DS1621
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ADI (Maxim) digital thermometer and thermostat, I2C, SOIC-8. 9-bit, -55 to 125 C, TOUT alarm. Datasheet-verified.
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markdownDS1621
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
Same part, different packaging or reel option.
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)
- 3D model files:
ds1621-etched.step/ds1621-etched.glbcarry the MPN laser-etched on the die in a toggleableAdom.LaserEtchgroup (Fusion-ready);ds1621.step/ds1621.glbare the bare package body.
Provenance
Data extracted from the manufacturer datasheet, not a distributor listing:
- Datasheet: Analog Devices datasheet (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).