HTS221
Capacitive digital sensor for relative humidity and temperature
Datasheet - production data
Applications
Air conditioning, heating and ventilation
Air humidifiers
Refrigerators
Wearable devices
Smart home automation
Industrial automation
HLGA-6L
(2 x 2 x 0.9 mm)
Respiratory equipment
Asset and goods tracking
Description
Features
0 to 100% relative humidity range
Supply voltage: 1.7 to 3.6 V
Low power consumption: 2 μA @ 1 Hz ODR
Selectable ODR from 1 Hz to 12.5 Hz
High rH sensitivity: 0.004% rH/LSB
Humidity accuracy: ± 3.5% rH, 20 to +80% rH
Temperature accuracy: ± 0.5 °C,15 to +40 °C
Embedded 16-bit ADC
16-bit humidity and temperature output data
SPI and I²C interfaces
The HTS221 is an ultra-compact sensor for
relative humidity and temperature. It includes a
sensing element and a mixed signal ASIC to
provide the measurement information through
digital serial interfaces.
The sensing element consists of a polymer
dielectric planar capacitor structure capable of
detecting relative humidity variations and is
manufactured using a dedicated ST process.
The HTS221 is available in a small top-holed cap
land grid array (HLGA) package guaranteed to
operate over a temperature range from -40 °C to
+120 °C.
Factory calibrated
Tiny 2 x 2 x 0.9 mm package
ECOPACK® compliant
Table 1. Device summary
Order code
Temperature range [°C]
Package
Packing
HTS221TR
-40 to +120
HLGA-6L
Tape and reel
August 2016
This is information on a product in full production.
DocID026333 Rev 4
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www.st.com
Contents
HTS221
Contents
1
HTS221 block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1
2
Sensor parameters and electrical specifications . . . . . . . . . . . . . . . . . . 8
2.1
2.2
3
4
Communication interface characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1.1
SPI - serial peripheral interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1.2
I²C - control interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1
IC interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.2
Factory calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Application hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.1
5
Pin information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Soldering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Digital interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.1
I2C serial interface (CS = HIGH or unconnected CS) . . . . . . . . . . . . . . . 14
5.1.1
5.2
I²C operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
SPI bus interface (CS = LOW) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5.2.1
SPI write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
5.2.2
SPI read . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
6
Register mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
7
Register description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2/33
7.1
WHO_AM_I (0Fh) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
7.2
AV_CONF (10h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
7.3
CTRL_REG1 (20h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
7.4
CTRL_REG2 (21h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
7.5
CTRL_REG3 (22h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
7.6
STATUS_REG (27h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
7.7
HUMIDITY_OUT_L (28h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
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HTS221
Contents
7.8
HUMIDITY_OUT_H (29h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
7.9
TEMP_OUT_L (2Ah) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
7.10
TEMP_OUT_H (2Bh) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
8
Humidity and temperature data conversion . . . . . . . . . . . . . . . . . . . . . 26
9
Package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
10
9.1
HLGA-6L package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
9.2
HLGA-6L packing information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
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33
List of tables
HTS221
List of tables
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
Table 7.
Table 8.
Table 9.
Table 10.
Table 11.
Table 12.
Table 13.
Table 14.
Table 15.
Table 16.
Table 17.
Table 18.
Table 19.
Table 20.
Table 21.
Table 22.
4/33
Device summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Humidity and temperature parameter specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
SPI slave timing values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
I²C slave timing values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Serial interface pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Serial interface pin description I2C terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
SAD + Read/Write patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Transfer when master is writing one byte to slave . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Transfer when master is writing multiple bytes to slave . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Transfer when master is receiving (reading) one byte of data from slave . . . . . . . . . . . . . 16
Transfer when master is receiving (reading) multiple bytes of data from slave . . . . . . . . . 16
Register address map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Humidity and temperature average configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Output data rate configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Typical power consumption with heater ON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Decoding the coefficients in the sensor Flash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
HLGA-6L (2 x 2 x 0.9 mm) mechanical data outer dimensions . . . . . . . . . . . . . . . . . . . . . 29
Reel dimensions for carrier tape of HLGA-6L package . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Document revision history. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
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HTS221
List of figures
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
HTS221 block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Pin configuration (bottom view). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
SPI slave timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
HTS221 electrical connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
SPI write protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Multiple byte SPI write protocol (2-byte example). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
SPI read protocol in 3-wires mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Step 1: Linear interpolation to convert LSB to °C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Step 2: Linear interpolation to convert LSB to rH% . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
HLGA-6L (2 x 2 x 0.9 mm) package outline and mechanical data . . . . . . . . . . . . . . . . . . . 29
Carrier tape information for HLGA-6L package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
HLGA-6L package orientation in carrier tape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Reel information for carrier tape of HLGA-6L package. . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
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33
HTS221 block diagram
1
HTS221
HTS221 block diagram
Figure 1. HTS221 block diagram
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Pin information
6/33
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Figure 2. Pin configuration (bottom view)
DocID026333 Rev 4
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HTS221
HTS221 block diagram
Table 2. Pin description
Pin n°
Name
1
VDD
2
SCL/SPC
3
DRDY
4
SDA/SDI/SDO
5
GND
6
SPI enable
Function
Power supply
I²C serial clock (SCL)
SPI serial port clock (SPC)
Data Ready output signal
I²C serial data (SDA)
3-wire SPI serial data input /output (SDI/SDO)
Ground
I²C/SPI mode selection
(1: SPI idle mode / I²C communication enabled;
0: SPI communication mode / I²C disabled)
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33
Sensor parameters and electrical specifications
2
HTS221
Sensor parameters and electrical specifications
Conditions at VDD = 2.5 V, T = 25 °C, unless otherwise noted.
