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View Full Version : Vishay's Si4511DY FETs


Twinblade
2011.01.22, 04:47 PM
Hi guys!

It's been a long while since I last posted here.
I found a local mini-z track and decided to start racing again.

Now, I have an account on Vishay's website. I checked to order some Si4562DY again, but Vishay proposes the Si4511DY as a replacement.

I checked the specs and they are quite a step up from the Si4562DYs. I ordered a bunch but found nothing at all about them here.

Any one had experience with them?

I plan on rebuilding a Plasma-Tomic to run on my car, along with a few custom wound armatures I have laying around. Last time I raced, a 2x3 stack of 4562 was enough to run the motors. They had a 6A rate. The new 4511 have 9.6A rated on N-channel and exactly the same specs on P-channel. That leads me to think that the 4511 would only require 2x2 stacks to run the Plasma...

That would be great since the race track I plan on going to have rules on the stacks, basically you can run any motor that requires at most 2x2 stacks.

I will try to gather some data on theses new FETs when I get them (I guess in about 2-3 weeks).

mdowney
2011.01.23, 03:06 AM
Can you post a link to the website? I'm new around here and don't know who Vishay is but I'd like to read up on what you're talking about. Thanks!

ub0211042
2011.01.23, 09:12 AM
Hi,

Found the datasheet for Si4511DY (http://www.vishay.com/docs/72223/72223.pdf)
and for comparison here's the SP8M4 (http://www.farnell.com/datasheets/12639.pdf)

Hope someone can point which one's better..

Thanks.

Action B
2011.01.23, 11:42 AM
FET – N+P resistance = Total resistance
8858cz - .0345 + .02 = .0545
SI4511DY - .017 +.033 = .0500
SPM84 - .035 + .024 = .0590

This is just a reference. There are lots of other factors that determine how well a FET will perform. For instance, the 8858 switches on about twice as fast as the SI4511DY when data sheets are compared. There are many other specs to look at. "Best" has a lot more to do with what you want. Lots of people feel different FETs are best based upon individual taste, testing, spec evaluation and even mythology lol.

Twinblade
2011.01.23, 04:49 PM
Switch time should not be that important in this case. If I remember correctly, the ESCs in the Mini-Z boards are set at 25KHz, and the stock 3004 fets where able to switch fast enough. We are talking about a 50 nano-seconds difference for complete charge/discharge cycle. For a the up-time of the PWM, that means 0.125% more efficiency in the cycle...

While the 4511 is 0.917% less resistive than the 8858. Making the advantage of the faster switching nonexistent.

I will see when they arrive. One thing for sure, they are better than the 4562DY we used to install in the cars. Too bad I don't have all the tools I would like to test...

Action B
2011.01.23, 05:16 PM
Switch time should not be that important in this case. If I remember correctly, the ESCs in the Mini-Z boards are set at 25KHz, and the stock 3004 fets where able to switch fast enough. We are talking about a 50 nano-seconds difference for complete charge/discharge cycle. For a the up-time of the PWM, that means 0.125% more efficiency in the cycle...

While the 4511 is 0.917% less resistive than the 8858. Making the advantage of the faster switching nonexistent.

I will see when they arrive. One thing for sure, they are better than the 4562DY we used to install in the cars. Too bad I don't have all the tools I would like to test...

I admit I don't know much about electrical engineering or about the switching time of the board etc. I was just trying to help out since you were asking which was better. I have an interest in FETs since I upgrade so many cars with them. In the future I will disregard switch times from my FET comparisons.

I'd like to try those FETs you have noticed too, however, I really doubt that I could tell the difference between any of the above listed FETs. We are all trying to squeeze the most out of our cars and I understand that but .917% resistance is just so miniscule that I'm probably not going to notice.

That being said, a lot of people swear by the PN FETs and top level drivers use them all the time. I doubt they have the lowest resistance though there is no actual spec sheet to look at since they hide the detailed specs and FET type they are actually selling. In my own experiment I was unable to find a difference between the throttle resolution of PN and 8858 FETs. So as you said, I guess just try them and let us know what you think...

Twinblade
2011.01.24, 07:21 PM
Throttle resolution won't change with the FETs.

The FETs are controlled by a MOSFET driver. That is driven by the PWM that is converted from the digital signal from the remote.

On regular AM radios, that is 512 steps at most (including both directions, so 256 for gaz and 255 for reverse).

On 2.4GHz, they are usually 1024 steps, so double resolution.

Then again I don't think that the receiver and MOSFET driver will be that high resolution. The MOSFET driver is probably receiving a 8bits PWM signal, blocking the actual resolution to 512 steps.

Switching time would important in the case of an audio or high frequency amplifier. You would not want to lose clarity for this.

Felix2010
2011.02.14, 04:17 PM
Any news on these MOSFETs? I'm addicted to FET science:)

Felix2010
2011.02.17, 04:12 AM
I will see when they arrive. One thing for sure, they are better than the 4562DY we used to install in the cars. Too bad I don't have all the tools I would like to test...

Twinblade - Thanks for posting your finding these 4511's. There is always a need for good FET info for us Mini-Z tuning addicts who change setups like we change socks...:)

Have you taken delivery of your si4511's yet and given a 2x2 stack a shot?

Looking forward to reading about these FETs:cool: