How to Use PCA9515A: Examples, Pinouts, and Specs

The PCA9515A is a dual bidirectional I2C bus buffer designed to extend I2C bus signals over longer distances while maintaining signal integrity. It supports both standard-mode (up to 100 kHz) and fast-mode (up to 400 kHz) I2C communication. The device is particularly useful in applications where multiple I2C masters and slaves are connected, as it isolates capacitance and ensures reliable communication.

• Extending I2C bus signals in large systems
• Multi-master and multi-slave I2C configurations
• Industrial control systems
• Consumer electronics with long I2C wiring
• Signal integrity improvement in high-capacitance environments

• Supply Voltage (Vcc): 2.3 V to 3.6 V
• I2C Bus Speed: Standard-mode (100 kHz) and Fast-mode (400 kHz)
• Operating Temperature Range: -40°C to +85°C
• Low Standby Current: 1 µA (typical)
• Propagation Delay: 0.5 ns (typical)
• Capacitance Isolation: Supports up to 400 pF on each side of the buffer
• ESD Protection: ±4 kV (HBM)

The PCA9515A is available in an 8-pin SOIC package. Below is the pinout and description:

1. Power Supply:

   • Connect the VCC pin to a 2.3 V to 3.6 V power source.
   • Connect the GND pin to the ground of the circuit.

2. I2C Bus Connections:

   • Connect the SDA and SCL lines of the first I2C bus to pins A0 and A1, respectively.
   • Connect the SDA and SCL lines of the second I2C bus to pins B0 and B1, respectively.

3. Enable Pin:

   • Drive the EN pin high to enable the buffer. If the EN pin is low, the buffer is disabled, and the A and B sides are isolated.

4. Pull-Up Resistors:

   • Ensure that each side of the I2C bus (A and B) has appropriate pull-up resistors. The PCA9515A does not provide internal pull-ups.

5. Capacitance Considerations:

   • The PCA9515A isolates the capacitance of the A and B sides, allowing up to 400 pF on each side. Ensure that the total capacitance on each bus does not exceed this limit.

• Avoid connecting multiple PCA9515A devices in series, as this may cause signal integrity issues.
• Ensure that the EN pin is properly controlled to avoid unintentional isolation of the I2C buses.
• Use proper decoupling capacitors (e.g., 0.1 µF) near the VCC pin to stabilize the power supply.
• Verify that the I2C devices connected to the A and B sides operate within the same voltage range as the PCA9515A.

Below is an example of how to use the PCA9515A to extend an I2C bus with an Arduino UNO:

• Connect the Arduino's SDA (A4) and SCL (A5) pins to the A0 and A1 pins of the PCA9515A.
• Connect the B0 and B1 pins to the extended I2C bus.
• Use pull-up resistors (e.g., 4.7 kΩ) on both sides of the buffer.

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

void setup() {
  Wire.begin(); // Initialize the I2C bus
  Serial.begin(9600); // Start serial communication for debugging
  Serial.println("PCA9515A I2C Bus Buffer Example");
}

void loop() {
  Wire.beginTransmission(0x50); // Start communication with a slave device
  Wire.write(0x00); // Send a command or data
  if (Wire.endTransmission() == 0) {
    Serial.println("Data sent successfully!");
  } else {
    Serial.println("Error: Failed to communicate with the device.");
  }
  delay(1000); // Wait for 1 second before repeating
}

1. No Communication on the I2C Bus:

   • Cause: The EN pin is not driven high.
   • Solution: Ensure the EN pin is connected to a high logic level (e.g., VCC).

2. Signal Distortion or Noise:

   • Cause: Missing or incorrect pull-up resistors.
   • Solution: Verify that appropriate pull-up resistors (e.g., 4.7 kΩ) are present on both sides of the buffer.

3. I2C Bus Not Extending Properly:

   • Cause: Excessive capacitance on one or both sides of the buffer.
   • Solution: Measure the capacitance and ensure it does not exceed 400 pF on either side.

4. Device Overheating:

   • Cause: Incorrect power supply voltage.
   • Solution: Verify that the VCC pin is supplied with a voltage between 2.3 V and 3.6 V.

Q1: Can I use the PCA9515A with 5V I2C devices?
A1: No, the PCA9515A operates at a maximum voltage of 3.6 V. Use level shifters if interfacing with 5V devices.

Q2: How many PCA9515A devices can I use in a single system?
A2: You can use multiple PCA9515A devices, but avoid connecting them in series to prevent signal integrity issues.

Q3: Do I need pull-up resistors on both sides of the buffer?
A3: Yes, each side of the I2C bus requires its own pull-up resistors, as the PCA9515A does not provide internal pull-ups.