How to Use LS-BIDI-4: Examples, Pinouts, and Specs

The LS-BIDI-4 is a bidirectional level shifter designed to enable communication between devices operating at different voltage levels. It is commonly used to bridge the gap between 3.3V and 5V systems, ensuring seamless data transfer in both directions. This component is particularly useful for interfacing microcontrollers, sensors, and other peripherals with varying voltage requirements. Its compact design and reliable performance make it a popular choice in embedded systems and IoT applications.

• Interfacing 3.3V microcontrollers (e.g., ESP32, STM32) with 5V peripherals (e.g., Arduino, sensors).
• Bridging communication between 5V logic devices and 3.3V logic devices.
• Level shifting for I2C, SPI, UART, and GPIO signals.
• Voltage translation in mixed-voltage systems.

• Operating Voltage (High Side, VCCB): 3.3V to 5.5V
• Operating Voltage (Low Side, VCCA): 1.8V to 3.6V
• Maximum Data Rate: 100 kHz (I2C) / 10 Mbps (SPI, UART)
• Number of Channels: 4 bidirectional channels
• Input/Output Logic Levels: Automatically adjusts based on VCCA and VCCB
• Operating Temperature Range: -40°C to +85°C
• Package Type: SOP-8 or similar

The LS-BIDI-4 has 8 pins, as described in the table below:

1. Power Connections:

   • Connect the lower voltage system's power supply to the VCCA pin.
   • Connect the higher voltage system's power supply to the VCCB pin.
   • Ensure both systems share a common ground by connecting their grounds to the GND pin.

2. Signal Connections:

   • Connect the low-voltage signals to the A1 to A4 pins.
   • Connect the corresponding high-voltage signals to the B1 to B4 pins.
   • The LS-BIDI-4 will automatically translate signals between the two voltage levels.

3. Enable the Level Shifter:

   • Pull the OE pin high to enable the level shifting functionality.
   • If the OE pin is left floating or pulled low, the level shifter will be disabled.

4. I2C Example:

   • For I2C communication, connect the SDA and SCL lines of the low-voltage device to A1 and A2, and the SDA and SCL lines of the high-voltage device to B1 and B2.

• Ensure that the voltage levels on VCCA and VCCB are within the specified operating range.
• Do not exceed the maximum data rate for the protocol being used.
• Use pull-up resistors on I2C lines if required, but ensure they are appropriate for the voltage levels on each side.
• Avoid leaving unused pins floating; tie them to ground or the appropriate voltage level.

Below is an example of using the LS-BIDI-4 to interface an Arduino UNO (5V logic) with a 3.3V I2C sensor:

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

void setup() {
  Wire.begin(); // Initialize I2C communication
  Serial.begin(9600); // Start serial communication for debugging

  // Example: Communicate with a 3.3V I2C sensor
  Wire.beginTransmission(0x40); // Start communication with sensor at address 0x40
  Wire.write(0x00); // Send a command to the sensor
  Wire.endTransmission(); // End the transmission
}

void loop() {
  Wire.requestFrom(0x40, 2); // Request 2 bytes of data from the sensor
  if (Wire.available() == 2) { // Check if 2 bytes are available
    int data = Wire.read() << 8 | Wire.read(); // Read and combine the two bytes
    Serial.println(data); // Print the sensor data to the serial monitor
  }
  delay(1000); // Wait for 1 second before the next read
}

1. No Signal Translation:

   • Cause: The OE pin is not enabled.
   • Solution: Ensure the OE pin is pulled high to enable the level shifter.

2. Data Corruption or Communication Errors:

   • Cause: Incorrect pull-up resistor values for I2C lines.
   • Solution: Use appropriate pull-up resistors for the voltage levels on each side (e.g., 4.7kΩ for 3.3V, 10kΩ for 5V).

3. Device Not Responding:

   • Cause: Incorrect voltage levels on VCCA or VCCB.
   • Solution: Verify that the voltage levels on VCCA and VCCB are within the specified range.

4. Overheating:

   • Cause: Excessive current draw or short circuit.
   • Solution: Check for wiring errors and ensure the connected devices are within the current limits of the LS-BIDI-4.

Q1: Can the LS-BIDI-4 be used for SPI communication?
A1: Yes, the LS-BIDI-4 supports SPI communication with data rates up to 10 Mbps. Ensure proper connections for MOSI, MISO, and SCK lines.

Q2: Is the LS-BIDI-4 compatible with 1.8V systems?
A2: Yes, the LS-BIDI-4 supports low-side voltages as low as 1.8V on the VCCA pin.

Q3: Do I need external pull-up resistors for GPIO signals?
A3: No, pull-up resistors are not required for GPIO signals unless specified by the connected devices.

Q4: Can I leave unused channels unconnected?
A4: It is recommended to tie unused channels to ground or the appropriate voltage level to avoid floating inputs.