PCF8523 Real-Time Clock

{
  "schema_version": 1,
  "type": "component",
  "slug": "pcf8523",
  "title": "PCF8523 Real-Time Clock",
  "brief": "Low-power I2C real-time clock and calendar with battery backup and alarm.",
  "version": "0.1.0",
  "license": "CC-BY-SA-4.0",
  "tags": [
    "rtc",
    "real-time-clock",
    "i2c",
    "calendar",
    "low-power",
    "nxp",
    "soic-8"
  ],
  "component": {
    "mpn": "PCF8523",
    "manufacturer": "NXP",
    "package": "SOIC-8",
    "pin_count": 8,
    "category": "Clock / Timing",
    "subcategory": "Real-Time Clock (RTC)",
    "datasheet": "https://www.nxp.com/docs/en/data-sheet/PCF8523.pdf",
    "parts": {
      "symbol": "pcf8523.kicad_sym",
      "footprint": "pcf8523.kicad_mod",
      "model_3d": "pcf8523-etched.glb",
      "model_3d_plain": "pcf8523.glb",
      "model_3d_step": "pcf8523-etched.step",
      "model_3d_step_plain": "pcf8523.step",
      "lbr": "pcf8523.lbr"
    },
    "distributor_links": {},
    "pins": [
      {
        "number": "1",
        "name": "OSCI",
        "type": "input",
        "description": "32.768 kHz crystal oscillator input; high-impedance node. Connect to one terminal of the 32.768 kHz quartz crystal; internal load capacitors are selectable (7 pF or 12.5 pF via CAP_SEL). Keep wire length between quartz and package minimal."
      },
      {
        "number": "2",
        "name": "OSCO",
        "type": "output",
        "description": "32.768 kHz crystal oscillator output; high-impedance node. Connect to the other terminal of the 32.768 kHz quartz crystal."
      },
      {
        "number": "3",
        "name": "VBAT",
        "type": "power_in",
        "description": "Battery supply voltage input. Feeds the on-chip battery switch-over circuit which automatically supplies the RTC from the backup battery when VDD drops."
      },
      {
        "number": "4",
        "name": "VSS",
        "type": "power_in",
        "description": "Ground supply voltage (0 V reference)."
      },
      {
        "number": "5",
        "name": "SDA",
        "type": "bidirectional",
        "description": "I²C-bus serial data input/output. Open-drain; requires external pull-up resistor. Supports Fast-mode Plus up to 1 MHz."
      },
      {
        "number": "6",
        "name": "SCL",
        "type": "input",
        "description": "I²C-bus serial clock input. Requires external pull-up resistor. Supports Fast-mode Plus up to 1 MHz."
      },
      {
        "number": "7",
        "name": "INT1/CLKOUT",
        "type": "output",
        "description": "Interrupt 1 / clock output (open-drain). Selectable via register: either drives the active-LOW INT1 interrupt (alarm/timer/second) or the programmable CLKOUT (32.768 kHz / 16.384 kHz / 8.192 kHz / 4.096 kHz / 1.024 kHz / 32 Hz / 1 Hz). Requires external pull-up."
      },
      {
        "number": "8",
        "name": "VDD",
        "type": "power_in",
        "description": "Main supply voltage input. Operating range 1.0 V to 5.5 V; typical backup current 150 nA at VDD = 3.0 V, Tamb = 25 °C."
      }
    ],
    "provenance": {
      "extractor": "ds2sf",
      "datasheet": {
        "url": "https://www.nxp.com/docs/en/data-sheet/PCF8523.pdf",
        "pages": 78,
        "sha256": "409cb5ca8b0d04bc",
        "source_tier": "mfr"
      },
      "cad": "KiCad official (CC-BY-SA 4.0)",
      "pins": {
        "total": 8,
        "described": 8,
        "cites_pages": true,
        "refuses_to_fabricate": true
      }
    },
    "viewers": {
      "symbol": "viewers/symbol.html",
      "footprint": "viewers/footprint.html"
    },
    "models_3d": [
      {
        "file": "pcf8523.step",
        "role": "plain",
        "up": "Z",
        "units": "mm",
        "origin": "footprint origin = pad-pattern centre",
        "seat": "z = 0",
        "extents_mm": [
          6.0,
          4.9,
          1.75
        ],
        "zmin_mm": -0.0,
        "centre_offset_mm": 0.0,
        "footprint_binding": "identity",
        "sha256": "07f46cff378d30e6c27dfd5a03092c795323f86d91c71fc7e743f4f418dc553a",
        "checked": "2026-10-07",
        "checked_by": "factory/step_pose.py (Z-up, origin, seat, binding)"
      },
      {
        "file": "pcf8523-etched.step",
        "role": "eda",
        "up": "Z",
        "units": "mm",
        "origin": "footprint origin = pad-pattern centre",
        "seat": "z = 0",
        "extents_mm": [
          6.0,
          4.9,
          1.75
        ],
        "zmin_mm": -0.0,
        "centre_offset_mm": 0.0,
        "footprint_binding": "identity",
        "sha256": "9e5c80a080a77d03c4f309b31b5159d9c3e9467475c3e98fcc237d0d8c88c404",
        "checked": "2026-10-07",
        "checked_by": "factory/step_pose.py (Z-up, origin, seat, binding)"
      }
    ]
  },
  "metadata": {
    "specs": {
      "Type": "I2C real-time clock / calendar",
      "Interface": "I2C (up to 1 MHz)",
      "Timekeeping": "Seconds to year, leap-year compensated",
      "Backup": "Battery switch-over",
      "Features": "Alarm, timer, programmable clock output",
      "Supply voltage": "1.8 V to 5.5 V",
      "Operating temperature": "-40 C to 85 C"
    }
  },
  "sections": [
    "hero",
    "viewers",
    "readme",
    "breadcrumbs",
    "info"
  ],
  "discovery_triggers": [
    "real-time clock",
    "I2C RTC",
    "battery-backed clock",
    "calendar timekeeping",
    "alarm"
  ],
  "discovery_pitch": "A low-power I2C RTC that keeps time and date on a backup battery, with alarm and timer functions.",
  "author": {
    "name": "Ray",
    "email": "[email protected]"
  },
  "dependencies": {},
  "hero": {
    "type": "image",
    "path": "docs/hero.png"
  },
  "files": [
    "page.json",
    "README.md",
    "pcf8523.kicad_sym",
    "pcf8523.kicad_mod",
    "pcf8523.glb",
    "pcf8523.step",
    "pcf8523.lbr",
    "docs/hero.png",
    "docs/pcf8523-datasheet.pdf",
    "viewers/symbol.html",
    "viewers/footprint.html",
    "pcf8523-etched.step"
  ],
  "variants": [
    {
      "mpn": "PCF8523T",
      "kind": "unknown"
    },
    {
      "mpn": "PCF8523T/1",
      "kind": "unknown"
    },
    {
      "mpn": "PCF8523TK",
      "kind": "unknown"
    },
    {
      "mpn": "PCF8523TK/1",
      "kind": "unknown"
    },
    {
      "mpn": "PCF8523TS",
      "kind": "unknown"
    },
    {
      "mpn": "PCF8523TS/1",
      "kind": "unknown"
    },
    {
      "mpn": "PCF8523U/12AA/1",
      "kind": "unknown"
    }
  ]
}