SHT15 SENSIRION, SHT15 Datasheet - Page 7

• Manufacturer Part Number: SHT15
• Description: Humidity Sensor
• Manufacturer: SENSIRION

Specifications of SHT15

• Sensing Accuracy: 2%
• Sensor Output: Digital
• Sensor Terminals: SMD
• Humidity Accuracy ±: 2%
• Peak Reflow Compatible (260 C): Yes
• Terminal Type: PCB Surface Mount
• Humidity Range: 0 To 100% RH
• Response Time: 8s
• Leaded Process Compatible: Yes
• Package / Case: 4-LCC SMD
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Datasheet SHT1x
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 measurement
and communication are completed.
Important: To keep self heating below 0.1°C, SHT1x
should not be active for more than 10% of the time – e.g.
maximum one measurement per second at 12bit accuracy
shall be made.
3.4
If communication with the device is lost the following signal
sequence will reset the serial interface: While leaving
DATA high, toggle SCK nine or more times – see Figure
13. 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.
Figure 13: Connection Reset Sequence
3.5
The whole digital transmission is secured by an 8bit
checksum. It ensures that any wrong data can be detected
and eliminated. As described above this is an additional
feature of which may be used or abandoned. Please
consult Application Note “CRC Checksum” for information
on how to calculate the CRC.
Figure 17: Example RH measurement sequence for value “0000’0100“0011’0001” = 1073 = 35.50%RH (without temperature
compensation). DATA valid times are given and referenced in boxes on DATA line. Bold DATA lines are controlled by sensor while plain
lines are controlled by the micro-controller.
www.sensirion.com
SCK
DATA
SCK
DATA
SCK
DATA
SCK
DATA
Connection reset sequence
CRC Checksum calculation
1
15
2
Transmission Start
7
15
MSb
7
3
2
14
14
6
Idle Bits
6
4 - 8
13
13
5
5
CRC-8 Checksum
12
12
4
9
4
Transmission Start
11
MSb
11
3
3
10
10
2
Address = ‘000’
A2
A2
2
9
9
1
A1
A1
1
Version 4.3 – May 2010
8
8
LSb
0
A0
20%
80%
20%
A0
80%
0
C4
C4
ACK
ACK
12bit Humidity Data
ACK
ACK
Command = ‘00101’
C3
C3
7
3.6
Some of the advanced functions of the SHT1x such as
selecting measurement resolution, end-of-battery notice,
use of OTP reload or using the heater may be activated by
sending a command to the status register. The following
section gives a brief overview of these features.
After the command Status Register Read or Status
Register Write – see Table 4 – the content of 8 bits of the
status register may be read out or written. For the
communication compare Figure 14 and Figure 15 – the
assignation of the bits is displayed in Table 5.
Figure 14: Status Register Write
Figure 15: Status Register Read
Examples of full communication cycle are displayed in
Figure 16 and Figure 17.
Figure 16: Overview of Measurement Sequence. TS = Trans-
mission Start, MSB = Most Significant Byte, LSB = Last
Significant Byte, LSb = Last Significant Bit.
7
Sleep (wait for next
0 0 0 0 0 1 1 0
0 0 0 0 0 1 1 1
C2
C2
0 0 0 Command
6
measurement)
6
Status Register
C1
C1
5
5
C0
C0
LSB
4
4
ACK
ACK
DATA ready
3
Wait for
3
Transmission Start
Status Register
Status Register
2
Sensor pulls DATA line low after
completion of measurement
2
(80ms for 12bit)
Measurement
0 0
1
1
Checksum
LSb
0
0
MSB
Skip ACK to end transmission
(if no CRC is used)
ACK
ACK
Checksum
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