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# MCP3421 18-Bit ADC Breakout - STEMMA QT / Qwiic

**Brand:** Adafruit

**URL:** https://littlebirdelectronics.com.au/products/adafruit-mcp3421-18-bit-adc-stemma-qt-qwiic

## Pricing

- **Price:** $14.20
- **Stock:** In stock at supplier
- **Local warehouse:** 0 units
- **Supplier (Adafruit):** 76 units
- **SKU:** AF-5870

## Description

This compact breakout adds a high-resolution, single-channel ADC to your I2C bus, making it a handy choice for precision differential measurements. It is built around the MCP3421, a simple and low-cost 18-bit ΔΣ converter with adjustable gain, a built-in precision reference voltage, and support for I2C clock rates up to 3.4MHz.Because it is designed for differential inputs, it is well suited to sensors such as strain gauges, pressure sensors, and thermocouples. Both input signals need to stay between 0 and 2.048V, so it is not the best fit for general single-ended measurements like reading a potentiometer across the full 0 to VCC range. You can trade conversion speed for resolution, from 240 samples per second at 12-bit down to 3.75 samples per second at 18-bit.Adafruit has already mounted the chip on a STEMMA QT breakout, with connectors on both sides for quick solderless hookup. These connectors are compatible with SparkFun Qwiic, so it drops neatly into many I2C-based prototyping setups and can be chained with other compatible boards using a suitable cable. An Arduino library is available to select sample rate and precision, choose one-shot or continuous mode, and read values over I2C. The board has a fixed I2C address, includes a strip of 0.1" header for breadboard or perfboard use, and has four mounting holes for easy installation. QT cable is not included.Specifications:ADC type: 18-bit ΔΣ ADCInput operation: Differential Input OperationCalibration: Self Calibration of Internal Offset and Gain Per Each ConversionOn-Board Voltage Reference Accuracy: 2.048V ± 0.05%On-Board Voltage Reference Drift: 15 ppm/°COn-Board Programmable Gain Amplifier (PGA): Gains of 1,2, 4 or 8Oscillator: On-Board OscillatorINL: 10 ppm of FSR (FSR = 4.096V/PGA)Programmable Data Rate: 3.75 SPS (18 bits)Programmable Data Rate: 15 SPS (16 bits)Programmable Data Rate: 60 SPS (14 bits)Programmable Data Rate: 240 SPS (12 bits)Conversion options: One-Shot or Continuous Conversion OptionsProduct Dimensions: 25.4mm x 17.8mm x 12.3mm / 1.0" x 0.7" x 0.5"Product Weight: 3.0g / 0.1ozA good fit for precision sensor work where differential measurement matters, especially in STEMMA QT and Qwiic ecosystems.

**Product Type:** ADC Breakout Board

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*Source: [MCP3421 18-Bit ADC Breakout - STEMMA QT / Qwiic](https://littlebirdelectronics.com.au/products/adafruit-mcp3421-18-bit-adc-stemma-qt-qwiic)*