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MCP3421 18-Bit I2C ADC

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by Ray

18-bit delta-sigma ADC with I2C, on-chip reference and PGA, in a tiny SOT-23-6.

adcdelta-sigma18-biti2cpgamicrochipsot-23-6
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MCP3421

Microchip · Analog-to-Digital Converter · SOT-23-6

The MCP3421 is an 18-bit delta-sigma analog-to-digital converter with an I2C interface. It integrates a 2.048 V reference and a programmable gain amplifier (1x to 8x), and converts a single differential input at selectable 12, 14, 16, or 18-bit resolution. Its tiny SOT-23-6 package suits precision sensor and instrumentation measurement where board space is tight.

Pinout

Pin Name Type Function
1 VIN+ input Positive differential analog input. Absolute voltage range VSS-0.3 V to VDD+0.3 V. Differential input range ±2.048 V/PGA; common-mode input impedance ~25 MΩ.
2 VSS power_in Ground / analog return. Tie to the analog ground plane through a low-impedance connection.
3 SCL input I2C serial clock input (slave). Accepts standard, Fast, and High-Speed mode clocks; data on SDA is shifted on SCL edges.
4 SDA bidirectional I2C bidirectional serial data. Open-drain; requires external pull-up. VIH ≥ 0.7·VDD, VIL ≤ 0.3·VDD, VOL ≤ 0.4 V at 3 mA.
5 VDD power_in Positive supply, 2.7 V to 5.5 V. Bypass with 0.1 µF ceramic (and additional 10 µF tantalum recommended) to VSS.
6 VIN- input Negative differential analog input. Tie to VSS for single-ended operation. Absolute voltage range VSS-0.3 V to VDD+0.3 V.

Key specifications

Parameter Value
Resolution 12/14/16/18-bit (selectable)
Architecture Delta-sigma
Inputs 1 differential
Reference Internal 2.048 V
PGA gain 1x, 2x, 4x, 8x
Interface I2C
Supply voltage 2.7 V to 5.5 V
Operating temperature -40 C to 125 C

Ordering variants

Same part, different packaging or reel option.

  • MCP3421A0T
  • MCP3421A1T
  • MCP3421A2T
  • MCP3421A3T

CAD (KiCad official)

  • Symbol: mcp3421.kicad_sym
  • Footprint: mcp3421.kicad_mod
  • 3D model: SOT-23-6 body from KiCad Package_TO_SOT_SMD/SOT-23-6.

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

  • Datasheet: Microchip datasheet (42 pp, sha256 5249b67ed71256bc, retrieved 2026-08-17, tier: manufacturer)
  • Extractor: ds2sf (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
  • CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF