TE HTU20D Instantaneous desaturation after long periods in saturation phase Datasheet

HTU20D(F) RH/T SENSOR IC
Digital Relative Humidity sensor with
Temperature output
SPECIFICATIONS






FEATURES




Full
interchangeability
with
no
calibration
required
in
standard
conditions
Instantaneous desaturation after long
periods in saturation phase
Compatible with automatized assembly
processes, including Pb free and reflow
processes
Individual marking for compliance to
stringent
traceability
requirements
APPLICATIONS





Home Appliance
Medical
Printers
Humidifier
Multimedia: Smartphone, Tablet, …
DFN type package
Relative Humidity and Temperature Digital Output, I²C
interface
Fully calibrated
Lead free sensor, reflow solderable
Low power consumption
Fast response time
HTU20D(F), is a new digital humidity sensor with temperature
output of MEAS. Setting new standards in terms of size and
intelligence, it is embedded in a reflow solderable Dual Flat No
leads (DFN) package with a small 3 x 3 x 0.9 mm foot print. This
sensor provides calibrated, linearized signals in digital, I²C
format.
HTU20D(F) digital humidity sensors are dedicated humidity and
temperature plug and play transducers for OEM applications
where reliable and accurate measurements are needed. Direct
interface with a micro-controller is made possible with the
module for humidity and temperature digital outputs. These low
power sensor are designed for high volume and cost sensitive
applications with tight space constraints.
Every sensor is individually calibrated and tested. Lot
identification is printed on the sensor and an electronic
identification code is stored on the chip – which can be read out
by command. Low battery can be detected and a checksum
improves communication reliability. The resolution of these
digital humidity sensor can be changed by command (8/12bit up
to 12/14bit for RH/T).
With MEAS’ improvements and miniaturization of this sensor,
the performance-to-price ratio has been improved – and
eventually, any device should benefit from the cutting edge
energy saving operation mode.
Optional PTFE filter/membrane (F) protects HTU20D digital
humidity sensors against dust and water immersion, as well as
against contamination by particles. PTFE filter/membrane
preserves a high response time. The white PTFE
filter/membrane is directly stuck on the sensor housing. This
membrane is allowing an IP67 compliant protection.
SENSOR SOLUTIONS /// HPC202_5 HTU20D(F) Sensor Datasheet
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HTU20D(F) RH/T SENSOR IC
Digital Relative Humidity sensor with Temperature output
SENSOR SOLUTIONS /// HPC202_5 HTU20D(F) Sensor Datasheet
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HTU20D(F) RH/T SENSOR IC
Digital Relative Humidity sensor with Temperature output
NOMENCLATURE
HTU2XY(F)
With embedded PTFE filter/membrane: HTU2XYF
Output Sensor:
Y = D/A for Digital, I2C protocol
= P for PWM interface, analog output
Humidity accuracy :
X = 0: +/-5%RH max tolerance @55%RH
= 1: +/-3%RH max tolerance @55%RH
HTU2XY Modules
HTU2XYF Modules
PERFORMANCE SPECS
MAXIMUM RATINGS
Ratings
Storage Temperature
Symbol
Value
Unit
Tstg
-40 to 125
°C
Supply Voltage (Peak)
Vcc
3.8V
Vdc
Humidity Operating Range
RH
0 to 100
%RH
Temperature Operating Range
Ta
VDD to GND
Digital I/O pins (DATA/SCK) to VDD
Input current on any pin
-40 to +125
°C
-0.3 to 3.6V
V
-0.3 to VDD+0.3
V
-10 to +10
mA
Peak conditions : less than 10% of the operating time
Exposure to absolute maximum rating conditions for extended periods may affect the sensor reliability
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HTU20D(F) RH/T SENSOR IC
Digital Relative Humidity sensor with Temperature output
ELECTRICAL AND GENERAL ITEMS
(@T = 25°C, @Vdd = 3V)
Characteristics
Voltage Supply
VDD
1.5
(1) Conditions:
Unit
3.6
V
µA
450
500
µA
Sleep mode
0.06
0.5
µW
Average 8bit (2)
2.7
idd
300
µW
digital 2-wire interface, I²C protocol
5.5mW/ΔT=+0.5-1.5°C
VDD=3V
Storage
(2) Conditions:
Max
0.14
Communication
Heater
Typ
3.0
Measuring
Power Dissipation
Min
0.02
Sleep mode
Current
consumption (1)
Symbol
-40°C/125°C
Vdd = 3V, SCK= 400kHz at 25°C
Vdd = 3V, SCK= 400kHz, Temp<60°C, duty cycle <10%
SENSOR PERFORMANCE
RELATIVE HUMIDITY
(@T = 25°C, @Vdd = 3V)
Characteristics
Resolution
Symbol
12 bits
8 bits
RH
0
typ
max
Max
Unit
100
%RH
%RH
%RH
±3
See graph 1
fully interchangeable
Replacement
Temperature coefficient (from 0°C to 80°C)
Tcc
%RH
%RH
-0.15
%RH/°C
12 bits
11 bits
10 bits
±1
14
7
4
16
8
5
%RH
ms
ms
ms
8 bits
2
3
ms
±10
LSB
Humidity Hysteresis
Measuring Time (1)
Typ
0.04
0.7
Humidity Operating Range
Relative Humidity Accuracy
@25°C (20%RH to 80%RH)
Min
PSRR
Recovery time after 150 hours of condensation
t
10
0.5
τRH
5
Long term drift
Response Time (at 63% of signal) from 33 to 75%RH
(2)
s
%RH/yr
10
s
(1)
Typical values are recommended for calculating energy consumption while maximum values shall be applied for calculating
waiting times in communication.
(2) At 1m/s air flow
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HTU20D(F) RH/T SENSOR IC
Digital Relative Humidity sensor with Temperature output
Delta Relative Humidity (%RH)
GRAPH1 : RELATIVE HUMIDITY ERROR BUDGET CONDITIONS AT 25°C
10
9
8
7
6
5
4
3
2
1
0
Maximal
Tolerance
0
10
20
30
40
50
60
70
Relative Humidity (%RH)
80
90
100
 HTU20D(F) sensors are specified for optimum accuracy measurements within 5 to 95%RH.
 Operation out of this range (< 5% or > 95% RH, including condensation) is however possible.
TEMPERATURE COEFFICIENT COMPENSATION EQUATION
For other temperatures than 25°C, the following temperature coefficient compensation equation can be used and
will guarantee Relative Humidity accuracy given in table1, from 0°C to 80°C:
RH compensatedT  RH actualT  f (T )
RHactualT
Tactual
f (T )
Ambient humidity in %RH, computed from HTU21D(F) sensor
Humidity cell temperature in °C, computed from HTU21D(F) sensor
RH correction (in %RH) is a linear function of the temperature T (°C) as described
below :
f (T )  0.15 * (25  T )
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HTU20D(F) RH/T SENSOR IC
Digital Relative Humidity sensor with Temperature output
TEMPERATURE
Characteristics
Symbol
Resolution
14 bit
Typ
0.01
12 bit
0.04
Temperature Operating Range
T
+125
14 bit
13 bit
12 bit
11 bit
PSSR
Long term drift
Response Time (at 63% of signal) from 15°C to 45°C
(2)
τT
°C
°C
See graph 2
Replacement
Unit
°C
°C
±0.3
max
(1)
Max
-40
typ
Temperature Accuracy @25°C
Measuring time
Min
fully interchangeable
44
50
22
25
11
13
6
7
±25
0.04
10
°C
ms
ms
ms
ms
LSB
°C/yr
s
(1)
Typical values are recommended for calculating energy consumption while maximum values shall be applied for calculating
waiting times in communication.
(2) At 1m/s air flow
GRAPH 2 : TEMPERATURE ERROR BUDGET
Maximal Tolerance
Typical Tolerance
Delta Temperature (°C)
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
-40
-20
0
SENSOR SOLUTIONS /// HPC202_5 HTU20D(F) Sensor Datasheet
20
40
60
Temperature (°C)
9/2015
80
100
120
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HTU20D(F) RH/T SENSOR IC
Digital Relative Humidity sensor with Temperature output
USER GUIDE HTU20D(F)
APPLICATION INFORMATION

