LTC4440 LTSpice simulation problems?

[MattQ]

Am I trying to use the LTC4440 as a high side mosfet driver, but when I run the demo simulation in LTSPice, this is what I get from the output from TG. There seems to be no boost to the gate control, so how can this drive any MOSFET, much less a FET with a drain voltage of 70 as specified on the spec sheet?

Included the schematic

 

[gnurf]

[..] when I run the demo simulation in LTSPice, this is what I get from the output from TG.

Did you forget the attachment?

 

[berkeman]

Am I trying to use the LTC4440 as a high side mosfet driver, but when I run the demo simulation in LTSPice, this is what I get from the output from TG. There seems to be no boost to the gate control, so how can this drive any MOSFET, much less a FET with a drain voltage of 70 as specified on the spec sheet?

Included the schematic

Thanks for adding the attachment. You have not connected the Boost section correctly. You are missing at least a diode... Check the datasheet again for the 4440.

 

[gnurf]

I got your circuit working only after adding the diode (as advised by the datasheet) and changing the mosfet model from the default "NMOS" to an actual model from the library (I arbitrarily picked BSH114). I suspect this might have something to do with this quote from the datasheet:

The LTC4440 is capable of driving a 1nF load with 10ns rise and 7ns fall times using a bootstrapped supply voltage VBOOST–TS of 12V

You should probably also extend the simulation time as well and make sure it behaves as you want in the steady state region—for some combinations of load resistance and mosfet model I saw some weird things happen after a while. Good luck.