Table 3. Humidity and temperature parameter specifications
Symbol
Parameter
Hop
Operating humidity range
Hbit
Humidity output data
Hs
Humidity sensitivity
Hacc
Hnoise
Hhys
Test condition
Humidity accuracy(2)
Min.
Typ.(1)
Max.
Unit
0
–
100
% rH
16
–
bit
0.004
%rH/LSB
256
LSB/%rH
20 to 80% rH
±3.5
0 to 100% rH
±5
Humidity noise(3)
0.03
RMS
±1
% rH
t @ 63%
10
s
20 to 80% rH
0.5
%rH/yr
Humidity hysteresis
time(4)
Hstep
Humidity response
Hdrift
Humidity long-term drift
Top
Operating temperature range
Tbit
Temperature output data
Ts
Temperature sensitivity
Tacc
Temperature accuracy
% rH
-40
–
120
°C
–
16
–
bit
0.016
°C/LSB
64
LSB/°C
15 to 40 °C
±0.5
0 to 60 °C
±1
Tnoise
Temperature noise(3)
Tstep
Temperature response time
t @ 63%
Tdrift
Temperature long-term drift
T = 0 to 80 °C
ODR
Humidity and temperature digital output
data rate
°C
0.007
RMS
15
s
0.05
°C/yr
1/7/12.
5
Hz
1. Typical specifications are not guaranteed
2. Accuracy in non condensing environment including hysteresis
3. Default value; noise value can be modified by AV_CONF (10h)
4. Valid at 25 °C and 1 m/s airflow
Table 4. Electrical characteristics
Symbol
VDD
IDD
IDDPDN
Parameter
Test condition
Supply voltage
Supply current
1.7
(2)
1 Hz, 25 °C, 2.5 V
Supply current in power-down mode
T = 25 °C
25 °C, 2.5 V
1. Typical specifications are not guaranteed
2. Refer to Table 16.
8/33
Min. Typ.(1)
DocID026333 Rev 4
–
Max.
Unit
3.6
V
2
–
0.5
μA
–
μA
HTS221
Sensor parameters and electrical specifications
2.1
Communication interface characteristics
2.1.1
SPI - serial peripheral interface
Subject to general operating conditions for VDD and TOP
Table 5. SPI slave timing values
Value (1)
Symbol
Parameter
Unit
Min.
tc(SPC)
SPI clock cycle
fc(SPC)
SPI clock frequency
tsu(CS)
CS setup time
6
th(CS)
CS hold time
8
tsu(SI)
SDI input setup time
5
th(SI)
SDI input hold time
15
tv(SO)
SDO valid output time
th(SO)
SDO output hold time
tdis(SO)
SDO output disable time
Max.
100
ns
10
MHz
ns
50
9
50
1. Values are guaranteed at 10 MHz clock frequency for SPI, based on characterization results, not tested in
production.
Figure 3. SPI slave timing diagram
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Note:
Measurement points are done at 0.2·VDD and 0.8·VDD, for both ports.
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33
Sensor parameters and electrical specifications
2.1.2
HTS221
I²C - control interface
Subject to general operating conditions for VDD and TOP.
Table 6. I²C slave timing values
Symbol
Parameter
I²C standard
mode (1)
(1)
Unit
Min.
Max.
Min.
Max.
0
100
0
400
SCL clock frequency
f(SCL)
I²C fast mode (1)
tw(SCLL)
SCL clock low time
4.7
1.3
tw(SCLH)
SCL clock high time
4.0
0.6
tsu(SDA)
SDA setup time
250
100
th(SDA)
SDA data hold time
0.01
3.45
μs
ns
0
0.9
(2)
300
300
tr(SDA) tr(SCL)
SDA and SCL rise time
1000
20 + 0.1Cb
tf(SDA) tf(SCL)
SDA and SCL fall time
300
20 + 0.1Cb (2)
th(ST)
START condition hold time
tsu(SR)
Repeated START condition setup time
tsu(SP)
STOP condition setup time
tw(SP:SR)
Bus free time between STOP and
START condition
4
0.6
4.7
0.6
4
0.6
4.7
1.3
kHz
μs
ns
μs
1. Data based on standard I²C protocol requirement, not tested in production.
2. Cb = total capacitance of one bus line, in pF.
Figure 4. I²C slave timing diagram
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10/33
WZ 6&//
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Measurement points are done at 0.2·VDD and 0.8·VDD, for both ports.