Soldering instructions: Lead free reflow soldering recommended process
For soldering HTU20D(F) sensor standard reflow soldering ovens may be used.
HTU20D(F) sensor as a humidity sensitive component (as classified by IPC/JEDEC J-STD-020 or equivalent
documented procedure with peak temperature at 260°C during up to 30 seconds for Pb-free assembly in
IR/convection reflow ovens) must be handled in a manner consistent with IPC/JEDEC J-STD-033 or an equivalent
documented procedure. IPC-1601 provides humidity control, handling and packing of PCBs.
The H T U 2 0 D ( F ) s ensor is qualified to withstand one lead free reflow soldering recommended process profile
below according to JEDEC standard.
Mount parts within 24 hours after printing solder paste to avoid potential dry up.
For manual soldering, contact time must be limited to 5 seconds at up to 350°C.
For the design of the HTU20D(F) sensor footprint, it is recommended to use dimensions according to figure below.
Recommended footprint for HTU20D(F) sensors. Values in mm.
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HTU20D(F) RH/T SENSOR IC
Digital Relative Humidity sensor with Temperature output
No specific conditioning of devices is necessary after soldering process, either manual or reflow soldering.
Optimized performance in case of metrological measurements can be reached with stabilization of devices (24
hours at 25°C / 55%RH). Similar process is advised after exposure of the devices to extreme relative humidity
conditions.
In no case, neither after manual nor reflow soldering, a board wash shall be applied. Therefore, it is strongly
recommended to use a “no-clean” solder paste. In case of applications with exposure of the sensor to corrosive
gases or condensed water (i.e. environments with high relative humidity) the soldering pads shall be sealed (e.g.
conformal coating) to prevent loose contacts or short cuts.

