# An 8-bit, unipolar successive approximation Register type ADC is used to convert 3.5 V to digital equivalent output. The reference voltage is +5V. The

148 views

closed
An 8-bit, unipolar successive approximation Register type ADC is used to convert 3.5 V to digital equivalent output. The reference voltage is +5V. The output of the ADC at the end of third clock pulse after start of conversion, is
1. 1010 0000
2. 1000 0000
3. 0000 0001
4. 0000 0011

by (37.3k points)
selected

Correct Answer - Option 1 : 1010 0000

Concept:

successive-approximation ADC is a type of analog-to-digital converter that converts a continuous analog waveform into a discrete digital representation using a binary search through all possible quantization levels before finally converging upon a digital output for each analog voltage conversion

If Vin  ≥ VDAC ⇒ maintain a loaded bit

Vin ≤  VDAC⇒ clear the loaded bit

Calculation:

Given,

Reference voltage VR = 5 V, number of bits n is 8

Resolution $= \frac{5}{{{2^8} - 1}} \approx 20\ mv$

Clock pulse 1:

1 st clock = 10000000

Output voltage V0 = 20 mV × 27 = 2.5 V

As 3.5 V > 2.5 V it maintains the loaded bit

Clock pulse 2:

2 nd clock pulse = 11000000

Output voltage V0 = 20 mV × (27 + 26) = 3.75 V

As 3.5V < 3.75 V it clears the loaded bit

Clock pulse 3:

So at the end of the 3rd clock pulse output is = (10100000)2