Data Sheet

Datasheet SHT3x-DIS
www.sensirion.com May 2018- Version 5 14/22
the checksum only these two previously transmitted data
bytes are used.
Property
Value
Name
CRC-8
Width
8 bit
Protected data
read and/or write data
Polynomial
0x31 (x
8
+ x
5
+ x
4
+ 1)
Initialization
0xFF
Reflect input
False
Reflect output
False
Final XOR
0x00
Examples
CRC (0xBEEF) = 0x92
Table 20 I2C CRC properties.
4.13 Conversion of Signal Output
Measurement data is always transferred as 16-bit values
(unsigned integer). These values are already linearized
and compensated for temperature and supply voltage
effects. Converting those raw values into a physical
scale can be achieved using the following formulas.
Relative humidity conversion formula (result in %RH):
1

16
RH
2
S
100 RH
Temperature conversion formula (result in °C & °F):
 
 
1
1




16
T
16
T
2
S
315 49 F T
2
S
175 45 C T
S
RH
and S
T
denote the raw sensor output for humidity
and temperature, respectively. The formulas work only
correctly when S
RH
and S
T
are used in decimal
representation.
4.14 Communication Timing
Parameter
Symbol
Conditions
Min.
Typ.
Max.
Units
Comments
SCL clock frequency
f
SCL
0
-
1000
kHz
Hold time (repeated) START
condition
t
HD;STA
After this period, the first
clock pulse is generated
0.24
-
-
µs
LOW period of the SCL
clock
t
LOW
0.53
-
-
µs
HIGH period of the SCL
clock
t
HIGH
0.26
-
-
µs
SDA hold time
t
HD;DAT
0
-
250
ns
Transmitting data
0
-
-
ns
Receiving data
SDA set-up time
t
SU;DAT
100
-
-
ns
SCL/SDA rise time
t
R
-
-
300
ns
SCL/SDA fall time
t
F
-
-
300
ns
SDA valid time
t
VD;DAT
-
-
0.9
µs
Set-up time for a repeated
START condition
t
SU;STA
0.26
-
-
µs
Set-up time for STOP
condition
t
SU;STO
0.26
-
-
µs
Capacitive load on bus line
CB
-
-
400
pF
Low level input voltage
V
IL
0
-
0.3xV
DD
V
High level input voltage
V
IH
0.7xV
DD
-
1xV
DD
V
Low level output voltage
V
OL
3 mA sink current
-
-
0.4
V
Table 21 Timing specifications for I2C communication, valid for T=-40°C … 125°C and VDD = VDD
min
… VDD
max
. The nomenclature
above is according to the I2C (UM10204, Rev. 6, April 4, 2014).