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slime , 01-14-2025, 12:30 AM

Hello, I wanted to try and complete my first hardware project that’s been shelved for a very long time. It’s for a Nixie Clock, and I need help finding out a way to go about creating a level translation from 3.3v from my ESP32-S3-WROOM-1 microcontroller to a high-voltage shift register 12v.

I’m not sure if Im reading into this datasheet correctly, but it looks like the chip im using has some strict requirements and needs a maximum of 1 μA for highs and -1 μA for lows. It also allows clock lines to run at 8MHz so I would need something that keeps up with that too.

I see a lot of people who decide to drive them with a BJT inverter circuit (as shown below) but I’m really confused because whenever I try to simulate it in LTspice it seems like the clock speed is way too fast and the low logic current is nowhere near a microamp.

Would anyone here have any recommendations on how to construct such a driving circuit that meets this criteria? I feel like I may be overcomplicating things or forgetting something and I wanted to ask around.

HV Shift Register Chip Datasheet:
https://www.microchip.com/en-us/product/hv5530

Reference Schematic from Another Project:
https://github.com/GadgetReboot/
HV5222_Breakout/blob/ymain/Sch_HV5222_Breakout.pdf

(This example breakout board uses an arduino hence the 5V vin in the spice simulation)

QDrives , 01-14-2025, 08:49 PM

That the shift register can handle 8MHz, does not mean you have to **do** 8MHz.
You can go a lot slower.

Robert Feranec , 01-15-2025, 06:15 AM

exactly as @QDrives says .... do you really need 8MHz? Is that what you are going to send out from ESP32? If this is used to control the clock segments, you should be able to run it at much lower speed

slime , 01-16-2025, 01:06 AM

Ah forgive me, you’re both right. I was originally using the HV5222 which is from the same family and they had 8MHz as a recommended condition so I may have gotten the two mixed up. I can definitely pull that down yo even the Hz level if its just to change the digits.

Do you also think that I should still be concerned about what I highlighted for the criteria for IH/IL? Specifically with the reversed current for IL.

I don’t believe the behavior of this switching circuit consistently holds a negative value for a low-logic level (There are only negative dips in the transition from high to low as shown above).

QDrives , 01-16-2025, 04:57 PM

That is in nA.
Simulations have these kind of 'problems'. Noting to worry about.