How to Use MAX9814: Examples, Pinouts, and Specs

The MAX9814 is a low-noise microphone preamplifier with an integrated automatic gain control (AGC) circuit, designed to deliver high-quality audio performance. Manufactured by Arduino, this component is ideal for applications requiring consistent audio levels and minimal distortion. The built-in AGC dynamically adjusts the gain based on the input signal level, ensuring clear and consistent audio output.

• Voice recognition systems
• Portable audio devices
• Conference systems
• Smart home devices (e.g., voice assistants)
• Audio recording equipment

• Supply Voltage (Vcc): 2.7V to 5.5V
• Quiescent Current: 3mA (typical)
• Input Signal Range: 20mV to 1V (RMS)
• Output Voltage Swing: 200mV to Vcc - 200mV
• Automatic Gain Control (AGC): Adjustable from 40dB to 60dB
• Noise Performance: Low-noise design for high-quality audio
• Operating Temperature Range: -40°C to +85°C
• Package Type: 8-pin SOIC or TDFN

The MAX9814 has 8 pins, each serving a specific function. The table below outlines the pin configuration:

1. Power Supply: Connect the Vcc pin to a stable power source (2.7V to 5.5V) and the GND pin to the system ground.
2. Microphone Connection: Connect the microphone's positive terminal to the IN+ pin and the negative terminal to the IN- pin.
3. Bypass Capacitor: Place a 0.1µF capacitor between the BYPASS pin and ground to filter noise.
4. Gain Adjustment: Connect a resistor to the GAIN pin to set the desired gain level. Refer to the datasheet for resistor values corresponding to specific gain levels.
5. AGC Threshold: Connect a resistor to the TH pin to set the AGC threshold. This determines the input signal level at which the AGC activates.
6. Output Connection: Connect the OUT pin to the next stage of the audio circuit, such as an amplifier or ADC.

• Use decoupling capacitors (e.g., 0.1µF) near the Vcc pin to stabilize the power supply and reduce noise.
• Ensure proper grounding to minimize interference and noise in the audio signal.
• Select appropriate resistor values for the GAIN and TH pins based on your application requirements.
• Avoid placing the MAX9814 near high-frequency components to prevent interference.

The MAX9814 can be easily interfaced with an Arduino UNO for audio signal processing. Below is an example circuit and code:

• Vcc: Connect to the Arduino's 5V pin.
• GND: Connect to the Arduino's GND pin.
• OUT: Connect to an analog input pin on the Arduino (e.g., A0).
• IN+ and IN-: Connect to the microphone terminals.
• GAIN and TH: Connect appropriate resistors to set gain and AGC threshold.

// MAX9814 Audio Signal Processing Example
// Reads audio signal from the MAX9814 and prints the analog value to the Serial Monitor

const int audioPin = A0; // Analog pin connected to MAX9814 OUT pin

void setup() {
  Serial.begin(9600); // Initialize serial communication at 9600 baud
}

void loop() {
  int audioValue = analogRead(audioPin); // Read the audio signal
  Serial.println(audioValue); // Print the audio signal value to the Serial Monitor
  delay(10); // Small delay to avoid overwhelming the Serial Monitor
}

1. No Output Signal:

   • Cause: Incorrect wiring or loose connections.
   • Solution: Double-check all connections, especially the microphone and power supply.

2. Distorted Audio Output:

   • Cause: Incorrect gain or AGC threshold settings.
   • Solution: Adjust the resistor values on the GAIN and TH pins to optimize performance.

3. High Noise Levels:

   • Cause: Poor grounding or insufficient bypass capacitor.
   • Solution: Ensure proper grounding and use a 0.1µF capacitor on the BYPASS pin.

4. Low Output Volume:

   • Cause: Low input signal or incorrect gain settings.
   • Solution: Increase the microphone input level or adjust the gain resistor.

Q1: Can the MAX9814 work with a 3.3V power supply?
Yes, the MAX9814 operates within a supply voltage range of 2.7V to 5.5V, making it compatible with 3.3V systems.

Q2: What type of microphone is compatible with the MAX9814?
The MAX9814 is designed for use with electret microphones.

Q3: How do I calculate the resistor values for the GAIN and TH pins?
Refer to the MAX9814 datasheet for detailed resistor value tables corresponding to specific gain and AGC threshold levels.

Q4: Can I use the MAX9814 for stereo audio applications?
No, the MAX9814 is a single-channel preamplifier. For stereo applications, you will need two MAX9814 modules.

Q5: Is the MAX9814 suitable for battery-powered devices?
Yes, the MAX9814's low quiescent current (3mA typical) makes it ideal for battery-powered applications.