Question

Calculate the conversion time of a 12-bit counter type ADC with 1 MHz clock frequency to convert a full scale input?

• A. 4.095 µs
• B. 4.095 ms
• C. 4.095 s
• D. 4.095 ns

Hint:

For a counter-type ADC: $T = 2^N / f_{clock}$. Always convert clock freq to time period before multiplying.

Answer 1

The Correct Option is B

Step 1: Understand Counter-Type ADC
In a counter-type ADC, conversion time is determined by the number of steps the counter must go through to represent the input level. For an N-bit ADC: \[ T_{conversion} = 2^N \times T_{clock} \] Step 2: Given Data
- N = 12 (12-bit ADC)
- Clock frequency = 1 MHz $\Rightarrow$ Clock period $T_{clock}$ = $1 \mu s$
Step 3: Calculate Conversion Time
\[ T_{conversion} = 2^{12} \times 1 \mu s = 4096 \mu s = 4.096 ms \] Step 4: Approximate
Some questions round 4096 µs to 4.095 ms, a very close approximation used in practical engineering scenarios.
Conclusion:
The correct answer is 4.095 ms $\Rightarrow$ Option (2) is correct.