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HTS221
2.2
Sensor parameters and electrical specifications
Absolute maximum ratings
Stress above those listed as “Absolute maximum ratings” may cause permanent damage to
the device. This is a stress rating only and functional operation of the device under these
conditions is not implied. Exposure to maximum rating conditions for extended periods may
affect device reliability.
Table 7. Absolute maximum ratings
Symbol
Note:
Ratings
VDD
Supply voltage
VIN
Input voltage on any control pin
TSTG
Storage temperature range
ESD
Electrostatic discharge protection
Maximum value
Unit
-0.3 to 4.8
V
-0.3 to VDD +0.3
V
-40 to +125
°C
2 (HBM)
kV
Supply voltage on any pin should never exceed 4.8 V.
This device is sensitive to mechanical shock, improper handling can cause
permanent damage to the part.
This device is sensitive to electrostatic discharge (ESD), improper handling can
cause permanent damage to the part.
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33
Functionality
3
HTS221
Functionality
The HTS221 is a digital humidity and temperature sensor, packaged in an HLGA holed
package.The device includes the sensing element and an IC (integrated circuit) interface
able to take information from the sensing element and provide a digital signal to the
application, communicating through I²C/SPI interfaces with the host controller.
3.1
IC interface
The complete measurement chain consists of a low-noise capacitive amplifier, which
converts the capacitive imbalance of the humidity sensor into an analog voltage signal, and
an analog-to-digital converter is used to generate the digital information.
The converter is coupled with a dedicated hardware (HW) averaging filter to remove the
high-frequency component and reduce the serial interface traffic.
The relative humidity and temperature data can be accessed through an I²C/SPI interface,
making the device particularly suitable for direct interfacing with a microcontroller.
3.2
Factory calibration
The IC (integrated circuit) interface is factory calibrated and the coefficients required to
convert the ADC 16-bit values into rH% or degrees Celsius can be read through the internal
registers of the sensor. Further calibration by the user is not required.
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HTS221
4
Application hints
Application hints
Figure 5. HTS221 electrical connections
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The device is supplied through the VDD line. The power supply decoupling capacitor (100 nF
ceramic) should be placed as near as possible to the supply pad of the device (common
design practice).
The functionality of the device and the measured data outputs are selectable and accessible
through the I²C/SPI interfaces. To select the I²C interface, the CS line must be tied high (i.e.
connected to VDD) or left unconnected (thanks to the internal pull-up).
All the voltage and ground supplies must be present at the same time to have proper
behavior of the IC (refer to Figure 5).
4.1
Soldering information
The HLGA package is compliant with the ECOPACK® standard and it is qualified for
soldering heat resistance according to JEDEC J-STD-020. After soldering, the accuracy
specification of the sensor can be guaranteed after re-hydration of the sensor element in a
stabilized environment (25 °C / 55% rH) for 3 days or at 70% rH for 12 h. Otherwise the
sensor may read an offset that slowly disappears if exposed to ambient conditions.
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33
Digital interfaces
5
HTS221
Digital interfaces
The registers embedded in the HTS221 may be accessed through both the I²C and SPI
3-wire serial interfaces.
The serial interfaces are mapped onto the same pins.To select the I²C interface, the CS line
must be tied high (i.e. connected to VDD) or unconnected (internal pull-up); to select the SPI
interface, the CS line must be tied low (i.e. connected to GND).
Table 8. Serial interface pin description
Pin name
CS
SCL/SPC
SDA/SDI/SDO
5.1
Pin description
I²C/SPI mode selection
1: SPI idle mode / I²C communication enabled
0: SPI communication mode / I²C disabled)
I²C serial clock (SCL)
SPI serial clock (SPC)
I²C serial data (SDA)
3-wire SPI serial data input /output (SDI/SDO)
I2C serial interface (CS = HIGH or unconnected CS)
The HTS221 I²C is a bus slave. The I²C is employed to write data into registers whose
content can also be read back.
The relevant I²C terminology is provided in Table 9.
Table 9. I2C terminology
Term
Transmitter
Receiver
Description
The device which sends data to the bus
The device which receives data from the bus
Master
The device which initiates a transfer, generates clock signals and terminates a
transfer
Slave
The device addressed by the master
There are two signals associated with the I²C bus: the serial clock line (SCL) and the serial
data line (SDA). The latter is a bi-directional line used for sending and receiving the data
to/from the interface. Both lines must be connected to VDD through pull-up resistors.
