Datasheet SHT1x
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. Power supply pins (VDD, GND) must be
decoupled with a 100nF capacitor if wires are used.
Capacitor should be placed as close to the sensor as
possible. Please see the Application Note “ESD, Latch-up
and EMC” for more information.
1.10 ESD (Electrostatic Discharge)
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
amb
= 80°C according to JEDEC78A. See
Application Note “ESD, Latch-up and EMC” for more
information.
2.2 Serial clock input (SCK)
SCK is used to synchronize the communication between
microcontroller and SHT1x. Since the interface consists of
fully static logic there is no minimum SCK frequency.
2.3 Serial data (DATA)
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
SU
and T
HO
before the rising and after the falling edge of SCK,
respectively – see Figure 11. For reading data from the
sensor, DATA is valid T
V
after SCK has gone low and
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. 10kΩ) is
required to pull the signal high – it should be noted that
pull-up resistors may be included in I/O circuits of
microcontrollers. See Table 2 for detailed I/O characteristic
of the sensor.
2.4 Electrical Characteristics
The electrical characteristics such as power consumption,
low and high level input and output voltages depend on
the supply voltage. Table 2 gives electrical characteristics
of SHT1x with the assumption of 5V supply voltage if not
stated otherwise.
Parameter
Conditions
Power supply DC
10
measuring
Supply current
average
11
sleep
Low level output
I
OL
< 4 mA
voltage
High level output
R
P
< 25 kΩ
voltage
Low level input
Negative going
voltage
High level input
Positive going
voltage
Input current
on pads
on
Output current
Tri-stated (off)
min
2.4
2
0
90%
0%
80%
typ max Units
3.3 5.5
V
0.55
1
mA
28
µA
0.3 1.5
µA
250
mV
2 Interface Specifications
Pin Name
Comment
1 GND Ground
2 DATA Serial Data, bidirectional
3 SCK Serial Clock, input only
4 VDD Source Voltage
NC NC Must be left unconnected
NC
1
2
3
4
NC
NC
NC
NC
NC
A5Z
11
Table 1:
SHT1x pin assignment, NC remain floating.
2.1 Power Pins (VDD, GND)
The supply voltage of SHT1x must be in the range of 2.4 –
5.5V, recommended supply voltage is 3.3V. Power supply
pins Supply Voltage (VDD) and Ground (GND) must be
decoupled with a 100 nF capacitor – see Figure 10.
The serial interface of the SHT1x is optimized for sensor
readout and effective power consumption. The sensor
cannot be addressed by I
2
C protocol; however, the sensor
can be connected to an I
2
C bus without interference with
other devices connected to the bus. The controller must
switch between the protocols.
VDD
R
P
10kΩ
100% VDD
20% VDD
100% VDD
1
4
20
µA
mA
µA
GND
SHT1x
Micro-
Controller
(Master)
DATA
SCK
VDD
100nF
A5Z
10
11
(Slave)
GND
Table 2:
SHT1x DC characteristics. R
P
stands for pull up
resistor, while I
OL
is low level output current.
10
2.4 – 5.5V
Figure 10:
Typical application circuit, including pull up resistor
R
P
and decoupling of VDD and GND by a capacitor.
Recommended voltage supply for highest accuracy is 3.3V, due to sensor
calibration.
11
Minimum value with one measurement of 8bit resolution without OTP reload
per second. Typical value with one measurement of 12bit resolution per
second.
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