Re: [CAD_CAM_EDM_DRO] re:Re: HIP4081

ballendo@... wrote:

>
> >No I did not do anything special, I lost lots of mosfets to find out
> >that I can get no where near the promised upper limit of 80 volts.
> >As long as I stay down at 30 volts all is cool. If I had it to do
> >over again I would never use this chip again. I am building a
> >spindle drive, 100 volts 15 amps, that will be under pic servo
> >control, but it will use the ir2104. So far I have not had any
> >problems in my limited testing.

My original servo amp used the HIP4080, which uses a similar
output driver. The big thing was the built in charge pump for
high side fet bias. This allows you to leave the high-side fet
turned on as long as you like, whereas the bootstrap design
requires you to turn it off to rechage the bootstrap capacitor.
I had to replace the PWM modulator, the charge pump and a
bunch of other stuff with separate parts, and replace one HIP4080
with two IR2113s, but the results were worth it. Harris
throws the 80 V figure around in their documentation all
over, but when I pinned THE HIP4080 applications guy at Harris
down, he admitted that no one had ever gotten reliable operation
at over 54 Volts DC input. He was rather surprised that I was
able to get fully reliable operation at up to 59 V, and
had run one for quite a while at 69 V. The spikes kill it,
but I had problems with the high side driver, not the low side.
I DID spend a LOT of time on the layout of my servo amp,
it has 1/4" wide traces for all the power nets, and the loop area
of the high current paths were worked over for over 2 weeks to
get them as small as possible. The fact that I can have power
circuits switching 69 V at 100 KHz with 40-75 nS swings
of 69V (that's over 1000 V/uS dv/dt) without disturbing
sensitive analog circuits processing millivolt-level signals
less than an inch away, proves I did it right.

Jon