Storage Conditions and Handling Instructions
It is recommended to store HTU20D(F) sensor in its original packaging at following conditions: Temperature shall
be in the range of -40°C – 125°C.

Temperature Effects
Relative humidity reading strongly depends on temperature. Therefore, it is essential to
keep humidity sensors at the same temperature as the air of which the relative humidity
is to be measured.
In case of testing or qualification the reference sensor and test sensor must show equal
temperature to allow for comparing humidity readings.
The HTU20D(F) sensor should be mounted in a way that prevents heat transfer from
electronic sensor or that keeps it as low as possible. Advice can be ventilation, reduction
of copper layers between the HTU20D(F) sensor and the rest of the PCB or milling a
slit into the PCB around the sensor (1mm minimum width).
Example of HTU20D(F) sensor mounting
with slits mills to minimize heat transfer

Materials Used for Sealing / Mounting
For sealing and gluing (use sparingly), use high filled epoxy for electronic packaging and silicone. For any specific
material please request to [email protected].
Window must remain uncovered.

Wiring Considerations and Signal Integrity
Carrying the SCK and DATA signal parallel and in close proximity (e.g. in wires) for more than 10 cm may result in
cross talk and loss of communication.
This may be resolved by routing VDD and/or GND between the two data signals and/or using shielded cables.
Furthermore, slowing down SCK frequency will possibly improve signal integrity.
Power supply pins (VDD, GND) must be bypassed with a 100nF capacitor if wires are used. Capacitor should be
placed as close as possible to the sensor.
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HTU20D(F) RH/T SENSOR IC
Digital Relative Humidity sensor with Temperature output

ESD (ElectroStatic Discharge)
ESD immunity is qualified according to:
 JEDEC JESD22-A114 method (Human Body Model at ±4kV) for pads & open window
 JEDEC JESD22-A115 method (Machine Model ±200V)
 ESDA ESD-STM5.3.1-1999 and AEC-Q100-011 (charged device model, 750V corner pins, 500V other
pins)
Latch-up immunity is provided at a force current of ±100mA with Tamb=25°C according to JEDEC JESD78. For
exposure beyond named limits the sensor need additional protection circuit.
INTERFACE SPECIFICATION
N°
Function
Comment
1
DATA
Data bit-stream
2
GND
Ground
3
NC
Must be left unconnected
4
NC
5
VDD
Supply Voltage
6
SCK
Selector for RH or Temp
PAD
Must be left unconnected
Ground or unconnected
Typical application circuit, including pull-up resistor Rp and decoupling of VDD and GND by a capacitor.

Power Pins (VDD, GND)
The supply voltage of HTU20D(F) sensors must be in the range of 1.5VDC - 3.6VDC. Recommended supply
voltage is 3VDC (regulated).
However the typical application circuit includes a pull-up resistor R on data wire and a 100nF decoupling capacitor
between VDD and GND, placed as close as possible to the sensor.
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HTU20D(F) RH/T SENSOR IC
Digital Relative Humidity sensor with Temperature output

Serial clock input (SCK)
SCK is used to synchronize the communication between microcontroller and HTU20D(F) sensor. Since the interface
consists of fully static logic there is no minimum SCK frequency.
 Serial data (DATA)
The DATA pin is used to transfer data in and out of the device. For sending a command to the HTU20D(F) sensor,
DATA is valid on the rising edge of SCK and must remain stable while SCK is high. After the falling edge of SCK,
the DATA value may be changed. For safe communication DATA shall be valid t SU and tHD before the rising and
after the falling edge of SCK, respectively. For reading data from the HTU20D(F) sensor, DATA is valid t VD after
SCK has gone low and remains valid until the next falling edge of SCK.
An external pull-up resistor (e.g. 10kΩ) on SCK is required to pull the signal high only for open collector or open
drain technology microcontrollers. In most of the cases, pull-up resistors are internally included in I/O circuits of
microcontrollers.
ELECTRICAL CHARACTERISTICS

