Anthony Fremont said:
Needs way more than 3.3V drive unless you want to cook it. Vgs(th) is 3V
max, they spec it at 10Vgs to really turn it on, 5V will turn it on some
but 3.3V and it's really gonna be a bar-b-q with any current.
I'm thinking maybe the OP should look into IGBTs. I don't know about the
3.3V drive, but it's way easy to find IGBTs that will withstand 600Vds and
switch large currents. The down side is that giant cap sitting on the
gate(base). As long as you can dump the juice in fast enough, they're
slick. Of course I only played with them once and I used 5V drive. Mr
Hill is the man to ask about them.
That vn2224 looks realy cool, maybe I can add an offset to the gate drive of
1volts,
that will give me 4.3 volts drive and still be sure its off,
maybe set the vdd to the max of 3.6 volts and/or go for 1.2 volts, gate
offset.
the open drain 5v pull up isnt so nice when programming the device and the
outputs go tri state.
the graph shows at 1 amp its saturated at vgs=3v., I hadnt intended to need
more than 1amp,
its an inverter so the current is ramped from 0-1amp, average 50% duty
cycle, so 0.25A avg
I only need about 1.5W real power output from the device im driving,
although it seems I need a fair bit more due to reactive currents in the
load,
at 4vgs its over 4amps wich should be ample for my needs, typical ofc.
Theres a quad package too, maybe 2 in parallell will easily do, or I can use
the other 2 to save a discrete elsewhere.
As for devices with large input capacitance such as igbt, the current from
my PIC is somewhat limited, so switching speed will become unaceptable so I
would need a driver anyway wich then makes the fet selection easy anyway.
the output from the inverter is 1/2 sine wich is why its PWM is driven from
the PIC. it should drive the 2nc gate charge of the vn2222 quick enough.
Id rather drive everything from the 5v but its a bit of a jump from 5v to
150pk and demands a bigger device but the 12v supply is via a linear
regulator, the 5v via a switcher.
Unfortunatly the VN2222 that is stocked by RS and farnell seem to be 60v
spec to92 devices.
seems to be some confusion with part numbers here >.<
neither stock the vn2224 quad.
is the 200v version an unobtanium part ?
Think I might just plop for a driver and be done with it. I just tried a
dual driver I had available but cldnt get it to work, then reading the data
sheet realised the shutdown input had a threshold of 11v lol.
thanks
Colin =^.^=