A high-accuracy digital humidity and temperature sensor with an I2C interface, in a 2.5 x 2.5 mm DFN-8, from Sensirion's SHT3x family. It measures relative humidity to about plus/minus 2% RH and temperature to plus/minus 0.3 C, returning fully calibrated, linearized values over I2C at up to 1 MHz. An ADDR pin selects one of two I2C addresses, a programmable ALERT pin flags threshold crossings without polling, and an on-chip heater can drive off condensation for reliable readings in humid environments. It is a precise, drop-in upgrade from the older DHT-style sensors for weather stations, HVAC, and environmental logging. Runs 2.15-5.5 V. The 3D model shown is a representative small SMD package; the real package is DFN-8 (2.5 x 2.5 mm).

Pinout

Pin	Name	Type	Function
1	SDA	bidirectional	I2C serial data line (input/output). Open-drain; requires external pull-up to VDD (e.g. 10 kΩ). Fast Mode up to 400 kHz; frequencies up to 1 MHz supported.
2	ADDR	input	I2C address select input. Tie to VSS for I2C address 0x44 (default), or to VDD for 0x45. Must not be left floating. May be switched dynamically to change address at runtime, but must remain constant between START and STOP.
3	ALERT	output	Alarm condition output. Switches high when programmed RH/T alert limits are exceeded. Drive strength IOH ≈ 1.5 × VDD (see Table 3). Leave floating if unused.
4	SCL	input	I2C serial clock input (also driven low by sensor during clock stretching). Open-drain; requires external pull-up to VDD (e.g. 10 kΩ). Clock frequency 0-1000 kHz.
5	VDD	power_in	Supply voltage, 2.15 V to 5.5 V (typ. 3.3 V). Decouple with 100 nF placed as close as possible to the sensor.
6	nRESET	input	Active-low hardware reset input. Minimum low pulse of 1 µs triggers a reset. Internally pulled up to VDD via ≈50 kΩ; if unused, leave floating or tie to VDD through a series resistor ≥2 kΩ.
7	R	passive	No electrical function. Must be connected to VSS (ground).
8	VSS	power_in	Ground reference. The exposed die pad (center pad) is internally connected to VSS and should be soldered to the PCB ground for mechanical strength.

Key specifications

Parameter	Value
Type	I2C humidity + temperature sensor
Humidity accuracy	±2% RH
Temperature accuracy	±0.3 °C
Interface	I2C up to 1 MHz
Addresses	2 (via ADDR pin)
Extras	programmable ALERT + on-chip heater
Supply voltage	2.15-5.5 V
Package	DFN-8 (2.5 x 2.5 mm)

Ordering variants

Same part, different packaging or reel option.

SHT31-DIS-B (DFN-8)
SHT31-DIS-F (with filter membrane)

CAD (KiCad official)

Symbol: Sensor_Humidity:SHT30-DIS
Footprint: Sensor_Humidity:Sensirion_DFN-8-1EP_2.5x2.5mm_P0.5mm_EP1.1x1.7mm
3D model: representative small SMD (real package DFN-8 2.5x2.5mm)

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

Datasheet: Sensirion datasheet (22 pp, sha256 095b1853e7f4328f, 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