Datasheet – STS4x
4th Generation, High-Accuracy, Ultra-Low-Power, 16-bit
Temperature Sensor Platform

Highlights
•
•
•
•
•

Temperature accuracy: up to ±0.2 °C
Supply voltage: 1.08 V … 3.6 V
Average current: 0.4 µA (at meas. rate 1 Hz)
Idle current: 80 nA
I2C fast mode plus, CRC checksum

•
•
•
•
•

Available with multiple I2C addresses
Operating range: -40…125 °C
NIST traceability
JEDEC JESD47 qualification
Mature technology from global market leader

The STS4x is a fully digital temperature sensor platform offering different accuracy classes. The I 2C interface
provides multiple preconfigured I2C addresses and enables an ultra-low power budget. Designed to cost, thisfour-pin dual-flat-no-leads package is suitable for surface mount technology (SMT) processing.

Device Overview
Product

Functional Block Diagram
Details

STS4L-xD1B

0.4°C T accur., possible I2C addr.:
0x44, 0x45, 0x46.

STS40-xD1B

0.2°C T accur., possible I2C addr.:
0x44, 0x45, 0x46..

STS41-xD1B

best T accur., possible I2C addr.:
0x44, 0x45, 0x46.,
coming soon

See full product list on page 13.

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Contents
1

Quick Start – Hello World ................................................................................................................................................................ 3

2

Sensor Performance .......................................................................................................................................................................... 4

3

Electrical Specifications .................................................................................................................................................................... 5
3.1 Electrical Characteristics ........................................................................................................................................................ 5
3.2 Timings ......................................................................................................................................................................................... 6
3.3 Absolute Maximum Ratings ................................................................................................................................................. 6

4

Sensor Operation ................................................................................................................................................................................ 7
4.1 I2C Communication ................................................................................................................................................................. 7
4.2 Data Type & Length ................................................................................................................................................................ 7
4.3 Checksum Calculation ............................................................................................................................................................ 7
4.4 Command Overview................................................................................................................................................................ 8
4.5 Conversion of Signal Output ............................................................................................................................................... 8
4.6 Serial Number ............................................................................................................................................................................ 8
4.7 Reset & Abort ............................................................................................................................................................................ 85

Physical Specification ........................................................................................................................................................................ 9
5.1 Package Description................................................................................................................................................................ 9
5.2 Package Outline ........................................................................................................................................................................ 9
5.3 Land Pattern .............................................................................................................................................................................10
5.4 Pin Assignment & Laser Marking ....................................................................................................................................10

6

Quality and Material Contents ....................................................................................................................................................10

7

Tape and Reel Packaging ..............................................................................................................................................................11

8

Nomenclature ....................................................................................................................................................................................12

9

Ordering Information ......................................................................................................................................................................13

10 Revision History .................................................................................................................................................................................14

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1

Quick Start – Hello World

Figure 1 shows a typical application circuit for the STS4x on the left-hand side. After reaching the minimal
supply voltage and allowing for the maximal power-up time of 1 ms, the sensor is ready for I2C
communication. The quickest way to measure temperature is pseudo-coded on the right-hand side of
Figure 1. Using the conversion formulae given in equations ( 1 ) and ( 2 ), the digital signal can be translated
into temperature readings.

Typical application circuit

Pseudo code

I2C MasterI2C Slave
GND

SDA
MCU

STS4x
SCL

100 nFVDD

10 kΩ

i2c_write(i2c_addr=0x44, tx_bytes=[0xFD])
wait_seconds(0.01)
rx_bytes = i2c_read(i2c_addr=0x44,
number_of_bytes=3)t_ticks = rx_bytes[0] * 256 + rx_bytes[1]t_degC = -45 + 175 * t_ticks/65535

10 kΩ

Figure 1. Typical application circuit (left) and pseudo code (right) for easy startup.
For Code resources, embedded drivers, and CAD files, please refer to the SHT4x files available on GitHub and
SnapEDA.

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2

Sensor Performance

Parameter
STS4L T Accuracy1
STS40 T Accuracy1
STS41 T Accuracy1
Repeatability2
Resolution3
Specified range4
Response time5
Long-term drift6
Table 1. General temperature sensor specifications.
±1.0

Conditions
typ.
max.
typ.
max.
typ.
max.
high
medium
low
t63%
typ.

