SHT1x / SHT7x Relative Humidity & Temperature Sensor System
www.sensirion.com
v2.01 March 2003
4/9
Command
wait for data ready
MSB
LSB
Checksum
0
0
0
0
Figure 6 Overview of Measurement Sequence (TS = Transmission Start)
2.3 Status Register
Some of the advanced functions of the SHTxx are available
through the status register. The following section gives a
brief overview of these features. A more detailed description
is available in the application note “Status Register”
Command
Status
Reg
00
0
11
0
0
0
Figure 7 Status Register Write
Command
Status
Reg
Checksum
0011
0
0
0
1
Figure 8 Status Register Read
Bit Type Description
Default
7
reserved
0
6
R
End of Battery (low voltage detection)
‘0’ for Vdd > 2.47
‘1’ for Vdd < 2.47
X No default value,
bit
is
only
updated after a
measurement
5
reserved
0
4
reserved
0
3
For Testing only, do not use
0
2
R/W
Heater
0
off
1
R/W
no reload from OTP
0
reload
0
R/W
’1’ = 8bit RH / 12bit Temperature resolution
’0’ = 12bit RH / 14bit Temperature resolution
0
12bit RH
14bit Temp.
Table 3
Status Register Bits
2.3.1
Measurement resolution
The default measurement resolution of 14bit (temperature)
and 12bit (humidity) can be reduced to 12 and 8bit. This is
especially useful in high speed or extreme low power
applications.
2.3.2
End of Battery
The “End of Battery” function detects VDD voltages below
2.47 V. Accuracy is
±0.05 V
2.3.3
Heater
An on chip heating element can be switched on. It will
increase the temperature of the sensor by approximately 5°C
(9 °F). Power consumption will increase by ~8 mA @ 5 V.
Applications:
By comparing temperature and humidity values before and
after switching on the heater, proper functionality of both
sensors can be verified.
• In high (>95 %RH) RH environments heating the sensor
element will prevent condensation, improve response
time and accuracy
Warning: While heated the SHTxx will show higher
temperatures and a lower relative humidity than with no
heating.
2.4 Electrical Characteristics(1)
VDD=5V, Temperature = 25 °C unless otherwise noted
Parameter
Conditions
Min. Typ. Max. Units
Power supply DC
2.4
5
5.5 V
measuring
550
µA
Supply current
average
2(2)
28(3)
µA
sleep
0.3
1
µA
Low level output voltage
0
20% Vdd
High level output voltage
75%
100% Vdd
Low level input voltage Negative going
0
20% Vdd
High level input voltage Positive going 80%
100% Vdd
Input current on pads
1
µA
Output peak current
on
4
mA
Tristated (off)
10
µA
Table 4
SHTxx DC Characteristics
Parameter
Conditions
Min Typ. Max. Unit
VDD > 4.5 V
10 MHz
FSCK SCK frequency
VDD < 4.5 V
1 MHz
Output load 5 pF
3.5 10
20 ns
TRFO DATA fall time
Output load 100 pF 30 40 200 ns
TCLx SCK hi/low time
100
ns
TV
DATA valid time
250
ns
TSU
DATA set up time
100
ns
THO
DATA hold time
0
10
ns
TR/TF SCK rise/fall time
200
ns
Table 5
SHTxx I/O Signals Characteristics
SCK
DATA
TSU
TF
TR
THO
TCLH
FSCK
TV
Figure 9 Timing Diagram
1)
Parameters are periodically sampled and not 100% tested
(2)
With one measurement of 8 bit accuracy without OTP reload per second
(3)
With one measurement of 12bit accuracy per second
Russian ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
