SENSIRION STS32-DIS Manuale utente

www.sensirion.com / D1 Version 3 –December 2022 1/24

STS32/33-DIS

3th Generation, High-Reliability, Certified

Digital Temperature Sensor

Features

•Accuracy ±0.4 °C

•VDD = 2.15 V … 5.5 V

•Low drift, <0.01 °C per year

•Sensor-specific calibration certificate acc. to

ISO 17025:2017, 3-point temp. calibration

•Operating range: −40…125 °C

•True NIST-traceability, unique serial number

•JEDEC JESD47 qualification

•I2C FM, CRC checksum, multip. I2C addr.

•Tiny 8-pin DFN package with ALERT pin

General Description

The STS32/33-DIS are Sensirion’s new low-drift digital calibrated and ISO17025 certified

temperature sensors. Both rely on the industry proven CMOSens® technology, enabling

increased computational power, reliability and improved accuracy specifications compared to

its predecessors. Itsfunctionality includes enhanced signal processing, two distinctive and user

selectable I2C addresses and communication speeds of up to 1 MHz. The DFN package has

a footprint of 2.5 x 2.5 mm2while keeping a height of 0.9 mm. Every STS32 or STS33 is

identified by its unique serial number and is supplied with an ISO17025-accredited calibration

certificate. The calibration certificate comprises three temperatures, −30 °C, 5 °C, and 70 °C.

In terms of communication, electrical specifications, and footprint, the SHT33-DIS is fully identical

with the STS3x-DIS.

Device Overview

Functional Block Diagram

Products

Details

STS32-DIS

ISO17025 3-point calibration certificate

accuracy profile 1

STS33-DIS

ISO17025 3-point calibration certificate

accuracy profile 2

Full product list on page 22

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Contents 
Features........................................................................................................................................................................1 
General Description...................................................................................................................................................1 
Device Overview.........................................................................................................................................................1 
Functional Block Diagram........................................................................................................................................1 
Contents........................................................................................................................................................................2 
Sensor Performance..............................................................................................................................................4 
1 Temperature.....................................................................................................................................................4 
2 ISO17025 certification with 3-point calibration data.............................................................................5 
Electrical Specifications........................................................................................................................................6 
1 Electrical Characteristics..............................................................................................................................6 
2 Timings...............................................................................................................................................................7 
3 Absolute Maximum Ratings.........................................................................................................................7 
Pin Assignment........................................................................................................................................................8 
1 Power Pins (VDD, VSS) ...............................................................................................................................8 
2 Serial Clock and Serial Data (SCL, SDA)...............................................................................................8 
3 Die Pad (center pad)......................................................................................................................................9 
4 ADDR Pin..........................................................................................................................................................9 
5 ALERT Pin........................................................................................................................................................9 
6 nRESET Pin .....................................................................................................................................................9 
Operation and Communication.........................................................................................................................10 
1 Power-Up and Communication Start......................................................................................................10 
2 Starting a Measurement.............................................................................................................................10 
3 Measurement Commands for Single Shot Data Acquisition...........................................................10 
4 Readout of Measurement Results for Single Shot Method.............................................................11 
5 Measurement Commands for Periodic Data Acquisition Mode......................................................11 
6 Readout of Measurement Results for Periodic Mode........................................................................12 
7 Break command/ Stop Periodic Data Acquisition Mode...................................................................13 
8 Reset.................................................................................................................................................................13 
9 Heater...............................................................................................................................................................14 
10 Status Register............................................................................................................................................15 
11 Serial Number..............................................................................................................................................15 
12 Checksum Calculation..............................................................................................................................17 
13 Conversion Signal Output........................................................................................................................17 
14 Communication Timing.............................................................................................................................18 
Packaging................................................................................................................................................................19 
1 Traceabilty.......................................................................................................................................................19 
2 Package Outline............................................................................................................................................19 
3 Land Pattern...................................................................................................................................................20 
Shipping Package.................................................................................................................................................21 

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7 Quality and Material Contents...........................................................................................................................21

8 Product Nomenclature.........................................................................................................................................22

9 Ordering Information............................................................................................................................................22

10 Bibliography..........................................................................................................................................................22

11 Revision History..................................................................................................................................................23

www.sensirion.com / D1 Version 3 –December 2022 4/24

1 Sensor Performance

Every STS33/32 is individually tested and calibrated and is identifiable by its unique serial number

(see section 4.11 for details on the serial number). For the calibration, Sensirion uses transfer

standards, which are subject to a scheduled calibration procedure. The calibration of the reference,

used for the calibration of the transfer standards, is NIST traceable through an ISO/IEC 17025

accredited laboratory.

