Data Sheet

Datasheet SHT3x-DIS
www.sensirion.com May 2018- Version 5 8/22
3 Pin Assignment
The SHT3x-DIS comes in a 8-pin DFN package – see
Table 7.
Pin
Name
Comments
1
SDA
Serial data; input / output
2
ADDR
Address pin; input; connect to either
logic high or low, do not leave floating
3
ALERT
Indicates alarm condition; output; must
be left floating if unused
4
SCL
Serial clock; input / output
5
VDD
Supply voltage; input
6
nRESET
Reset pin active low; input; if not used it
is recommended to be left floating; can
be connected to VDD with a series
resistor of R ≥2 kΩ
7
R
No electrical function; to be connected
to VSS
8
VSS
Ground
Table 7 SHT3x-DIS pin assignment (transparent top view).
Dashed lines are only visible if viewed from below. The die
pad is internally connected to VSS.
3.1 Power Pins (VDD, VSS)
The electrical specifications of the SHT3x-DIS are shown
in Table 3. The power supply pins must be decoupled
with a 100 nF capacitor that shall be placed as close to
the sensor as possible – see Figure 11 for a typical
application circuit.
3.2 Serial Clock and Serial Data (SCL, SDA)
SCL is used to synchronize the communication between
microcontroller and the sensor. The clock frequency can
be freely chosen between 0 to 1000 kHz. Commands
with clock stretching according to I2C Standard
11
are
supported.
The SDA pin is used to transfer data to and from the
sensor. Communication with frequencies up to 400 kHz
must meet the I2C Fast Mode
11
standard.
11
http://www.nxp.com/documents/user_manual/UM10204.pdf
Communication frequencies up to 1 Mhz are supported
following the specifications given in Table 21.
Both SCL and SDA lines are open-drain I/Os with diodes
to VDD and VSS. They should be connected to external
pull-up resistors (please refer to Figure 11). A device on
the I2C bus must only drive a line to ground. The external
pull-up resistors (e.g. R
p
=10 kΩ) are required to pull the
signal high. For dimensioning resistor sizes please take
bus capacity and communication frequency into account
(see for example Section 7.1 of NXPs I2C Manual for
more details
11
). It should be noted that pull-up resistors
may be included in I/O circuits of microcontrollers. It is
recommended to wire the sensor according to the
application circuit as shown in Figure 11.
Figure 11 Typical application circuit. Please note that the
positioning of the pins does not reflect the position on the
real sensor. This is shown in Table 7.
3.3 Die Pad (center pad)
The die pad or center pad is visible from below and
located in the center of the package. It is electrically
connected to VSS. Hence electrical considerations do
not impose constraints on the wiring of the die pad.
However, due to mechanical reasons it is recommended
to solder the center pad to the PCB. For more
information on design-in, please refer to the document
“SHTxx_STSxx Design Guide”.
3.4 ADDR Pin
Through the appropriate wiring of the ADDR pin the I2C
address can be selected (see Table 8 for the respective
addresses). The ADDR pin can either be connected to
logic high or logic low. The address of the sensor can be
changed dynamically during operation by switching the
level on the ADDR pin. The only constraint is that the
level has to stay constant starting from the I2C start
condition until the communication is finished. This allows
to connect more than two SHT3x-DIS onto the same bus.
1
2
3
4
5
8
7
6
V
DD
RR
PP
100nF
ADDR(2)
ALERT(3)
die
pad
R(7)
SDA(1)
SCL(4)
VDD(5)
VSS(8)
nRESET(6)