Microchip MCP3221A5T-I/OT 12-Bit ADC: Datasheet, Application Circuit, and Programming Guide
The Microchip MCP3221A5T-I/OT is a single-channel, 12-bit resolution analog-to-digital converter (ADC) that provides a simple and effective solution for adding high-accuracy measurement capabilities to embedded systems. Operating from a 2.7V to 5.5V supply, this device is ideal for a wide range of battery-powered and low-power applications. Its small SOT-23-5 package makes it perfect for space-constrained designs.
Datasheet Overview and Key Specifications
The MCP3221 is a successive approximation register (SAR) ADC with an I2C compatible serial interface, supporting standard (100 kbps) and fast (400 kbps) mode communication. Key specifications from the datasheet include:
Resolution: 12 Bits
Integral Non-Linearity (INL): ±1 LSB (max)
Differential Non-Linearity (DNL): ±0.5 LSB (max)
Sample Rate: Up to 22.3 kSPS (at 5V)
Low Typical Current: 250 µA (during conversion, at 5V)
Shutdown Current: 1 µA (max)
The 'A5' variant in the part number specifies a fixed I2C address of 1010 0101 (0x52 for a 7-bit write address), which helps avoid bus conflicts in multi-device systems.
Typical Application Circuit
The MCP3221 requires very few external components, making board layout straightforward. A typical application circuit for reading a analog voltage from a sensor is shown below:
1. Power Decoupling: A 0.1 µF ceramic decoupling capacitor must be placed as close as possible to the VDD and VSS pins.
2. Analog Input (VIN): The signal to be measured is connected to the VIN pin. For signals with high output impedance, a small capacitor (e.g., 100pF) to ground on this pin can help reduce noise.
3. I2C Bus Lines: The Serial Data (SDA) and Serial Clock (SCL) lines are connected to the corresponding pins of the microcontroller. 2.2 kΩ to 10 kΩ pull-up resistors are required on both SDA and SCL lines to VDD.
4. Voltage Reference: A key advantage of the MCP3221 is that it uses VDD as its voltage reference. This means the input voltage range is from VSS to VDD. Therefore, a stable and clean power supply is critical for accurate conversion results.
Programming Guide (Arduino Example)
Communicating with the MCP3221 via I2C is simple. Below is a basic code example for an Arduino environment.
1. Include the Wire Library: This library handles I2C communication.
`include
2. Define the I2C Address:
`define MCP3221_ADDR 0x4D // 7-bit address 0x52 shifted right once (0x52 >> 1 = 0x4D) for Arduino's Wire library`
3. Setup Function: Initialize the I2C bus and serial monitor.
```
void setup() {
Wire.begin();
Serial.begin(9600);
}
```
4. Loop Function: Read and calculate the voltage.
```
void loop() {
Wire.requestFrom(MCP3221_ADDR, 2); // Request 2 bytes of data
if (Wire.available() >= 2) {
int high_byte = Wire.read(); // Reads the first byte (MSB)
int low_byte = Wire.read(); // Reads the second byte (LSB)
// Combine the two bytes into a 12-bit value
int digital_value = ((high_byte & 0x0F) << 8) | low_byte;
// Convert digital value to voltage (assuming VDD = 5.0V)
float voltage = (digital_value 5.0) / 4095.0;
Serial.print("Digital Value: ");
Serial.print(digital_value);
Serial.print(" | Voltage: ");
Serial.print(voltage, 3);
Serial.println(" V");
}
delay(1000);
}
```
Important Note: The device requires a conversion time between the I2C request and the data being ready. The code above uses `Wire.requestFrom` which handles this timing correctly. For other microcontrollers, ensure you consult the datasheet for timing requirements.
ICGOODFIND: The Microchip MCP3221A5T-I/OT is an exceptional choice for designers seeking a compact, low-power, and high-accuracy ADC solution. Its minimal external component count and straightforward I2C interface significantly reduce development time and complexity. Whether for sensor data acquisition, battery monitoring, or portable instrumentation, this ADC delivers reliable performance and excellent value.
Keywords: 12-Bit ADC, I2C Interface, Low-Power, MCP3221A5T-I/OT, Successive Approximation Register (SAR)
