mosfet driver for 13.56 MHz class E amplifier

[scarzacosta]

Hi,

I'm looking for an appropriate mosfet driver for my setup.
I'm working on a class E driver, switching at 13.56MHz. The power mosfet that I'm using is STB13NM60N from STMicroelectronics.
I'm currently driving the mosfet with the EL7104 mosfet driver from Intersil, output straight connected to the gate, Vdd of driver decoupled with 10microFarad tantalum cap. Results are poor at this moment. At 1MHz it works fine, but at higher frequencies, it becomes inverted and more of a sinusoidal wave; also the mosfet isn't switching on and off properly (sometimes it doesn't switch off properly, and it just draws a lot of current from the power supply).

Should the EL7104 driver be able to work up to 13.56MHz?
Any suggestions, ideas to get it working?
Or anyone know of a driver that works well at high frequencies?
(I've found for example the DRF1200 from Microsemi, but unfortunately the local supplier where I need to order my components, doesn't offer it for sale).

thanks

 

[scarzacosta]

I'm currently looking at the MIC4452. Will that one do the job?
Datasheet says it can charge a 15nF cap in 20ns. Gate cap of my mosfet is about 3nF. But I'm worried about the long delay time of 15ns and 35ns?
Heating might be a problem too at 13.56MHz? Don't know if there exist some kind of heat sink for the plastic DIP package?

 

[dick_freebird]

Slapping a 10nF MOSFET gate around at 13MHz will want a
whole lot of gate driver peak current. That's thing one.

Pulsed current needs to come from somewhere. A simple
10uF bypass cap may not have the ESR / ESL to support
the current-throw you need. That's thing 2. I'd be looking
for a couple of high-Q ceramics totaling at least 100X
Qgg, with net ESR < (100mV/Ipeak) and net ESL <
100mV/dI/dt_peak across that FET driver supply.

I suggest you put some probes to the FET gate, FET
source, driver output, driver VIN, driver GND and see
which of them are flaking out.

Personally I think you may be looking to step away
from power MOSFETs; 600nS period means you need
your drain rise / fall times to be something like 50nS.
And you have to manage bridge shoot-through (non-
overlap) pretty tightly within that cycle as well. A
RF LDMOS or a GaN FET might make a lot more sense.

 

[FvM]

13.56 RFID is always small band, so state-of-the art LC impedance matching seems much more appropriate to drive the output stage with minimal driver power than any wideband or switching driver. I also won't expect a considerable efficiency improvement with square wave versus overdriven sine input.