I got some time to work on the divergence meter project more, now that the new board revision is in.  I assembled the boost converter portion of the circuit and plugged in a signal generator to see what sort of performance I can get out of it.  The bad news: I was rather dumb in choosing a FET, so the one I have is fast, but can’t be driven fully on with my 3.3V MSP430.  Good news is that with 5V PWM input to the FET, I was able to handily get 190V on the Nixie supply rail.

Looking at possible FET replacements, I discovered that my choice of part, the IRFD220, appears to be the only MOSFET that Mouser sell that’s available in a 4-pin DIP package.  Since it seems incredibly wasteful to create another board revision at this point, I went ahead with designing a daughterboard to plug in where the FET currently does.

I got some ICL7667 FET driver samples from Maxim and have assembled this unit onto some perfboard, but have not yet tested it.  Given I was driving the FET with a 9V square wave while testing, it’s possible that I blew out the timer output to the FET on my microcontroller while testing.  Next time I get to work on this, I’ll be exercising that output to see if I blew it with high voltages, and connecting up the perfboard driver to try the high voltage supply all driven on-board.