Re: [CAD_CAM_EDM_DRO] Re: Re: H bridge progress

beer@... wrote:

> On 12 Jun, CAD_CAM_EDM_DRO@yahoogroups.com wrote:
>
> > A resistor from gate to DRAIN will turn it ON! To turn it off, you want
> > a resistor from gate to SOURCE! But, the 2A or so drivers from IR do
> > a fine job of turning fets on and off, and also handle driving the high-side
> > fet, whose source is swinging through the full DC voltage supply.
>
> Sorry, brain fade here .. yes, Jon is correct.
>
> The circuit I was thinking about uses a resistor from gate to drain to
> turn it on relatively quickly, and a transistor to turn it off even
> quicker.
>
> It's true, the 2104 does ease the ugly task of driving the high side
> FETs, but more than one designer has reported problems with the charge
> pump aspect of these devices.

I started with the Harris HIP4080, and blew over 25 of them, trying to get them
to work at 69 Volts (the data sheet says it's good to 80!) I finally talked to an
engineer at Harris who admitted all the flaws in that chip. I had to add about 8
chips to my design to replace all the functions of the Harris part, but from prototype
to production, using two of the IR 2113S half-bridge driver chips, I have never
blown ONE SINGLE 2113 or FET! This was AMAZING for what is essentially
a completely new design! I previously had very good luck driving IGBTs (which are
a lot more picky about gate drive) in a 10 A 400 V inverter design.

> More to the point, I'm always nervous about designs with single sourced
> parts - little guys frequently sent way to the back of the line.
>
> I had a product with a Motorola part that was just wonderful. Come
> time to produce a second batch, I was informed that there was
> no stock and the earliest delivery date was 9 months from now ..
> maybe.
>
> Apparently, Ford had bought up the entire production. Somehow, my
> request for a hundred of them just didn't match up against Ford's
> request for every one of them in the world and every one to come.

Yes, I have also run into this on occasion. I have never had a problem with
IR. I HAVE had a problem with Motorola parts that could find their way into
a cell phone, though. Usually, if you are persistant, you can find SOMEBODY
that has a modest number of parts in stock. The web is ENORMOUSLY helpful
in finding those hard to get parts.

Jon