The I²C interface is compliant with fast mode (400 kHz) I²C standards as well as with normal
mode.
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HTS221
5.1.1
Digital interfaces
I²C operation
The transaction on the bus is started through a START (ST) signal. A start condition is
defined as a HIGH to LOW transition on the data line while the SCL line is held HIGH. After
this has been transmitted by the master, the bus is considered busy. The next byte of data
transmitted after the start condition contains the address of the slave in the first 7 bits and
the eighth bit tells whether the master is receiving data from the slave or transmitting data to
the slave. When an address is sent, each device in the system compares the first seven bits
after a start condition with its address. If they match, the device considers itself addressed
by the master.
The 8-bit slave address (SAD) associated to the HTS221 humidity sensor is BEh (write) and
BFh (read).
Data transfer with acknowledge is mandatory. The transmitter must release the SDA line
during the acknowledge pulse. The receiver must then pull the data line LOW so that it
remains stable low during the HIGH period of the acknowledge clock pulse. A receiver
which has been addressed is obliged to generate an acknowledge after each byte of data
received.
The I²C embedded in the HTS221 behaves like a slave device and the following protocol
must be adhered to. After the start condition (ST) a slave address is sent, once a slave
acknowledge (SAK) has been returned, an 8-bit sub-address (SUB) will be transmitted: the
7 LSB represents the actual register address while the MSB enables address autoincrement. If the MSB of the SUB field is ‘1’, the SUB (register address) will be automatically
increased to allow multiple data read/write.
The slave address is completed with a Read/Write bit. If the bit was ‘1’ (Read), a repeated
START (SR) condition must be issued after the two sub-address bytes; if the bit is ‘0’ (Write)
the master will transmit to the slave with direction unchanged. Table 10 explains how the
SAD + read/write bit pattern is composed, listing all the possible configurations.
Table 10. SAD + Read/Write patterns
Command
SAD[6:0]
R/W
SAD+R/W
Read
1011111
1
10111111 (BFh)
Write
1011111
0
10111110 (BEh)
Table 11. Transfer when master is writing one byte to slave
Master
ST
SAD + W
Slave
SUB
SAK
DATA
SP
SAK
SAK
Table 12. Transfer when master is writing multiple bytes to slave
Master
Slave
ST
SAD + W
SUB
SAK
DATA
SAK
DocID026333 Rev 4
DATA
SAK
SP
SAK
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33
Digital interfaces
HTS221
Table 13. Transfer when master is receiving (reading) one byte of data from slave
Master
ST
SAD + W
Slave
SUB
SAK
SR
SAD + R
SAK
NMAK
SAK
SP
DATA
Table 14. Transfer when master is receiving (reading) multiple bytes of data from
slave
Master
Slave
ST
SAD+W
SUB
SAK
SR
SAD+R
SAK
MAK
SAK
DATA
MAK
DATA
NMAK
SP
DATA
Data are transmitted in byte format (DATA). Each data transfer contains 8 bits. The number
of bytes transferred per transfer is unlimited. Data is transferred with the most significant bit
(MSB) first. If a receiver can’t receive another complete byte of data until it has performed
some other functions, it can hold the clock line, SCL LOW to force the transmitter into a wait
state. Data transfer only continues when the receiver is ready for another byte and releases
the data line. If a slave receiver does not acknowledge the slave address (i.e. it is not able to
receive because it is performing some real-time function) the data line must be kept HIGH
by the slave. The master can then abort the transfer. A LOW to HIGH transition on the SDA
line while the SCL line is HIGH is defined as a STOP condition. Each data transfer must be
terminated by the generation of a STOP (SP) condition.
In order to read multiple bytes incrementing the register address, it is necessary to assert
the most significant bit of the sub-address field. In other words, SUB(7) must be equal to 1
while SUB(6-0) represents the address of the first register to be read.
In the presented communication format MAK is master acknowledge and NMAK is no
master acknowledge.
I²C high speed HS-mode devices can transfer information at bit rates of up to 3.4 Mbit/s, yet
they remain fully downward compatible with fast or standard-mode (F/S-mode) devices for
bi-directional communication in a mixed-speed bus system. With the exception that
arbitration and clock synchronization is not performed during the HS-mode transfer, the
same serial bus protocol and data format is maintained as with the F/S-mode system.
HS-mode can only begin after the following conditions (all of which are in F/S-mode):
1. START condition (S)
2. 8-bit master code (00001XXX)
3. not-acknowledge bit (A)
This master code has two main functions:
It allows arbitration and synchronization between competing masters at F/S-mode speeds,
resulting in one winning master.
It indicates the beginning of an HS-mode transfer. HS-mode master codes are reserved
8-bit codes, which are not used for slave addressing or other purposes.
