Author Topic: Single transistor with 7 pins!?  (Read 388 times)

0 Members and 1 Guest are viewing this topic.

Offline MrZwing

  • Regular Contributor
  • *
  • Posts: 91
  • Country: se
  • Ohh! what does this button do? *click*
Single transistor with 7 pins!?
« on: February 21, 2017, 08:02:05 AM »
http://www.wolfspeed.com/downloads/dl/file/id/145/product/1/c3m0065090j.pdf

Why does this transistor have several "source" pins and what are the uses for it? i have been scratching my head quite a bit over this one.

does anyone have an answer for me why so many source pins? is there a special application for it?

/MrZ
 

Offline Benta

  • Frequent Contributor
  • **
  • Posts: 397
  • Country: de
Re: Single transistor with 7 pins!?
« Reply #1 on: February 21, 2017, 08:13:33 AM »
It has 5 source pins to keep resistance low. Drain is the tab, which is big enough.

 

Offline MrZwing

  • Regular Contributor
  • *
  • Posts: 91
  • Country: se
  • Ohh! what does this button do? *click*
Re: Single transistor with 7 pins!?
« Reply #2 on: February 21, 2017, 08:15:46 AM »
so you hook up all 5 of them to source so the elektrons can pick and choose their way? :D
 

Offline Benta

  • Frequent Contributor
  • **
  • Posts: 397
  • Country: de
Re: Single transistor with 7 pins!?
« Reply #3 on: February 21, 2017, 08:28:30 AM »
so you hook up all 5 of them to source so the elektrons can pick and choose their way? :D

Yes. It's called "paralleling". A lot of us engineers use it in practice. If you grind off the top of the device, you'll also see 5 parallel bond wires.

« Last Edit: February 21, 2017, 08:31:00 AM by Benta »
 

Offline MrZwing

  • Regular Contributor
  • *
  • Posts: 91
  • Country: se
  • Ohh! what does this button do? *click*
Re: Single transistor with 7 pins!?
« Reply #4 on: February 21, 2017, 08:39:16 AM »
ahh nice good to know sounds like a good practice.
 

Offline Phoenix

  • Regular Contributor
  • *
  • Posts: 175
  • Country: au
Re: Single transistor with 7 pins!?
« Reply #5 on: February 21, 2017, 12:33:20 PM »
One of the source pins is also called driver source. It's purpose is to provide a dedicated gate driver return path. This helps stop the gate driver being effected by the power current.
 

Offline T3sl4co1l

  • Super Contributor
  • ***
  • Posts: 7691
  • Country: us
  • Expert, Analog Electronics, PCB Layout, EMC
    • Seven Transistor Labs
Re: Single transistor with 7 pins!?
« Reply #6 on: February 21, 2017, 12:48:36 PM »
Pins have equivalent inductance, and when you're switching, let's see, about 30A in 10 nanoseconds, every nanohenry counts.

Each pin on a D2PAK sized device has about 4nH inductance.  (For a regular D2PAK, that's all you need to know.  For this one, the pins are connected in parallel, so the inductances also act in parallel.  You can ignore coupling between them, for a wave-of-the-hands analysis.)

The Kelvin source connection, for gate drive, is very nice as well.

Homework 1: given the numbers I just wrote, how much voltage error, or overshoot, do you expect?  Where does that error appear in the circuit?  Why would it be important?  How much difference is there, using one pin versus all in parallel?

Homework 2: draw out the equivalent circuit of a transistor, including its pin/lead inductances, stray trace/wiring/PCB inductance, and so on for everything else in the power switching circuit.  Show us your schematic, and reflect on its meaning. :)

Tim
Seven Transistor Labs, LLC
Electronic Design, from Concept to Layout.
Need engineering assistance? Drop me a message!
 

Offline blueskull

  • Supporter
  • ****
  • Posts: 5581
  • Country: cn
  • Final year EE PhD
Re: Single transistor with 7 pins!?
« Reply #7 on: February 21, 2017, 01:30:09 PM »
Google term: common source inductance. The beast that screws up MHz converters.
These SiC devices are capable of running at extremely high dv/dt and di/dt, which can be potentially really good for reducing switching loss, but also poses serious trouble for gate driving and EMI solutions.
When frequency goes up, G-S loop inductance, D-S loop inductance and GD-S common inductance all become very critical.
SIGSEGV is inevitable if you try to talk more than you know.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf