2007.12.15, 12:33 AM
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#16
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Mosport Tragic
Join Date: Dec 2007
Location: Bathurst
Posts: 25
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Great info LBRC,
Our local Mini-Z guy swears by the SP8M4.
As I am going to FET about 4 cars soon and don't want to do it again, the hassle factor is way more expensive than the chips so it's worth getting it right the first time. Which would be the better The 8858 or SP8M4? The comparison I've seen rates the SP8M4 VERY close to the 4562. I run lipos in a few cars.
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2007.12.15, 03:24 PM
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#17
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Registered User
Join Date: Mar 2004
Location: Northwest
Posts: 550
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Rohm SP8M4 data sheet.
http://www.rohm.com/products/databook/tr/pdf/sp8m4.pdf
Hm, very slight spec sheet P-channel current to the 8858, much higher N but since we need both a P and an N the lowest value is the weak link so not much help there, total RdsOn is extremely close.
Note the different current levels on the spec sheet test 4.5 volt test levels for RdsOn, a good example of why it’s also so hard to nail down actual in car results and why they can very so much from the spec sheets.
Me, I think you should go with the 8858’s just so you could compare the two and tell us which one you like. Or better yet do two M4’s and two 8858’s
__________________
Jungle Outlaw Micro Racing
If the track is wet, then the tent is leaking.
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2007.12.17, 10:09 AM
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#18
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Mosport Tragic
Join Date: Dec 2007
Location: Bathurst
Posts: 25
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I have decided to buy 5 nano racers and set them all up as test beds, they are an absolute clone of of a MR02 and are cheap enough to make mistakes affordable.
I've just become serious about small scale and I reckon if I could blow 60-70 grand over the years on planes trains and automobiles I can blow a few a few K getting this right. I am building a 4 point scale wind tunnel so a few bucks on FET's won't tickle the the budget too far. My biggest problem is getting enough space for a full time track with enough length.
Talking about FETs, it's a bit like what oil do you use? What Beer do you drink? 12 people = 12 answers. It's the same in the bigger scales as a lot of you know.
I guess I'll "suck it and see"
Get back to you.
Check the "do spoilers work" thread for up dates on the wind tunnel.
Last edited by BryceVR; 2007.12.17 at 11:15 PM.
Reason: Tpyo Doh!
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2008.03.15, 10:47 AM
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#19
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Registered User
Join Date: Mar 2008
Posts: 184
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Where can I get this 8858 fets?
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2008.03.15, 03:55 PM
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#20
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Registered User
Join Date: Mar 2004
Location: Northwest
Posts: 550
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An on-line electronic supply warehouse like DigiKey, or just about any local electronic supply store in the US can order Fairchild products (true electronic store though not a Rat Shack).
Manufacturer: Fairchild
Part Number: FDS8858CZ
Note
The part number is important, you need to make sure the "8858" you are ordering is not an older NDS8858H or an "8958" series both of which would work but be disappointing with much higher resistance and lower current handling abilities.
__________________
Jungle Outlaw Micro Racing
If the track is wet, then the tent is leaking.
Last edited by LBRC; 2008.03.15 at 04:21 PM.
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2008.03.15, 11:04 PM
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#21
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Registered User
Join Date: Mar 2008
Posts: 184
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Quote:
Originally Posted by LBRC
An on-line electronic supply warehouse like DigiKey, or just about any local electronic supply store in the US can order Fairchild products (true electronic store though not a Rat Shack).
Manufacturer: Fairchild
Part Number: FDS8858CZ
Note
The part number is important, you need to make sure the "8858" you are ordering is not an older NDS8858H or an "8958" series both of which would work but be disappointing with much higher resistance and lower current handling abilities.
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I just been to DigiKey web and under the Item Number key they listed either FDS8858CZCT-ND or FDS8858CZ. So according to your advice above it is the FDS8858CZ to choose right? The minimum order is 2500 pieces. Is there anywhere I can just get like 10 or 20 pieces?
Last edited by dameetz; 2008.03.15 at 11:10 PM.
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2008.03.16, 01:06 AM
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#23
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Registered User
Join Date: Mar 2004
Location: Northwest
Posts: 550
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The above Mouser link looks like a good deal especially since DigiKey has a surcharge for orders under $25.
As for DigiKey you are looking at the DigiKey part number instead of the Manufacturer’s PN, if you look again you’ll notice that they are all the same manufacturer PN just in different packages the “TR-ND” at the end of the DigiKey PN stands for Tape & Real while “CT-ND” stands for Cut Tape which is what you would want to order, an individual number of mosfet packages cut off of a tape real.
http://search.digikey.com/scripts/Dk...FDS8858CZCT-ND
__________________
Jungle Outlaw Micro Racing
If the track is wet, then the tent is leaking.
