How to Use ADS1220: Examples, Pinouts, and Specs

The ADS1220 is a 24-bit analog-to-digital converter (ADC) designed for precision measurement applications. It features a low-noise, low-drift architecture, and includes programmable gain amplifiers (PGAs), making it ideal for interfacing with sensors and performing high-accuracy data acquisition. The ADS1220 is commonly used in industrial, medical, and scientific applications where precise and reliable measurements are critical.

• Temperature measurement using thermocouples or RTDs
• Pressure sensors and strain gauges
• Industrial process control
• Medical instrumentation
• Portable measurement devices

The ADS1220 offers a range of features that make it a versatile and high-performance ADC. Below are its key technical specifications:

The ADS1220 is available in a 16-pin TSSOP package. Below is the pinout and description:

The ADS1220 is typically used in precision measurement circuits. Below are the steps and considerations for using the ADS1220:

1. Power Supply: Connect AVDD and DVDD to appropriate power sources (e.g., 3.3 V or 5 V for AVDD, and 3.3 V for DVDD). Connect GND to the system ground.
2. Analog Inputs: Connect the sensor or signal source to the AINx pins. For differential measurements, use pairs of AIN pins (e.g., AIN0 and AIN1).
3. Reference Voltage: Use the internal reference or connect an external reference voltage to REFP and REFN.
4. SPI Interface: Connect the SPI pins (SCLK, DIN, DOUT, and CS) to a microcontroller or processor.

• Use the SPI interface to configure the ADS1220's registers. Key settings include:
  • Input Multiplexer: Select the input channel or differential pair.
  • Gain: Set the PGA gain (1x to 128x).
  • Data Rate: Choose the desired data rate (20 SPS to 2000 SPS).
  • Reference Source: Select internal or external reference.

Below is an example of how to interface the ADS1220 with an Arduino UNO using SPI:

#include <SPI.h>

// Pin definitions
#define CS_PIN 10  // Chip select pin
#define DRDY_PIN 9 // Data ready pin

void setup() {
  // Initialize SPI
  SPI.begin();
  pinMode(CS_PIN, OUTPUT);
  pinMode(DRDY_PIN, INPUT);
  digitalWrite(CS_PIN, HIGH); // Set CS high to deselect ADS1220

  // Configure ADS1220
  configureADS1220();
}

void loop() {
  // Wait for data ready signal
  if (digitalRead(DRDY_PIN) == LOW) {
    long adcValue = readADC();
    Serial.println(adcValue); // Print ADC value
  }
}

void configureADS1220() {
  digitalWrite(CS_PIN, LOW); // Select ADS1220
  SPI.transfer(0x40);        // Write to configuration register 0
  SPI.transfer(0x01);        // Set PGA gain to 1x, select AIN0-AIN1
  SPI.transfer(0x04);        // Set data rate to 20 SPS
  SPI.transfer(0x10);        // Enable internal reference
  digitalWrite(CS_PIN, HIGH); // Deselect ADS1220
}

long readADC() {
  digitalWrite(CS_PIN, LOW); // Select ADS1220
  SPI.transfer(0x10);        // Send read data command
  long result = 0;
  result |= SPI.transfer(0x00) << 16; // Read MSB
  result |= SPI.transfer(0x00) << 8;  // Read middle byte
  result |= SPI.transfer(0x00);       // Read LSB
  digitalWrite(CS_PIN, HIGH); // Deselect ADS1220
  return result;
}

• Use decoupling capacitors (e.g., 0.1 µF and 10 µF) near the power supply pins to reduce noise.
• Ensure proper grounding to minimize interference.
• Use shielded cables for long sensor connections to reduce EMI.

1. No Data Output:

   • Ensure the SPI connections are correct.
   • Verify that the CS pin is being toggled correctly.
   • Check the power supply and reference voltage connections.

2. Incorrect Measurements:

   • Verify the input signal is within the ADC's input range.
   • Check the PGA gain and input multiplexer settings.
   • Ensure the reference voltage is stable and accurate.

3. High Noise in Readings:

   • Use a lower data rate to reduce noise.
   • Add filtering capacitors to the input signal.

Q: Can I use the ADS1220 with a 5 V microcontroller?
A: Yes, the ADS1220 supports a supply voltage of up to 5.5 V. Ensure the SPI logic levels are compatible with the microcontroller.

Q: How do I measure a thermocouple with the ADS1220?
A: Connect the thermocouple to a differential input pair (e.g., AIN0 and AIN1). Use the internal reference and configure the PGA for the appropriate gain.

Q: What is the maximum sampling rate of the ADS1220?
A: The maximum data rate is 2000 samples per second (SPS).