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A $4$ bit ripple counter and a $4$ bit synchronous counter are made using flip-flops having a propagation delay of $10$ ns each. If the worst case delay in the ripple counter and the synchronous counter be $R$ and $S$ respectively, then

  1. $R = 10$ ns, $S = 40$ ns
  2. $R = 40$ ns, $S = 10$ ns
  3. $R = 10$ ns, $S = 30$ ns
  4. $R = 30$ ns, $S = 10$ ns
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4 Answers

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option (b) is correct.

for rippel counter:- $T_{delay}$=nx$T_{ff}$+$T_{cc}$

for synchronous counter:- $T_{delay}$=$T_{ff}$+$T_{cc}$
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For Ripple Counter

for $2^n$  state no of Flipflop required is n. As this is async counter so Delay = $N*Propagation Delay$ so $4*10 ms = 40 ms$

For Sync Counter

Delay = $1*Propagation Delay$ as Sync counter has Clock  same clock

Hence $Delay = 10ms$

Correct Ans is: $B$
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B is the answer.
Time delay is constant since it’s synchronous. Ripple will be 10 + 10 + 10 + 10 = 40
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ANS : B

R=40R=40 ns, S=10S=10 ns
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