How to Use 2-Channel Logic Level Shifter: Examples, Pinouts, and Specs

The TXS0102 is a 2-channel bidirectional logic level shifter manufactured by Texas Instruments. It is designed to facilitate communication between devices operating at different voltage levels. This component is particularly useful in mixed-voltage systems, where one device operates at a lower voltage (e.g., 1.8V) and another at a higher voltage (e.g., 3.3V or 5V). The TXS0102 ensures seamless voltage translation without compromising signal integrity.

• Interfacing microcontrollers (e.g., Arduino, Raspberry Pi) with sensors or modules operating at different logic levels.
• Communication between 1.8V, 3.3V, and 5V devices in embedded systems.
• Voltage level translation in I²C, SPI, UART, and GPIO applications.
• Mixed-voltage environments in consumer electronics, industrial automation, and IoT devices.

The TXS0102 is a compact and efficient solution for voltage level shifting. Below are its key technical details:

• Voltage Range (VCCA): 1.2V to 3.6V
• Voltage Range (VCCB): 1.65V to 5.5V
• Data Rate: Up to 24 Mbps (push-pull) or 2 Mbps (open-drain)
• Channels: 2 bidirectional channels
• Operating Temperature Range: -40°C to +85°C
• Package Options: Available in small packages such as DCT (SOT-23-8) and DCU (VSSOP-8)

The TXS0102 comes in an 8-pin package. Below is the pinout and description:

The TXS0102 is straightforward to use in circuits. Below are the steps and considerations for proper usage:

1. Power Connections:

   • Connect the lower voltage supply (e.g., 1.8V or 3.3V) to the VCCA pin.
   • Connect the higher voltage supply (e.g., 3.3V or 5V) to the VCCB pin.
   • Ensure a common ground connection between the TXS0102 and all devices in the circuit.

2. Data Lines:

   • Connect the lower voltage logic signals to the A1 and A2 pins.
   • Connect the higher voltage logic signals to the B1 and B2 pins.
   • The TXS0102 automatically detects the direction of data flow, so no additional control is required.

3. Output Enable (OE):

   • Pull the OE pin HIGH to enable the device.
   • Pull the OE pin LOW to disable the device and place all I/O pins in a high-impedance state.

4. Pull-Up Resistors:

   • For open-drain communication protocols like I²C, use external pull-up resistors on both the A and B sides.
   • Choose resistor values based on the operating voltage and desired data rate.

Below is an example of using the TXS0102 to interface an Arduino UNO (5V logic) with a 3.3V sensor:

• VCCA: Connect to the 3.3V supply.
• VCCB: Connect to the 5V supply from the Arduino.
• GND: Connect to the common ground.
• A1/A2: Connect to the 3.3V sensor's data lines.
• B1/B2: Connect to the Arduino's data lines.
• OE: Connect to 5V (HIGH) to enable the device.

// Example: Reading data from a 3.3V sensor using TXS0102 with Arduino UNO

#include <Wire.h> // Include Wire library for I²C communication

void setup() {
  Wire.begin(); // Initialize I²C communication
  Serial.begin(9600); // Start serial communication for debugging
  Serial.println("TXS0102 Level Shifter Example");
}

void loop() {
  Wire.beginTransmission(0x40); // Address of the 3.3V sensor
  Wire.write(0x00); // Command to read data (example command)
  Wire.endTransmission();

  Wire.requestFrom(0x40, 2); // Request 2 bytes of data from the sensor
  if (Wire.available() == 2) {
    int data = Wire.read() << 8 | Wire.read(); // Combine two bytes into one value
    Serial.print("Sensor Data: ");
    Serial.println(data);
  }

  delay(1000); // Wait 1 second before the next read
}

• Ensure that the VCCA voltage is always less than or equal to the VCCB voltage.
• Avoid leaving the OE pin floating; always connect it to a defined logic level.
• For high-speed signals, minimize trace lengths to reduce signal degradation.
• Use decoupling capacitors (e.g., 0.1 µF) near the VCCA and VCCB pins to stabilize the power supply.

1. No Signal Translation:

   • Ensure the OE pin is pulled HIGH to enable the device.
   • Verify that the power supply voltages are within the specified ranges.

2. Signal Distortion or Noise:

   • Check for proper grounding and minimize trace lengths.
   • Add decoupling capacitors near the power supply pins.

3. I²C Communication Fails:

   • Ensure pull-up resistors are present on both the A and B sides.
   • Verify the I²C address and connections.

4. Device Overheating:

   • Confirm that the supply voltages do not exceed the maximum ratings.
   • Check for short circuits or excessive current draw.

Q1: Can the TXS0102 handle SPI communication?
A1: Yes, the TXS0102 supports SPI communication as long as the data rate does not exceed 24 Mbps.

Q2: Do I need external pull-up resistors for GPIO signals?
A2: No, pull-up resistors are not required for push-pull signals. However, they are necessary for open-drain protocols like I²C.

Q3: Can I use the TXS0102 for 5V to 1.8V level shifting?
A3: Yes, the TXS0102 supports level shifting between 5V and 1.8V as long as the supply voltages are correctly configured.

Q4: What happens if I leave the OE pin floating?
A4: Leaving the OE pin floating may cause unpredictable behavior. Always connect it to a defined logic level (HIGH or LOW).