Microchip MCP3204T-CI/SL 12-Bit 4-Channel ADC: Datasheet, Pinout, and Application Circuit Design

The Microchip MCP3204T-CI/SL is a 12-bit resolution, 4-channel analog-to-digital converter (ADC) that provides a versatile and cost-effective solution for embedded systems requiring precise analog signal acquisition. Communicating via the ubiquitous SPI serial interface, it is designed for easy integration with a wide range of microcontrollers (MCUs), making it a popular choice for industrial control, data acquisition, and sensor interface applications.

Datasheet Overview and Key Specifications

The MCP3204 datasheet outlines a component built with successive approximation register (SAR) architecture. Its key specifications define its performance envelope:

Resolution: 12-bit, providing 4096 (2^12) possible digital output codes.

Input Channels: 4 single-ended or 2 pseudo-differential input channels, selected by software.

Supply Voltage: Operates from a single 2.7V to 5.5V supply, compatible with both 3.3V and 5V logic systems.

Maximum Sampling Rate: Up to 100 kilosamples per second (ksps) at 5V.

Integral Nonlinearity (INL): ±1 LSB (max), ensuring strong linearity performance.

Package: The "T-CI/SL" suffix denotes a standard 14-pin plastic small outline (SOIC) package, suitable for surface-mount technology (SMT).

Pinout and Functional Description

Understanding the pinout is crucial for circuit design. The 14-pin SOIC package has the following key pins:

1. CH0-CH3 (Pins 1-4): Analog input channels 0 through 3.

2. VSS / DGND (Pin 5): Digital ground reference.

3. VREF (Pin 6): Reference voltage input. The analog input voltage range is 0V to VREF. A stable and low-noise VREF is critical for accurate conversions.

4. AGND (Pin 7): Analog ground reference. For best performance, this should be connected to a clean ground point, often star-connected to VSS.

5. CS/SHDN (Pin 8): Chip Select/Shutdown input. Activates the device when driven low.

6. DIN (Pin 9): Serial Data Input. Receives instructions from the MCU.

7. DOUT (Pin 10): Serial Data Output. Sends conversion results to the MCU.

8. CLK (Pin 11): Serial Clock Input. Driven by the SPI master (MCU) to synchronize data transfer.

9. VDD / AVDD (Pins 12, 13): Positive supply voltage (2.7V - 5.5V).

10. NC (Pin 14): No Connect.

Application Circuit Design

A typical application circuit for interfacing the MCP3204 with a microcontroller is straightforward but requires attention to detail for optimal performance.

1. Basic SPI Connection:

Connect the CS, CLK, DIN, and DOUT pins of the MCP3204 directly to the corresponding SPI pins (SS, SCK, MOSI, MISO) on the microcontroller.

Ensure the MCU's SPI peripheral is configured for Mode 0,0 (clock polarity CPOL=0, clock phase CPHA=0) or Mode 1,1 (CPOL=1, CPHA=1), as both are supported.

2. Power Supply and Decoupling:

Apply a stable DC power source (e.g., 3.3V or 5V) to VDD.

Place a 0.1µF ceramic decoupling capacitor as close as possible to the VDD pin and AGND. A larger bulk capacitor (e.g., 10µF) may also be used on the supply rail. This is essential for filtering high-frequency noise on the power supply.

3. Reference Voltage (VREF):

For full-scale accuracy, use a stable and precise voltage reference source connected to the VREF pin. This can be the same as VDD for less critical applications, but a dedicated low-noise reference IC (e.g., 2.048V, 4.096V) is recommended for highest accuracy.

4. Analog Input Conditioning:

For signals from high-impedance sources or noisy environments, a simple RC low-pass filter (e.g., 1kΩ resistor and a 100nF capacitor to AGND) on each analog input channel is highly advised. This limits aliasing and reduces noise.

5. Grounding:

While the MCP3204 has separate AGND and DGND pins, they must be tied together at the device. The best practice is to connect both to a common solid ground plane on the PCB to minimize ground loop errors.

ICGOOODFIND

The Microchip MCP3204T-CI/SL stands out as a highly practical and robust 12-bit ADC solution for embedded designers. Its simple SPI interface, flexible input configuration, and wide operating voltage range make it exceptionally easy to implement. By adhering to fundamental design principles—proper power decoupling, a stable voltage reference, and careful grounding—engineers can reliably achieve the converter's full 12-bit performance, making it an excellent choice for a vast array of data acquisition tasks.

Keywords: MCP3204, 12-Bit ADC, SPI Interface, Voltage Reference, Analog Input Conditioning.