SN74HC688 8-Bit Comparator

{
  "schema_version": 1,
  "type": "component",
  "slug": "sn74hc688",
  "title": "SN74HC688 8-Bit Comparator",
  "brief": "8-bit magnitude/identity comparator with a single active-low equality output.",
  "version": "0.1.0",
  "license": "CC-BY-SA-4.0",
  "tags": [
    "logic",
    "comparator",
    "identity",
    "magnitude",
    "74hc",
    "ti",
    "soic-20"
  ],
  "component": {
    "mpn": "SN74HC688",
    "manufacturer": "Texas Instruments",
    "package": "SOIC-20",
    "pin_count": 20,
    "category": "Logic",
    "subcategory": "Comparator",
    "datasheet": "https://www.ti.com/lit/ds/symlink/sn74hc688.pdf",
    "parts": {
      "symbol": "sn74hc688.kicad_sym",
      "footprint": "sn74hc688.kicad_mod",
      "model_3d": "sn74hc688-etched.glb",
      "model_3d_plain": "sn74hc688.glb",
      "lbr": "sn74hc688.lbr",
      "model_3d_step": "sn74hc688-etched.step",
      "model_3d_step_plain": "sn74hc688.step"
    },
    "distributor_links": {},
    "pins": [
      {
        "number": "1",
        "name": "OE",
        "type": "input",
        "description": "Active-low output-enable. When high, forces the P=Q output high regardless of data inputs. When low, enables the comparator output."
      },
      {
        "number": "2",
        "name": "P0",
        "type": "input",
        "description": "P-word bit 0 data input. Compared against Q0 via an XNOR stage."
      },
      {
        "number": "3",
        "name": "Q0",
        "type": "input",
        "description": "Q-word bit 0 data input. Compared against P0 via an XNOR stage."
      },
      {
        "number": "4",
        "name": "P1",
        "type": "input",
        "description": "P-word bit 1 data input. Compared against Q1 via an XNOR stage."
      },
      {
        "number": "5",
        "name": "Q1",
        "type": "input",
        "description": "Q-word bit 1 data input. Compared against P1 via an XNOR stage."
      },
      {
        "number": "6",
        "name": "P2",
        "type": "input",
        "description": "P-word bit 2 data input. Compared against Q2 via an XNOR stage."
      },
      {
        "number": "7",
        "name": "Q2",
        "type": "input",
        "description": "Q-word bit 2 data input. Compared against P2 via an XNOR stage."
      },
      {
        "number": "8",
        "name": "P3",
        "type": "input",
        "description": "P-word bit 3 data input. Compared against Q3 via an XNOR stage."
      },
      {
        "number": "9",
        "name": "Q3",
        "type": "input",
        "description": "Q-word bit 3 data input. Compared against P3 via an XNOR stage."
      },
      {
        "number": "10",
        "name": "GND",
        "type": "power_in",
        "description": "Ground reference (0 V) for the device."
      },
      {
        "number": "11",
        "name": "P4",
        "type": "input",
        "description": "P-word bit 4 data input. Compared against Q4 via an XNOR stage."
      },
      {
        "number": "12",
        "name": "Q4",
        "type": "input",
        "description": "Q-word bit 4 data input. Compared against P4 via an XNOR stage."
      },
      {
        "number": "13",
        "name": "P5",
        "type": "input",
        "description": "P-word bit 5 data input. Compared against Q5 via an XNOR stage."
      },
      {
        "number": "14",
        "name": "Q5",
        "type": "input",
        "description": "Q-word bit 5 data input. Compared against P5 via an XNOR stage."
      },
      {
        "number": "15",
        "name": "P6",
        "type": "input",
        "description": "P-word bit 6 data input. Compared against Q6 via an XNOR stage."
      },
      {
        "number": "16",
        "name": "Q6",
        "type": "input",
        "description": "Q-word bit 6 data input. Compared against P6 via an XNOR stage."
      },
      {
        "number": "17",
        "name": "P7",
        "type": "input",
        "description": "P-word bit 7 (MSB) data input. Compared against Q7 via an XNOR stage."
      },
      {
        "number": "18",
        "name": "Q7",
        "type": "input",
        "description": "Q-word bit 7 (MSB) data input. Compared against P7 via an XNOR stage."
      },
      {
        "number": "19",
        "name": "P=Q",
        "type": "output",
        "description": "Active-low comparator output. Asserted low when the P and Q words are equal AND OE is low; otherwise forced high. Drives ±4 mA at 5 V, up to 10 LSTTL loads."
