DS1302 Trickle-Charge RTC

{
  "schema_version": 1,
  "type": "component",
  "slug": "ds1302",
  "title": "DS1302 Trickle-Charge RTC",
  "brief": "Trickle-charge real-time clock with 31 bytes of RAM and a simple 3-wire interface.",
  "version": "0.1.0",
  "license": "CC-BY-SA-4.0",
  "tags": [
    "rtc",
    "real-time-clock",
    "trickle-charge",
    "3-wire",
    "timing",
    "adi",
    "sop-8"
  ],
  "component": {
    "mpn": "DS1302",
    "manufacturer": "Analog Devices",
    "package": "SOP-8 (208 mil)",
    "pin_count": 8,
    "category": "Clock / Timing",
    "subcategory": "Real-Time Clock (RTC)",
    "datasheet": "https://www.analog.com/media/en/technical-documentation/data-sheets/DS1302.pdf",
    "parts": {
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      "footprint": "ds1302.kicad_mod",
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      "lbr": "ds1302.lbr",
      "model_3d_step": "ds1302-etched.step",
      "model_3d_step_plain": "ds1302.step"
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    "distributor_links": {},
    "pins": [
      {
        "number": "1",
        "name": "VCC2",
        "type": "power_in",
        "description": "Primary power-supply pin in dual-supply configuration. The DS1302 operates from the larger of VCC1 or VCC2. When VCC2 is greater than VCC1 + 0.2V, VCC2 powers the DS1302; when VCC2 is less than VCC1, VCC1 powers the DS1302. Operating range 2.0V to 5.5V."
      },
      {
        "number": "2",
        "name": "X1",
        "type": "passive",
        "description": "Connection for a standard 32.768kHz quartz crystal. Internal oscillator is designed for a crystal with 6pF specified load capacitance. Can also be driven by an external 32.768kHz oscillator applied to X1 (with X2 floated)."
      },
      {
        "number": "3",
        "name": "X2",
        "type": "passive",
        "description": "Second connection for the 32.768kHz quartz crystal. Left floating when an external oscillator drives X1."
      },
      {
        "number": "4",
        "name": "GND",
        "type": "power_in",
        "description": "Device ground."
      },
      {
        "number": "5",
        "name": "CE",
        "type": "input",
        "description": "Chip enable input. CE must be asserted high during a read or write to enable the control logic and shift register access. Has an internal 40k-ohm (typ) pulldown to ground. Previous datasheet revisions referred to this pin as /RST; functionality is unchanged."
      },
      {
        "number": "6",
        "name": "I/O",
        "type": "bidirectional",
        "description": "Bidirectional serial data pin for the 3-wire interface. Push-pull output during read, high-impedance when CE is low, tri-stated on rising edge of SCLK. Has an internal 40k-ohm (typ) pulldown to ground."
      },
      {
        "number": "7",
        "name": "SCLK",
        "type": "input",
        "description": "Serial clock input used to synchronize data movement on the 3-wire serial interface. Has an internal 40k-ohm (typ) pulldown to ground."
      },
      {
        "number": "8",
        "name": "VCC1",
        "type": "power_in",
        "description": "Low-power/battery-backup supply pin. In systems using the trickle charger the rechargeable energy source (e.g. supercap or lithium cell) is connected to this pin. UL-recognized reverse-charging protection is required when used with a lithium battery."
      }
    ],
    "provenance": {
      "extractor": "ds2sf",
      "datasheet": {
        "url": "https://www.analog.com/media/en/technical-documentation/data-sheets/DS1302.pdf",
        "pages": 13,
        "sha256": "fb627b436b89e8c9",
        "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": "ds1302.step",
        "role": "plain",
        "up": "Z",
        "units": "mm",
        "origin": "footprint origin = pad-pattern centre",
        "seat": "z = 0",
        "extents_mm": [
          7.8,
          5.3,
          2.16
        ],
        "zmin_mm": 0,
        "centre_offset_mm": 0,
        "footprint_binding": "identity",
        "sha256": "121aee742692bb7bc9ef49972786ecb89d1b2d62ab089ed278651a884c800331",
        "checked": "2026-10-07",
        "checked_by": "factory/step_pose.py (Z-up, origin, seat, binding)"
      },
      {
        "file": "ds1302-etched.step",
        "role": "eda",
        "up": "Z",
        "units": "mm",
        "origin": "footprint origin = pad-pattern centre",
        "seat": "z = 0",
        "extents_mm": [
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        "checked": "2026-10-07",
        "checked_by": "factory/step_pose.py (Z-up, origin, seat, binding)"
      }
    ]
  },
  "metadata": {
    "specs": {
      "Type": "Real-time clock (RTC)",
      "Interface": "3-wire (CE, SCLK, I/O)",
      "Timekeeping": "Seconds to year, leap-year compensated to 2100",
      "RAM": "31 bytes scratchpad",
      "Backup": "Trickle-charge circuit for cap/cell",
      "Supply voltage": "2.0 V to 5.5 V",
      "Operating temperature": "-40 C to 85 C"
    }
  },
  "sections": [
    "hero",
    "viewers",
    "readme",
    "breadcrumbs",
    "info"
  ],
  "discovery_triggers": [
    "real-time clock",
    "battery-backed clock",
    "timekeeping",
    "3-wire RTC"
  ],
  "discovery_pitch": "A low-cost RTC that keeps date and time with a backup cell and talks over a simple 3-wire bus.",
  "author": {
    "name": "Ray"
  },
  "dependencies": {},
  "hero": {
    "type": "image",
    "path": "docs/hero.png"
  },
  "files": [
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  "variants": [
    {
      "mpn": "DS1302+",
      "kind": "unknown"
    },
    {
      "mpn": "DS1302N+",
      "kind": "unknown"
    },
    {
      "mpn": "DS1302S+",
      "kind": "unknown"
    },
    {
      "mpn": "DS1302SN+",
      "kind": "unknown"
    },
    {
      "mpn": "DS1302Z+",
      "kind": "unknown"
    },
    {
      "mpn": "DS1302ZN+",
      "kind": "unknown"
    }
  ]
}