Re: Return of "What is JS214A?" (prev MOSFET Testing)

From: Franc Zabkar (fzabkar_at_optussnet.com.au)
Date: 08/11/04 

Date: Thu, 12 Aug 2004 07:03:07 +1000

On Wed, 11 Aug 2004 11:32:46 GMT, "alpha_uma" <no_one@nonesuch.com>
put finger to keyboard and composed:

>"Franc Zabkar" <fzabkar@optussnet.com.au> wrote in message
>news:5onjh013bsqmrb7skil752mkannf0enfuh@4ax.com...
>> On Wed, 11 Aug 2004 00:59:36 -0700, "Watson A.Name - \"Watt Sun, the
>> Dark Remover\"" <NOSPAM@dslextreme.com> put finger to keyboard and
>> composed:
>>
>> >
>> >"Franc Zabkar" <fzabkar@optussnet.com.au> wrote in message
>> >news:aldih01b5vi5k60rbjc5irnq2h2fe6com0@4ax.com...
>> >> On 10 Aug 2004 18:23:45 GMT, "Walter Harley"
>> >> <walterh@cafewalterNOSPAM.com> put finger to keyboard and composed:
>> >>
>> >> >Personally, I'm skeptical, although Watson's probably looked at more
>> >old
>> >> >components than I have. Firstly, I see no reason to believe that the
>> >> >back-to-back-diode logo means the contents are diodes: after all, do
>> >you
>> >> >know of any other components that are marked that way?
>> >>
>> >> Good point, but I've seen many twin diodes marked this way.
>> >>
>> >> See http://www.wagner.net.au/Catalogue/01_19.pdf
>> >
>> >Here's one dual diode in the same packages that power transistors and
>> >power FETs come in. I couldn't see the scrambled package, so the OP
>> >will have to determine which package it's in.
>> >
>> >http://www.st.com/stonline/books/pdf/docs/10182.pdf
>> >
>> >My guess is that the JS214 is the date code - 14th week of 2002, and the
>> >real key to the part number is the B55Q whatever.
>>
>> I suspect the B55QS03 is a 55A device. I believe it is configured as a
>> flywheel diode in the Vcore regulator circuit(s).
>>
>> IIRC, the OP's motherboard is the earlier K7S5A which uses a KA7500B
>> PWM controller.
>>
>> http://www.overclockers.com.au/pic.php?pic=techstuff/r_ecs_k7s5a/k7s5a.jpg
>> http://www.fairchildsemi.com/ds/KA/KA7500B.pdf
>>
>> In the OP's case, I suspect the Vcore circuit(s) look something like
>> this (part of an M571 socket 7 motherboard):
>>
>> ferrite L20
>> beads FET coil
>> L18 |---| ===== to JP8
>> +5V o--|--[]-[]--|---------|Q9 |----|---/\/\/---|--o core jumper
>> +_|_ +_|_ |-|-| _|_ +_|_
>> EC18 ___ ___ EC22 | / \ Q8 ___ EC27
>> EC35 | 4000uF | 1500uF | /-|-\ diode | EC32 3500uF
>> EC36 _|_ _|_ | _|_ _|_ EC24
>> EC21 = = ___|___ = =
>> | |
>> |KA7500B|
>> |_______|
>>
>> FWIW, my ECS L7S7A2 motherboard uses 3 pairs of MOSFETs (NEC 2SK3296 +
>> Philips PHB55N03LTA) rather than the traditional configuration of 3
>> MOSFETs plus 3 flywheel diodes. Coincidentally (?) the second MOSFET
>> part number is similar to the OP's twin diode. It is rated at 55A,
>> 25V. The function of the MOSFET pairs is described in the following
>> data***.
>>
>> RT9237A Multi-Phase DC/DC Controller for CPU Core Power Supply:
>>
>http://www.richtek.com/ch/count.asp?catalog=product&item=data***&id=70&file=../Product/Docs/DS9237A-00P.pdf
>>
>>
>
>You guys are amazingly resourceful! Thanks for helping. I'm still digesting
>the last few messages that you guys posted, especially the latest one from
>Franc.
>
>I was reading Fairchild's Application Note 558 titled "Introduction to Power
>MOSFETs & Their Applications":
>
> http://www.fairchildsemi.com/an/AN/AN-558.pdf#page=1
>
>Many of the MOSFET driver techniques mentioned in the article employ diodes
>and zener diodes. See, for example, Figures 22, 24 and 25 in that article.
>So, I'm beginning to lean toward the suggestion that those three "JS214A"
>ICs are some kind of dual diode in D^2-style paks.
>
>Here is a link to a picture of my motherboard:
>http://members.shaw.ca/ra11dec50/my_mosfets.jpg

OK, it's not a K7S5A, but the Vcore circuit looks similar.

>Any suggestion of what kind of driver technique they might be using on my
>motherboard?
> Al-U

The circuit is probably similar to that in my diagram above, except
that yours probably has three MOSFET/diode/coil/cap sets wired in
parallel. Each of the twin diode packs are probably wired as a single
larger capacity diode by connecting together the two outside pins.
IIRC, your previous testing confirms this.

FWIW, here are my notes for an M571/M571lmr socket 7 motherboard which
uses a Vcore circuit similar to yours:
 http://members.optusnet.com.au/~fzabkar/LMRvcore.txt
 http://members.optusnet.com.au/~fzabkar/pwrnotes.txt
 http://members.optusnet.com.au/~fzabkar/v32corev.txt
 http://members.optusnet.com.au/~fzabkar/voltcalc.txt
 http://members.optusnet.com.au/~fzabkar/voltcore.txt

The LMR board uses BIOS to control the Vcore (probably similar to
yours), the other uses jumpers.

- Franc Zabkar 

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