How to Use Adafruit TXB0108 8-channel Bi-directional Logic Level Converter: Examples, Pinouts, and Specs

The Adafruit TXB0108 8-channel Bi-directional Logic Level Converter is a versatile breakout board designed for interfacing between circuits operating at different voltage levels. It is capable of bidirectional level shifting, making it suitable for use in applications where communication between low-voltage and high-voltage devices is necessary. This component is particularly useful in scenarios where microcontrollers like the Arduino UNO (operating at 5V) need to communicate with modern sensors or other ICs that operate at lower voltages (e.g., 3.3V).

• Interfacing 5V microcontrollers with 3.3V sensors
• Connecting 3.3V peripherals to a 5V system
• Data transfer between devices with different voltage domains
• Prototyping with mixed-voltage systems

• Voltage Levels: Bidirectional shifting between 1.2V to 3.6V on the low side and 1.65V to 5.5V on the high side
• Channels: 8 bidirectional data paths
• Current Transfer Rate: Up to 60 mA per channel
• Dimensions: 0.5" x 0.75" x 0.1" inches (LxWxH)

1. Power Connections:

   • Connect the LV pin to the lower voltage power supply (e.g., 3.3V).
   • Connect the HV pin to the higher voltage power supply (e.g., 5V).
   • Connect the GND pin to the common ground of both power supplies.

2. Signal Connections:

   • Connect the low-voltage device signals to A1-A8.
   • Connect the high-voltage device signals to B1-B8.

3. Enable the Converter:

   • Set the OE pin high to enable the level shifter.

• Ensure that the power supplies are stable and within the specified voltage ranges before connecting them to the LV and HV pins.
• Do not exceed the current transfer rate of 60 mA per channel to prevent damage to the device.
• Avoid applying signals to the I/O pins before the power supplies are stable and the OE pin is set high.
• Use bypass capacitors close to the LV and HV pins to filter out noise and provide a stable power supply.

• Signal Integrity Problems: Ensure that the connections are secure and that there is no excessive noise in the power supply lines.
• Device Not Working: Check that the OE pin is set high to enable the level shifter. Also, verify that the power supplies are within the specified voltage ranges.

• If the level shifter is not functioning, double-check the power supply voltages and connections.
• For signal integrity issues, consider using shorter connections and shielding to reduce noise.
• Ensure that the OE pin is connected and set to a high logic level to enable the level shifter.

Q: Can the TXB0108 be used with I2C or SPI communication? A: The TXB0108 is not recommended for use with I2C or SPI as it does not have the necessary pull-up resistors for these protocols.

Q: What happens if the OE pin is left floating? A: If the OE pin is left floating, the level shifter may not operate correctly. It should be tied to a high logic level to enable the device.

Q: Is it possible to use fewer than 8 channels? A: Yes, you can use as many channels as needed. Unused channels can be left unconnected.

// Example code to demonstrate the use of the Adafruit TXB0108 with an Arduino UNO
// This example assumes a 3.3V sensor is connected to channel A1 and the Arduino is on channel B1

void setup() {
  pinMode(2, OUTPUT); // Arduino pin connected to B1 on the TXB0108
  digitalWrite(2, LOW); // Initialize the pin to LOW
}

void loop() {
  // Send a HIGH signal to the 3.3V sensor through the level shifter
  digitalWrite(2, HIGH);
  delay(1000); // Wait for 1 second
  // Send a LOW signal to the 3.3V sensor through the level shifter
  digitalWrite(2, LOW);
  delay(1000); // Wait for 1 second
}

Remember to adjust the pin numbers and logic levels according to your specific application and circuit design.