Asynchronous (ripple) counters — What major limitation affects their use at high frequencies?

Introduction:
Ripple counters are simple and hardware-efficient, but their stage-to-stage triggering creates timing skew. Recognizing this limitation helps you decide when to choose synchronous counters instead.

Given Data / Assumptions:

• Asynchronous counter with cascaded flip-flops (output of one is clock for the next).
• Non-zero propagation delay for each flip-flop.
• Interest is in maximum reliable counting frequency.

Concept / Approach:

Because each stage toggles after the previous one, total response time accumulates roughly as the sum of propagation delays through multiple stages. At high input clock rates, the outputs may not settle before the next clock edge, causing miscounts or decoding errors.

Step-by-Step Solution:

Verification / Alternative check:

Timing diagrams show glitch windows during ripple transitions. Synchronous designs eliminate these by clocking all stages together, supporting much higher f_max.

Why Other Options Are Wrong:

• Low-frequency limitation: Delays are negligible at low frequency.
• No drawbacks / no delays: Physically inaccurate; every device has finite delay.
• Voltage-only limitation: Speed is fundamentally timing-limited, not just supply-limited.

Common Pitfalls:

• Decoding ripple outputs without registering them, which can capture transient states.
• Underestimating worst-case t_pd across PVT (process, voltage, temperature).

Final Answer:

high-frequency applications are limited because of internal propagation delays