1.1 Temperature

Parameter

Conditions

Value

Units

STS32 Accuracy

max. 0°C to 65°C

0.4

°C

max.

See Figure 1

STS33 T Accuracy

max. −30°C to 70°C

0.48

°C

max.

See Figure 1

Repeatability1

high

0.04

°C

medium

0.08

°C

low

0.15

°C

Resolution

0.01

°C

Specified range

–40 to +125

°C

Response time2

63%

Long-term drift

typ.

<0.01

°C/y

Table 1. General temperature sensor specifications.

Figure 1. Maximal Temperature accuracy of the STS32 (left) and STS33 (right), respectively. The green lines

represent the calibration points for ISO-17025 certification.

The stated repeatability is 3 times the standard deviation (3σ) of multiple consecutive measurements at the stated repeatability and at constant ambient conditions.

It is a measure for the noise on the physical sensor output.

Temperature response time depends on heat conductivity of sensor substrate and design-in of sensor in application. [2]

±0.0

±0.5

±1.0

±1.5

-40 -20 0 20 40 60 80 100 120

Temperature (°C)

STS32

maximal tolerance

DT (°C)

±0.0

±0.5

±1.0

±1.5

-40 -20 0 20 40 60 80 100 120

Temperature (°C)

STS33

maximal tolerance

DT (°C)

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1.2 ISO17025 certification with 3-point calibration data

All STS32 and STS33 can be uniquely identified by their serial number (read out command see

paragraph 4.11). For each sensor an individual 3-point calibration is performed, accredited to

ISO/IEC 17025:2017. The accreditation is performed and granted by the Swiss Accreditation

Service (SAS), a public institution of the Swiss Government. The accreditation is documented on

the SAS website under the name SCS 0158 and can be downloaded from this link

. The three

calibration temperatures are T = −30 °C, T = 5 °C, and T = 70 °C. Measurement uncertainties and

decision rules according to the SAS are given in Table 2.

Metrological traceability of the calibration is in accordance to ch. 6.5 of ISO/IEC 17025:2017,

encompassing but not limited to NIST traceability or traceability to other national metrology

institutes, according to the CIPM Mutual Recognition Arrangement (CIPM MRA).

Reel-wise calibration certificates and data for each STS32/33 can be downloaded through a web-

client and through an API from libellus.sensirion.com, which allows for efficient processing by

automated systems. For detailed documentation, kindly refer to the Libellus documentation.

Temperature

Expanded measurement uncertainty (k=2)*

Decision rule

−30 °C

0.40 °C

Shared risk (JCGM 106:2010, 8.2)

5 °C

0.20 °C

Shared risk (JCGM 106:2010, 8.2)

70 °C

0.20 °C

Shared risk (JCGM 106:2010, 8.2)

Table 2. Measurement uncertainty and decision rule for the accredited calibration according to Swiss

Accreditation Service (SAS). *Measurement uncertainties represent a confidence level of 95% using a

coverage factor of k = 2.

https://www.sas.admin.ch/sas/en/home/akkreditiertestellen/akkrstellensuchesas.exturl.html/aHR0cHM6Ly9zYXNkYi5jbGllbnRzLmxpaXAuY2gvc2VhcmNoLm/h0bWw=.html?csrfmiddlewa

retoken=2Ie2f1aOTUge9YQ3nuaL0ILEYS980ZMdH60doLdY8Nh1sHC3wpw3YvLLVBezmDRn&lang=en&search_term=0158&accreditation_type=2&submit=Start+search

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2 Electrical Specifications

2.1 Electrical Characteristics

Parameter

Symbol

Condition

Min.

Typ.

Max.

Units

Comments

Supply

voltage

VDD

2.15

3.3

5.5

Power-

up/down level

VPOR

1.8

2.1

2.15

Slew rate

change of the

supply voltage

VDD,slew

V/ms

Voltage changes

on the VDD line

between VDD,min

and VDD,max should

be slower than the

maximum slew

rate; faster slew

rates may lead to

reset;

Supply current

IDD

idle state

(single shot

mode)

T = 25 °C

0.2

2.0

µA

Current when

sensor is not

performing a

measurement

during single shot

mode

idle state

(single shot

mode)

T = 125 °C

6.0

idle state

(periodic data

acquisition

mode)

µA

Current when

sensor is not

performing a

measurement

during periodic data

acquisition mode

Measuring

600

1500

µA

Current

consumption while

sensor is

measuring

Average

1.7

µA

Current

consumption

(operation with one

measurement per

second at lowest

repeatability, single

shot mode)

Alert Output

driving

strength

IOH

1.5x

VDD

See also section

3.5

Heater power

PHeater

Heater running

3.6

Depending on the

supply voltage

Table 3. Electrical specifications, typical values are valid for T = 25 °C, min. & max. values for

T = −40 °C …125 °C.