The master code indicates to other devices that an HS-mode transfer is to begin and the
connected devices must meet the HS-mode specification. As no device is allowed to
acknowledge the master code, the master code is followed by a not-acknowledge (A). After
the not-acknowledge bit (A), and the SCLH line has been pulled up to a HIGH level, the
active master switches to HS-mode and enables (at time tH, see data transfer in HS mode)
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DocID026333 Rev 4
HTS221
Digital interfaces
the current-source pull-up circuit for the SCLH signal. As other devices can delay the serial
transfer before tH by stretching the LOW period of the SCLH signal, the active master will
enable its current-source pull-up circuit when all devices have released the SCLH line and
the SCLH signal has reached a HIGH level, thus speeding up the last part of the rise time of
the SCLH signal. The active master then sends a repeated START condition (Sr) followed
by a 7-bit slave address (or 10-bit slave address; see previous section) with a R/W bit
address, and receives an acknowledge bit (A) from the selected slave.
After a repeated START condition and after each acknowledge bit (A) or not-acknowledge
bit (A), the active master disables its current-source pull-up circuit. This enables other
devices to delay the serial transfer by stretching the LOW period of the SCLH signal. The
active master re-enables its current-source pull-up circuit again when all devices have
released and the SCLH signal reaches a HIGH level, and so speeds up the last part of the
SCLH signal’s rise time. Data transfer continues in HS-mode after the next repeated START
(Sr), and only switches back to F/S-mode after a STOP condition (P). To reduce the
overhead of the master code, it’s possible that a master links a number of HS-mode
transfers, separated by repeated START conditions (Sr).
5.2
SPI bus interface (CS = LOW)
The HTS221 SPI is a slave bus that can operate in 0 and 3 SPI modes. The SPI allows
writing to and reading from the registers of the device. The serial interface interacts with the
application through 3 wires: CS, SPC, SDI/SDO.
CS is the serial port enable and is controlled by the SPI master. It goes low at the start of the
transmission and goes back high at the end. SCL is the serial port clock and it is controlled
by the SPI master. It is stopped high when CS is high (no transmission). SDI/SDO is the
serial port data input and output. This line is driven at the falling edge of SCL and should be
captured at the rising edge of SCL.
Both the read register and write register commands are completed in 16 clock pulses or in
multiples of 8 in case of multiple read/write bytes. Bit duration is the time between two falling
edges of SCL. The first bit (bit 0) starts at the first falling edge of SCL after the falling edge
of CS while the last bit (bit 15, bit 23,...) starts at the last falling edge of SCL just before the
rising edge of CS.
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33
Digital interfaces
5.2.1
HTS221
SPI write
Figure 6. SPI write protocol
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The SPI write command is performed with 16 clock pulses. A multiple byte write command
is performed by adding blocks of 8 clock pulses to the previous one.
bit 0: WRITE bit. The value is 0.
bit 1: MS bit. When 0, does not increment the address; when 1, increments the address in
multiple writes.
bit 2 -7: address AD(5:0). This is the address field of the indexed register.
bit 8-15: data DI(7:0) (write mode). This is the data that will be written inside the device
(MSB first).
bit 16-...: data DI(...-8). Further data in multiple byte writes.
Figure 7. Multiple byte SPI write protocol (2-byte example)
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18/33
DocID026333 Rev 4
*$066*
HTS221
5.2.2
Digital interfaces
SPI read
Figure 8. SPI read protocol in 3-wire mode
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The SPI read command is performed with 16 clock pulses:
bit 0: READ bit. The value is 1.
bit 1: MS bit. When 0, does not increment the address, when 1, increments the address in
multiple reads.
bit 2-7: address AD(5:0). This is the address field of the indexed register.
bit 8-15: data DO(7:0) (read mode). This is the data that is read from the device (MSB first).
A multiple read command is also available in 3-wire mode.
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33
Register mapping
6
HTS221
Register mapping
The table below provides a list of the 8-bit registers embedded in the device and the related
addresses.
Table 15. Register address map
Name
Type
Register address (hex)
Default (hex)
00-0E
Do not modify
Reserved
WHO_AM_I
R
0F
BC
AV_CONF
R/W
10
1B
11-1C
Do not modify
Reserved
CTRL_REG1
R/W
20
0
CTRL_REG2
R/W
21
0
CTRL_REG3
R/W
22
0
23-26
Do not modify
Reserved
STATUS_REG
R
27
0
HUMIDITY_OUT_L
R
28
Output
HUMIDITY_OUT_H
R
29
Output
TEMP_OUT_L
R
2A
Output
TEMP_OUT_H
R
2B
Output
2C-2F
Do not modify
30-3F
Do not modify
Reserved
CALIB_0..F
R/W
Registers marked as Reserved must not be changed. Writing to those registers may cause
permanent damage to the device.
The content of the CALIB_0..F registers that are loaded at power-on from device internal
non-volatile memory should never be modified.
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HTS221
7
Register description
Register description
The device contains a set of registers which are used to control its behavior and to retrieve
humidity and temperature data. The register address, made up of 7 bits, is used to identify
and to read/write the data, through the serial interfaces.
