Mosfet and its driver
Mosfet and its driver
(OP)
Hi everyone, I am new on here..
I am designing a pulsing circuit for one of my RF amps.
Pulsing/DC supplies is not really my background.
These are my specs:
- Vd = 33V
- Id = 6A (ie load = 5 ohms approx)
- Need the switch on the drain of the amplifier (the amplifier is connected to GND after that: the load is grounded)
- pulsing frequency = 600kHz
- duty cycle = 35%
- pulse timing signal: 0/5V
- tr/tf = 70ns
I established so far I need a P-channel MOSFET (eg Si4401BDY), source connected to the 32V supply, drain connected to my load.
Would anyone be able to give me advice on driving the P-channel mosfet gate?
- I cant connect directly from a CMOS buffer, as it's higher than the CMOS Vdd
- DO I need a kind of level shifter?
- But if so, how will this supply enough peak current into the P-channel gate?
- Or shall I use more like an integrated IRS2117 to drive an NMOS?
Thanks in advance!
Tom
I am designing a pulsing circuit for one of my RF amps.
Pulsing/DC supplies is not really my background.
These are my specs:
- Vd = 33V
- Id = 6A (ie load = 5 ohms approx)
- Need the switch on the drain of the amplifier (the amplifier is connected to GND after that: the load is grounded)
- pulsing frequency = 600kHz
- duty cycle = 35%
- pulse timing signal: 0/5V
- tr/tf = 70ns
I established so far I need a P-channel MOSFET (eg Si4401BDY), source connected to the 32V supply, drain connected to my load.
Would anyone be able to give me advice on driving the P-channel mosfet gate?
- I cant connect directly from a CMOS buffer, as it's higher than the CMOS Vdd
- DO I need a kind of level shifter?
- But if so, how will this supply enough peak current into the P-channel gate?
- Or shall I use more like an integrated IRS2117 to drive an NMOS?
Thanks in advance!
Tom





RE: Mosfet and its driver
Dan - Owner

http://www.Hi-TecDesigns.com
RE: Mosfet and its driver
RE: Mosfet and its driver
Go to Infineon's website, click on "Automotive ICs", select "Smart High- and Low-Side Switches", choose "PROFET" and find your device.
Benta.
RE: Mosfet and its driver
1 generic Pfet at rated load (STMicro STD10PF06T4) is priced at $0.29 @ quantities of 2500 (Digikey).
1 generic Nfet at rated load (Vishay SI2318DS-T1-E3) is priced at $0.17 @ quantities of 3000 (Digikey).
2 0603 resistors (Panasonic ERJ-3GEYJ243V) are priced at $0.003 @ quantities of 5000 (Digikey).
Even with adding $0.02 per component for assembly my circuit costs 40% of what your circuit costs. I think that is why my boss pays me to "muck around" with this stuff.
RE: Mosfet and its driver
Benta.
RE: Mosfet and its driver
I am with Benta. Go with a driver. The IRS2117 you mentioned would work with IRZ44 N channel MOSFET. You will need an VCC less that 25V though.
Dean Cooper
dclabseng.com
RE: Mosfet and its driver
RE: Mosfet and its driver
Thanks for all the comments.
Yes I have seen the NMOS/PMOS option around, just didnt manage to make it work on a breadboard, but I am thinking I had some grounding issues (high current in the load).
Benta, that's a great pointer, the Infineon circuits are very interesting; although I have seen the Tr/Tf on the datasheet is in the order of 100-500us. I need more 100ns, I'll have a look if there's a similar type of IC around.
Cheers
Thomas
RE: Mosfet and its driver
Most drivers switch in the nS range.
IRS2117 Tr/Tf 75-135 ns
HIP2101 Tr/Tf 10nS w/ Cl = 1000pf
Dean Cooper
dclabseng.com
RE: Mosfet and its driver
thomasIt, if the driver recommended by DCLabs doesn't work for some reason, and you have not found another option then you may want to try a PNP BJT instead of a PFET. They are a current mode device, so you need to drive them a bit differently, but with a BJT you do not have gate capacitance so they are inherently faster.
RE: Mosfet and its driver
Note, also, that the base current for the PNP would be a constant current drain, so long as the transistor is on, so if the duty cycle is high, the power dissipation adds up. If you assume a Beta.sat=10, then you're looking at 0.6A base current, which, with the 33V supply, results in nearly 20W of dissipation.
TTFN
FAQ731-376: Eng-Tips.com Forum Policies
RE: Mosfet and its driver
You can not expect a device with switching times in the 100 µs range to switch at 600 kHz.
But I'd also like to see how Henneshoe can drive a Mosfet at 600 kHz with two resistors, even if the rating is increased.
In this application you can expect the driver to cost at least the same as Mosfet.
RE: Mosfet and its driver
http://w
will let you drive an N channel MOSFET (amp for amp cheaper than the equivalent P channel device) on the high side at high frequency.