[Cryptech Tech] Alpha Avalanche Noise Block

[Павел Шатов]

On 10.04.2015 16:11, Fredrik Thulin wrote:
> On Friday, April 10, 2015 01:07:21 PM Павел Шатов wrote:
>> Hello!
>>
>> Fredrik, I've attached my variant of power supply regulator for an
>> updated version of avalanche noise block. It will output stable +12V
>> with input voltage starting from around +7V and up to +18V. If +12V is
>> not enough, you can increase value of R1 to trim output voltage. It
>> would be great if you could update schematics when you have time.
>
> Great, thank you. I'm planning on doing some Cryptech catch up this weekend.
>
> Would it be possible to lower the required input voltage to +5v? That way I
> could use this same circuit with my USB based test units.

Yes, it is possible. This regulator can operate from +2.8V, so +5V is 
fine. One feature of this regulator is programmable under-voltage 
lockout. It is controlled by resistor R4. In my circuit I've set 
under-voltage threshold at +6V using R4=33k. If you want nominal input 
voltage to be +5V, then you can set under-voltage threshold to say +4V 
with R4=18k. There's a formula in the datasheet, that you can use to 
calculate R4 value given desired under-voltage threshold. If you don't 
need this under-voltage lockout feature during your experiments, you can 
disable it altogether by shorting out R4.

--
With best regards,
Pavel Shatov

>
>> As far
>> as I remember, we also decided to replace hex Schmitt trigger with
>> smaller one-gate variant (74HC1G14). After your measurements, we also
>> found out, that protection bus transceiver is not necessary.
>
> Yes.
>
> /Fredrik
>
>