Input/output DC characteristics
(VDD=3V, Temperature=25°C unless otherwise noted)
Characteristics
Low level output
voltage
VDD=3V
-4mA<IOL<0mA
High level output voltage
Symbol
Min
Typ
Max
Unit
VOL
0
-
0.4
V
VOH
70%VDD
-
VDD
V
Low level input voltage
VIL
0
-
30%VDD
V
High level input voltage
VIH
70%VDD
-
VDD
V

Timing specifications of digital input/output pads for I²C fast mode
Characteristics
Symbol
Min
Typ
Max
Unit
SCK frequency
fSCK
0
-
0.4
MHz
SCK high time
tSCKLH
0.6
-
-
µs
SCK low time
tSCLL
1.3
-
-
µs
DATA set-up time
tSU
100
-
-
ns
DATA hold-time
tHD
0
-
900
ns
DATA valid-tile
tVD
0
-
400
ns
SCK/DATA fall time
tF
0
-
100
ns
SCK/DATA rise time
tR
0
-
300
ns
Capacitive load on bus line
CB
0
-
500
pF
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HTU20D(F) RH/T SENSOR IC
Digital Relative Humidity sensor with Temperature output

Timing diagram for digital input/output pads
DATA directions are seen from the HTU20D(F) sensor. DATA line in bold is controlled by the sensor. DATA valid
read time is triggered by falling edge of anterior toggle.
COMMUNICATION PROTOCOL WITH HTU20D(F) SENSOR

Start-up sensor
The HTU20D(F) sensor requires a voltage supply between 1.5V and 3.6V. After power up, the device needs at
most 15ms while SCK is high for reaching idle state (sleep mode), i.e to be ready accepting commands from the
MCU. No command should be sent before that time. Soft reset is recommended at start, refer p.13.

Start sequence (S)
To initiate transmission, a start bit has to be issued. It consists of a lowering of the DATA line
while SCK is high followed by lowering SCK.

Stop sequence (P)
To stop transmission, a stop bit has to be issued. It consists of a heightening of the DATA line
while SCK is high preceded by a heightening of the SCK.
HTU20D(F) SENSOR LIST OF COMMANDS AND REGISTER ADRESSES
For sample source code, please request to [email protected].

Sending a command
After sending the start condition, the subsequent I²C header consist of a 7-bit I²C device address 0x40 and a DATA
direction bit (‘0’ for Write access :0x80). The HTU20D(F) sensor indicates the proper reception of a byte by pulling
the DATA pin low (ACK bit) after the falling edge of the 8th SCK clock. After the issue of a measurement command
(0xE3 for temperature, 0xE5 for relative humidity), the MCU must wait for the measurement to complete. The basic
commands are given in the table below:
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HTU20D(F) RH/T SENSOR IC
Digital Relative Humidity sensor with Temperature output

