http://www.datasheet4u.com

900,000+ Datasheet PDF Search and Download

Datasheet4U offers most rated semiconductors datasheets pdf


ETC
ETC

SHT75 Datasheet

Humidity & Temperature Sensor


SHT75 Datasheet Preview


SHT1x / SHT7x
Humidity & Temperature Sensor
Evaluation Kit
Available
- Relative humidity and temperature sensors
- Dew point
- Fully calibrated, digital output
- Excellent long-term stability
- No external components required
- Ultra low power consumption
- Surface mountable or 4-pin fully interchangeable
- Small size
- Automatic power down
SHT7x
SHT1x
SHT1x / SHT7x Product Summary
The SHTxx is a single chip relative humidity and
temperature multi sensor module comprising a calibrated
digital output. Application of industrial CMOS processes with
patented micro-machining (CMOSens® technology) ensures
highest reliability and excellent long term stability. The
device includes a capacitive polymer sensing element for
relative humidity and a bandgap temperature sensor. Both
are seamlessly coupled to a 14bit analog to digital converter
and a serial interface circuit on the same chip. This results in
superior signal quality, a fast response time and insensitivity
to external disturbances (EMC) at a very competitive price.
Each SHTxx is individually calibrated in a precision humidity
chamber with a chilled mirror hygrometer as reference. The
calibration coefficients are programmed into the OTP
memory. These coefficients are used internally during
measurements to calibrate the signals from the sensors.
The 2-wire serial interface and internal voltage regulation
allows easy and fast system integration. Its tiny size and low
power consumption makes it the ultimate choice for even
the most demanding applications.
The device is supplied in either a surface-mountable LCC
(Leadless Chip Carrier) or as a pluggable 4-pin single-in-line
type package. Customer specific packaging options may be
available on request.
Applications
_ HVAC
_ Automotive
_ Consumer Goods
_ Weather Stations
_ Humidifiers
_ Dehumidifiers
_ Test & Measurement
_ Data Logging
_ Automation
_ White Goods
_ Medical
1
Ordering Information
Part
Number
Humidity
accuracy
[%RH]
Temperature
accuracy [K]
@ 25 °C
Package
SHT11
SHT15
SHT71
SHT75
±3.0
±2.0
±3.0
±1.8
±0.4 SMD (LCC)
±0.3 SMD (LCC)
±0.4 4-pin single-in-line
±0.3 4-pin single-in-line
Block Diagram
%RH
Sensor
Temp.
Sensor
Calibration
Memory
D
A
Digital 2-
wire
Interface
&
CRC
generator
SCK
DATA
GND
VDD
www.sensirion.com
Sensirion, Eggbühlstr. 14, 8052 Zürich, Switzerland, Tel: +41 1 306 40 00, Fax: +41 1 306 40 30 v2.02
Page 1

SHT1x / SHT7x Relative Humidity & Temperature Sensor System
1 Sensor Performance Specifications
Parameter
Conditions Min. Typ. Max. Units
Humidity
Resolution (2)
0.5 0.03 0.03 %RH
8 12 12 bit
Repeatability
±0.1 %RH
Accuracy (1)
linearized see figure 1
Uncertainty
Interchangeability
Fully interchangeable
Nonlinearity
raw data
±3
%RH
linearized
<<1
%RH
Range
0 100 %RH
Response time
Hysteresis
1/e (63%)
slowly moving air
4
±1
s
%RH
Long term stability typical
< 0.5 %RH/yr
Temperature
Resolution (2)
Repeatability
Accuracy
Range
Response Time
1/e (63%)
0.04 0.01 0.01
0.07 0.02 0.02
12 14 14
±0.1
±0.2
see figure 1
-40 123.8
-40 254.9
5 30
°C
°F
bit
°C
°F
°C
°F
s
Table 1 Sensor Performance Specifications
Relative Humidity absolute accuracy
%RH
±5
±4
± 3 SHT11/71
± 2 SHT15
± 1 SHT75
± 0 %RH
0 10 20 30 40 50 60 70 80 90 100
±3 °C
Temperature accuracy
±5.4 °F
±2 °C
SHT11/71
±3.6 °F
±1 °C
±1.8 °F
SHT15/75
0 °C
-40°C
-40°F
0 °F
0°C
40°C
80°C
120°C
32°F
104°F
176°F
248°F
±5 °C Dewpoint accuracy @ 25 °C (typical) ±9.0 °F
±4 °C
±7.2 °F
±3 °C
±5.4 °F
±2 °C SHT15
±3.6 °F
SHT11/71
±1 °C
±1.8 °F
±0 °C
SHT75
%RH
0 10 20 30 40 50 60 70 80 90 100
Figure 1 Rel. Humidity, Temperature and Dewpoint accuracies
2 Interface Specifications
uC
(master)
Vdd
GND
DATA
SCK
Vdd 2.4 - 5.5V
Figure 2 Typical application circuit
SHT1x
(slave)
2.1 Power Pins
The SHTxx requires a voltage supply between 2.4 and 5.5 V.
After powerup the device needs 11ms to reach its “sleep”
state. No commands should be sent before that time.
Power supply pins (VDD, GND) may be decoupled with a
100 nF capacitor.
2.2 Serial Interface (Bidirectional 2-wire)
The serial interface of the SHTxx is optimized for sensor
readout and power consumption and is not compatible with
I2C interfaces, see FAQ for details.
2.2.1 Serial clock input (SCK)
The SCK is used to synchronize the communication between
a microcontroller and the SHTxx. Since the interface
consists of fully static logic there is no minimum SCK
frequency.
2.2.2 Serial data (DATA)
The DATA tristate pin is used to transfer data in and out of
the device. DATA changes after the falling edge and is
valid on the rising edge of the serial clock SCK. During
transmission the DATA line must remain stable while SCK is
high. To avoid signal contention the microcontroller should
only drive DATA low. An external pull-up resistor (e.g. 10 k)
is required to pull the signal high. (See Figure 2) Pull-up
resistors are often included in I/O circuits of microcontrollers.
See Table 5 for detailed IO characteristics.
(1) Each SHTxx is tested to be fully within RH accuracy specifications at 25 °C (77 °F) and 48 °C (118.4 °F)
(2) The default measurement resolution of 14bit (temperature) and 12bit (humidity) can be reduced to 12 and 8 bit through the status register.
www.sensirion.com
v2.02 July 2004
2/9
Page 2

