Driving Nixie tubes with a MAX6922 VFD driver

The MAX6922 is a driver for VFDs. It takes standard 3.3v or 5v logic inputs via something close to SPI, and controls 32 separate outputs. Each output can be pulled low, sinking 15mA, or pulled high to a separate high voltage supply (up to 76 VDC), sourcing 45mA.

You can also daisy chain the drivers to add as many outputs as you want.

It's alive! Pro Trinket on left, transistors "stored" on the breadboard, MAX6922 on SchmartBoard PLCC adapter.

It's alive! Pro Trinket on left, transistors "stored" on the breadboard, MAX6922 on SchmartBoard PLCC adapter.

It seems like a powerful enough chip to replace the standard 74141/K155ID1 chips, with a more convenient input as well. Here's a circuit I put together showing the MAX6922 driving three IN-12B tubes. I left out the decimal points, since they would require 33 outputs, not 32. Since the drivers can be daisy chained, this wouldn't be a limitation.

Is it worth it? You can get them at Digikey, quantity 1, for USD 7.45 each, with price breaks at 10, 25, and so on, with a bit of shipping. For the same circuitry, you'd need three K155ID1s (about USD 1.50 each, plus shipping from Ukraine, Russia, or some other former Soviet Bloc country). So that would ordinarily deal the K155ID1 a win, but then, do you want to drive that decimal point? You need more parts. Do you not want to use up pins on your microcontroller? Then you need a GPIO expander running on I2C or SPI. Do you want the driver within the next few days? Then you probably shouldn't get a K155ID1.

I'm not going to argue about availability. There are probably a bazillion K155ID1s still out there, and likely MAX6922s will never be produced in such quantities. Nevertheless, the MAX6922 is worth a hard look if you need to drive a few Nixies.