Command
Code
Comment
Trigger Temperature Measurement
0xE3
Hold master
Trigger Humidity Measurement
0xE5
Hold master
Trigger Temperature Measurement
0xF3
No Hold master
Trigger Humidity Measurement
0xF5
No Hold master
Write user register
0xE6
Read user register
0xE7
Soft Reset
0xFE
Hold/No Hold master modes
There are two different operation modes to communicate with the HTU20D(F) sensor: Hold Master mode and No
Hold Master mode.
In the first case, the SCK line is blocked (controlled by HTU20D(F) sensor) during measurement process while in
the second case the SCK line remain open for other communication while the sensor is processing the
measurement.
No Hold Master mode allows for processing other I²C communication tasks on a bus while the HTU20D(F) sensor
is measuring. A communication sequence of the two modes is available below.
In the Hold Master mode, the HTU20D(F) pulls down the SCK line while measuring to force the master into a wait
state. By releasing the SCK line, the HTU20D(F) sensor indicates that internal processing is completed and that
transmission may be continued.
In the No Hold Master mode, the MCU has to poll for the termination of the internal processing of the HTU20D(F)
sensor. This is done by sending a start condition followed by the I²C header (‘1’ for Read access : 0x81) as shown
below. If the internal processing is finished, the HTU20D(F) sensor acknowledges the poll of the MCU and data can
be read by the MCU. If the measurement processing is not finished, the HTU20D(F) sensor answers no ACK bit
and start condition must be issued once more.
For both modes, since the maximum resolution of the measurement is 14 bits, the two last least significant bits
(LSBs, bits 43 and 44) are used for transmitting status information. Bit 1 of the two LSBs indicates the measurement
type (‘0’: temperature, ‘1’: humidity). Bit 0 is currently not assigned.
S
1
2
1
0
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
0
0
0
0
0
0
ACK
1
1
1
0
0
1
0
1
ACK
I²C address + write
S
Command (see table p.9)
19
20
21
22
23
24
25
26
27
1
0
0
0
0
0
0
1
ACK
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
0
1
1
1
1
1
0
0
ACK
1
0
0
0
0
0
1
0
ACK
46
47
48
1
0
0
Measurement
I²C address + read
Hold during measurement
Data (MSB)
Data (LSB)
49
50
51
52
53
54
1
0
1
1
1
NACK
Status
P
Checksum
Hold Master communication sequence
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HTU20D(F) RH/T SENSOR IC
Digital Relative Humidity sensor with Temperature output
S
1
2
1
0
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
0
0
0
0
0
0
ACK
1
1
1
1
0
1
0
1
ACK
I²C address + write
Command (see table p.9)
Measurement
S
19
20
21
22
23
24
25
26
27
1
0
0
0
0
0
0
1
NACK
19
20
21
22
23
24
25
26
27
1
0
0
0
0
0
0
1
ACK
measuring
I²C address + read
Measurement
S
continue measuring
28
29
30
0
1
1
I²C address + read
31
32
33
34
35
36
37
38
1
1
1
0
0
ACK
1
0
Data (MSB)
39
40
41
42
43
44
45
0
0
0
0
1
0
ACK
Data (LSB)
46
47
48
49
50
51
52
53
54
1
0
0
1
0
1
1
1
NACK
Status
P
Checksum
No Hold Master communication sequence
Grey blocks are controlled by HTU20D(F) sensor.
For Hold Master sequence, bit 45 may be changed to NACK followed by a stop condition to omit checksum
transmission.
For No Hold Master sequence, if measurement is not completed upon “read” command, sensor does not provide
ACK on bit 27 (more of these iterations are possible). If bit 45 is changed to NACK followed by stop condition,
checksum transmission is omitted.
In those examples, the HTU20D(F) sensor output is S RH = ‘0111’1100’1000’0000 (0x7C80). For the calculation of
physical values status bits must be set to ‘0’. Refer to “Conversion of signal outputs” section p.16.
The maximum duration for measurement depends on the type of measurement and resolution chosen. Maximum
values shall be chosen for the communication planning of the MCU. Refer to the table p.4 and p.6 regarding
measuring time specifications.
I²C communication allows for repeated start conditions without closing prior sequence with stop condition.

Soft reset
This command is used for rebooting the HTU20D(F) sensor switching the power off and on again. Upon reception
of this command, the HTU20D(F) sensor system reinitializes and starts operation according to the default settings
with the exception of the heater bit in the user register. The soft reset takes less than 15ms.
S
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
1
0
0
0
0
0
0
0
ACK
1
1
1
1
1
1
1
0
ACK
I²C address + write
P
Soft Reset Command
Grey blocks are controlled by HTU20D(F) sensor.
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HTU20D(F) RH/T SENSOR IC
Digital Relative Humidity sensor with Temperature output

User register
The content of user register is described in the table below. Reserved bits must not be changed and default values
of respective reserved bits may change over time without prior notice. Therefore, for any writing to user register,
default values of reserved bits must be read first.
The “End of Battery” alert/status is activated when the battery power falls below 2.25V.
The heater is intended to be used for functionality diagnosis: relative humidity drops upon rising temperature. The
heater consumes about 5.5mW and provides a temperature increase of about 0.5-1.5°C.
OTP reload is a safety feature and load the entire OTP settings to the register, with the exception of the heater bit,
before every measurement. This feature is disabled per default and it is not recommended for use. Please use soft
reset instead as it contains OTP reload.
Bit
#Bits
Description/Coding
7,0
2
Measurement resolution
Bit 7
Bit 0
RH
0
0
12 bits
0
1
8 bits
1
0
10 bits
1
1
11 bits
Default
‘00’
Temp
14 bits
12 bits
13 bits
11 bits
‘0’
Status: End of Battery(1)
‘0’: VDD>2.25V
‘1’: VDD<2.25V
3, 4, 5
3
Reserved
2
1
Enable on-chip heater
1
1
Disable OTP reload
(1) This status bit is updated after each measurement
6
1
‘0’
‘0’
‘1’
Cut-off value for “End of Battery” signal may vary by ±0.1V.
Reserved bits must not be changed.
OTP reload active loads default settings after each time a measurement command is issued.

