MCP3421 18-Bit I2C ADC

@@ -0,0 +1,52 @@+# 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++- `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](https://ww1.microchip.com/downloads/en/DeviceDoc/22003e.pdf) (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](docs/mcp3421-datasheet.pdf)

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