0603 are tiny and really difficult to work with manually. 0805 are about the smallest components I can work with and keep my sanity.= =A0 Those protection diodes are good to have and cover all possible bases, but = probably aren't needed unless your load has enough inductive energy to exce= ed Vds or Vgs. What I do sometimes in my prototypes is lay out the optional components tha= t may become necessary, buy a few and experiment to see what will work. If it turns out that one of them is unnecessary, just leave it out of the f= inal design. Cheers, Robert ---------------------------------------- From: joshybear@gmail.com Date: Sat, 7 Feb 2015 22:39:55 -0500 Subject: Re: [EE] N Channel MOSFETs...again To: piclist@mit.edu So far I've been working off of this design note: http://www.semtech.com/images/datasheet/transient_voltage_protection_of_mos= fets.pdf In it, they mention using a TVS diode, DS, as well as one GS. I have done some searching, but I'm not entirely sure I interpreted their guidelines correctly. For the DS diode, they say: "The working voltage of the TVS diode (Vrwm) must exceed the worst case supply voltage" and "The TVS diode clamping voltage (Vc) must be less than the minimum breakdown voltage of the MOSFET under peak pulse current conditions." For my application, the breakdown voltage of the MOSFET I'm currently planning on is 40V (https://www.fairchildsemi.com/datasheets/FD/FDD8647L.pdf page 2 - BVdss =3D 40V). Maximum supply voltage we'll say is 32V. It should really never be above 24V, but I want to give a little bit of room just in case. Based on that I'm looking at a Bourns SMBJ33A part (http://www.digikey.ca/product-detail/en/SMBJ33A/SMBJ33ABCT-ND/2254198). It has a breakdown voltage of 36.7V, and a Vrwm of 33V. How does that sound? For the GS diode, following your suggestion of a Zener rated a volt or so above the gate voltage (in my case 5V), I am looking at this one from Bourns: http://www.digikey.ca/product-detail/en/CD0603-Z6V2/CD0603-Z6V= 2CT-ND/3534311 - I like it because it's an 0603 package, which is great for board space. It's rated at 6.2V, 150mW. There are 6.8V and 7.5V versions from a company called Comchip Technology if you think I should go higher. I'm currently looking at the Microchip TC4427A Dual MOSFET driver. It's a non-inverting unit with a voltage range of 4.5 - 18V. I'd be running it at 5V. I've attached a quick schematic of what I'm thinking. The second channel of the driver will end up doing something just like the first. Also, I may be wrong on the symbol for the DS diode. Interested in feedback! Thanks! Josh -- A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools. -Douglas Adams -- http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist =20 --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .