Ripple versus binary counter ICs

[ADWSystems]

OK, silly question (don't worry the questions will get smarter). What is the difference between a ripple counter (like CD4020) versus binary counter (like 7493)? Besides the fact that one is 4 bit and the other 14 bit.

 

[ericgibbs]

OK, silly question (don't worry the questions will get smarter). What is the difference between a ripple counter (like CD4020) versus binary counter (like 7493)? Besides the fact that one is 4 bit and the other 14 bit.

hi,
Look at these two links for synchronous and asynchronous counter, all will be revealed.

**broken link removed**

**broken link removed**

 

[ADWSystems]

Apparently I'm having a mental block on this topic. I understand the timing and output sequence for the 7493 4 bit counter. Typical of what I would expect from a counter. What makes the ripple counter different? I can't figure out what the output/timing sequence will look like for the ripple counter. I'm currently picturing and output similar to a decade counter (4017), but I'm sure there's something different.

 

[ericgibbs]

Apparently I'm having a mental block on this topic. I understand the timing and output sequence for the 7493 4 bit counter. Typical of what I would expect from a counter. What makes the ripple counter different? I can't figure out what the output/timing sequence will look like for the ripple counter. I'm currently picturing and output similar to a decade counter (4017), but I'm sure there's something different.

hi,
The counter in a 4017 is a Johnson counter with is synchronous.

For a ripple [asynchronous] counter the clock input for a stage is the output state of the previous stage. This means for a 8 stage ripple counter the is a delay as each stage has to switch state in order to clock the next stage of the divider. While the stages are changing state in this way, any decoding logic connected to the outputs would see 'glitches' caused by the delays in the counter.

For synchronous counters every stage is clocked by the main clocking source at the same instant. So the out outputs are not subject to switching delays which any external logic could see as 'glitches'

Do you follow OK.?

 

[ADWSystems]

I'm following now. The datasheet I read for the 4020 gives the impression it works like a 4017 with only one output on at a time. I have found high bit ripple counters (12 and 14 bit) and low count (4 and 8 bit) sync counters. Are low count ripple counters available or high count sync counters as a single chip? I don't actually need either, only curious as I'm finding that I don't find a lot of stuff that is actually available.

 

[ericgibbs]

I'm following now. The datasheet I read for the 4020 gives the impression it works like a 4017 with only one output on at a time. I have found high bit ripple counters (12 and 14 bit) and low count (4 and 8 bit) sync counters. Are low count ripple counters available or high count sync counters as a single chip? I don't actually need either, only curious as I'm finding that I don't find a lot of stuff that is actually available.

hi,
A 4020 is a 14 stage binary ripple counter.

Look at the 4022, 4029 ,40160, 40161 for synchronous

For ripple[async] 4024,4510,4060

EDIT:

 

[RCinFLA]

Ripple counter are typically used just for a specific binary divider.

If you need several outputs along the line that need to show up at the same time without signifcant misalignment then you use a syncronous counter. A syncronous counter uses the master input clock to simultaneous change the state transitions on all the flip flops in the divider.

If you want to trap at a particular count you want a syncronous counter so you can latch multiple outputs to take a snap shot. A ripple counter may have too much delay slew between subsequent stages to do a parallel trap.

Ripple counter will have less current drain since each subsequent flip flop is clocked at half the frequency of prior flip flop. Syncronous counter will have a least some of each stage's gates driven at the high clock frequency.

 

[crutschow]

I believe it's clear, but to reiterate, whether it is a ripple counter or a synchronous counter has nothing to do with the logic output of the count, only the method that is used to generate the count. Thus you can have binary ripple and binary synchronous counters, and both will have the same output sequence.

 

[ADWSystems]

It was clear to me until this morning. A mental block I guess. When I was thinking 'ripple' I was thinking decade counter style with only one output/bit active at a time. When I should have been thinking of the internal mechanics instead of the external.