How to Use Logic Level Converter: Examples, Pinouts, and Specs

The SparkFun Logic Level Converter is a compact and versatile device designed to enable communication between circuits operating at different voltage levels. It is particularly useful when interfacing low-voltage microcontrollers (e.g., 3.3V) with higher-voltage peripherals (e.g., 5V). By safely shifting voltage levels, the Logic Level Converter ensures reliable and damage-free data transfer between devices.

• Interfacing 3.3V microcontrollers (e.g., Arduino, ESP32, Raspberry Pi) with 5V sensors, modules, or peripherals.
• Bridging communication between devices with mismatched voltage levels in I2C, SPI, UART, or GPIO applications.
• Protecting low-voltage devices from damage caused by higher voltage signals.

The SparkFun Logic Level Converter is based on a bi-directional design, allowing it to shift voltage levels in both directions. Below are the key technical details:

• Voltage Range (High Side): 3.3V to 5V
• Voltage Range (Low Side): 1.8V to 3.3V
• Maximum Data Rate: 100 kHz (I2C) or higher for other protocols
• Channels: 4 bi-directional channels
• Dimensions: 19.3mm x 15.2mm
• Operating Temperature: -40°C to 85°C

The Logic Level Converter has 8 pins, divided into two groups for the high-voltage (HV) and low-voltage (LV) sides. Below is the pinout:

1. Power Connections:

   • Connect the HV pin to the high-voltage source (e.g., 5V).
   • Connect the LV pin to the low-voltage source (e.g., 3.3V).
   • Connect the GND pin to the common ground of both voltage sources.

2. Signal Connections:

   • For each channel, connect the low-voltage signal to the corresponding TXI pin.
   • The shifted high-voltage signal will be available at the corresponding TXO pin.
   • Similarly, signals from the high-voltage side can be connected to TXO pins, and the shifted low-voltage signals will appear at the corresponding TXI pins.

3. Protocol-Specific Notes:

   • For I2C communication, connect the SDA and SCL lines to two of the available channels (e.g., TXI1/TXO1 and TXI2/TXO2).
   • Ensure pull-up resistors are present on both the high-voltage and low-voltage sides of the I2C bus.

• Always ensure the HV and LV power inputs are connected to the correct voltage levels. Reversing these connections may damage the Logic Level Converter.
• Use appropriate pull-up resistors for I2C communication to ensure proper signal integrity.
• Avoid exceeding the maximum voltage ratings for both the high and low sides.
• Keep the ground connection common between all devices in the circuit to prevent communication issues.

Below is an example of using the Logic Level Converter to interface a 3.3V sensor with a 5V Arduino UNO:

• Connect the Arduino's 5V pin to the HV pin of the Logic Level Converter.
• Connect the sensor's 3.3V power pin to the LV pin of the Logic Level Converter.
• Connect the Arduino's GND pin and the sensor's GND pin to the GND pin of the Logic Level Converter.
• Connect the sensor's data pin to TXI1, and connect TXO1 to the corresponding Arduino input pin.

// Example code for reading data from a 3.3V sensor using a Logic Level Converter
// connected to an Arduino UNO (5V logic).

const int sensorPin = 2; // Arduino pin connected to TXO1 of the Logic Level Converter

void setup() {
  Serial.begin(9600); // Initialize serial communication
  pinMode(sensorPin, INPUT); // Set the sensor pin as input
}

void loop() {
  int sensorValue = digitalRead(sensorPin); // Read the sensor value
  Serial.println(sensorValue); // Print the sensor value to the Serial Monitor
  delay(500); // Wait for 500ms before reading again
}

1. No Signal on the Output Pins:

   • Verify that the HV and LV pins are connected to the correct voltage sources.
   • Ensure the ground connection is common between all devices in the circuit.

2. Data Corruption in I2C Communication:

   • Check that pull-up resistors are present on both the high-voltage and low-voltage sides of the I2C bus.
   • Ensure the data rate does not exceed the maximum supported frequency (100 kHz for I2C).

3. Device Overheating:

   • Confirm that the voltage levels on the HV and LV pins do not exceed the specified ranges.
   • Check for short circuits in the wiring.

Q: Can the Logic Level Converter handle analog signals?
A: No, the Logic Level Converter is designed for digital signals only. For analog signals, consider using a dedicated voltage divider or level-shifting circuit.

Q: Can I use the Logic Level Converter for SPI communication?
A: Yes, the Logic Level Converter can be used for SPI communication. However, ensure that the SPI clock frequency is within the supported range for reliable operation.

Q: Do I need external pull-up resistors for GPIO signals?
A: Pull-up resistors are not required for general GPIO signals but are necessary for open-drain communication protocols like I2C.

By following this documentation, you can safely and effectively use the SparkFun Logic Level Converter in your projects.