Breaktru Forum

eCigarette Forum => Modding => Parts for Mods => Topic started by: Breaktru on March 27, 2014, 12:08:54 PM

Title: Power Block II Synchronous Buck MOSFETs
Post by: Breaktru on March 27, 2014, 12:08:54 PM

Power Block II Synchronous Buck MOSFETs (http://focus.ti.com/general/docs/video/Portal.tsp?entryid=0_fg4h8uji&lang=en&sp_rid_pod4=ODY2OTIzNDczMgS2&sp_mid_pod4=45460939)
Title: Re: Power Block II Synchronous Buck MOSFETs
Post by: CraigHB on March 27, 2014, 04:21:34 PM
Pretty amazing part. 

Those guys at TI are always coming up with the best stuff, generally their switches are really good.  I took a look at the data sheet for the 30A part.  It's an N-channel pair so you're limited to certain types of controllers with that.  A lot of them are using NMOS rectifiers now so it's probably not a big deal.

It would have been better if the pair was matched a little closer, but I guess that's a space saving thing.  The gate charge is a little high on the rectifier and the on resistance is a little high on the energizer (relatively speaking).  I'd rather have a more matched pair with a more median trade off for gate charge and on resistance.  That's always the trade-off, gate charge for on resistance.  You don't want to go too high on either with a converter.  High gate charge reduces switching speed and increases load on the gate driver.  High on resistance increases power loss and heating.

This part would actually be better; http://www.ti.com/product/csd86360q5d   You have to reflow solder the version II part which can be a limitation for a hobbyist.  The 5x6 SON package can be soldered by hand with the right circuit board layout, just need a couple big vias under the center pad.  Also, that part I linked has better specs.  You sacrifice some performance for that extremely small form factor with the version II. 

I've looked at those Power Block parts before, but I hadn't seen the new version II parts.  If I do a design with a different controller that uses an NMOS pair, I may use one of the 5x6 SON parts.  The controller I'm using right now uses an N-P pair.  That part can also be used for a booster.  The only difference between buck and boost is which side of the inductor the MOSFET pair is connected to.