7.1
WHO_AM_I (0Fh)
Device identification
7
6
5
4
3
2
1
0
1
0
1
1
1
1
0
0
This read-only register contains the device identifier, set to BCh
7.2
AV_CONF (10h)
Humidity and temperature resolution mode
7
6
Reserved
5
4
3
2
1
0
AVGT2
AVGT1
AVGT0
AVGH2
AVGH1
AVGH0
To configure humidity/temperature average.
[7:6]
Reserved
[5:3]
AVGT2-0: To select the numbers of averaged temperature samples (2 - 256), see Table 16.
[2:0]
AVGH2-0: To select the numbers of averaged humidity samples (4 - 512), see Table 16.
Table 16. Humidity and temperature average configuration
AVGx2:0
Nr. internal average
Noise (RMS)
IDD 1 Hz
Temperature (AVGT)
Humidity (AVGH)
Temp (°C)
rH %
μA
000
2
4
0.08
0.4
0.80
001
4
8
0.05
0.3
1.05
010
8
16
0.04
0.2
1.40
16
32
0.03
0.15
2.10
100
32
64
0.02
0.1
3.43
101
64
128
0.015
0.07
6.15
110
128
256
0.01
0.05
11.60
111
256
512
0.007
0.03
22.50
(1)
011
1. Default configuration
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33
Register description
7.3
HTS221
CTRL_REG1 (20h)
Control register 1
7
6
5
PD
4
Reserved
[7]
[6:3]
[2]
[1:0]
3
2
1
0
BDU
ODR1
ODR0
PD: power-down control
(0: power-down mode; 1: active mode)
Reserved
BDU: block data update
(0: continuous update; 1: output registers not updated until MSB and LSB reading)
ODR1, ODR0: output data rate selection (see table 17)
The PD bit is used to turn on the device. The device is in power-down mode when PD = ‘0’
(default value after boot). The device is active when PD is set to ‘1’.
The BDU bit is used to inhibit the output register update between the reading of the upper
and lower register parts. In default mode (BDU = ‘0’), the lower and upper register parts are
updated continuously. If it is not certain whether the read will be faster than output data rate,
it is recommended to set the BDU bit to ‘1’. In this way, after the reading of the lower (upper)
register part, the content of that output register is not updated until the upper (lower) part is
read also.
This feature prevents the reading of LSB and MSB related to different samples.
The ODR1 and ODR0 bits permit changes to the output data rates of humidity and
temperature samples.The default value corresponds to a “one-shot” configuration for both
humidity and temperature output. ODR1 and ODR0 can be configured as described in
Table 17.
Table 17. Output data rate configuration
22/33
ODR1
ODR0
0
0
0
1
1 Hz
1 Hz
1
0
7 Hz
7 Hz
1
1
12.5 Hz
12.5 Hz
DocID026333 Rev 4
Humidity (Hz)
Temperature (Hz)
One-shot
HTS221
7.4
Register description
CTRL_REG2 (21h)
Control register 2
7
6
5
BOOT
4
3
2
Reserved
[7]
[6:2]
1
0
Heater
ONE_SHOT
BOOT: Reboot memory content
(0: normal mode; 1: reboot memory content)
Reserved
[1]
Heater
(0: heater disable; 1: heater enable)
[0]
One-shot enable
(0: waiting for start of conversion; 1: start for a new dataset)
The BOOT bit is used to refresh the content of the internal registers stored in the Flash
memory block. At device power-up, the content of the Flash memory block is transferred to
the internal registers related to trimming functions to permit good behavior of the device
itself. If, for any reason, the content of the trimming registers is modified, it is sufficient to
use this bit to restore the correct values. When the BOOT bit is set to ‘1’ the content of the
internal Flash is copied inside the corresponding internal registers and is used to calibrate
the device. These values are factory trimmed and are different for every device. They permit
good behavior of the device and normally they should not be changed. At the end of the
boot process, the BOOT bit is set again to ‘0’.
The ONE_SHOT bit is used to start a new conversion. In this situation a single acquisition of
temperature and humidity is started when the ONE_SHOT bit is set to ‘1’. At the end of
conversion the new data are available in the output registers, the STATUS_REG[0] and
STATUS_REG[1] bits are set to ‘1’ and the ONE_SHOT bit comes back to ‘0’ by hardware.
The Heater bit is used to control an internal heating element, that can effectively be used to
speed up the sensor recovery time in case of condensation. The heater can be operated
only by an external controller, which means that it has to be switched on/off directly by FW.
Humidity and temperature output should not be read during the heating cycle; valid data can
be read out once the heater has been turned off, after the completion of the heating cycle.
Typical power consumption related to VDD is described in Table 18.
