I took a quick look at the HV5532 datasheet, and the 15V output-low voltage 
is at 100mA, which is far more current than you will need for a nixie. The 
outputs will tolerate an anode supply of +220V, so that gives plenty of 
margin.

So, if you have an anode supply of +200V, you can calculate a rough value 
for your anode resistor from R = (Vcc-Vnixie)/Inixie  . Assuming Vcc=200, 
Vnixie=145, Inixie=4ma you get about 13K for the anode resistor. These are 
approximate values to get stated; you definitely need to bench-test the 
design and pick the appropriate resistor to maximize tube life. Tweak the 
anode resistor until you get the recommended anode current.  Be sure to use 
a large-enough power-rating for the resistor. In this example, the power is 
220mW so I would use a 1/2W resistor, not a 1/4W.

Be careful driving in HV5532 from 3.3V logic levels. Per the datasheet, Vih 
(min) is 0.8*Vcc, or 4.0V. Technically, a logic signal from a 3.3V device *will 
not meet spec*. It might work in certain conditions, but I question it's 
reliability. I personally would not implement any design that violates 
spec, as it's an invitation for trouble even though it might 'work' under 
certain conditions.

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