SI4431-B1-FM

{
  "slug": "si4431-b1-fm",
  "version": "0.1.0",
  "type": "component",
  "description": "SILICON LABS RF Transceiver ICs, QFN-20(4x4). Pinout cross-checked by two models against the datasheet, KiCad symbol/footprint/3D.",
  "tags": [
    "component",
    "radio frequency chip-antenna",
    "si4431-b1-fm",
    "factory-2.0.0",
    "extractor-text"
  ],
  "dependencies": {},
  "hero": {
    "type": "image",
    "path": "docs/hero.png"
  },
  "files": [
    "page.json",
    "README.md",
    "si4431-b1-fm.kicad_sym",
    "si4431-b1-fm.kicad_mod",
    "si4431-b1-fm.glb",
    "si4431-b1-fm.step",
    "si4431-b1-fm.lbr",
    "docs/hero.png",
    "docs/si4431-b1-fm-datasheet.pdf",
    "viewers/symbol.html",
    "viewers/footprint.html",
    "si4431-b1-fm-hero.glb",
    "si4431-b1-fm-hero.overlay.json",
    "si4431-b1-fm-etched.glb"
  ],
  "component": {
    "mpn": "SI4431-B1-FM",
    "manufacturer": "SILICON LABS",
    "package": "QFN-20(4x4)",
    "pin_count": 21,
    "category": "Radio Frequency Chip/Antenna",
    "subcategory": "RF Transceiver ICs",
    "datasheet": "https://datasheet.lcsc.com/datasheet/pdf/b1880380f93bf93be3f4d9f9a4cdfefa.pdf",
    "parts": {
      "symbol": "si4431-b1-fm.kicad_sym",
      "footprint": "si4431-b1-fm.kicad_mod",
      "model_3d": "si4431-b1-fm-hero.glb",
      "model_3d_plain": "si4431-b1-fm-etched.glb",
      "model_3d_step": "si4431-b1-fm-etched.step",
      "model_3d_step_plain": "si4431-b1-fm.step",
      "lbr": "si4431-b1-fm.lbr"
    },
    "distributor_links": {
      "lcsc": "C3606893",
      "digikey": "336-2521-5-ND",
      "mouser": "634-SI4431-B1-FM"
    },
    "distributor_check": {
      "checked_at": "2026-10-31T18:42:35Z",
      "source": "Component Ocean /api/assign-pns",
      "digikey": {
        "pn": "336-2521-5-ND",
        "status": "found"
      },
      "mouser": {
        "pn": "634-SI4431-B1-FM",
        "status": "found"
      }
    },
    "pins": [
      {
        "number": "1",
        "name": "VDD_RF",
        "type": "power_in",
        "description": "Supply input to all analog +1.7 V regulators, with a supply range of +1.8 to +3.6 V and a recommended +3.3 V."
      },
      {
        "number": "2",
        "name": "TX",
        "type": "output",
        "description": "Transmit output is an open-drain PA output, so the L-C match must supply VDD (+3.3 VDC nominal) to this pin."
      },
      {
        "number": "3",
        "name": "RXp",
        "type": "input",
        "description": "Differential RF input pin of the LNA, connected through the application matching network."
      },
      {
        "number": "4",
        "name": "RXn",
        "type": "input",
        "description": "Differential RF input pin of the LNA, connected through the application matching network."
      },
      {
        "number": "5",
        "name": "NC",
        "type": "unconnected",
        "description": "No Connect pin, not connected internally to any circuitry."
      },
      {
        "number": "6",
        "name": "ANT",
        "type": "output",
        "description": "Extra antenna or TR switch control output, a hardwired version of GPIO setting 11000 (Antenna 2) that can be controlled by the antdiv[2:0] bits in register 08h."
      },
      {
        "number": "7",
        "name": "GPIO_0",
        "type": "bidirectional",
        "description": "General purpose digital I/O configurable through registers for functions such as MCU clock output, FIFO status, POR, wake-up timer, low battery detect, TRSW and antenna diversity control."
      },
      {
        "number": "8",
        "name": "GPIO_1",
        "type": "bidirectional",
        "description": "General purpose digital I/O configurable through registers for functions such as MCU clock output, FIFO status, POR, wake-up timer, low battery detect, TRSW and antenna diversity control."
      },
      {
        "number": "9",
        "name": "GPIO_2",
        "type": "bidirectional",
        "description": "General purpose digital I/O configurable through registers for functions such as MCU clock output, FIFO status, POR, wake-up timer, low battery detect, TRSW and antenna diversity control."
      },
      {
        "number": "10",
        "name": "VR_DIG",
        "type": "power_out",
        "description": "Regulated output of the digital 1.7 V regulator, which requires a 1 µF decoupling capacitor."
      },
      {
        "number": "11",
        "name": "NC",
        "type": "unconnected",
        "description": "Internally tied to the package paddle, so it should be left unconnected or connected to GND only."