Table 18. Typical power consumption with heater ON
VDD [V]
I [mA]
3.3
33
2.5
22
1.8
12
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33
Register description
7.5
HTS221
CTRL_REG3 (22h)
Control register 3
7
6
DRDY_H_L
PP_OD
5
4
3
Reserved
2
1
DRDY
0
Reserved
Control register for data ready output signal
[7]
DRDY_H_L: Data Ready output signal active high, low
(0: active high - default;1: active low)
[6]
PP_OD: Push-pull / Open Drain selection on pin 3 (DRDY)
(0: push-pull - default; 1: open drain)
[5:3]
[2]
[1:0]
Reserved
DRDY_EN: Data Ready enable
(0: Data Ready disabled - default;1: Data Ready signal available on pin 3)
Reserved
The DRDY_EN bit enables the DRDY signal on pin 3. Normally inactive, the DRDY output
signal becomes active on new data available: logical OR of the bits STATUS_REG[1] and
STATUS_REG[0] for humidity and temperature, respectively. The DRDY signal returns
inactive after both HUMIDITY_OUT_H and TEMP_OUT_H registers are read.
7.6
STATUS_REG (27h)
Status register
7
6
5
4
Reserved
3
2
1
0
H_DA
T_DA
Status register; the content of this register is updated every one-shot reading, and after
completion of every ODR cycle, regardless of the BDU value in CTRL_REG1.
[7:2]
Reserved
[1]
H_DA: Humidity data available.
(0: new data for humidity is not yet available; 1: new data for humidity is available)
[0]
T_DA: Temperature data available.
(0: new data for temperature is not yet available; 1: new data for temperature is available)
H_DA is set to 1 whenever a new humidity sample is available. H_DA is cleared anytime
HUMIDITY_OUT_H (29h) register is read.
T_DA is set to 1 whenever a new temperature sample is available. T_DA is cleared
anytime TEMP_OUT_H (2Bh) register is read.
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HTS221
7.7
Register description
HUMIDITY_OUT_L (28h)
Relative humidity data (LSB)
7
6
5
4
3
2
1
0
HOUT7
HOUT6
HOUT5
HOUT4
HOUT3
HOUT2
HOUT1
HOUT0
Humidity data (see HUMIDITY_OUT_H)
[7:0]
7.8
HOUT7 - HOUT0: Humidity data LSB
HUMIDITY_OUT_H (29h)
Relative humidity data (MSB)
15
14
13
12
11
10
9
8
HOUT15
HOUT14
HOUT13
HOUT12
HOUT11
HOUT10
HOUT9
HOUT8
Humidity data are expressed as HUMIDITY_OUT_H & HUMIDITY_OUT_L in 2’s
complement. Values exceeding the operating humidity range (see Table 3) must be clipped
by SW.
[7:0]
7.9
HOUT15 - HOUT8: Humidity data MSB
TEMP_OUT_L (2Ah)
Temperature data (LSB)
7
6
5
4
3
2
1
0
TOUT7
TOUT6
TOUT5
TOUT4
TOUT3
TOUT2
TOUT1
TOUT0
[7:0]
7.10
TOUT7 - TOUT0: Temperature data LSB (see TEMPERATURE_OUT_H)
TEMP_OUT_H (2Bh)
Temperature data (MSB)
15
14
13
12
11
10
9
8
TOUT15
TOUT14
TOUT13
TOUT12
TOUT11
TOUT10
TOUT9
TOUT8
[15:8]
TOUT15 - TOUT8: Temperature data MSB.
Temperature data are expressed as TEMP_OUT_H & TEMP_OUT_L as 2’s complement
numbers.
The relative humidity and temperature values must be computed by linear interpolation of
current registers with calibration registers, according to Table 19 and scaling as described in
Section 8.
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33
Humidity and temperature data conversion
8
HTS221
Humidity and temperature data conversion
The Registers in 30h..3Fh address range contain calibration coefficients. Every sensor
module has individual coefficients. Before the first calculation of temperature and humidity,
the master reads out the calibration coefficients.
