ADC Resolution (LSB)

LSB = Vref / 2^N

Quick answer

This calculator solves LSB = Vref / 2^N for LSB Voltage. With Reference Voltage 12 V, Resolution (bits) 12 bits, the result is 2.93 mV. It solves in 3 directions, so you can enter the values you have and get the one you need.

Calculator

LSB Voltage (mV)
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Formula

LSB = Vref / 2^N

Description

The least significant bit (LSB) of an ADC represents the smallest voltage change it can detect, determined by dividing the full-scale reference voltage by the number of quantization levels (2^N). A 12-bit ADC with a 3.3V reference has an LSB of 3.3/4096 = 0.806 mV. This sets the theoretical resolution limit; actual performance is often limited by noise, which makes several LSBs of the reading uncertain. The effective number of bits (ENOB) is always less than the stated resolution due to noise, INL, DNL, and other error sources.

Variables

  • LSB — Least significant bit voltage (V)
  • Vref — ADC reference voltage (V)
  • N — ADC resolution in bits

Practical Notes

Common ADC resolutions: 8-bit (256 levels, ~20mV LSB at 5V), 10-bit (1024 levels, ~3.2mV at 3.3V), 12-bit (4096 levels, ~0.8mV at 3.3V), 16-bit (65536 levels, ~50µV at 3.3V), 24-bit (16M levels, used for precision measurement). Noise-free resolution is typically 2-4 bits less than the stated resolution. Oversampling by 4x gains 1 extra bit of effective resolution.

Symbols and units

Symbol Meaning Default unit Accepted units
LSB LSB Voltage mV pV, nV, µV, mV, V, kV
Vref Reference Voltage V pV, nV, µV, mV, V, kV
N Resolution (bits) bits bits

Step by step

  1. 1. What you know: Reference Voltage 12 V, Resolution (bits) 12 bits
  2. 2. The relation: LSB = Vref / 2^N
  3. 3. Substitute: Vref = 12 V, N = 12 bits
  4. 4. Result: LSB Voltage = 2.93 mV

Worked examples

Minimum range

Given: Reference Voltage 0.33 V, Resolution (bits) 0.8 bits

Result: LSB Voltage = 0.1895 V

Low range

Given: Reference Voltage 3.3 V, Resolution (bits) 8 bits

Result: LSB Voltage = 12.89 mV

Typical

Given: Reference Voltage 12 V, Resolution (bits) 12 bits

Result: LSB Voltage = 2.93 mV

High range

Given: Reference Voltage 0.23 kV, Resolution (bits) 16 bits

Result: LSB Voltage = 3.51 mV

Maximum range

Given: Reference Voltage 2.3 V, Resolution (bits) 0.16 bits

Result: LSB Voltage = 2.059 V

Solving for each variable

Solve for LSB Voltage

Reference Voltage 0.33 V, Resolution (bits) 0.8 bits → 0.1895 V

Solve for Reference Voltage

LSB Voltage 10 mV, Resolution (bits) 0.8 bits → 17.41 mV

Solve for Resolution (bits)

LSB Voltage 10 mV, Reference Voltage 0.33 V → 5.044 bits

How LSB Voltage changes with Reference Voltage

Reference Voltage (input) LSB Voltage (result)
1.2 V 0.293 mV
3 V 0.7324 mV
6 V 1.465 mV
9 V 2.197 mV
12 V 2.93 mV
18 V 4.395 mV
24 V 5.859 mV
48 V 11.72 mV
84 V 20.51 mV
120 V 29.3 mV

The same result in other units

Unit Value
nV 2930000
µV 2930
mV 2.93
V 0.00293

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Frequently asked questions

How do you calculate ADC Resolution (LSB)?

Use LSB = Vref / 2^N. With Reference Voltage 12 V, Resolution (bits) 12 bits, LSB Voltage works out to 2.93 mV.

What is the formula for ADC Resolution (LSB)?

The formula is LSB = Vref / 2^N. The least significant bit (LSB) of an ADC represents the smallest voltage change it can detect, determined by dividing the full-scale reference voltage by the number of quantization levels (2^N).

How do you find Reference Voltage when you know the other values?

Rearrange for Reference Voltage: with LSB Voltage 10 mV, Resolution (bits) 0.8 bits, Reference Voltage is 17.41 mV.

How do you find Resolution (bits) when you know the other values?

Rearrange for Resolution (bits): with LSB Voltage 10 mV, Reference Voltage 0.33 V, Resolution (bits) is 5.044 bits.

What units does ADC Resolution (LSB) use?

LSB Voltage is shown in nV, µV, mV, V. Values are held in SI base units internally, so you can mix prefixes without converting by hand.

Related Concepts

All Sensors & ADC formulas →
ADC Resolution (LSB) ADC Theoretical SNR Steinhart-Hart Temperature Wheatstone Bridge Linear Sensor Transfer Function Oversampling SNR Improvement RTD Callendar-Van Dusen Strain Gauge Resistance Change

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