Voltage Level Shifter: 3.3V to 5V Conversion

This article explores voltage level shifting, specifically focusing on converting 3.3V to 5V and vice versa. We’ll cover various methods, including resistor dividers, MOSFET circuits, and bi-directional logic level converters, along with their advantages and disadvantages.

Introduction

Converting voltage from one level to another is a common requirement in electronics. Here are a few popular techniques:

• Using a simple resistor divider.
• Employing a MOSFET-based circuit.
• Utilizing a bi-directional logic level converter module.

Voltage Divider Method (5V to 3.3V)

The figure above illustrates a straightforward method using resistors to step down voltage. In this example, we’ll convert 5V to 3.3V. The output voltage (Vout) is calculated using the following formula:

$V_{out} = V_{in} * \frac{R_2}{R_1 + R_2}$

This formula is used in the calculator below.

This type of voltage converter circuit can be used, for example, to interface an Arduino (operating at 5V) with an ESP8266 (operating at 3.3V).

However, it’s important to note that this circuit works best with relatively slow signals and isn’t always the most reliable option. This is why many designers prefer using dedicated bi-directional logic level converter modules, which are readily available at affordable prices.

Voltage Divider Calculator

You can use the following calculator to determine the appropriate resistor values for your desired voltage conversion:

Example:

• Voltage Input ($V_{in}$): 5V
• Resistor 1 ($R_1$): 1 kΩ
• Resistor 2 ($R_2$): 2 kΩ

Voltage Output ($V_{out}$): 3.3V

Using a Bi-directional Logic Level Converter

The image above shows a typical logic level converter. These modules are bi-directional, meaning they can convert voltage from 5V to 3.3V and the reverse.

These devices, often I2C-based, are commonly available in multi-channel configurations (e.g., 4-channel, 8-channel). As labeled, the “HV” pin typically connects to the High Voltage (5V), while the “LV” pin connects to the Low Voltage (3.3V).

The 8-channel version is also a popular choice for hobbyists and circuit designers. These circuits are suitable for common digital interfaces, supporting both unidirectional and bi-directional communication.

Here are some typical technical specifications:

• Bi-directional voltage translation between 5V TTL and 3.3V TTL.
• Supports voltage level conversion from as low as 1.8V to as high as 5V, and vice versa.
• Compatible with digital interfaces like SPI, I2C, and asynchronous TTL serial.
• Can be used with various microcontrollers, including Raspberry Pi and Arduino.

Voltage Level Shifter (3.3V to 5V) using MOSFET

This figure illustrates a simple MOSFET-based circuit for shifting voltage levels between 3.3V and 5V. This MOSFET-based circuit is generally referred to as a voltage level shifter.

This circuit can function as a bi-directional voltage level converter.

You can purchase bi-directional logic level converter components from retailers like Robu.in (in India) or Sparkfun.com (in the USA).