Modern drive methods for nixies

[Martin Černý]

I wrote a short blog post about nixie cathode drive methods, specifically for modern systems, so 3.3V / 5V compatible with some pros and cons. Hope you guys find it useful.

https://nicethingsguy.com/blog/modern-drive-methods-for-nixie-tubes

Oh and if anyone happens to be using one of the chips mentioned in their clock, share a picture, I'd be happy to add it to the post. Any critique / suggestions are also welcome :)

[SWISSNIXIE - Jonathan F.]

Very nice article. 

Actually, there appears to be a modern HV-Driver driver that can be run completely at 3.3V, with the limitation that it can only sink around 5 mA of current and only have 16 outputs.

It's the Microchip HV509



I have one in my shopping list for the next order at Digi-Key.

[Martin Černý]

I didn't include that one because it can source/sink only 1mA. That is too little even for the smallest nixies. It is rather unfortunate because otherwise it would be a very good modern option. The only 3.3V logic option with integrated shift register I know of is the MAXIM line of VFD drivers. Two are mentioned in the article, but there are more models with different numbers of outputs.

Dne úterý 11. srpna 2026 v 22:03:51 UTC+2 uživatel SWISSNIXIE - Jonathan F. napsal:

[David Pye]

I'm always surprised that discrete drive transistors aren't used more.  Most of my designs have ended up using them rather than driver ICs.

There are plenty of sot-23 transistors that cost pennies, can handle the full voltage range required and can be either driven from shift register outputs or directly from MCU outputs (depending on the multiplex IO matrix). 

Yes the component count is higher, but the price is much lower than integrated driver ICs and availability is never an issue (eg JLC).   

If you're assembling with reflow (or paying for it) then it doesn't matter and they are still fairly easy to do by hand if good eyesight etc.

David

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[Dekatron42]

On page 4 of the datasheet for the HV509 there is a diagram that plots current sink versus bias voltage that shows higher current sink than 1mA.

[Martin Černý]

Beware that this is peak current. The chip is still rated for 1mA continuous.

Dne středa 12. srpna 2026 v 9:34:22 UTC+2 uživatel Dekatron42 napsal:

[Dekatron42]

Would the HV509 still be usable in a multiplexed drive with its current limit?

[Martin Černý]

That would work but you still need to keep average current under 1mA so you would have to run it dim. Tiny tubes like IN-16 would work fine, dim but not half brightness as the current would suggest due to logarithmic eye perception of pwm. 

st 12. 8. 2026 v 10:06 odesílatel Dekatron42 <martin....@gmail.com> napsal:

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[Mitch]

I've used the HV5530/HV5522 for years. They are not easy to source at the moment, but factory lead time on Mouser is listed as four weeks. Curiously, the PLCC version is available, but the PQFP version is listed as restricted availability.

[Martin Černý]

Personally I wouldn't recommend buying those chips today, they have far better alternatives. I'd personally buy one only if every other option was exhausted. Microchip chips are often out of stock and quite expensive and this one requires 12V supply and logic translator. I have some at home but only as spares for a pinball plasma display :) Actually HV5522 in particular is one of the reasons why I wrote the article. There's no reason to use it even if we stay within Microchip catalog but people still do because they simply don't know alternatives exist. Like HV9308 for example.

Dne středa 12. srpna 2026 v 12:22:30 UTC+2 uživatel Mitch napsal:

[Mitch]

Interesting. I would like to see a circuit using the HV9308. I had not considered using that chip. My concern would be the 80v sustained max voltage, and max current sinking.

[Mitch]

Continued - of 5mA.

[Tom Katt]

Apologies if this was mentioned here before (I didn't see it), but recently I saw this post in the r/nixie group on Reddit from someone claiming to be designing a brand new hybrid driver chip for Nixie tubes...

Attached is an image of the proposed datasheet.  Here is the link to the post on Reddit: Finally! New Hybrid IC for Nixie tube cathodes and RGB LED control : r/nixie

I was working for a quite long on this project, and finally, everything is ok - first batch of ICs is into production. So shortly, what is this? This is a special IC, which has 1 wire input interface and can control up to 13 cathodes with independent brightness setting for each (like IN-14 with both of it's dots or ZIN-70 with it's C/F sign or separator colons) and 3 LEDs for backlight. ICs can be daisy chained, supported by any hardware platform, such as Arduino and others. First batch will be available by early September, and I will be giving away 20 pcs (limit 1 per customer, you pay shipping) for free. You can check preliminary datasheet here.

[Martin Černý]

5mA is more than enough for most nixies, for example ZM1040 recommended current is 4.5mA. 80V is actually pretty high, some drivers I recommend in the article are lower voltage. ULN2003 typically used in cheap chinese boards is 50V, SN74141 is about 60V ;)

Dne středa 12. srpna 2026 v 16:49:27 UTC+2 uživatel Mitch napsal:

[Mitch]

Interesting! The email address doesn't work and there is nothing on the website, but here's hoping for something new.

