[sdiy] Alfa AS3350 power supply question

[Mike Beauchamp]

On 2025-01-20 22:25, David G Dixon via Synth-diy wrote:
> Hey SDIY Team,
> I just bought 100 AS3350 dual SVFs for a massive project.  The datasheet 
> is a bit strange.  In one place, it says that the supply can be from 
> +/-3V to +/-16V.  In another it says that the total supply voltage 
> should not exceed 26V.  On the diagram, it says that the supplies can be 
> +3 to +12V and -3 to -12V.
> So, obviously, they are intended for +/-12V supplies.
> My question is this:  What do you think would happen if I used my +/-15V 
> supply?  Would it a) work just fine, b) get too hot, or c) exploderate?
> Of course, I'll try it out, but if it works fine and doesn't get hot, is 
> there some hidden catastrophe that will take me by surprise later?  The 
> chip basically contains four exponential sources and six OTAs.  I don't 
> really understand why it should be that sensitive to supply voltage.
> In a related question, if I want to provide a +/-12V supply for the 
> chip, then what do you think about just dropping 15V to 12V and -12V 
> through a couple of opamps and using that as the supply for the chip?  
> Everything else on the board is perfectly happy with the +/-15V supply.  
> Alternatively, I could use 78L12 and 79L12, but I'd rather avoid that if 
> I could.
> Cheers,
> Dave Dixon

Hey DGD,

Too bad you didn't order 101 of them, so you could feed a sacrificial 
one +/-15V and monitor the output and IC temperature over 24h. Some 
real-world data is always better when a datasheet is murky.

If I was testing it, I'd also drop each rail to 0V then crank the 
voltage up to 16, 18V just to see what actually kills the chip before I 
deployed 100 of them.

I don't understand the preference for using opamps to lower the supply 
though.. are you saying you have 2 op-amps free for every AC3350? So.. 
200 unused op-amp cells in this single project? Maybe I'm not 
understanding it, but seems like removing the equivalent of 50 quad 
opamps and adding two regulators to create +/-12V rails to power all of 
the AC3350's seems like the easier way to go (if the chip even requires 
+/-12V).

Mike