How to Use Adafruit TXB0104 4-channel Bi-Directional Level Shifter: Examples, Pinouts, and Specs

The Adafruit TXB0104 is a versatile 4-channel bi-directional level shifter designed to interface between devices operating at different voltage levels. This component is essential for mixed-voltage level circuits, allowing for safe and reliable communication between devices such as microcontrollers, sensors, and other integrated circuits that operate at varying logic levels.

• Interfacing 3.3V sensors with 5V microcontrollers
• Connecting 1.8V or 2.5V devices to a 3.3V system
• Bridging communication between an Arduino UNO (operating at 5V) and newer devices that require 3.3V logic levels
• Prototyping with mixed-voltage level components on a breadboard

• Voltage Levels: Bidirectional translation between 1.2V to 3.6V on the low side and 1.65V to 5.5V on the high side
• Channels: 4 bidirectional channels
• Current Rating: 4 mA per channel
• Switching Speed: Up to 100 Mbps (for 3.3V to 5V translation)
• ESD Protection: 15 kV Human Body Model (HBM)

1. Power Supply: Connect VCCA to the lower voltage supply and VCCB to the higher voltage supply. Ensure that both grounds (pin 6 and 11) are connected to the common ground of your system.
2. Signal Connections: Connect the low-voltage signals to A1-A4 and the corresponding high-voltage signals to B1-B4.
3. Output Enable: Connect the OE pin to a high logic level (usually to VCCB) to enable the device. If you need to disable the level shifter temporarily, you can pull this pin low.

• Power Sequencing: VCCA must be supplied before (or at the same time as) VCCB to ensure proper operation.
• Signal Integrity: Keep the traces as short as possible to minimize signal degradation, especially at high speeds.
• Decoupling Capacitors: Place a 0.1 µF capacitor close to the VCCA and VCCB pins to filter out noise.
• Avoid Floating Inputs: Ensure that all input pins are driven to a valid logic level; do not leave them floating.

// Example code for interfacing a 3.3V sensor with a 5V Arduino UNO using the TXB0104 level shifter

// Define the sensor's data pin connected to the level shifter's low-voltage side (A1)
const int sensorPin = 2; // Arduino pin connected to TXB0104 A1

void setup() {
  // Initialize the sensor's data pin as an input
  pinMode(sensorPin, INPUT);
}

void loop() {
  // Read the sensor's data
  int sensorValue = digitalRead(sensorPin);
  
  // Process the sensor data (for demonstration purposes, we'll just print it)
  Serial.begin(9600);
  Serial.println(sensorValue);
  
  // Add a delay between reads for stability
  delay(500);
}

• No Signal Conversion: Ensure that the OE pin is set high and that the power supply voltages are correct and stable.
• Intermittent Functionality: Check for loose connections and verify that the decoupling capacitors are in place.
• Signal Distortion: Reduce the length of the connections and ensure that the data rate does not exceed the component's specifications.

• Power Supply Issues: Use a multimeter to verify that VCCA and VCCB are at the correct levels.
• OE Pin State: Confirm that the OE pin is connected properly and is receiving a high logic level.
• Input Levels: Make sure that the input signals are within the specified range for the respective voltage side.

Q: Can the TXB0104 be used for I2C or SPI communication? A: The TXB0104 is not recommended for I2C due to the lack of open-drain structure. For SPI, it can be used if the clock speeds are within the component's operating range.

Q: What happens if VCCA is higher than VCCB? A: The TXB0104 is designed to have VCCA at a lower voltage than VCCB. Applying a higher voltage to VCCA can damage the device.

Q: Is it necessary to connect all channels even if they are not in use? A: No, it is not necessary to connect all channels. Unused channels can be left unconnected. However, ensure that unused input pins are not left floating.

Q: Can the TXB0104 be used in a permanent installation? A: Yes, the TXB0104 can be used in permanent installations, provided that the design follows the recommended best practices for signal integrity and power supply stability.