ΔT (°C)±1.0

STS4L typ
STS4L max

±0.8

Value
0.4
see Figure 2
0.2
See Figure 3
0.2
see Figure 4
0.04
0.07
0.1
0.01
–40 to +1252<0.03

ΔT (°C)STS40 typ
STS40 max

±0.8

±0.6

±0.6

±0.4

±0.4

±0.2

±0.2

±0.0

Units
°C
°C
°C
°C
°C
°C
°C
°C
s
°C/y

±0.0
-40

-20

0

20

40

60

80 100 120
Temperature (°C)-40

Figure 2. STS4L typical and maximal
temperature accuracy.
±1.0

-20

0

20

40

60

80 100 120
Temperature (°C)

Figure 3. STS40 typical and maximal temperatureaccuracy.

ΔT (°C)STS41 typSTS41 max

±0.8
±0.6
±0.4
±0.2
±0.0
-40

-20

0

20

40

60

80 100 120
Temperature (°C)

Figure 4. STS41 typical and maximal temperature accuracy.

1

For definition of typ. and max. accuracy, please refer to the document “Sensirion Humidity Sensor Specification Statement”.

2

The stated repeatability is 3 times the standard deviation (3σ) of multiple consecutive measurement values at constant conditions andis a measure for the noise on the physical sensor output. Different repeatability commands are listed in Table 6.
3

Resolution of A/D converter.

4

Specified range refers to the range for which the temperature sensor specification is guaranteed.

5

Depends on heat conductivity of sensor substrate and design-in of sensor in application.

6

Max. value is < 0.04°C/y.

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3

Electrical Specifications

Valid for all electrical specifications: Typical values correspond to VDD = 3.3 V and T = 25 °C. Min. and max.
values are valid in the full temperature range -40 °C … 125 °C and at declared VDD levels.

3.1

Electrical Characteristics

Parameter
Supply voltage
Power-up/downlevel

Supply current

Powerconsumpt. at
VDD=1.2V
Low level input
voltageHigh level input
voltage
Pull up resistors

Low level output
voltage

Cap bus load

Symb
ol
VDD

Conditions

Min

Typ.

Max

Comments

3.6

Uni
ts
V

1.08

3.3

VPOR

Static power supply

0.6

-

1.08

V

-

Idle state

-

0.08

µA

Power-up

-

50

1.0
3.4
-

Measurement

-

320

500

µA

Aver., high repeatability
Aver., med. repeatability
Aver., low repeatability

-

2.2
1.2
0.4

-

Aver., high repeatability
Aver., med. repeatability
Aver., low repeatability

-

2.6
1.4
0.5

-

VIL

-

0

-

0.3*
VDD

V

At 25°C
At 125°C
Average current
consumption while
sensor is measuring
Aver. current
consumpt. (contin.
operation with 1
meas. per second)
Aver. power
consumpt. (contin.
operation with one
meas. per second)
-

VIH

-

-

VDD

V

-

0.2*
VDD
0.2*
VDD

Ω
Ω

-

V

-

V

-

IDD

-

Rp

VOL

Cb

VDD < 1.62 V
VDD ≥ 1.62 V
VDD < 1.62V,
Rpullup > 820 Ω
VDD = 1.62V … 2.0V,
Rpullup > 390 Ω
VDD > 2.0V,
Rpullup > 390 Ω

0.7*
VDD
820
390

µA

µA

µW

-

-

-

-

-

-

0.4

V

RP ≤ 820 Ω: fast mode

-

-

400

pF

Rp = 390 Ω,
VDD > 1.62 V: fastmode plus

-

-

340

pF

-

-

Capac. bus load canbe determined from
Cb < trise /(0.8473*Rp).
Rise times aretrise = 300 ns for fastmode andtrise = 120 ns for fastmode plus

Table 2. Electrical specifications.

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3.2

Timings

Max. values are measured at -40°C and 1.08 V supply voltage (based on characterization).
Parameter

SymbolConditions

Power-up timetPU

After hard reset,
VDD ≥ VPOR

Min.

Typ.

Max.

-

0.3

1

Units CommentsmsTime between VDD
reaching VPOR and sensor
entering idle stateSoft reset timetSR

After soft reset

-

-

1

ms

Time between ACK ofsoft reset command andsensor entering idle
state. Also valid for I2C
general call reset.

Waiting timetW

between I2C
commands

1

-

-

ms

minimal waiting time for
I2C communicationtMEAS,lLow repeatability

-

1.3

1.6

ms

tMEAS,mMed.
repeatability

-

3.7

4.5

ms

tMEAS,hHigh
repeatability

-

6.9

8.3

ms

Measurement
duration

The three repeatability
modes differ withrespect to measurement
duration, noise level andenergy consumption

Table 3. System timing specifications.

