Re: Bullet-Proof G201 / G210

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Mariss Freimanis
<mariss92705@y...>" <mariss92705@y...> wrote:

> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "jmkasunich
> <jmkasunich@y...>" <jmkasunich@y...> wrote:
>
> > Internal DC capacitor. Adding an external 470uF cap
> > seems like a band-aid
>
> This is a bit of a quandry. A goal is to keep the same form
> factor and pinout. Several of our large OEMs (> 1,000 units
> a year) mount the drives upside down on a PCB using their
> own PCB mounted 5mm sockets. The cap is also on the PCB.

Could you put the holes on the PCB for the cap, and either
sell two versions (with and without cap), or spec the cap
from somebody like Digikey and let the user install it?
Use a radial lead cap to save board space.

> It will use top-side current sensing. An interesting option
> I have running senses the top MOSFET "on" Vds using
> small-signal diodes and transistors. No wasteful "in-line"
> components. If the MOSFET "on" voltage exceeds a set value
> (1V or so), a fault condition is presumed.

Cool. Sounds like the "desat" protection we use for large
IGBT modules.

> This would also neatly detect over-temperature in the
> MOSFET directly because of the positive temperature
> coefficient for Rds.

Wow. Can you actually get good temperature resolution doing
that? I would expect one FET to be 1V at 100C and 8A, and
another FET to be 1V at 180C and 15A. I've never studied
the spec sheet tolerances and done the math.

John Kasunich