[gregebert]

I saw that too, but having 40 years of experience designing ICs, I'm skeptical about the HV capabilities because that requires special process/fabrication. SO many weird things happen with analog ICs when you run multiple lots. I'm sure anyone at Microchip who worked on the HV-series has plenty of stories to tell.

When I have traditional nixie-tube projects that use the same cathode current, I use the HV5530. Segmented tubes like the b7971 require different currents (based on segment length), so I use NPN transistors operating as current-limiters. Things get more interesting with other devices (NIMO, VFD, Numitron, electroluminescent, LED), and a custom driver is how I do it.

[Keith Moore]

Is there anything wrong with the Microchip Serial to Parallel Logic Converter 220V 32 Channel?   I am late to seeing this post. That is used in an old build I have used a lot. 

HV5622PG-G Microchip Technology | Mouser

[Martin Černý]

It's a 12V logic chip so it requires logic translator and 12V VCC. Nothing wrong with that (other than inconvenience), I was just focusing on chips that work with 3.3V and 5V logic in the article.

Dne středa 12. srpna 2026 v 21:05:47 UTC+2 uživatel Keith Moore napsal:

[Paul Andrews]

Personally I use the HV5523 and HV5623. Guess I’ll be moving to the newer versions, the HV5524 and HV5624. Yes they’re QFN and 5V but I crossed to the dark side a long time ago and a small level shifter is no problem - I need one for the LEDs anyway.

[Martin Černý]

I didn't know there was a updated version! Fixed that in the article, there's no reason to mention discontinued chips. Whenever you think QFN is bad, remember that BGA is a thing.

Dne čtvrtek 13. srpna 2026 v 1:24:56 UTC+2 uživatel Paul Andrews napsal:

[Jeremy Jones]

Why not use Microchip's HV507 it has 64 output lines and can handle 15mA, but it's 5v but TI's 74HCT245 can bump 3.3v to 5v easily, so attaching an ESP32 or any other MCU or MPU shouldn't be a problem.

[gregebert]

Using push-pull drivers for nixie tubes is an interesting idea, because inactive cathodes actually become anodes. My only concern would be higher electric field strength between adjacent cathodes where 1 is pulled low (ie, "ON") while the adjacent cathode(s) is(are) pulled high. Would it affect long term reliability ?

[Martin Černý]

HV507 can supply 1mA per channel. I don’t know where you read it can do 15mA :D that’s also the reason I was looking for HV3418 a while back that can supply 5mA (I think). Push pull drivers from microchip work fine and I suggest them in the article, just not this one. This specific driver is good for dot matrix displays like the Soviet gip-100000.

Dne sobota 15. srpna 2026 v 2:47:32 UTC+2 uživatel Jeremy Jones napsal:

[Jeremy Jones]

I read the datasheet, that's where I got the 15mA number from. Yes the product page does say 1mA per channel, the datasheet says something different. I trust datasheets more than product pages.

[Martin Černý]

I applaud you trusting the datasheets more than product pages, this is absolutely the correct attitude. But in this case, I'm sorry but either you've read the wrong datasheet or you've misinterpreted a value that has nothing to do with output current.

Dne neděle 16. srpna 2026 v 18:20:59 UTC+2 uživatel Jeremy Jones napsal:

[Jeremy Jones]

You are reading the datasheet and looking at the I_HVout = 1mA, at 300V and assuming that's acting like some kind of current limit. That is not how DMOS switching arrays work. The cathode current is determined by the anode resistor, not the driver chip.

[David Pye]

For my learning can you show me where the datasheet shows that?

The examples talk about sinking/sourcing 1mA per channel.  It does mention max input current of 500mA, but splitting that across all the channels would be limited by duty cycle in order to not exceed chip power dissipation.

David 

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[Martin Černý]

That's a really weird way of saying "yeah I was wrong, sorry". First you claim HV507 can push 15mA and that datasheet information is paramount to you. Turns out there's no such thing in there, so now you've decided to just ignore the datasheet and invoke infinite current limit? This overconfident misinformation is one of the reasons why I wrote the article btw.

Dne neděle 16. srpna 2026 v 18:49:06 UTC+2 uživatel Jeremy Jones napsal:

[gregebert]

Those datasheets are tricky to read, and Microchip doesn't do a very good job writing them. For the HV507, the 15mA max-current spec is for the +5V supply (IDD), not the high-voltage pins (IPP), which is 0.5mA.

This seems to contradict the  VOH and VOL specs further down, which specify a load-current of 1.0mA. However, that does not mean the pins can supply 1.0mA instead of the true spec 0f 0.5mA. What it means is that when the output is fully loaded (actually, overloaded), the output voltage is guaranteed to be between 35V and 265V when operating from a 300V supply. Though confusing and seemingly contradictory, it basically shows the part has margin at maximum load.