SHT1x / SHT7x Relative Humidity & Temperature Sensor System
2.2.3 Sending a command
To initiate a transmission, a “Transmission Start” sequence
has to be issued. It consists of a lowering of the DATA line
while SCK is high, followed by a low pulse on SCK and
raising DATA again while SCK is still high.
DATA
SCK
Figure 3 "Transmission Start" sequence
The subsequent command consists of three address bits
(only “000” is currently supported) and five command bits.
The SHTxx indicates the proper reception of a command by
pulling the DATA pin low (ACK bit) after the falling edge of
the 8th SCK clock. The DATA line is released (and goes
high) after the falling edge of the 9th SCK clock.
therefore the controller can continue with other tasks and
readout as convenient.
Two bytes of measurement data and one byte of CRC
checksum will then be transmitted. The uC must
acknowledge each byte by pulling the DATA line low. All
values are MSB first, right justified. (e.g. the 5th SCK is MSB
for a 12bit value, for a 8bit result the first byte is not used).
Communication terminates after the acknowledge bit of the
CRC data. If CRC-8 checksum is not used the controller may
terminate the communication after the measurement data
LSB by keeping ack high.
The device automatically returns to sleep mode after the
measurement and communication have ended.
Warning: To keep self heating below 0.1 °C the SHTxx
should not be active for more than 10% of the time
(e.g. max. 2 measurements / second for 12bit accuracy).
Command
Code
Reserved
0000x
Measure Temperature
00011
Measure Humidity
00101
Read Status Register
00111
Write Status Register
00110
Reserved
0101x-1110x
Soft reset, resets the interface, clears the 11110
status register to default values
wait minimum 11 ms before next command
Table 2 SHTxx list of commands
2.2.5 Connection reset sequence
If communication with the device is lost the following signal
sequence will reset its serial interface:
While leaving DATA high, toggle SCK 9 or more times. This
must be followed by a “Transmission Start” sequence
preceding the next command. This sequence resets the
interface only. The status register preserves its content.
DATA
Transmission Start
2.2.4 Measurement sequence (RH and T)
After issuing a measurement command (‘00000101’ for RH,
‘00000011’ for Temperature) the controller has to wait for the
measurement to complete. This takes approximately
11/55/210 ms for a 8/12/14bit measurement. The exact time
varies by up to ±15% with the speed of the internal oscillator.
To signal the completion of a measurement, the SHTxx pulls
down the data line and enters idle mode. The controller must
wait for this “data ready” signal before restarting SCK to
readout the data. Measurement data is stored until readout,
SCK 1 2 3 4 -8 9
Figure 4 Connection reset sequence
2.2.6 CRC-8 Checksum calculation
The whole digital transmission is secured by a 8 bit
checksum. It ensures that any wrong data can be detected
and eliminated.
Please consult application note “CRC-8 Checksum
Calculation” for information on how to calculate the CRC.
Transmission Start
Address=’000’
Command=’00101’
Bold = SHT1xx controls DATA line
Plain = uC controls DATA line
DATA
SCK
Measurement is finished when the
SHTxx pulls down the DATA line
a2
a1 a0 C4
C3 C2 C1 C0
ack
12 bit humidity data
Measurement
~55ms for 12 bit
~11ms for 8 bit
Skip acknowledge to end transmission
(if no CRC is used)
DATA
low low low low
11 10
9
8 ack
7
6 54
3 21
0 ack
SCK
MSB
LSB
CRC-8 Checksum
wait for next measurement Transmission Start
DATA
SCK
Figure 5
7 6 5 4 3 2 1 0 ack Skip acknowledge to
end transmission
MSB
LSB
Example RH measurement sequence for value “0000’1001 ’ 0011’0001”= 2353 = 75.79 %RH (without temperature compensation)
www.sensirion.com
v2.02 July 2004
3/9
Page 3

SHT1x / SHT7x Relative Humidity & Temperature Sensor System
wait for data ready
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
SCK
DATA
TCLH
FSCK
TV
TSU
TR
THO
TF
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
www.sensirion.com
v2.02 July 2004
4/9
Page 4
Part Number SHT75
Manufactur ETC
Description Humidity & Temperature Sensor
Total Page 9 Pages
PDF Download
SHT75 datasheet
Download PDF File
SHT75 datasheet
View Html for PC & Mobile


Related Datasheet

SHT71 , SHT71 , SHT75 , SHT75 ,

site map

webmaste! click here

contact us

Buy Components