HV-XXXX Driver IC's from Microchip

[SWISSNIXIE - Jonathan F.]

Hi

I noticed that the microchip HV-XXXX Series are often discussed in topics here.

Mostly the HV5530. I have used a few of the HV5122/HV5222 ones, and notices that some of them work with 5V, and some don't, in the Datasheet the recommended voltage supply (VDD) is from 10.8 to 13.2V, so they are meant to be driven with theses voltages.

I searched for a solution to use them properly with a standart 5V microcontroller and found a working solution that i like to share:


Case 1:
You have already a voltage between 10.8 and 13.2V on the circuit present, e.g. Circuit input is a 12V Wall-Wart.
In this Case the IC's can be supplied directly, and you only need a converter for the logic levels, herefor you can use a MC14504 Hex Level shifter. It allows shifting from TTL/CMOS to a Output up to 18V and has 6 Channels.


Case 2:
There is no voltage in the desired range available on the board, e.g 9-15V input.
For this case, we need to produce the supply voltage. This is done by a ST662 DC-DC Converter that works with only 4 external components. With an input of 4.5-5.5V, it can deliver an Output of 11-12V @ 30mA, which is optimal for around two of the HV IC's depending on type.
For logic signal translation, the MC14504 from Case 1 is needed.



I have attached a schematic and a part list with order numbers from different stores.
 

[Niek]

Alternatively, you can also use discrete BJT's or MOSFET's to drive your cathodes. If you have a multiplexed design (so you would e.g. only need them for driving 2 nixies at a time in a 6 digit clock) it's quite doable and probably cheaper/simpler/cleaner than using that HVXXXX chip + level shifters. You can also consider using the SN75468, with a zener on the common (pin 9), as shown here: http://lucsmall.com/2011/07/19/using-the-sn75468-as-a-nixie-tube-driver/

If you don't have enough pins on your MCU, you'd need a shift register (e.g. a 74595). Or just get an MCU with more pins, they're cheap anyway.

[gregebert]

I've used both methods with no problems, though in all cases it was direct-drive (non-multiplexed).

If you use a NPN cathode driver, it's easy to implement current-regulation with an emitter resistor. The nice thing about NPN's is that they can be driven by low-voltage I/O. Not just 3.3V, but even lower. The base-current is on the order of 200uA, so even wimpy I/Os can drive them.

If you use a NMOS cathode driver, you can still implement current-regulation, but you will want higher gate-drive-voltage to swamp-out uncertainty due to variations in Vgs(on). I use 10-12V. Drive-current is essentially zero.

If you use a HV5530 (or similar) and want to regulate the current, you will need to do that at the anode-side. My latest clock (fourteen IN-18 tubes) does this. Each tube requires it's own regulator; cheap insurance for expensive tubes.

Only my first clock design used a resistor to limit tube current. It's worked well over the years, but being paranoid about tube characteristics changing over time due to aging, I now use current-regulators. It's probably overkill, but I enjoy analog design work. My dying wish is to see my nixie clocks outlive me, and I hope to be around another 40-ish years.

[Tobias]

I find it easier to use a couple mosfets to do the level shifting for the HV-XXXX. They are inexpensive and take barely any space in the board. Although the solution presented by Phillips in the link below is bi-directional, it is my go-to solution for uni-directional level shifting as well.

https://cdn-shop.adafruit.com/datasheets/an97055.pdf

Tobias