MAX31865 RTD-to-Digital Converter

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  "type": "component",
  "slug": "max31865",
  "title": "MAX31865 RTD-to-Digital Converter",
  "brief": "Resistance-to-digital converter for PT100/PT1000 RTD temperature sensors, SPI.",
  "version": "0.1.0",
  "license": "CC-BY-SA-4.0",
  "tags": [
    "rtd",
    "pt100",
    "pt1000",
    "temperature",
    "spi",
    "adi",
    "tssop-20"
  ],
  "component": {
    "mpn": "MAX31865",
    "manufacturer": "Analog Devices",
    "package": "TSSOP-20",
    "pin_count": 20,
    "category": "Sensor",
    "subcategory": "RTD Interface",
    "datasheet": "https://www.analog.com/media/en/technical-documentation/data-sheets/MAX31865.pdf",
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    "distributor_links": {},
    "pins": [
      {
        "number": "1",
        "name": "DRDY",
        "type": "output",
        "description": "Active-low, push-pull data-ready output. DRDY goes low when a new conversion result is available in the RTD data register; it returns high after that register is read."
      },
      {
        "number": "2",
        "name": "DVDD",
        "type": "power_in",
        "description": "Digital supply voltage input, 3.0V-3.6V (nominally 3.3V). Bypass to DGND with a 0.1µF capacitor."
      },
      {
        "number": "3",
        "name": "VDD",
        "type": "power_in",
        "description": "Analog supply voltage input, 3.0V-3.6V (nominally 3.3V). Bypass to GND1 with a 0.1µF capacitor."
      },
      {
        "number": "4",
        "name": "BIAS",
        "type": "output",
        "description": "Bias voltage output (VBIAS ≈ 2.0V). Provides the bias for the reference and RTD networks; drives up to 5.75mA."
      },
      {
        "number": "5",
        "name": "REFIN+",
        "type": "input",
        "description": "Positive reference-voltage input. Connect to BIAS. Reference resistor (RREF, 350Ω-10kΩ) is placed between REFIN+ and REFIN-."
      },
      {
        "number": "6",
        "name": "REFIN-",
        "type": "input",
        "description": "Negative reference-voltage input. Reference resistor is connected between REFIN+ and REFIN-."
      },
      {
        "number": "7",
        "name": "ISENSOR",
        "type": "passive",
        "description": "Low side of RREF; connect to REFIN-. Carries the RTD bias current returning through the reference resistor."
      },
      {
        "number": "8",
        "name": "FORCE+",
        "type": "output",
        "description": "High-side RTD drive. Connect to FORCE2 when using the 3-wire connection configuration. Protected to ±45V."
      },
      {
        "number": "9",
        "name": "FORCE2",
        "type": "bidirectional",
        "description": "Positive input used in 3-wire configuration only. Tie to FORCE+ for 3-wire RTDs; ground for 2-wire and 4-wire configurations. Protected to ±45V."
      },
      {
        "number": "10",
        "name": "RTDIN+",
        "type": "input",
        "description": "Positive RTD sense input. Protected to ±45V."
      },
      {
        "number": "11",
        "name": "RTDIN-",
        "type": "input",
        "description": "Negative RTD sense input. Protected to ±45V."
      },
      {
        "number": "12",
        "name": "FORCE-",
        "type": "passive",
        "description": "Low-side RTD return. Protected to ±45V."
      },
      {
        "number": "13",
        "name": "GND2",
        "type": "power_in",
        "description": "Analog ground. Connect to GND1."
      },
      {
        "number": "14",
        "name": "SDI",
        "type": "input",
        "description": "SPI serial-data input (MOSI). Sampled on the rising edge of SCLK."
      },
      {
        "number": "15",
        "name": "SCLK",
        "type": "input",
        "description": "SPI serial-data clock input."
      },
      {
        "number": "16",
        "name": "CS",
        "type": "input",
        "description": "Active-low chip select. Drive CS low to enable the SPI interface."
      },
      {
        "number": "17",
        "name": "SDO",
        "type": "output",
        "description": "SPI serial-data output (MISO)."
      },
      {
        "number": "18",
        "name": "DGND",
        "type": "power_in",
        "description": "Digital ground."
      },
      {
        "number": "19",
        "name": "GND1",
        "type": "power_in",
        "description": "Analog ground. Connect to GND2."
      },
      {
        "number": "20",
        "name": "N.C.",
        "type": "unconnected",
        "description": "No internal connection. Do not connect."
      }
    ],
    "provenance": {
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      "datasheet": {
        "url": "https://www.analog.com/media/en/technical-documentation/data-sheets/MAX31865.pdf",
        "pages": 26,
        "sha256": "88f540410eb8c2ac",
        "source_tier": "mfr"
      },
      "cad": "KiCad official (CC-BY-SA 4.0)",
      "pins": {
        "total": 20,
        "described": 20,
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        "refuses_to_fabricate": true
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    },
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  },
  "metadata": {
    "specs": {
      "Type": "RTD-to-digital converter",
      "Sensors": "PT100 / PT1000 (2/3/4-wire)",
      "ADC": "15-bit",
      "Accuracy": "0.5% of full scale (max)",
      "Interface": "SPI",
      "Fault detection": "Open, short, overvoltage",
      "Supply voltage": "3.0 V to 3.6 V",
      "Operating temperature": "-40 C to 85 C"
    }
  },
  "sections": [
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    "breadcrumbs",
    "info"
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  "discovery_triggers": [
    "RTD to digital",
    "PT100 amplifier",
    "PT1000 interface",
    "precision temperature",
    "platinum RTD"
  ],
  "discovery_pitch": "Turn a PT100 or PT1000 platinum RTD into a precise digital temperature reading over SPI, with fault detection built in.",
  "author": {
    "name": "Ray"
  },
  "dependencies": {},
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}