Thanks Ian.
This is doing my head in.
Supertex data sheet is showing
Recommended Operating Conditions
VDD Logic voltage supply 10.8 12 13.2 V
HVOUT High voltage output -0.3 - 225 V
VIH High-level input voltage VDD -2.0 - VDD V
VIL Low-level input voltage 0 - 2.0 V
f
CLK Clock frequency - - 8.0 MHz
TA Operating free-air temperature
Plastic -40 - +85 OC
Ceramic -55 - +125
But the Microchip one is showing this.
ABSOLUTE MAXIMUM RATINGS†
Supply voltage, VDD ...-0.5V to +15V
Supply voltage, VPP ...-0.5V to +250V
Logic input levels ... -0.5V to VDD+0.5V
Ground current1 ... 1.5A
Continuous total power dissipation2... 1200mW
Operating temperature range... -40°C to +85°C
Storage temperature range ... -65°C to +150°C
Not at all sure which one to believe here.
I have seen other designs that use +5VDD so.... erm ?
Edit: looking at the wrong section. Datasheet agree.
But how can these guys be using 5V.... can't be right. Right ?
https://doayee.co.uk/files/NixieSchematic.pdf