How to Use AD5933 Impedance Converter: Examples, Pinouts, and Specs

The AD5933 is a high-precision impedance converter manufactured by Generic, with the part ID AD5933. It is designed to measure the impedance of a device under test (DUT) across a wide frequency range. The device integrates a frequency generator, an analog-to-digital converter (ADC), and a digital signal processor (DSP) to provide accurate impedance measurements. By generating a sine wave and analyzing the resulting voltage and phase shift, the AD5933 calculates the impedance of the DUT.

• Bio-impedance measurements for medical devices
• Material characterization in research and development
• Corrosion monitoring in industrial systems
• Sensor interfacing for capacitive, inductive, or resistive sensors
• Quality control in manufacturing processes

• Operating Voltage: 2.7 V to 5.5 V
• Frequency Range: 1 kHz to 100 kHz (programmable)
• Impedance Measurement Range: 1 kΩ to 10 MΩ (with external components)
• Output Excitation Voltage: Programmable (200 mV, 400 mV, or 1 V peak-to-peak)
• ADC Resolution: 12-bit
• Interface: I²C (2-wire serial interface)
• Operating Temperature Range: -40°C to +125°C
• Package: 16-lead TSSOP

The AD5933 is housed in a 16-lead TSSOP package. Below is the pin configuration:

1. Power Supply: Connect the VDD, AVDD, and DVDD pins to a stable power supply (2.7 V to 5.5 V). Connect AGND and DGND to the ground.
2. Frequency Configuration: Use the I²C interface to program the desired frequency range and excitation voltage.
3. Impedance Measurement:
   • Connect the DUT between the VOUT and VIN pins.
   • Use an appropriate feedback resistor (RFB) to set the gain factor for the measurement.
4. I²C Communication:
   • Use the SCL and SDA pins to communicate with a microcontroller or processor.
   • Write commands to configure the device and read back the impedance data.

• Feedback Resistor Selection: Choose an RFB value that matches the expected impedance range of the DUT for optimal accuracy.
• External Clock: If precise frequency control is required, provide an external clock signal to the MCLK pin.
• Bypass Capacitors: Place decoupling capacitors (e.g., 0.1 µF) close to the power supply pins to reduce noise.
• Temperature Effects: Ensure the device operates within the specified temperature range to maintain accuracy.
• I²C Pull-Up Resistors: Use appropriate pull-up resistors (e.g., 4.7 kΩ) on the SCL and SDA lines for reliable I²C communication.

Below is an example of how to interface the AD5933 with an Arduino UNO for basic impedance measurement:

• Connect VDD, AVDD, and DVDD to the Arduino's 5V pin.
• Connect AGND and DGND to the Arduino's GND pin.
• Connect SCL to Arduino's A5 pin (I²C clock).
• Connect SDA to Arduino's A4 pin (I²C data).
• Connect the DUT between VOUT and VIN.
• Add a feedback resistor (RFB) between RFB and VIN.

#include <Wire.h>

// AD5933 I2C address
#define AD5933_ADDR 0x0D

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

  // Configure AD5933 for impedance measurement
  configureAD5933();
}

void loop() {
  // Perform impedance measurement
  float impedance = measureImpedance();
  Serial.print("Impedance: ");
  Serial.print(impedance);
  Serial.println(" Ohms");

  delay(1000); // Wait 1 second before the next measurement
}

void configureAD5933() {
  // Example configuration: Set frequency range and excitation voltage
  Wire.beginTransmission(AD5933_ADDR);
  Wire.write(0x80); // Control register address
  Wire.write(0x10); // Example configuration: Start frequency sweep
  Wire.endTransmission();

  // Additional configuration commands can be added here
}

float measureImpedance() {
  // Placeholder function to calculate impedance
  // Implement actual impedance calculation based on AD5933 data
  return 1000.0; // Example: Return a dummy impedance value
}

1. No I²C Communication:

   • Ensure the SCL and SDA lines have proper pull-up resistors (e.g., 4.7 kΩ).
   • Verify the I²C address (default: 0x0D) matches the code.

2. Incorrect Impedance Readings:

   • Check the feedback resistor (RFB) value and ensure it matches the expected impedance range.
   • Verify the DUT is properly connected between VOUT and VIN.

3. Device Not Responding:

   • Confirm the power supply voltage is within the specified range (2.7 V to 5.5 V).
   • Check for proper grounding of AGND and DGND.

4. High Noise in Measurements:

   • Add bypass capacitors (e.g., 0.1 µF) near the power supply pins.
   • Minimize external noise sources near the circuit.

Q: Can the AD5933 measure both resistive and reactive components of impedance?
A: Yes, the AD5933 can measure both the magnitude and phase of impedance, allowing calculation of resistive and reactive components.

Q: What is the maximum frequency the AD5933 can generate?
A: The AD5933 can generate frequencies up to 100 kHz.

Q: Can I use an external clock with the AD5933?
A: Yes, an external clock can be provided to the MCLK pin for custom frequency generation.

Q: How do I improve measurement accuracy?
A: Use a precise feedback resistor, minimize noise, and ensure proper calibration of the device.