Table 19. Decoding the coefficients in the sensor Flash
Addr
Variable
Format
b7
b6
b5
b4
b3
b2
b1
b0
H7
H6
H5
H4
H3
H2
H1
H0
H15
H14
H13
H12
H11
H10
H9
H8
T7
T6
T5
T4
T3
T2
T1
T0
T15
T14
T13
T12
T11
T10
T9
T8
Output registers
28
29
2A
2B
H_OUT
(s16)
T_OUT
(s16)
Calibration registers
30
H0_rH_x2
(u8)
H0.7
H0.6
H0.5
H0.4
H0.3
H0.2
H0.1
H0.1
31
H1_rH_x2
(u8)
H1.7
H1.6
H1.5
H1.4
H1.3
H1.2
H1.1
H1.0
32
T0_degC_x8
(u8)
T0.7
T0.6
T0.5
T0.4
T0.3
T0.2
T0.1
T0.0
33
T1_degC_x8
(u8)
T1.7
T1.6
T1.5
T1.4
T1.3
T1.2
T1.1
T1.0
34
Reserved
(u16)
35
T1/T0 msb
(u2),(u2)
T1.9
T1.8
T0.9
T0.8
H0_T0_OUT
(s16)
36
37
38
39
3A
3B
3C
3D
3E
3F
Reserved
7
6
5
4
3
2
1
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
15
14
13
12
11
10
9
8
Reserved
H1_T0_OUT
(s16)
T0_OUT
(s16)
T1_OUT
(s16)
(u8) is the unsigned 8-bit quantity, and (s16) the signed 16-bit quantity using 2’s
complement format. In the following example, the two steps required to calculate
temperature and relative humidity output values are described. The T0 and T1 calibration
temperature values are actually composed of 10 bits (unsigned), where the 2 MSB are in
reg 35h, and the 8 LSB are in regs 32h and 33h, respectively. T0 and T1 are the actual
calibration temperature values multiplied by 8.
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HTS221
Humidity and temperature data conversion
Step 1: Temperature conversion from ADC_OUT (LSB) to °C
Data to build the Temperature calibration curve are stored in device registers.
Linear interpolation (example)
Input temperature LSB (ADC)
Output temperature (°C)
T0_OUT = 300
(Msb T0_degC U T0_degC)_x8 = 80 °C => 80/8 =
10.0°C
T1_OUT = 500
(Msb T1_degC U T1_degC)_x8 = 160 °C => 160/8 =
20.0°C
Temperature conversion:
T_OUT = 400
T_degC_x8 =120 °C =>T_degC=120/8 = 15.0 °C
Figure 9. Step 1: Linear interpolation to convert LSB to °C
Conclusion: current temperature is 15 °C.
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Humidity and temperature data conversion
HTS221
Step 2: Humidity conversion from ADC_OUT (LSB) to rH %
Linear interpolation for relative Humidity (example)
Input: relative Humidity LSB (ADC)
Output: relative Humidity (% rH)
H0_T0_OUT = 0x4000
H0_rH_x2 = 40% rH => 40/2 = 20.0% rH
H1_T0_OUT = 0x6000
H1_rH_x2 = 80% rH => 80/2 = 40% rH
Humidity conversion:
H_OUT = 0x5000
H_rH_x2 = 60% [interp.] => 60/2 = 30.0% rH
Figure 10. Step 2: Linear interpolation to convert LSB to rH%
5+
+ B 5 + FD O
+ B 5 + P H D V
+ B 5 + FD O
Conclusion: current relative humidity value is 30%.
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+ B 7 B 2 8 7 FDO
+ B 7 B 2 8 7 PHDV
+ B 7 B 2 8 7 FDO
/ 6 % $ ' &
HTS221
9
Package information
Package information
In order to meet environmental requirements, ST offers these devices in different grades of
ECOPACK® packages, depending on their level of environmental compliance. ECOPACK®
specifications, grade definitions and product status are available at: www.st.com.
ECOPACK is an ST trademark.
HLGA-6L package information
Figure 11. HLGA-6L (2 x 2 x 0.9 mm) package outline and mechanical data
/DQG6L]H
+
%277209,(:
:
3LQLQGLFDWRU
7239,(:
/
9.1
B$
Table 20. HLGA-6L (2 x 2 x 0.9 mm) outer dimensions
Item
Dimension [mm]
Tolerance [mm]
Length [L]
2
0.1
Width [W]
2
0.1
Height [H]
0.9
0.1
Land size
0.30 x 0.35
± 0.05
Dimensions are in millimeters unless otherwise specified.
General tolerance is ± 0.1 mm unless otherwise specified.
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33
Package information
9.2
HTS221
HLGA-6L packing information
Figure 12. Carrier tape information for HLGA-6L package
Figure 13. HLGA-6L package orientation in carrier tape
30/33
DocID026333 Rev 4
HTS221
Package information
Figure 14. Reel information for carrier tape of HLGA-6L package
7
PPPLQ
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PPPLQZLGWK
Table 21. Reel dimensions for carrier tape of HLGA-6L package
Reel dimensions (mm)
A (max)
330
B (min)
1.5
C
13 ±0.25
D (min)
20.2
N (min)
60
G
12.4 +2/-0
T (max)
18.4
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Revision history
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Revision history
Table 22. Document revision history
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Date
Revision
Changes
15-May-2014
1
Initial release
06-Apr-2015
2
Document reformatted to improve readability
Updated: Applications and Device summary in cover
page, Table 2: Pin description, Section 4: Application
hints, Section 5.1: I2C serial interface (CS = HIGH or
unconnected CS), Section 7: Register description and
Section 8: Humidity and temperature data conversion.
21-Oct-2015
3
Document update to align device performance
confirmed in volume production
30-Aug-2016
4
Minor textual changes
Added Section 9.2: HLGA-6L packing information
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