MOSFET Qgs and Qgd parameters.

[cupoftea]

Hi,
Why does the DMP8102LPS FET datasheet give Qgs without saying if it was at Vgs=10V, or Vgs = 4.5V?
They give the VDS condition for their Qgd parameter, so why not state Vgs for the Qgs parameter?

DMP8012LPS

https://www.diodes.com/assets/Datasheets/DMT8012LPS.pdf

 

[FvM]

Figure 11 clarifies the meaning of Qgs and Qgd parameters. They are neither measured at 4.5 nor 10 V Vgs.

 

[cupoftea]

Thanks, i see what you mean, and this gives real meaning for Qgd and Qgs...

https://en-support.renesas.com/knowledgeBase/16981004

..And we need to know Qgd/Qgs value for selection of synch Buck mosfet....but datasheet only states Qgd for one value of Vin of the buck..(which isnt the one we have in our application) .so we will have trouble selecting properly.

 

[dick_freebird]

I suppose you could try and find the SPICE model and
hope it's accurate in this respect, and simulate it like
you mean to use it.

Datasheets will never give you more than a single data
point (condition and limit-pair) and if you're lucky, a
graph. But graphs require characterization effort.