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2.2 Timings

Parameter

Symbol

Conditions

Min.

Typ.

Max.

Units

Comments

Power-up time

tPU

After hard reset,

VDD ≥ VPOR

0.5

1.5

Time between VDD

reaching VPOR and sensor

entering idle state

Soft reset time

tSR

After soft reset

Time between ACK of soft

reset command and

sensor entering idle state.

Measurement

duration

tMEAS,l

Low repeatability

2.5

4.5

The three repeatability

modes differ with respect

to measurement duration,

noise level and energy

consumption

tMEAS,m

Med. repeatability

4.5

6.5

tMEAS,h

High repeatability

12.5

15.5

Duration of reset

pulse

tRESETN

µs

See section 4.8

Table 4. System timing specifications (valid from −40 °C to 125 °C and VDD,min … VDD, max ).

2.3 Absolute Maximum Ratings

Stress levels beyond those listed in Table 5 may cause permanent damage or affect the reliability

of the device. These are stress ratings only and functional operation of the device at these

conditions is not guaranteed. Ratings are only tested each at a time.

Parameter

Rating

Supply voltage VDD

−0.3 V to 6 V

Max. voltage on any pin

VSS −0.3 V … VDD +0.3 V

Input current on any pin

±100 mA

Operating temperature range

−40 °C … 125 °C

Storage temperature range4

−40 °C …150 °C

ESD HBM5

4 kV

ESD CDM6

750 V

Table 5. Absolute maximum ratings. Values may be only applied for short time periods.

The recommended storage temperature range is 10-50 °C. Please consult the document “SHTxx Handling Instructions” [4] for more information.

According to ANSI/ESDA/JEDEC JS-001-2014; AEC-Q100-002.

According to ANSI/ESD S5.3.1-2009; AEC-Q100-011.

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3 Pin Assignment

The STS32/33-DIS come in a tiny 8-pin DFN package –see Table 6.

Name

Comments

SDA

Serial data; input / output

ADDR

Address pin; input; connect to either logic high or low, do not leave

floating

ALERT

Indicates alarm condition; output; must be left floating if unused

SCL

Serial clock; input / output

VDD

Supply voltage; input

nRESET

Reset pin active low; input; if not used it is recommended to be left

floating; can be connected to VDD with a series resistor of R ≥2 kΩ.

No electrical function; to be connected to VSS

VSS

Ground

Table 6. STS32/33-DIS pin assignment (transparent top view). Dashed lines are only visible if viewed from

below. The die pad is internally connected to VSS.

3.1 Power Pins (VDD, VSS)

The electrical specifications of the STS32/33-DIS are shown Table 3. The power supply pins must

be decoupled with a 100 nF capacitor that shall be placed as close to the sensor as possible –see

Figure 2 for a typical application circuit.

3.2 Serial Clock and Serial Data (SCL, SDA)

SCL is used to synchronize the communication between microcontroller and the sensor. The clock

frequency can be freely chosen between 0 to 1000 kHz. Commands with clock stretching according

to I2C Standard

are supported. The SDA pin is used to transfer data to and from the sensor.

Communication with frequencies up to 400 kHz must meet the I2C Fast Mode7standard.

Communication frequencies up to 1 MHz are supported following the specifications given in Table

20. Both SCL and SDA lines are open-drain I/Os with diodes to VDD and VSS. They should be

connected to external pull-up resistors (please refer to Figure 2). A device on the I2C bus must

only drive a line to ground. The external pull-up resistors (e.g. Rp = 10 kΩ) are required to pull the

signal high. For dimensioning resistor sizes please takebus capacity andcommunicationfrequency

into account (see for example Section 7.1 of NXPs I2C Manual for more details [1]). It should be

noted that pull-up resistors may be included in I/O circuits of microcontrollers. It is recommended

to wire the sensor according to the application circuit as shown in Figure 2.

www.sensirion.com / D1 Version 3 –December 2022 9/24

Figure 2. Typical application circuit. Please note that the positioning of the pins does not reflect the position

on the real sensor. This is shown in Table 6.

3.3 Die Pad (center pad)

The die pad or center pad is visible from below and located in the center of the package. It is

electrically connected to VSS. Hence electrical considerations do not impose constraints on the

wiring of the die pad. However, due to mechanical reasons it is recommended to solder the center

pad to the PCB. For more information on design-in, please refer to the document “SHTxx_STSxx

Design Guide” [2].