What irritates me the most about these devices is that Microchip does NOT provide a minimum prop-delay spec. Technically, you cant hook these in series and guarantee you satisfy the hold-timing for the serial data line. Because of this, I always put a retiming flip-flop between them.

[Dekatron42]

Has anyone built a working device with these chips that according to the datasheets have too low current capability (HV507/9)?

Has anyone asked Microchip if they have a suitable chip to work with Nixies above 1mA or thereabouts?

I've only seen IN-17 driven by these devices that says 1mA in the datasheet, nothing bigger - if anyone has seen anything with IN-12/B5991 or similar please let us know.

I asked (what seems to be an Ai-agent) at the Microchip webpage and was told that they didn't have any 300V 15mA 16 channel device (nor 8, 32 or 64) and I was told that they had one that could supply 10mA at 300V but those answers only showed single FET types. However another search resulted in the HV26XX/27XX devices which seems to be within specifications, although these are analogue Switches.

/Martin

[Martin Černý]

I think you misread it. Ipp is current consumption of the chip itself (idle current), irrespective of the outputs (you can see that in Conditions column). The only value given about output current is 1mA.

Dne neděle 16. srpna 2026 v 21:49:47 UTC+2 uživatel gregebert napsal:

[Martin Černý]

I did. As I mention above in this thread, I had decided to replace HV507 with HV3418. Those are pin-to-pin compatible chips, HV507 can do 1mA @ 300V per channel, HV3418 can do 5mA @ 180V per channel. Neither of these chips are particularly great for nixies, HV507 is just way too weak and HV3418 is literal unobtainium. I do mention several Microchip chips suitable for nixies in the article, so why don't you go ahead and give it a read? It's a short article if you can even call it that :P

Dne neděle 16. srpna 2026 v 22:07:03 UTC+2 uživatel Dekatron42 napsal:

[gregebert]

As much as I like the HV5530, I have this perpetual fear about the dreaded last-time-buy email from DigiKey or Mouser that these are ending production. I'm still puzzled how Microchip manages to sell enough of these to keep cranking them out.

[Martin Černý]

Microchip drivers are mostly used in massive industrial devices like printers, CNC etc. They are also used in EL displays and such. You don't hear about them much because these devices and parts for them are crazy expensive and today they are usually also supply locked so the parts don't appear on consumer market. For example NEC makes similar chips but they are vendor locked, average joe can't get their hands on them unless they would be intersted in thousands of units :D

Dne pondělí 17. srpna 2026 v 2:58:41 UTC+2 uživatel gregebert napsal:

[Tomasz Kowalczyk]

Seeing the amount of suggestions and debate about technical limitations of ICs, I suggest adding a list of drivers which might seem a good idea but actually aren't, with a short comment why. 

Also, I am curious how is HV5624 - QFN with 0,2 mm spacing between pads in suggested footprint - supposed to survive full advertised 220 VDC. I don't see a mention of this, but conformal coating might be necessary to use this part outside of bench testing. 

[Martin Černý]

I think you're right, conformal coating should be used and I think plasma TVs for example do coat the QFN chips used. Will note that in the article. But "survive" is a very strong wording there. Worst case scenario, two pins short and since it's a open-drain chip, you'll have two cathodes ON. Data pins are not placed directly next to a HV output so blowing up the chip for that reason is not likely.

I could add a section with less-than-desirable drivers, will think about it. Do you have any particular chips you'd like to see there?

Dne úterý 18. srpna 2026 v 8:52:27 UTC+2 uživatel Tomasz Kowalczyk napsal:

[Tomasz Kowalczyk]

Actually, pin 22 is HVOUT1 and 23 is data out. This might produce some whoopsies. Generally, a freshly soldered PCB shouldn't arc even at full 220 VDC, but as time passes, moisture and dust accumulates and increases the chance for current leaking into low voltage section. It's an oversight in my opinion, there are empty pins, so there could easily be an NC pin between all HV and LV pins.

For the less-than-desirable section - I am not super knowledgeable in the Microchip portfolio, but the 1 mA parts listed above are a good start.
I personally would put the classic 74141 in this section, but I guess that being a nixie specific part it does not deserve such harsh treatment. I'd add a note about up to 25 mA current draw of one in the paragraph about this part, as for a direct drive 6 digit clock this totals to a significant amount. 

[Martin Černý]

Actually pin 22 and pin 23 are not directly next to each other, they are separated by a corner ;) But then again, it should be coated.

As for 74141, I understand the issue of higher power consumption. But the aim was to list chips that natively work with 5V or 3.3V. 74141 is one of very few chips that can actually work with 3.3V logic so it by all means deserve to be there in my book. I'll add the note about it tho, it's good to point out.

Dne úterý 18. srpna 2026 v 18:31:59 UTC+2 uživatel Tomasz Kowalczyk napsal:

[Leroy Jones]

Let us not forget the 74142 counter/driver.   The 8T01 driver and the HLL series drivers.

[Tomasz Kowalczyk]

Oh, you're right! I did not check that little detail.