I²C communication reading and writing the user register example
In this example, the resolution is set to 8 bits / 12 bits (for RH/Temp) from default configuration.
S
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
1
0
0
0
0
0
0
0
ACK
1
1
1
0
0
1
1
1
ACK
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
1
0
0
0
0
0
0
1
ACK
0
0
0
0
0
0
1
0
NACK
I²C address + write
S
Read Register Command
I²C address + read
S
Register content
37
38
39
40
41
42
43
44
45
46
47
1
0
0
0
0
0
0
0
ACK
1
1
I²C address + write
48
49
50
51
52
53
54
1
0
0
1
1
0
ACK
Write Register Command
55
56
57
58
59
60
61
62
63
0
0
0
0
0
0
1
1
ACK
P
Register Content to be written
Grey blocks are controlled by HTU20D(F) sensor.
SENSOR SOLUTIONS /// HPC202_5 HTU20D(F) Sensor Datasheet
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HTU20D(F) RH/T SENSOR IC
Digital Relative Humidity sensor with Temperature output

CRC Checksum
HTU20D(F) sensor provides a CRC-8 checksum for error detection. The polynomial used is X8 + X5 + X4 + 1.
Basic Considerations
CRC stands for Cyclic Redundancy Check. It is one of the most effective error detection schemes and requires a
minimal amount of resources.
The types of errors that are detectable with CRC that is implemented in HTU20D(F) sensors are:
 Any odd number of errors anywhere within the data transmission
 All double-bit errors anywhere within the transmission
 Any cluster of errors that can be contained within an 8-bit window (1-8 bits incorrect)
 Most larger clusters of errors
A CRC is an error-detecting code commonly used in digital networks and storage devices to detect accidental
changes to raw data.
Blocks of data entering these systems get a short check value attached, based on the remainder of a polynomial
division of their contents; on retrieval the calculation is repeated, and corrective action can be taken against
presumed data corruption if the check values do not match.
CRCs are so called because the check (data verification) value is a redundancy (it expands the message without
adding information) and the algorithm is based on cyclic codes. CRCs are popular because they are simple to
implement in binary hardware, easy to analyze mathematically, and particularly good at detecting common errors
caused by noise in transmission channels. Because the check value has a fixed length, the function that generates
it is occasionally used as a hash function.
CRC for HTU20D(F) sensors using I²C Protocol
When HTU20D(F) sensors are run by communicating with the standard I²C protocol, an 8-bit CRC can be used to
detect transmission errors. The CRC covers all read data transmitted by the sensor. CRC properties for HTU20D(F)
sensors communicating with I²C protocol are listed in the table below.
CRC with I²C protocol
Generator polynomial
Initialization
Protected data
Final Operation
X8 + X5 + X4 + 1
0x00
Read data
none
CRC calculation
To compute an n-bit binary CRC, line the bits representing the input in a row, and position the (n+1)-bit pattern
representing the CRC's divisor (called a "polynomial") underneath the left-hand end of the row.
This is first padded with zeroes corresponding to the bit length n of the CRC.
If the input bit above the leftmost divisor bit is 0, do nothing. If the input bit above the leftmost divisor bit is 1, the
divisor is XORed into the input (in other words, the input bit above each 1-bit in the divisor is toggled). The divisor
is then shifted one bit to the right, and the process is repeated until the divisor reaches the right-hand end of the
input row.
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HTU20D(F) RH/T SENSOR IC
Digital Relative Humidity sensor with Temperature output
Since the left most divisor bit zeroed every input bit it touched, when this process ends the only bits in the input row
that can be nonzero are the n bits at the right-hand end of the row. These n bits are the remainder of the division
step, and will also be the value of the CRC function.
The validity of a received message can easily be verified by performing the above calculation again, this time with
the check value added instead of zeroes. The remainder should equal zero if there are no detectable errors.
CRC examples
The input message 11011100 (0xDC) will have as result 01111001 (0x79).
The input message 01101000 00111010 (0x683A: 24.7°C) will have as result 01111100 (0x7C).
The input message 01001110 10000101 (0x4E85: 32.3%RH) will have as result 01101011 (0x6B).
CONVERSION OF SIGNAL OUTPUTS
Default resolution is set to 12-bit relative humidity and 14-bit temperature readings. Measured data are transferred
in two byte packages, i.e. in frames of 8-bit length where the most significant bit (MSB) is transferred first (left
aligned). Each byte is followed by an acknowledge bit. The two status bits, the last bits of LSB, must be set to ‘0’
before calculating physical values.
To accommodate/adapt any process variation (nominal capacitance value of the humidity die), tolerances of the
sensor above 100%RH and below 0%RH must be considered. As a consequence:
 118%RH corresponds to 0xFF which is the maximum RH digital output that can be sent out from the ASIC.
RH output can reach 118%RH and above this value, there will have a clamp of the RH output to this value.
 -6%RH corresponds to 0x00 which is the minimum RH digital output that can be sent out from the ASIC.
RH output can reach -6%RH and below this value, there will have a clamp of the RH output to this value.

