The MAXIM device uses BiCMOS technology, so the I/O pins are probably NPN devices and should be more tolerant of voltages above 76 VDC.
It's best to follow the datasheet for all possible operating conditions, but I think you could use a bleeder resistor across the MAX6921 pins and GND. First, measure the leakage voltage on all of your nixie tubes with a DMM that has an input impedance of 10Megs. Basically, connect the anode of the nixie tube to the anode supply, and measure the voltage at all 10 cathodes to GND. If it's significantly lower than 76 volts and you get no noticeable glowing on the tube, you can use a 10Meg bleeder resistor. It's important that you take reading on several tubes. I've seen a lot of variation in leakage characteristics of b7971's. If you measure significant voltage, say 30 volts or more, you will need a smaller bleeder resistor to protect the MAX device. The problem is that when you reduce the bleeder resistor, the tube will glow more and it could be a problem with all 10 cathodes pulled-down. If you get intolerable glowing with a bleeder resistor that gets you a safe voltage for the MAX device, you should use a different driver. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/31d9ab7c-436f-40b7-a0f1-9278825b5797%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
