[time-nuts] HP 1820-0313 4.2V Logic (Flip-flop)

Hal Murray hmurray at megapathdsl.net
Wed May 17 02:18:05 EDT 2017

dgminala at mediacombb.net said:
> The 1820-0313 is a Fairchild 931HC or Motorola MC931G DTL clocked flipflop.
> I think if you toy with a TTL or CMOS JK-flipflop; it should work with no
> issues.  The only caveat would be the 4.2V Vcc.  The DTL logic was spec'ed
> to run at 5V, same as TTL, but don't know how TTL logic would work at 4.2V. 

CMOS runs fine at lower voltages - just slower.  Many data sheets for 5V 
parts include timings for 3.3V and 1.65V.  I'd try HC.

As a rule of thumb, speed (MHz) is roughly linear going through 0 at 0V and 
prop time is roughly linear going through 0 at absolute zero.

These are my opinions.  I hate spam.

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