SENSIRION STS32-DIS User manual

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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
1 Sensor Performance..............................................................................................................................................4
1.1 Temperature.....................................................................................................................................................4
1.2 ISO17025 certification with 3-point calibration data.............................................................................5
2 Electrical Specifications........................................................................................................................................6
2.1 Electrical Characteristics..............................................................................................................................6
2.2 Timings...............................................................................................................................................................7
2.3 Absolute Maximum Ratings.........................................................................................................................7
3 Pin Assignment........................................................................................................................................................8
3.1 Power Pins (VDD, VSS) ...............................................................................................................................8
3.2 Serial Clock and Serial Data (SCL, SDA)...............................................................................................8
3.3 Die Pad (center pad)......................................................................................................................................9
3.4 ADDR Pin..........................................................................................................................................................9
3.5 ALERT Pin........................................................................................................................................................9
3.6 nRESET Pin .....................................................................................................................................................9
4 Operation and Communication.........................................................................................................................10
4.1 Power-Up and Communication Start......................................................................................................10
4.2 Starting a Measurement.............................................................................................................................10
4.3 Measurement Commands for Single Shot Data Acquisition...........................................................10
4.4 Readout of Measurement Results for Single Shot Method.............................................................11
4.5 Measurement Commands for Periodic Data Acquisition Mode......................................................11
4.6 Readout of Measurement Results for Periodic Mode........................................................................12
4.7 Break command/ Stop Periodic Data Acquisition Mode...................................................................13
4.8 Reset.................................................................................................................................................................13
4.9 Heater...............................................................................................................................................................14
4.10 Status Register............................................................................................................................................15
4.11 Serial Number..............................................................................................................................................15
4.12 Checksum Calculation..............................................................................................................................17
4.13 Conversion Signal Output........................................................................................................................17
4.14 Communication Timing.............................................................................................................................18
5 Packaging................................................................................................................................................................19
5.1 Traceabilty.......................................................................................................................................................19
5.2 Package Outline............................................................................................................................................19
5.3 Land Pattern...................................................................................................................................................20
6 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

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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%
>2
s
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.
1
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.
2
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
3
. 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.
3
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
V
Power-
up/down level
VPOR
1.8
2.1
2.15
V
Slew rate
change of the
supply voltage
VDD,slew
-
-
20
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)
-
45
-
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
mA
See also section
3.5
Heater power
PHeater
Heater running
3.6
-
33
mW
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
ms
Time between VDD
reaching VPOR and sensor
entering idle state
Soft reset time
tSR
After soft reset
-
-
1
ms
Time between ACK of soft
reset command and
sensor entering idle state.
Measurement
duration
tMEAS,l
Low repeatability
-
2.5
4.5
ms
The three repeatability
modes differ with respect
to measurement duration,
noise level and energy
consumption
tMEAS,m
Med. repeatability
-
4.5
6.5
ms
tMEAS,h
High repeatability
-
12.5
15.5
ms
Duration of reset
pulse
tRESETN
1
-
-
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.
4
The recommended storage temperature range is 10-50 °C. Please consult the document “SHTxx Handling Instructions” [4] for more information.
5
According to ANSI/ESDA/JEDEC JS-001-2014; AEC-Q100-002.
6
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.
Pin
Name
Comments
1
SDA
Serial data; input / output
2
ADDR
Address pin; input; connect to either logic high or low, do not leave
floating
3
ALERT
Indicates alarm condition; output; must be left floating if unused
4
SCL
Serial clock; input / output
5
VDD
Supply voltage; input
6
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.
7
R
No electrical function; to be connected to VSS
8
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
7
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.
1
2
3
45
8
7
6

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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
RR
PP
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.