3.4 ADDR Pin

Through the appropriate wiring of the ADDR pin the I2C address can be selected (see Table 7 for

the respective addresses). The ADDR pin can either be connected to logic high or logic low. The

address of the sensor can be changed dynamically during operation by switching the level on the

ADDR pin. The only constraint is that the level has to stay constant starting from the I2C start

condition until the communication is finished. This allows to connect more than two STS32/33-DIS

onto the same bus. The dynamical switching requires individual ADDR lines to the sensors. Please

note that the I2C address is represented through the 7 MSBs of the I2C read or write header. The

LSB switches between read or write header. The wiring for the default address is shown Table 7

and Figure 2. The ADDR pin must not be left floating. Please note that only the 7 MSBs of the I2C

Read/Write header constitute the I2C Address.

STS32/33-DIS

I2C Address in Hex. representation

Condition

I2C address A

0x4A (default)

ADDR (pin 2) connected to logic low

I2C address B

0x4B

ADDR (pin 2) connected to logic high

Table 7. I2C Device addresses

3.5 ALERT Pin

The alert pin may be used to connect to the interrupt pin of a microcontroller. The output of the pin

depends on the value of the temperature reading relative to programmable limits. Its function is

explained in a separate application note. If not used, this pin must be left floating. The pin switches

high when alert conditions are met. The maximum driving loads are listed in Table 3. Be aware

that self-heating might occur, depending on the amount of current that flows. Self-heating can be

prevented if the Alert Pin is only used to switch a transistor.

3.6 nRESET Pin

The nReset pin may be used to generate a reset of the sensor. A minimum pulse duration of 1 µs

is required to reliably trigger a reset of the sensor. Its function is explained in more detail in section

4. If not used it is recommended to leave the pin floating or to connect it to VDD with a series

VDD

100nF

ADDR(2)

ALERT(3)

die

pad R(7)

SDA(1)

SCL(4)

VDD(5)

VSS(8)

nRESET(6)

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resistor of R≥2 kΩ. However, the nRESET pin is internally connectedto VDD with a pull up resistor

of R = 50 kΩ (typ.).

4 Operation and Communication

The STS32/33-DIS supports I2C fast mode (and frequencies up to 1000 kHz). Clock stretching can

be enabled and disabled through the appropriate user command. For detailed information on the

I2C protocol, refer to NXP I2C-bus specification [1]. After sending a command to the sensor a

minimal waiting time of 1 ms is needed before another command can be received by the sensor.

All STS32/33-DIS commands and data are mapped to a 16-bit address space. Additionally, data

and commands are protected with a CRC checksum. This increases communication reliability. The

16 bits commands to the sensor already include a 3 bit CRC checksum. Data sent from and

received by the sensor is always succeeded by an 8 bit CRC. In write direction it is mandatory to

transmit the checksum, since the STS32/33-DIS only accepts data if it is followed by the correct

checksum. In read direction it is left to the master to read and process the checksum.

4.1 Power-Up and Communication Start

The sensor starts powering-up after reaching the power-up threshold voltage VPOR specified in

Table 3. After reaching this threshold voltage the sensor needs the time tPU to enter idle state. Once

the idle state is entered it is ready to receive commands from the master (microcontroller). Each

transmission sequence begins with a START condition (S) and ends with a STOP condition (P) as

described in the I2C-bus specification. Whenever the sensor is powered up, but not performing a

measurement or communicating, it automatically enters idle state for energy saving. This idle state

cannot be controlled by the user.

4.2 Starting a Measurement

A measurement communication sequence consists of a START condition, the I2C write header (7-

bit I2C device address plus 0 as the write bit) and a 16-bit measurement command. The proper

reception of each byte is indicated by the sensor. It pulls the SDA pin low (ACK bit) after the falling

edge of the 8th SCL clock to indicate the reception. A complete measurement cycle is depicted in

Table 8. With the acknowledgement of the measurement command, the STS32/33-DIS starts

measuring the temperature.

4.3 Measurement Commands for Single Shot Data Acquisition

In this mode one issued measurement command triggers the acquisition of a 16 bit temperature

value. During transmission that value is always followed by a CRC checksum, see section 4.4. In

single shot mode different measurement commands can be selected. The 16 bit commands are

shown in Table 8. They differ with respect to repeatability (low, medium and high) and clock

stretching (enabled or disabled). The repeatability setting influences the measurement duration

and thus the overall energy consumption of the sensor. This is explained in section 2.2.

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