Summary of Generating Analog Voltage with Digital Circuit
The article explains how to generate analog voltages using a digital R-2R resistor ladder connected to microcontroller pins, offering a low-cost alternative to dedicated DACs. An 8-bit implementation uses only two resistor values (e.g., 1 kΩ and 2 kΩ) to produce weighted binary voltages, with microcontroller pins acting as DAC bits (LSB on the left, MSB on the right). Using two 1 kΩ in series can replace each 2 kΩ to simplify parts.
Parts used in the R-2R DAC project:
- Microcontroller with at least 8 digital output pins
- 1 kΩ resistors (multiple)
- 2 kΩ resistors (multiple) or pairs of 1 kΩ in series as substitutes
- Wiring/connectors to interface resistors to microcontroller pins
- Ground and reference voltage connections (from microcontroller)
he purpose of this article is how to generate analog voltage with digital circuit. Although the market provides today a very broad range of dedicated digital-to-analogue converters, putting such a device in the schematic has a negative impact on the overall cost of the system. There are however, cheap methods of creating the required voltage levels, and even of generating pseudo-analogue signals, using purely digital means.
1. Introduction
The method of generating an analog voltage use a digital circuit named R/2R resistor network. This method requires having a number of microcontroller pins available to be used for this specific task only. It is a very cheap method, as it only requires a few resistors of two different values only. The circuit shown in Figure 1 depicts an 8-bit DAC built around the available pins of the microcontroller using 2 kΩ and 1 kΩ resistors. To simplify the Bill of Materials, you could also use only 1 kΩ resistors, by using two of them in series instead of each 2 kΩ resistor.
2. Features
The advantage of this circuit, besides its very low cost, is the simple logic needed to operate it. The 8 pins of the microcontroller used have the exact functions of the 8 bits of a DAC, with the leftmost pin being the LSB and the rightmost pin being the MSB. The digital code applied by the microcontroller at its pins represents the exact value needed by a legitimate DAC to generate the required voltage:
For more detail: Generating Analog Voltage with Digital Circuit
- How does the R-2R resistor network generate analog voltage?
It uses a ladder of resistors with two values to weight microcontroller digital output bits so their combined voltage produces an analog level. - Can I use only one resistor value instead of 1 kΩ and 2 kΩ?
Yes; you can use only 1 kΩ resistors by placing two 1 kΩ resistors in series to replace each 2 kΩ resistor. - What microcontroller resources are required for the R-2R DAC?
An available set of 8 digital output pins dedicated to the DAC function is required. - Does this method act like a legitimate DAC?
Yes; the digital code applied to the pins represents the exact value a legitimate DAC would use to generate the required voltage. - What are the main advantages of this circuit?
Its main advantages are very low cost and simple logic to operate, using only a few resistors. - Which pin corresponds to the least significant bit?
The leftmost microcontroller pin in the described schematic corresponds to the LSB. - Which pin corresponds to the most significant bit?
The rightmost microcontroller pin in the described schematic corresponds to the MSB.