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2008.03.16, 09:48 AM
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#24
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Registered User
Join Date: Dec 2006
Location: Southern NH
Posts: 987
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LBRC - I know you warned against mistakingly ordering the Fairchild 8 958A Fet instead of the Fairchild 8 858CZ Fet. I was looking at the specifications for each of these two Fets on DigiKey and in the "Package/Case" column, for the 8958A Fet it says "8-SOIC" ; For the 8858CZ it says "SO-8". Could you tell me what this means? I have heard of the SO-8 package before, but I don't know what it is. Is the "SO-8" package superior?
I have seen the 8958A Fets for sale at EGRmart and I'm curious as to why the 8958A Fets are being sold by a Mini-Z hop-up site over some of the other "new" Fets out now like the 8858CZ and the Rohm SP8M4? Are there some good points about the 8958A Fets that we are overlooking? Just wondering, I am definitely not and expert on FETs.
Thanks for the great FET-info too, LBRC
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2008.03.16, 09:51 AM
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#25
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Registered User
Join Date: Mar 2008
Posts: 184
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Thanks for the above link, will try to order it from mouser.
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2008.03.16, 01:30 PM
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#26
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EE
Join Date: Feb 2007
Location: SK Canada
Posts: 109
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Quote:
Originally Posted by Felix2010
Could you tell me what this means? I have heard of the SO-8 package before, but I don't know what it is. Is the "SO-8" package superior?
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SO-8 and SOIC-8 referr to the same 8 lead package.
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2008.03.16, 10:30 PM
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#27
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Registered User
Join Date: Mar 2004
Location: Northwest
Posts: 550
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Quote:
Originally Posted by Felix2010
...I have seen the 8958A Fets for sale at EGRmart and I'm curious as to why the 8958A Fets are being sold by a Mini-Z hop-up site over some of the other "new" Fets out now like the 8858CZ and the Rohm SP8M4? Are there some good points about the 8958A Fets that we are overlooking? ...
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Somebody tried and liked them, supply, demand, availability? Got a good deal on a couple of thousand and now have to sell all 2+K before selling anything else, no way of really knowing. I posted the info on these because they seem to work well, but above all are cheep and easy to get in the US, EGR being in HK who knows…
One thing to keep in mind about different mosfets is that they do feel slightly different so when it comes to replacing stock or blown FETs as long as the new set or stack will handle a particular car/motor’s current needs the “best” with some concession to resistance usually ends up being a matter of personal preference. Even then I might like the way one FET with superior specks “feels” but the lap timer may actually prefer a mosfet with less impressive specs.
__________________
Jungle Outlaw Micro Racing
If the track is wet, then the tent is leaking.
Last edited by LBRC; 2008.03.16 at 10:35 PM.
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2008.03.17, 06:08 AM
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#28
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Registered User
Join Date: Dec 2006
Location: Southern NH
Posts: 987
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kja812 - Thanks for answering my "SO-8 / SOIC-8" question.
LBRC - Thanks again for all the great Fet info. I hope to get a hold of some of the Fairchild 8858CZ Fets you recommended.
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2008.03.17, 11:55 AM
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#29
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Registered User
Join Date: Dec 2006
Location: Southern NH
Posts: 987
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@LBRC - While I was shopping for some 8858CZ Fets using the link provided by pinoyboy(Thank you ), I did a search for the 8958A Fets and there were three versions listed. One was listed as "obsolete", but the other two were In-Stock: One FET was listed as manufacturer part#512-FDS8958A_Q and the other was listed as manufacturer part#512-FDS8958A . The prices for these FETs are different: The 512-FDS8958A_Q version costs $1.57 per Fet; The 512-FDS8958A version costs $3.03 per Fet. I am thinking about ordering a few of these 8958A Fets to try when I order the 8858CZ Fets - Could you tell me which one is the "correct" 8958A Fet that I should purchase? Thank you!
LBRC & pinoyboy - Are there any other Fets that you recommend I should look at buying to try on Mini-Zs while I'm here placing an order?
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2008.03.17, 02:30 PM
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#30
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EE
Join Date: Feb 2007
Location: SK Canada
Posts: 109
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I checked mouser's site for you.
The _Q parts are non-lead free while the other parts are newer lead-free production parts. Save the couple bucks and order the _Q parts.
Looks like they have stock of the ever popular Vishay SI4562DY.
They also have stock of a few other Fairchild parts that aren't quite as good as the two you're looking at: FDS4897/FDS8960/FDS8962/FDS4885.
Hope this helps.
Last edited by kja812; 2008.03.17 at 02:33 PM.
Reason: extra info
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