{
  "metadata": {
    "id": "sht45",
    "name": "Sensirion SHT45 Precision Temperature & Humidity Sensor",
    "type": "sensor",
    "description": "Ultra-high-accuracy digital humidity and temperature sensor with fixed-address I2C, integrated heater, factory calibration, and a compact DFN package for direct PCB integration.",
    "manufacturer": "Sensirion",
    "part_number": "SHT45-AD1B-R2",
    "datasheet_url": "https://sensirion.com/media/documents/33FD6951/67EB9032/HT_DS_Datasheet_SHT4x_5.pdf",
    "tags": [
      "sht45",
      "humidity",
      "temperature",
      "i2c",
      "0x44",
      "environmental",
      "factory-calibrated",
      "heater",
      "dfn-4",
      "precision"
    ],
    "schema_version": "1.4.0",
    "version": "1.0",
    "taxonomy": [
      "sensor.environmental"
    ]
  },
  "domains": [
    {
      "domain": "electrical",
      "power_domains": [
        {
          "id": "vdd",
          "name": "VDD",
          "nominal_voltage_V": 3.3,
          "voltage_range_V": [
            1.08,
            3.6
          ],
          "isolation_type": "non_isolated",
          "ground_reference": "common",
          "description": "Main supply input for the sensor core and digital interface."
        }
      ],
      "resources": [
        {
          "id": "pin1_sda",
          "name": "SDA",
          "description": "I2C serial data",
          "functions": [
            {
              "name": "I2C_SDA",
              "direction": "bidirectional",
              "signal_class": "data"
            }
          ],
          "power_domain_id": "vdd",
          "connector_type": "surface_pad",
          "notes": "Open-drain data line; provide an external pull-up on the bus."
        },
        {
          "id": "pin2_vdd",
          "name": "VDD",
          "description": "Supply input",
          "functions": [
            {
              "name": "VDD_IN",
              "direction": "sink",
              "signal_class": "power"
            }
          ],
          "power_domain_id": "vdd",
          "connector_type": "surface_pad"
        },
        {
          "id": "pin3_gnd",
          "name": "GND",
          "description": "Ground",
          "functions": [
            {
              "name": "GND",
              "direction": "sink",
              "signal_class": "ground"
            }
          ],
          "power_domain_id": "vdd",
          "connector_type": "surface_pad"
        },
        {
          "id": "pin4_scl",
          "name": "SCL",
          "description": "I2C serial clock",
          "functions": [
            {
              "name": "I2C_SCL",
              "direction": "sink",
              "signal_class": "clock"
            }
          ],
          "power_domain_id": "vdd",
          "connector_type": "surface_pad",
          "notes": "Supports I2C standard, fast, and fast-mode plus operation."
        }
      ],
      "interfaces": [
        {
          "id": "i2c_target",
          "name": "I2C target",
          "protocol": {
            "type": "i2c",
            "role": "target"
          },
          "requires": [
            {
              "function": "I2C_SDA",
              "count": 1,
              "shareable_with": [
                "I2C_SCL"
              ]
            },
            {
              "function": "I2C_SCL",
              "count": 1,
              "shareable_with": [
                "I2C_SDA"
              ]
            }
          ],
          "timing": {
            "max_i2c_freq_hz": 1000000
          },
          "description": "Fixed 7-bit I2C address 0x44 for the AD1B ordering option."
        },
        {
          "id": "power_supply",
          "name": "Power supply",
          "protocol": {
            "type": "power_supply",
            "role": "supply"
          },
          "requires": [
            {
              "function": "VDD_IN",
              "count": 1
            },
            {
              "function": "GND",
              "count": 1
            }
          ]
        }
      ],
      "supply_voltage_V": [
        1.08,
        3.6
      ],
      "metadata": {
        "i2c_address_7bit": "0x44",
        "i2c_max_frequency_hz": 1000000,
        "relative_humidity_range_percent": [
          0,
          100
        ],
        "temperature_accuracy_typical_C": 0.1,
        "relative_humidity_accuracy_typical_percent": 1,
        "average_supply_current_uA": 0.4,
        "clock_stretching_supported": false
      }
    },
    {
      "domain": "mechanical",
      "resources": [],
      "interfaces": [],
      "package_type": "4-DFN",
      "dimensions_mm": {
        "length": 1.5,
        "width": 1.5,
        "height": 0.5
      },
      "metadata": {
        "mounting_method": "surface_mount",
        "terminal_pitch_mm": 0.8
      }
    },
    {
      "domain": "thermal",
      "resources": [],
      "interfaces": [],
      "operating_temperature_C": [
        -40,
        125
      ],
      "metadata": {
        "storage_temperature_C": [
          -40,
          150
        ],
        "integrated_heater_levels_mW": [
          20,
          110,
          200
        ],
        "heater_pulse_options_s": [
          0.1,
          1
        ]
      }
    }
  ],
  "design_rules": [
    "Place a 100 nF decoupling capacitor between VDD and VSS close to the sensor and keep the I2C pull-ups sized for the total bus capacitance.",
    "Do not place copper under the sensing cavity other than the package pads, and avoid adhesives, coatings, or enclosure features that obstruct airflow to the sensor opening.",
    "Use the integrated heater only in short pulses for decontamination or condensation recovery; repeated heater use biases the immediate humidity reading and increases self-heating.",
    "Do not rely on clock stretching with SHT4x devices; the host must wait the documented conversion time or poll after the command interval.",
    "If you need multiple SHT4x devices on one bus, select different fixed-address ordering options or use an I2C switch because the AD1B variant is fixed at 0x44."
  ],
  "usage_notes": "The SHT45 is a bare surface-mount sensor intended for direct PCB integration. It returns calibrated temperature and relative-humidity measurements over I2C and can be used as a reference-grade ambient sensor for calibration, compensation, and environmental monitoring in compact systems.",
  "application_examples": [
    "Reference humidity and temperature sensing for multi-sensor environmental nodes.",
    "HVAC, thermostats, and indoor comfort monitoring.",
    "Battery-powered dataloggers and portable calibration fixtures."
  ],
  "compatibility_notes": "The AD1B ordering option uses fixed 7-bit I2C address 0x44. Other SHT4x variants use alternate fixed addresses or protective options, but they are distinct orderable parts and should not be assumed interchangeable without checking the exact suffix.",
  "warnings": [
    "This part is not a ready-to-wire breakout board; it requires PCB land pattern design, I2C pull-ups, and local decoupling.",
    "Aggressive heater use and nearby hot components can skew local temperature and humidity measurements.",
    "Do not use this sensor as a certified life-safety alarm element or as the sole control input for critical safety systems."
  ]
}