Relative Humidity conversion
With the relative humidity signal output SRH, the relative humidity is obtained by the following formula (result in
%RH), no matter which resolution is chosen:
RH  6  125 
S RH
216
In the example given p.10, the transferred 16-bit relative humidity data is 0x7C80: 31872. The relative humidity
results to be 54.8%RH.

Temperature conversion
The temperature T is calculated by inserting temperature signal output S Temp into the following formula (result in
°C), no matter which resolution is chosen:
Temp  46 .85  175 .72 
SENSOR SOLUTIONS /// HPC202_5 HTU20D(F) Sensor Datasheet
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HTU20D(F) RH/T SENSOR IC
Digital Relative Humidity sensor with Temperature output
APPLICATION: DEW POINT TEMPERATURE MEASUREMENT
The dew point is the temperature at which the water vapor in the air becomes saturated and condensation begins.
The dew point is associated with relative humidity. A high relative humidity indicates that the dew point is closer to
the current air temperature. Relative humidity of 100% indicates that the dew point is equal to the current
temperature (and the air is maximally saturated with water). When the dew point stays constant and temperature
increases, relative humidity will decrease.
Dew point temperature of the air is calculated using Ambient Relative Humidity and Temperature measurements
from HTU20D(F) sensor with following formulas given below:
Partial Pressure (PPTamb) formula from Ambient Temperature:
PPTamb  10


B

 A
 (Tamb  C ) 
Dew point Temperature (Td) formula from Partial Pressure (PPTamb):


B
Td   
PPTamb


 log 10  RH amb  100


PPTamb
RHamb
Tamb
Td
A, B, C


 C


 A



Partial Pressure in mmHg at ambient temperature (T amb)
Ambient humidity in %RH, computed from HTU20D(F) sensor
Humidity cell temperature in °C, computed from HTU20D(F) sensor
Calculated Dew Point in °C
Constants: A=8.1332; B=1762.39; C=235.66
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HTU20D(F) RH/T SENSOR IC
Digital Relative Humidity sensor with Temperature output
PACKAGE OUTLINE

HTU20D Sensor Dimensions
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HTU20D(F) RH/T SENSOR IC
Digital Relative Humidity sensor with Temperature output

HTU20DF Sensor Dimensions
Dimensions are given in mm, tolerances are ±0.1mm. The die pad (thermal center pad) is internally connected
to GND.

Packaging Type
HTU20D(F) sensors are provided in DFN packaging. DFN stands for Dual Flat No leads.
The HTU20D(F) sensor chip is mounted to a lead frame made of Cu and plated with Ni/Pd/Au. Chip and lead frame
are over molded by green epoxy-based mold compound. Please note that side walls of sensors are diced and hence
lead frame at diced edge is not covered with respective protective coating.
The total weight of the sensor is 0.025g.
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HTU20D(F) RH/T SENSOR IC
Digital Relative Humidity sensor with Temperature output

Traceability Information
All HTU20D(F) sensors are laser marked with an alphanumeric, five-digit code on the sensor as pictured below.
The marking of the HTU20D(F) sensor consists of two lines with five digits each :
 The first line denotes the sensor type: HTU20.
 The second line denotes several information as:
o The first digit of the second line defines the output mode:
 D = digital and I²C
 P = PWM
o The second digit defines the manufacturing year: 3 = 2013, 4 = 2014, etc.
o The last three digits represent an alphanumeric tracking code. That code represents the day of the
year.
Laser marking on HTU20D(F) sensor
Reels are also labeled, as displayed below and give additional traceability information.
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HTU20D(F) RH/T SENSOR IC
Digital Relative Humidity sensor with Temperature output
With:
XX:
O:
(F):
TTTTTTTTT:
YY:
DDD:
QQQQ:
Sensor Type (20)
Output mode (D = Digital, P = PWM)
Sensor with PTFE membrane
MEAS Traceability Code
Last two digits of the year
Day of the year
Quantity per reel (5000 units)
 Tape and Reel Packaging
HTU20D(F) sensors are shipped in tape & reel packaging, sealed into antistatic ESD bags.
Standard packaging size is 5000 units per reel. Each reel contains 440mm (55 pockets) header tape and 200mm
(25 pockets) trailer tape. The drawing of the packaging tapes with sensor orientation is shown in the picture below.
USER DIRECTION
OF UNREELING

Packaging reels
For 5000 units: outside diameter of 13” (330mm) and a 1/2” (13mm) diameter arbor hole.