3.3

Absolute Maximum Ratings

Stress levels beyond those listed in Table 4 may cause permanent damage or affect the reliability of the device.
Kindly note that the reported values are stress ratings only, implying that functional operation of the device
under these conditions is not guaranteed. Ratings are only tested separately.
Parameter
RatingMax. voltage on any pin
VSS - 0.3 V … VDD + 0.3 V
Operating temperature range-40 °C … 125 °C
Storage temperature range-40 °C …150 °C
ESD HBM
2 kV
ESD CDM
500 V
Latch up, JESD78 Class II, 125°C+-100 mA
Table 4. Absolute maximum ratings.

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4

Sensor Operation

4.1

I2C Communication

I2C communication is based on NXP’s I2C-bus specification and user manual UM10204, Rev.6, 4 April 2014.
Supported I2C modes are standard, fast mode, and fast mode plus. Data is transferred in multiples of 16-bitwords and an 8-bit check sum (cyclic redundancy check = CRC). All transfers must begin with a start
condition (S) and terminate with a stop condition (P). To finish a read transfer, send not acknowledge (NACK)
and stop condition (P). Addressing a specific slave device is done by sending its 7-bit I2C address followed byan eighth bit, denoting the communication direction: “zero” indicates transmission to the slave, i.e. “write”, a“one” indicates a “read” request. Schematics of the I2C transfer types are sketched in Figure 5.

Figure 5. I2C transfer types: First a write header is sent to the I2C slave, followed by a command, for example“measure T with highest precision”. After the measurement is finished the read request directed to this I 2C
slave will be acknowledged and transmission of data will be started by the slave.
The I2C address is defined by Sensirion and selectable by choosing from a selection of 0x44, 0x45, or 0x46
before ordering. For ordering details, kindly refer to section 8 and 9.

4.2 Data Type & Length
The I2C bus operates with 8-bit data packages. Information from the sensor to the master has a checksum
after every second 8-bit data package. Therefore, the temperature data will always be transmitted in thefollowing way (2 * 8-bit data + 8-bit CRC).

4.3 Checksum Calculation
For read transfers each 16-bit data is followed by a checksum with the following properties
Property
Value
Name
CRC-8
Message Length
16-bit8
Polynomial
0x31 (x + x5 + x4 +1)
Initialization
0xFF
Reflect Input/Output
false/false
Final XOR
0x00
ExamplesCRC(0xBEEF) = 0x92
Table 5. Data check sum properties.
The master may abort a read transfer after the 16-bit data, if it does not require a checksum.

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4.4 Command Overview
Commandbinhex

Response
length incl.
CRC (bytes)
3

Description

1111
FD
measure T with high precision (high repeatability)1101[2 * 8-bit T-data; 8-bit CRC]
1111
F6
3
measure T with medium precision (medium repeatability)0110[2 * 8-bit T-data; 8-bit CRC]
1110
E0
3
measure T with lowest precision (low repeatability)0000[2 * 8-bit T-data; 8-bit CRC]
1000
89
6
read serial
1001[2 * 8-bit data; 8-bit CRC; 2 * 8-bit data; 8-bit CRC]
1001
94
soft reset
0100
[ACK]
Table 6. Overview of I2C commands. If the sensor is not ready to process a command, e.g. because it is stillmeasuring, it will response with NACK to the I2C read header.

4.5 Conversion of Signal Output
The digital sensor signal ST corresponds to temperatures, as described in Eqs. (1), and (2).
𝑆

(1)

𝑆

(2)

𝑇 = (−45 + 175 ∙ 216T−1) °C
𝑇 = (−49 + 315 ∙ 216T−1) °F

4.6 Serial Number
Each sensor has a unique serial number that is assigned by Sensirion during production. It is stored in the
one-time-programmable memory and cannot be manipulated after production. The serial number isaccessible via I2C and is transmitted as two 16-bit words, each followed by an 8-bit CRC.

4.7

Reset & Abort

A reset of the sensor can be achieved in three ways:
1. Soft reset: send the reset command described in Table 6.
2. I2C general call: all devices on the I2C bus are reset by sending the command 0x06 to the I2C address
0x00.
3. Power down (incl. pulling SCL and SDA low)
Any command that triggers an action at the sensor can be aborted via I2C general call reset or soft reset.

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5

Physical Specification

5.1

Package Description

The STS4x is provided in a dual flat no lead (DFN) package, and comprises the sensor chip made of silicon,
which is hosted on a copper leadframe and overmolded by an epoxy-based mold compound. The exposed
bottom side of the leadframe with the metallic contacts is Sn plated, while the side walls are bare copper.
While moisture sensitivity level (MSL) 1 according to IPC/JEDEC J-STD-020 is met, we recommend to process
the sensors within one year after date of delivery.

