"Staircase counter" ? - UK Vintage Radio Repair and Restoration Discussion Forum

G6Tanuki · 2nd Jul 2020, 7:52 pm

Historically, divide-by-powers-of-two circuits have been easy - you just chained a series of flip-flops.

But for odd-powers-of-two things were harder.

I recall a circuit designed to do both odd-and-even division: basically it used a half-wave-diode-voltage-doubler fed by a really-narrow capacitor integrator - so it only 'saw' the leading-edge 0-to-1 transition - and then fed the integrated pulses into a capacitor, whose charge ramped-up with each pulse, in staircase-fashion.

Then there was a Unijunction-transistor that 'looked' at the charge on the capacitor and when it considered it was at the top of the staircase, triggered - so providing the required output-pulse and also dumping the charge on the 'staircase' back to the bottom.

These worked OK for divide-by-3 or 5, but component-drift made them unreliable for divide-by-7 or divide-by-9.

Thankfully, in the 1970s we got the TTL 7490/7493 chips which did it all digitally and much-more-reliably.

But I'm wondering - was there an official name for the "staircase" divider ??

Radio Wrangler · 2nd Jul 2020, 8:17 pm

Charge-pump divider, sometimes

David

2nd Jul 2020, 7:52 pm	#1
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,998	"Staircase counter" ? Historically, divide-by-powers-of-two circuits have been easy - you just chained a series of flip-flops. But for odd-powers-of-two things were harder. I recall a circuit designed to do both odd-and-even division: basically it used a half-wave-diode-voltage-doubler fed by a really-narrow capacitor integrator - so it only 'saw' the leading-edge 0-to-1 transition - and then fed the integrated pulses into a capacitor, whose charge ramped-up with each pulse, in staircase-fashion. Then there was a Unijunction-transistor that 'looked' at the charge on the capacitor and when it considered it was at the top of the staircase, triggered - so providing the required output-pulse and also dumping the charge on the 'staircase' back to the bottom. These worked OK for divide-by-3 or 5, but component-drift made them unreliable for divide-by-7 or divide-by-9. Thankfully, in the 1970s we got the TTL 7490/7493 chips which did it all digitally and much-more-reliably. But I'm wondering - was there an official name for the "staircase" divider ?? Last edited by G6Tanuki; 2nd Jul 2020 at 8:15 pm.

2nd Jul 2020, 8:17 pm	#2
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,877	Re: "Staircase counter" ? Charge-pump divider, sometimes David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done