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PSE vs. PD power dissipation again

Yair, Dieter, and all:

Speaking both as an engineer having started with thermionics and now working
with integrated power MOSFETs, and as someone who has a direct exposure to
the semiconductor industry, I believe I can say the following with both
history and present knowledge to back me up:

A discrete MOSFET in conjunction with a low-voltage controller circuit for
the PSE may be a lower parts-cost-per-port solution today, and for a year or
two.  That is TBD.  But eventually (sooner rather than later), the MOSFET
will be integrated, as board space and circuit complexity has a way of
becoming more expensive than silicon - or conversely, silicon just keeps
getting cheaper.  I suggest the examples of Power Integrations (the
"TopSwitch" family) and the similar ST Micro "Viper" family of one-chip
off-line power supplies.  Open any 'ATX'-type computer power supply.  It
can't be done for the price, but by the miraculous alchemy our industry
works to turn sand into gold, it is.

Conclusion:  Multiple-port PSE switches with integrated MOSFETs will become
an available, cost-effective, and viable alternative to
multiple-component-per-port implementations.

Thanks for letting me sound off here.

Peter Schwartz
Applications Engineer
Micrel Semiconductor
Phone:	408.435.2460
FAX:	408.456.0490

[Yair Darshan]

>         3. Reducing PSE switch size allows integrating the mosfet in the >
chip - allow lower cost solution. - Not accurate.
>                         - Chip vendors says that it will cost more due to>
the mixed technologies used (HV & LV)
>                         - Chip vendors says that to support 350mA/80V with
> low dissipation, large die size required, chip package increased, overall
> cost increase compared to >                           small LV chip with
external Mosfet.

[Dieter Knollman]
This depends on technology.  The goal is to achieve a multi port PSE
solution with internal switches.The automotive industry has octal switches
with build in protection.  The voltage is lower, but the current is higher.
Can a semiconductor vendor address this point?  I've always been a fan of
dis-integration, but I'm trying to change.