5.2

Package Outline

A
Figure 6. Dimensional drawing of the STS4x including package tolerances (units mm). The Pin 1 is
identified by the laser dot on the top side and the cutout of the die pad, visible from the bottom. In the
middle of the DFN top side, a lasered character (“A”, “B”, or “C”) indicates the I2C address as detailed inTables 7 and 8.

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5.3

Land Pattern

We recommend designing the land pattern to the used PCB and soldering process together with the physicalouter dimensions of the sensor. For reference, the land pattern used with Sensirion’s PCBs and soldering
processes is given in Figure 7.
Soldering of the central die pad is optional.

Figure 7. Recommended land pattern (in mm). Details can varyand depend on used PCBs and solder processes. There shall be
no copper under the sensor other than at the pin pads.

5.4 Pin Assignment & Laser Marking
Pin
1
2
3
4

Name
SDA
SCL
VDD
VSS

Comments
Serial data, bidirectional
Serial clock, unidirectional input
Supply voltage
Ground14

23Figure 8. Pin assignment (transparent top view). Dashed lines are only visible if sensor is viewed frombelow. The die pad is not directly connected to any pin. Pin-1 is indicated by the cutout of the die padfrom the bottom side (see dashed lines) and the top side laser marking (dot in upper left corner).

6

Quality and Material Contents

Qualification of STS4x is performed based on the JEDEC JESD47 qualification test method (currently pending).
The device is fully RoHS and WEEE compliant, e.g. free of Pb, Cd, and Hg.

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7

Tape and Reel Packaging

All specifications for the tape and reel packaging can be found in
Figure 9. The reel diameter for the 10k packaging is 13 inches.

Figure 9. Tape and reel specifications including a depiction of two sensors in their corresponding
pockets. In this orientation, Pin 1 is in the upper right corner, as indicated by the dot on the sensor andin the drawing.

In contrast to other products from the SHT4x line, the STS4x features shortened reel numbers for efficiency,
as not all digits present for the SHT4x family (ZZZZZ) would be used for the STS4x family.
Kindly note the differences described below:
SHT4x:YYZZZZZSSSSSSSNNNNNN(YY: Year, SSSSSS: material number, NNNNNN: reel code)
STS4x:YYSSSSSSSNNNNNN(YY: Year, SSSSSS: material number, NNNNNN: reel code)www.sensirion.com / D1

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8

Nomenclature

Position

Value

Explanation

1

S

Sensirion

2T

Temperature

3

S

Sensor4

4

Fourth product generation

5

L
0
1

0.4°C T accuracy
0.2°C T accuracy
Improved 0.2°C T accuracy

6-

delimiter

7

A
B
C

I C interface with 0x44 address
I2C interface with 0x45 address
I2C interface with 0x46 address

8D

DFN package

91reserved

10

B

reserved

11-

delimiter

12

R

Tape on reel packaging

13

3

Packaging article contains 10’000 pieces

2

Table 7. STS4x product nomenclature.

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9

Ordering Information

Material Description

Material Number

Details

STS4L-AD1B-R3

3.001.160

base T accuracy, 0x44 I C addr.,
Lasermarking “A”

10’000STS4L-BD1B-R3

3.001.161

base T accuracy, 0x45 I2C addr.
Lasermarking “B”

10’000STS4L-CD1B-R3

3.001.162

base T accuracy, 0x46 I2C addr.
Lasermarking “C”

10’000STS40-AD1B-R3

3.000.781

intermediate T accuracy, 0x44 I2C addr.,
Lasermarking “A”

10’000STS40-BD1B-R3

3.000.782

intermediate T accuracy, 0x45 I2C addr.
Lasermarking “B”

10’000STS40-CD1B-R3

3.000.780

intermediate T accuracy, 0x46 I2C addr.
Lasermarking “C”

10’000tbd

best T accuracy, 0x44 I2C addr.,
Lasermarking “A”,
coming soon

10’000tbd

best T accuracy, 0x45 I2C addr.
Lasermarking “B”,
coming soon

10’000tbd

best T accuracy, 0x46 I2C addr.
Lasermarking “C”,
coming soon

10’000STS41-AD1B-R3

STS41-BD1B-R3

STS41-CD1B-R3

Quantity (pcs)2

Table 8. STS4x ordering options.

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10

Revision History

Date

VersionPage(s)ChangesNovember 2020

0.1

all

Initial release, preliminary version.

June 2021

0.2

1, 11

Updated ordering options.

