DS1621

@@ -0,0 +1,52 @@+# DS1621++**Analog Devices** · Temperature sensor / thermostat · SOIC-8++Measures temperature over I2C and also acts as a standalone thermostat. It reports 9-bit readings (0.5 C steps) from -55 to 125 C, and a TOUT pin switches high or low when the temperature crosses user-set high and low registers, with programmable hysteresis, so it can drive a fan or heater without a host in the loop. Three address pins put up to eight on one bus. The settings are stored in nonvolatile memory. A self-contained temperature switch plus digital readout.++## Pinout++| Pin | Name | Type | Function |+|---|---|---|---|+| 1 | SDA | bidirectional | 2-wire serial data input/output (open-drain). Requires external pull-up to VDD. |+| 2 | SCL | input | 2-wire serial clock input/output (open-drain). Clock line for I²C-compatible communication. |+| 3 | TOUT | output | Thermostat output. Active when measured temperature exceeds TH; deasserts when temperature falls below TL, providing programmable hysteresis. |+| 4 | GND | power_in | Ground reference pin (0 V). |+| 5 | A2 | input | Chip address input pin (MSB of 3-bit slave-address selector). Tie to VDD or GND to set device address on shared 2-wire bus. |+| 6 | A1 | input | Chip address input pin. Tie to VDD or GND to set device address on shared 2-wire bus. |+| 7 | A0 | input | Chip address input pin (LSB of 3-bit slave-address selector). Tie to VDD or GND to set device address on shared 2-wire bus. |+| 8 | VDD | power_in | Supply voltage input pin. Operating range 2.7 V to 5.5 V. Bypass to GND with a 0.1 µF capacitor close to the pin. |++## Key specifications++| Parameter | Value |+|---|---|+| Type | Digital thermometer + thermostat |+| Interface | I2C (8 addresses) |+| Resolution | 9-bit (0.5 C) |+| Range | -55 to 125 C |+| Thermostat output | TOUT with programmable trip + hysteresis |+| Nonvolatile | Trip points stored in EEPROM |+| Supply | 2.7-5.5 V |+| Package | SOIC-8 |++## Ordering variants++- `DS1621S+ (SOIC-8)`+- `DS1621+ (PDIP-8)`++## CAD (KiCad official)++- Symbol: `Sensor_Temperature:DS1621 (KiCad official)`+- Footprint: `Package_SO:SOIC-8_3.9x4.9mm_P1.27mm`+- 3D model: SOIC-8 (KiCad packages3D, STEP)++## Provenance++Data extracted from the manufacturer datasheet, not a distributor listing:++- **Datasheet:** [Analog Devices datasheet](https://www.analog.com/media/en/technical-documentation/data-sheets/DS1621.pdf) (16 pp, sha256 `faa68e65a7b2f8f0`, retrieved 2026-08-17, tier: manufacturer)+- **Extractor:** `ds2sf` (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.+- **CAD:** KiCad official libraries (CC-BY-SA 4.0).++[Datasheet PDF](docs/ds1621-datasheet.pdf)

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