      },
      {
        "number": "20",
        "name": "VCC",
        "type": "power_in",
        "description": "Positive supply voltage, 2 V to 6 V recommended (5 V nominal). Requires a 0.1 µF bypass capacitor placed close to the pin."
      }
    ],
    "provenance": {
      "extractor": "ds2sf",
      "datasheet": {
        "url": "https://www.ti.com/lit/ds/symlink/sn74hc688.pdf",
        "pages": 24,
        "sha256": "d600a33f4ebb7089",
        "source_tier": "mfr"
      },
      "cad": "KiCad official (CC-BY-SA 4.0)",
      "pins": {
        "total": 20,
        "described": 20,
        "cites_pages": true,
        "refuses_to_fabricate": true
      }
    },
    "viewers": {
      "symbol": "viewers/symbol.html",
      "footprint": "viewers/footprint.html"
    },
    "logic": {
      "family_id": "74HC688",
      "logic_family": "74HC",
      "function_code": "688",
      "function_class": "Comparator",
      "function_name": "8-Bit Magnitude Comparator",
      "manufacturer": "Texas Instruments",
      "is_specialty": false
    },
    "models_3d": [
      {
        "file": "sn74hc688.step",
        "role": "plain",
        "up": "Z",
        "units": "mm",
        "origin": "footprint origin = pad-pattern centre",
        "seat": "z = 0",
        "extents_mm": [
          10.3,
          12.8,
          2.75
        ],
        "zmin_mm": 0,
        "centre_offset_mm": 0,
        "footprint_binding": "identity",
        "sha256": "59a10b341e6972b31d81802a048060326da627d8b92dcf4263064f4f62ec808e",
        "checked": "2026-10-07",
        "checked_by": "factory/step_pose.py (Z-up, origin, seat, binding)"
      },
      {
        "file": "sn74hc688-etched.step",
        "role": "eda",
        "up": "Z",
        "units": "mm",
        "origin": "footprint origin = pad-pattern centre",
        "seat": "z = 0",
        "extents_mm": [
          10.3,
          12.8,
          2.75
        ],
        "zmin_mm": 0,
        "centre_offset_mm": 0,
        "footprint_binding": "identity",
        "sha256": "6e43838cc298e662bbfe392fe9d85429ff00677f73dbc801585a0471880f4fec",
        "checked": "2026-10-07",
        "checked_by": "factory/step_pose.py (Z-up, origin, seat, binding)"
      }
    ]
  },
  "metadata": {
    "specs": {
      "Type": "8-bit identity (magnitude) comparator",
      "Logic family": "74HC (CMOS)",
      "Output": "Single active-low P = Q",
      "Enable": "Active-low",
      "Supply voltage": "2 V to 6 V",
      "Propagation delay": "20 ns typ at 5 V",
      "Operating temperature": "-40 C to 85 C"
    }
  },
  "sections": [
    "hero",
    "viewers",
    "readme",
    "breadcrumbs",
    "info"
  ],
  "discovery_triggers": [
    "8-bit comparator",
    "identity comparator",
    "address decode match",
    "equality detect"
  ],
  "discovery_pitch": "Compare two 8-bit words and get a single active-low output when they match, for address decoding and equality checks.",
  "author": {
    "name": "Ray"
  },
  "dependencies": {},
  "hero": {
    "type": "image",
    "path": "docs/hero.png"
  },
  "files": [
    "page.json",
    "README.md",
    "sn74hc688.kicad_sym",
    "sn74hc688.kicad_mod",
    "sn74hc688.glb",
    "sn74hc688.lbr",
    "docs/hero.png",
    "docs/sn74hc688-datasheet.pdf",
    "viewers/symbol.html",
    "viewers/footprint.html",
    "sn74hc688-etched.step"
  ],
  "variants": [
    {
      "mpn": "SN74HC688DW",
      "kind": "unknown"
    },
    {
      "mpn": "SN74HC688N",
      "kind": "unknown"
    },
    {
      "mpn": "SN74HC688PWR",
      "kind": "unknown"
    },
    {
      "mpn": "SN74HC688PW",
      "kind": "unknown"
    },
    {
      "mpn": "SN74HC688J",
      "kind": "unknown"
    },
    {
      "mpn": "SN74HC688FK",
      "kind": "unknown"
    }
  ]
}