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RE: PSE vs. PD power dissipation again

Hi Peter,

Thanks for your info, However now I am more confused., I got other info, and
in order to be sure that we are talking about the same parameters I have
some questions to you. See below.

> -----Original Message-----
> From:	Schwartz, Peter [SMTP:Peter.Schwartz@xxxxxxxxxx]
> Sent:	ה, מרץ 22, 2001 10:11 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
> 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.  
	[Yair Darshan]  

	1. Are you taking in account that the Mosfet need to be rated to
1A/80V with low enough Rdson that can meet our requirements?
	2. Are you saying that integrating the Mosfet into the chip will
cost less than using low voltage chip with external Mosfet?

> 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.  
	[Yair Darshan]  

	1. Using low cost chip say 8pin if we are lucky with the above rated
Mosfet will not drive us to larger package? Please advise?

> I suggest the examples of Power Integrations (the
> "TopSwitch" family) and the similar ST Micro "Viper" family of one-chip
> off-line power supplies. 
	[Yair Darshan]  

	This examples shows my point, they are TO220 package with 3-5 pins,
and this is exactly my point you are not saving board space. 
	It is about the same or worth, aspecially for multi port.

	In addition, better layout in some application is achieved if the
Mosfet is located on Area A and the Control on Area B for controlling high
	etc. specially in multi port environment.

>  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.
	[Yair Darshan]  

	And finally if you check your examples for high quantities you will
see that Integrated solution will cost 1.2 - 1.5 (Power Integration and
	and discreet solution will cost : Controller + Mosfet = 0.4$ + 0.33$
= 0.73$ which is less.. 

> Thanks for letting me sound off here.
	[Yair Darshan]  
	Please let me know what is your opinion on the above comments.


> Peter Schwartz
> Applications Engineer
> Micrel Semiconductor
> Phone:	408.435.2460
> FAX:	408.456.0490
> peter.schwartz@xxxxxxxxxx
> [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.