SHT71 SENSIRION, SHT71 Datasheet - Page 4

• Manufacturer Part Number: SHT71
• Description: Humidity Sensor
• Manufacturer: SENSIRION

Specifications of SHT71

• Sensing Accuracy: 3%
• Sensor Output: Digital
• Sensor Terminals: Through Hole
• Peak Reflow Compatible (260 C): Yes
• Terminal Type: PCB Surface Mount
• Humidity Range: 0 To 100% RH
• Response Time: 8s
• Humidity Accuracy ±: 3%
• Rohs Compliant: Yes
• Leaded Process Compatible: Yes
• Package / Case: 4-SIP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Datasheet SHT7x
1.6
The SHT7x is not light sensitive. Prolonged direct
exposure to sunshine or strong UV radiation may age the
housing.
1.7
Many materials absorb humidity and will act as a buffer
increasing response times and hysteresis. Materials in the
vicinity of the sensor must therefore be carefully chosen.
Recommended materials are: Any metals, LCP, POM
(Delrin), PTFE (Teflon), PE, PEEK, PP, PB, PPS, PSU,
PVDF, PVF.
For sealing and gluing (use sparingly): Use high filled
epoxy for electronic packaging (e.g. glob top, underfill),
and Silicone. Out-gassing of these materials may also
contaminate the SHT7x (see Section 1.3). Therefore try to
add the sensor as a last manufacturing step to the
assembly, store the assembly well ventilated after
manufacturing or bake at 50°C for 24h to outgas
contaminants before packing.
1.8
SHT7x are often applied using wires. Carrying the SCK
and DATA signal parallel and in close proximity more than
10cm may result in cross talk and loss of communication.
This may be resolved by routing VDD and/or GND
between the two data signals and/or using shielded
cables. Furthermore, slowing down SCK frequency will
possibly improve signal integrity.
Please see the Application Note “ESD, Latch-up and
EMC” for more information.
1.9
ESD immunity is qualified according to MIL STD 883E,
method 3015 (Human Body Model at 2 kV).
Latch-up immunity is provided at a force current of
100mA with T
Application Note “ESD, Latch-up and EMC” for more
information.
2 Interface Specifications
www.sensirion.com
Pin
1
2
3
4
Light
Wiring Considerations and Signal Integrity
ESD (Electrostatic Discharge)
Materials Used for Sealing / Mounting
Name
DATA
GND
SCK
VDD
amb
= 80°C according to JEDEC78A. See
Comment
Serial Clock, input only
Source Voltage
Ground
Serial Data, bidirectional
Version 4.3 – May 2010
Table 1: SHT7x pin assignment.
2.1
The supply voltage of SHT7x must be in the range of 2.4
and 5.5V, recommended supply voltage is 3.3V.
Decoupling of VDD and GND by a 100nF capacitor is
integrated on the backside of the sensor packaging.
The serial interface of the SHT7x is optimized for sensor
readout and effective power consumption. The sensor
cannot be addressed by I
can be connected to an I
other devices connected to the bus. Microcontroller must
switch between protocols.
Figure 5: Typical application circuit, including pull up resistor R
2.2
SCK is used to synchronize the communication between
microcontroller and SHT7x. Since the interface consists of
fully static logic there is no minimum SCK frequency.
2.3
The DATA tri-state pin is used to transfer data in and out
of the sensor. For sending a command to the sensor,
DATA is valid on the rising edge of the serial clock (SCK)
and must remain stable while SCK is high. After the falling
edge of SCK the DATA value may be changed. For safe
communication DATA valid shall be extended T
before the rising and after the falling edge of SCK,
respectively – see Figure 6. For reading data from the
sensor, DATA is valid T
remains valid until the next falling edge of SCK.
To avoid signal contention the microcontroller must only
drive DATA low. An external pull-up resistor (e.g. 10 kΩ) is
required to pull the signal high – it should be noted that
pull-up resistors may be included in I/O circuits of
Controller
Power Pins (VDD, GND)
Serial clock input (SCK)
Serial data (DATA)
(Master)
Micro-
GND
VDD
2
V
2
C protocol, however, the sensor
C bus without interference with
after SCK has gone low and
SCK
DATA
(Slave)
SHT7x
1 2 3 4
B2G
71
SU
and T
4/11
HO
P
.