How to Use Pimoroni PGA2350: Examples, Pinouts, and Specs

The Pimoroni PGA2350 is a high-performance programmable gain amplifier (PGA) designed for precise control of signal amplification. It features a digital interface, enabling seamless integration with microcontrollers and other digital systems. The PGA2350 is particularly well-suited for audio applications, sensor signal conditioning, and other scenarios requiring fine-tuned signal amplification.

• Audio signal processing and volume control
• Sensor signal conditioning for precise measurements
• Laboratory instrumentation and test equipment
• High-fidelity audio systems
• Industrial automation and control systems

The following table outlines the key technical specifications of the Pimoroni PGA2350:

The Pimoroni PGA2350 is housed in a 16-pin SSOP package. The pinout and descriptions are as follows:

1. Power Supply: Connect the VDD pin to a stable 5V power supply and the GND pin to ground.
2. Input and Output: Connect the input signal to the IN1 and/or IN2 pins. The amplified output signal will be available at the OUT1 and/or OUT2 pins.
3. SPI Communication: Use the SCLK, SDI, and CS pins to interface with a microcontroller via SPI. Ensure the SPI clock frequency is within the supported range.
4. Gain Control: Configure the gain settings by sending appropriate commands over the SPI interface. The gain can be adjusted in 0.5 dB steps from -95.5 dB to +31.5 dB.
5. Mute Function: Use the MUTE pin to mute the output signal when necessary. Drive the pin high to activate mute.

• Decoupling Capacitors: Place decoupling capacitors (e.g., 0.1 µF and 10 µF) close to the VDD pin to ensure stable operation.
• Signal Integrity: Use short and shielded cables for input and output signals to minimize noise and interference.
• SPI Configuration: Ensure the microcontroller's SPI settings (clock polarity, phase, and speed) match the PGA2350's requirements.
• Thermal Management: Operate the device within the specified temperature range to avoid performance degradation.

Below is an example of how to control the PGA2350 using an Arduino UNO via SPI:

#include <SPI.h>

// Define SPI pins for the PGA2350
const int CS_PIN = 10; // Chip select pin

void setup() {
  // Initialize SPI communication
  SPI.begin();
  pinMode(CS_PIN, OUTPUT);
  digitalWrite(CS_PIN, HIGH); // Set CS pin high (inactive)

  // Configure SPI settings
  SPI.beginTransaction(SPISettings(1000000, MSBFIRST, SPI_MODE0));
}

void setGain(float gain) {
  // Convert gain to a 16-bit command
  // Gain range: -95.5 dB to +31.5 dB in 0.5 dB steps
  int gainSteps = (int)((gain + 95.5) * 2); // Convert gain to step value
  byte highByte = (gainSteps >> 8) & 0xFF; // Extract high byte
  byte lowByte = gainSteps & 0xFF;         // Extract low byte

  // Send the command to the PGA2350
  digitalWrite(CS_PIN, LOW); // Activate chip select
  SPI.transfer(highByte);    // Send high byte
  SPI.transfer(lowByte);     // Send low byte
  digitalWrite(CS_PIN, HIGH); // Deactivate chip select
}

void loop() {
  // Example: Set gain to 0 dB
  setGain(0.0);
  delay(1000);

  // Example: Set gain to -10 dB
  setGain(-10.0);
  delay(1000);
}

1. No Output Signal:

   • Ensure the input signal is properly connected to the IN1/IN2 pins.
   • Verify that the gain is set to an appropriate value via SPI.
   • Check if the MUTE pin is accidentally activated (high).

2. Distorted Output:

   • Ensure the input signal amplitude is within the acceptable range.
   • Verify that the power supply voltage is stable and within the specified range.

3. SPI Communication Failure:

   • Double-check the SPI wiring (SCLK, SDI, CS).
   • Ensure the SPI clock frequency and settings match the PGA2350's requirements.

4. Excessive Noise:

   • Use proper grounding and shielding techniques.
   • Add decoupling capacitors near the power supply pins.

Q: Can the PGA2350 be used with 3.3V microcontrollers?
A: Yes, but you will need level shifters for the SPI signals, as the PGA2350 operates at 5V logic levels.

Q: What is the maximum gain of the PGA2350?
A: The maximum gain is +31.5 dB, adjustable in 0.5 dB steps.

Q: How do I mute the output?
A: Drive the MUTE pin high to mute the output signal.