      },
      {
        "number": "12",
        "name": "VDD_DIG",
        "type": "power_in",
        "description": "Supply input to the digital +1.7 V regulator, with a supply range of +1.8 to +3.6 V and a recommended +3.3 V."
      },
      {
        "number": "13",
        "name": "SDO",
        "type": "output",
        "description": "Serial readback digital output of the internal control registers, swinging 0 to VDD V."
      },
      {
        "number": "14",
        "name": "SDI",
        "type": "input",
        "description": "Serial data input of the 4-line serial bus, a 0 to VDD V digital input."
      },
      {
        "number": "15",
        "name": "SCLK",
        "type": "input",
        "description": "Serial clock input of the 4-line serial bus, a 0 to VDD V digital input; data is clocked in on positive edge transitions."
      },
      {
        "number": "16",
        "name": "nSEL",
        "type": "input",
        "description": "Serial interface select (enable) input, a 0 to VDD V digital input that also signals burst read/write mode."
      },
      {
        "number": "17",
        "name": "nIRQ",
        "type": "output",
        "description": "Microcontroller interrupt status output that is driven low when an interrupt event occurs, and needs no external pull-up unless multiple interrupt lines are tied together."
      },
      {
        "number": "18",
        "name": "XOUT",
        "type": "output",
        "description": "Crystal oscillator output for an external 30 MHz crystal or source; an external source without crystal needs dc coupling at a nominal 0.8 VDC with at least 700 mVpp amplitude."
      },
      {
        "number": "19",
        "name": "XIN",
        "type": "input",
        "description": "Crystal oscillator input for an external 30 MHz crystal, or left floating when driving an external source on XOUT."
      },
      {
        "number": "20",
        "name": "SDN",
        "type": "input",
        "description": "Shutdown input, a 0 to VDD V digital input that must be 0 in all modes except shutdown; setting it to 1 fully shuts down the chip and loses register contents."
      },
      {
        "number": "21",
        "name": "PADDLE_GND",
        "type": "passive",
        "description": "Exposed pad (from the footprint; not named in the datasheet pin table)."
      }
    ],
    "provenance": {
      "extractor": "extract_pins 0.3",
      "factory_chain": {
        "factory": "2.0.0",
        "extractor": "extract_pins 0.3",
        "primary_model": "claude-haiku-5-5",
        "primary_mode": "text",
        "consensus_model": "claude-sonnet-5-5",
        "consensus": "agreed",
        "guards": "pin_guards 0.1: passed",
        "guard_notes": [
          "extractor flagged: The datasheet covers Si4430/31/32 and the Si4431-B1-FM is listed as QFN-20 Pb-free in the ordering t",
          "2/21 pins cited to the wrong page (name found elsewhere): ['18:XOUT@p66', '19:XIN@p66']"
        ],
        "pages_sent": 10,
        "cost_usd": 0.025,
        "at": "2026-10-31T18:42:22"
      },
      "datasheet": {
        "url": "https://datasheet.lcsc.com/datasheet/pdf/b1880380f93bf93be3f4d9f9a4cdfefa.pdf",
        "pages": 74,
        "sha256": "a0dc9f652a3ee30e",
        "source_tier": "lcsc"
      },
      "cad": "KiCad official (CC-BY-SA 4.0)",
      "pins": {
        "total": 21,
        "described": 21,
        "cites_pages": true,
        "refuses_to_fabricate": true
      }
    },
    "viewers": {
      "symbol": "viewers/symbol.html",
      "footprint": "viewers/footprint.html"
    },
    "models_3d": [
      {
        "file": "si4431-b1-fm.step",
        "role": "plain",
        "up": "Z",
        "units": "mm",
        "origin": "footprint origin = pad-pattern centre",
        "seat": "z = 0",
        "extents_mm": [
          4.0,
          4.0,
          0.77
        ],
        "zmin_mm": 0.0,
        "centre_offset_mm": 0.0,
        "footprint_binding": "identity",
        "sha256": "c9476a1612023de37f27b4972110ab6ac6dc0eaf5ac48957a2e1c497650082a5",
        "checked": "2026-10-31",
        "checked_by": "factory/step_pose.py (Z-up, origin, seat, binding)"
      },
      {
        "file": "si4431-b1-fm-etched.step",
        "role": "eda",
        "up": "Z",
        "units": "mm",
        "origin": "footprint origin = pad-pattern centre",
        "seat": "z = 0",
        "extents_mm": [
          4.0,
          4.0,
          0.77
        ],
        "zmin_mm": 0.0,
        "centre_offset_mm": 0.0,
        "footprint_binding": "identity",
        "sha256": "39d6b32f6afa76f7e1e8bb1db4863135cbe836a7c2972503ddfbd7558fa99861",
        "checked": "2026-10-31",
        "checked_by": "factory/step_pose.py (Z-up, origin, seat, binding)"
      }
    ]
  }
}