SHT11 Datasheet, PDF (4/9 Pages) List of Unclassifed Manufacturers – Humidity & Temperature Sensor

SHT1x / SHT7x Relative Humidity & Temperature Sensor System
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000
0
MSB
LSB
Checksum
Command
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”
0 00 0 01 1 0
Status
Reg
Command
Figure 7 Status Register Write
000 0 0 1 1 1
Status
Reg
Command
Figure 8 Status Register Read
Checksum
Bit Type
7
6R
5
4
3
2 R/W
1 R/W
0 R/W
Table 3
Description
reserved
End of Battery (low voltage detection)
‘0’ for Vdd > 2.47
‘1’ for Vdd < 2.47
reserved
reserved
For Testing only, do not use
Heater
no reload from OTP
’1’ = 8bit RH / 12bit Temperature resolution
’0’ = 12bit RH / 14bit Temperature resolution
Status Register Bits
Default
0
X No default value,
bit is only
updated after a
measurement
0
0
0
0 off
0 reload
0 12bit RH
14bit Temp.
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 5-15 °C (9-27 °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
Supply current
measuring
average
sleep
Low level output voltage
550
µA
2⁽²⁾ 28⁽³⁾
µA
0.3 1 µA
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
Output peak current on
1 µA
4 mA
Tristated (off)
10
µA
Table 4 SHTxx DC Characteristics
Parameter
Conditions
Min Typ. Max. Unit
FSCK SCK frequency VDD > 4.5 V
VDD < 4.5 V
TRFO DATA fall time Output load 5 pF
Output load 100 pF
TCLx SCK hi/low time
TV DATA valid time
TSU DATA set up time
THO DATA hold time
TR/TF SCK rise/fall time
3.5 10
30 40
100
250
100
0 10
200
10 MHz
1 MHz
20 ns
200 ns
ns
ns
ns
ns
ns
Table 5 SHTxx I/O Signals Characteristics
TCLH
TR
FSCK
TF
SCK
DATA
TV
T_SU
THO
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}
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v2.02 July 2004
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