Handling / Storage recommendations
In order to use and preserve the high quality performance of the HTU21 humidity and temperature sensor, the
following recommendations have to be followed concerning storage and packaging.
Please read the paragraph below carefully and note that all precautions are applicable for design phases, production
phases as well as in case of returned material to Measurement Specialties.
When sensors are not used or assembled, we recommend to store them in their original sealed anti ESD
packaging. If sensors have been removed from their original packaging, we recommend to keep them into anti
static shielded ESD bags.
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HTU20D(F) RH/T SENSOR IC
Digital Relative Humidity sensor with Temperature output
Such SMD type sensors that are sensitive to moisture are classified MSL level 2 according to IPC/JEDEC J-STD020.1 for storage, packaging and handling. The shelf life is thus 1 year in following conditions of temperature and
relative humidity ≤30°C 60%RH.
Protection against ESD mandatory
MSL level 2 classification
ORDERING INFORMATION
** HTU20D – I.C 20D RH/T DIGITAL **
PACKAGE: TAPE AND REEL M.P.Q OF 400 PIECES, 1500 PIECES OR 5000 PIECES



HPP845E034R4 – I.C 20D RH/T DIGITAL in tape and reel of 400 pieces
HPP845E034R1 – I.C 20D RH/T DIGITAL in tape and reel of 1500 pieces
HPP845E034R5 – I.C 20D RH/T DIGITAL in tape and reel of 5000 pieces
** HTU20DF – I.C 20DF RH/T DIGITAL WITH PTFE MEMBRANE **
PACKAGE: TAPE AND REEL M.P.Q OF 5000 PIECES

HPP845E134R5 - I.C 20DF RH/T DIGITAL in tape and reel of 5000 pieces
** I.C 21D DEMOKIT – HPP845KIT **
This is a USB device for MEAS Model HTU20D Digital Relative Humidity & Temperature sensor demonstration.
Supporting up to 4 sensor acquisitions at the same time, it shows the consistency of different sensors and test
sensor functions conveniently.
For detailed information, please request to [email protected].
SENSOR SOLUTIONS /// HPC202_5 HTU20D(F) Sensor Datasheet
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HTU20D(F) RH/T SENSOR IC
Digital Relative Humidity sensor with Temperature output
Revision
0
1
Comments
Document creation
General update
Who
D. LE GALL
D. LE GALL-ZIRILLI
Date
November 12
July 13
M.ROBERT
October 13
M.ROBERT
January 14
M.ROBERT
M.ROBERT
April 14
October 14
Correction of I²C communication reading and writing,
2
3
4
5
correction of soldering peak temperature, correction of
Demokit designation
Obsolescence of HTU2XS (SDM interface) version
Update of external package dimensions
Part number and designation modification
General update
EUROPE
Measurement Specialties, Inc - MEAS France
Impasse Jeanne Benozzi
CS 83 163
31027 Toulouse Cedex 3
FRANCE
Tel:+33 (0)5°820.822.02
Fax:+33 (0)5.820.821.51
Sales: [email protected]
TE.com/sensorsolutions
Measurement Specialties, Inc., a TE Connectivity company.
Measurement Specialties, TE Connectivity, TE Connectivity (logo) and EVERY CONNECTION COUNTS are trademarks. All other logos, products and/or company names referred to herein
might be trademarks of their respective owners.
The information given herein, including drawings, illustrations and schematics which are intended for illustration purposes only, is believed to be reliable. However, TE Connectivity makes
no warranties as to its accuracy or completeness and disclaims any liability in connection with its use. TE Connectivity‘s obligations shall only be as set forth in TE Connectivity‘s Standard
Terms and Conditions of Sale for this product and in no case will TE Connectivity be liable for any incidental, indirect or consequential damages arising out of the sale, resale, use or misuse
of the product. Users of TE Connectivity products should make their own evaluation to determine the suitability of each such product for the specific application.
© 2015
TE Connectivity Ltd. family of companies
All Rights Reserved.
SENSOR SOLUTIONS /// HPC202_5 HTU20D(F) Sensor Datasheet
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