoring service that delivers powerful full stack analytics. Optimize and monitor your browser, app, & servers with just a few lines of code. Try New Relic and get this awesome Nerd Life shirt! http://p.sf.net/sfu/newrelic_d2d_may _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
