Embedded calculator
ADC resolution
An ADC is a staircase: N bits give 2^N steps across the reference.
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The example, worked out
Given
- Bits
- 12
- Reference (full scale)
- 3.3 V
- Sampling rate
- 1 MHz
Working
- the reference split into 2^N steps
- for a full-scale sine: each bit is 6 dB
Results
The formulas
- LSB = Vref / 2^Nthe reference split into steps
- SNR = 6.02 N + 1.76 dBeach bit is 6 dB
- ENOB = (SNR − 1.76) / 6.02the same line read backwards
The usual traps
- A noisy reference flickers the last bits whatever the resolution.
- Anything above half the sampling rate folds back as a ghost.
Questions
What is the resolution of my ADC?
LSB = Vref / 2^N: the reference split into steps. SNR = 6.02 N + 1.76 dB: each bit is 6 dB. ENOB = (SNR − 1.76) / 6.02: the same line read backwards.
What does it give for typical values?
12 bits on 3.3 V: 806 µV per step, 74 dB ideal. One step (LSB): 806 µV; Steps: 4,096 codes.
What are the usual mistakes?
A noisy reference flickers the last bits whatever the resolution. Anything above half the sampling rate folds back as a ghost.
In the app
Your circuit, drawn live
Change a value: the schematic redraws with your numbers on the parts.
The part you can buy
Results rounded to standard values (E12, E24, E96) and power ratings.
The working, shown
Every step written out. Try it first by hand, then check.
Into your notebook
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Open the calculatorOpens in the app on 1 December, with Circuit Notebook 1.0
Also in Embedded
- 555 timer Astable frequency and duty, or the pulse of a monostable.
- MCU timer & PWM Prescaler and reload value for a period; the PWM resolution it leaves.