RE: PSE vs. PD power dissipation again
I must agree with Peter. Multi-port PSE with integrated FETs is very viable
today and offers many benefits. Higher level of integration means smaller
size and less component count, thus reduces system complexity and over all
cost while at the same time increases system reliability.
Sr. Mkts. Corp. Apps. Engr.
Maxim Integrated Products
> -----Original Message-----
> From: Schwartz, Peter [SMTP:Peter.Schwartz@xxxxxxxxxx]
> Sent: Thursday, March 22, 2001 12:11 PM
> To: Dieter Knollman; Yair Darshan
> Cc: stds-802-3-pwrviamdi@xxxxxxxx
> Subject: PSE vs. PD power dissipation again
> Yair, Dieter, and all:
> Speaking both as an engineer having started with thermionics and now
> 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
> 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
> 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
> the mixed technologies used (HV & LV)
> > - Chip vendors says that to support 350mA/80V
> > low dissipation, large die size required, chip package increased,
> > 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
> Can a semiconductor vendor address this point? I've always been a fan of
> dis-integration, but I'm trying to change.