February 2022

1

1, 7, 11, 12
9, 10
9
1

Updated ordering and I2C address options.
Updated laser marking description.
Corrected typo in package outline.
Added functional block diagram.

July 2022

1.1

12
12

Updated reel numbers and description.
Updated ordering numbers.

June 2023

1.2

1, 10, 132

Added laser marking I2C address indicator
Updated SnapEDA link

September 2023

2

1, 10

Rendering on page one and Fig 4. on page 10:
I2C address indicator position and size change

June 2024

3

all

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Important Notices
Warning, Personal Injury
Do not use this product as safety or emergency stop devices or in any other application where failure of the product could
result in personal injury. Do not use this product for applications other than its intended and authorized use. Before installing,
handling, using or servicing this product, please consult the data sheet and application notes. Failure to comply with these
instructions could result in death or serious injury.
If the Buyer shall purchase or use SENSIRION products for any unintended or unauthorized application, Buyer shall defend,
indemnify and hold harmless SENSIRION and its officers, employees, subsidiaries, affiliates and distributors against all claims, costs,
damages and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or deathassociated with such unintended or unauthorized use, even if SENSIRION shall be allegedly negligent with respect to the designor the manufacture of the product.
ESD Precautions
The inherent design of this component causes it to be sensitive to electrostatic discharge (ESD). To prevent ESD-induced damage
and/or degradation, take customary and statutory ESD precautions when handling this product. See application note “ESD, Latchup
and EMC” for more information.
Warranty
SENSIRION warrants solely to the original purchaser of this product for a period of 12 months (one year) from the date of delivery
that this product shall be of the quality, material and workmanship defined in SENSIRION’s published specifications of the product.
Within such period, if proven to be defective, SENSIRION shall repair and/or replace this product, in SENSIRION’s discretion, freeof charge to the Buyer, provided that:•
notice in writing describing the defects shall be given to SENSIRION within fourteen (14) days after their appearance;•such defects shall be found, to SENSIRION’s reasonable satisfaction, to have arisen from SENSIRION’s faulty design, material,
or workmanship;•
the defective product shall be returned to SENSIRION’s factory at the Buyer’s expense; and•the warranty period for any repaired or replaced product shall be limited to the unexpired portion of the original period.
This warranty does not apply to any equipment which has not been installed and used within the specifications recommended by
SENSIRION for the intended and proper use of the equipment. EXCEPT FOR THE WARRANTIES EXPRESSLY SET FORTH HEREIN,SENSIRION MAKES NO WARRANTIES, EITHER EXPRESS OR IMPLIED, WITH RESPECT TO THE PRODUCT. ANY AND ALL
WARRANTIES, INCLUDING WITHOUT LIMITATION, WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULARPURPOSE, ARE EXPRESSLY EXCLUDED AND DECLINED.
SENSIRION is only liable for defects of this product arising under the conditions of operation provided for in the data sheet andproper use of the goods. SENSIRION explicitly disclaims all warranties, express or implied, for any period during which the goods
are operated or stored not in accordance with the technical specifications.
SENSIRION does not assume any liability arising out of any application or use of any product or circuit and specifically disclaims
any and all liability, including without limitation consequential or incidental damages. All operating parameters, including without
limitation recommended parameters, must be validated for each customer’s applications by customer’s technical experts.
Recommended parameters can and do vary in different applications.
SENSIRION reserves the right, without further notice, (i) to change the product specifications and/or the information in thisdocument and (ii) to improve reliability, functions and design of this product.

Headquarters and Subsidiaries
Sensirion AG
Laubisruetistr. 50
CH-8712 Staefa ZH
Switzerland

Sensirion Inc., USA
phone: +1 312 690 5858
info-us@sensirion.com
www.sensirion.com

Sensirion Korea Co. Ltd.
phone: +82 31 337 7700~3
info-kr@sensirion.com
www.sensirion.com/kr

phone: +41 44 306 40 00
fax:+41 44 306 40 30
info@sensirion.com
www.sensirion.com

Sensirion Japan Co. Ltd.
phone: +81 45 270 4506
info-jp@sensirion.com
www.sensirion.com/jp

Sensirion China Co. Ltd.
phone: +86 755 8252 1501
info-cn@sensirion.com
www.sensirion.com/cn

Sensirion Taiwan Co. Ltd
phone: +886 2 2218-6779
info@sensirion.com
www.sensirion.com

To find your local representative, please visit
www.sensirion.com/distributors

Copyright © 2024, by SENSIRION. CMOSens® is a trademark of Sensirion. All rights reserved
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