Electronics > Beginners
Are logic level gate mosfet slower than regular mosfet?
<< < (6/7) > >>
spec:

--- Quote from: T3sl4co1l on November 01, 2018, 09:01:22 am ---doc format?  But... that's almost as bad, what's wrong with plain text? |O

Here's plain text, cleaned up a bit; view with tab size 4.  I'm not sure if that imports into, say, Excel cleanly.

Tim

--- End quote ---

Don't be too hard on me- I'm just a simple person :)
spec:

--- Quote from: exe on November 01, 2018, 10:07:12 am ---BTW, while higher gate voltage means lower Rds(on), I found there is a diminishing return. E.g., a 10V drive was barely better than 7V drive. So, it may not make much sense for charge pumps, etc for a logic-level fet. I suggest do some measurements (but leave some voltage headroom for process variation, temperature effects, etc).

Also datasheets often provide guaranteed Rds(on) at specific voltages, the actual resistance is even smaller (but do not rely on this in mass production).

--- End quote ---

True, and temperature has a big impact on Rds.

The charge pump gate driver was suggested as a way to use standard MOSFETs, which are more common, cheaper, and tend to have lower parasitic capacitances.

You mention the law of diminishing returns in regard to drive voltage/Rds. As you imply, the secret is to establish the sweet spot in a design :)
exe:
There are also mosfets with integrated drivers. E.g., this one: https://www.onsemi.com/pub/Collateral/NCP5369-D.PDF (just first one from Google).

There are devices with integrated charge pump, over-current, over-voltage (not sure what this exactly means, check datasheet if important) and thermal protection.

Other devices are below. Just google "smart fet", "protected fet", etc.  At least some of them declare switching speed up to 1MHz.

- https://www.infineon.com/dgdl/Infineon-ApplicationNote_v12-AN-v01_00-EN.pdf?fileId=5546d4625b62cd8a015bc8c8e5ae31d1
- https://eu.mouser.com/new/diodes-inc/diodes-zxms-mosfets/
exe:

--- Quote from: spec on November 01, 2018, 10:26:39 am ---As you imply, the secret is to establish the sweet spot in a design :)

--- End quote ---

Yeah, but for a one-off device I'd suggest save time and just get the best part. Sort of overkill, but saves a lot of time... and often board space.

I have CSD17313Q2T (that I'm yet to try), but even at 3V drive it gives less than 50mOhm over entire temperature range (hope it's not a "typical performance") and has very good performance in terms of Rds(on) vs gate charge.

There are inexpensive parts with threshold of less than 1V in sot-23 package with quite low Rds(on). Like AO3414. I bought it because it's cheap (yet to try it, don't have a lab at the moment) :). Just threshold voltage can be as low as 0.4V, so be sure driver can pull that low.
Ian.M:

--- Quote from: T3sl4co1l on November 01, 2018, 09:01:22 am ---doc format?  But... that's almost as bad, what's wrong with plain text? |O

Here's plain text, cleaned up a bit; view with tab size 4.  I'm not sure if that imports into, say, Excel cleanly.

--- End quote ---
It doesn't import cleanly.  I've gone back to Spec's list in the .doc, used '_' as the separator then cleaned up out of order columns to get a CSV file that should import OK to any spreadsheet.
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod