Datasheet SHT1x

www.sensirion.com

Version 5 – December 2011

5/12

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

Application Note “ESD, Latch-up and EMC” for more

information.

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

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

other devices connected to the bus. The controller must

switch between the protocols.

Figure 10: Typical application circuit, including pull up resistor

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

before the rising and after the falling edge of SCK,

respectively – see Figure 11. For reading data from the

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. 10k ) 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

min

typ

max Units

2.4

3.3

5.5

V

Supply current

measuring

0.55

1

mA

2

28

A

sleep

0.3

1.5

A

Low level output

voltage

0

250

mV

High level output

voltage

90%

100% VDD

Low level input

voltage

Negative going

0%

20% VDD

High level input

voltage

Positive going

80%

100% VDD

1

A

Output current

on

4

mA

Tri-stated (off)

10

20

A

calibration.

per second. Typical value with one measurement of 12bit resolution per

second.

A5Z

11

NC

NC

NC

NC

NC

NC

1

2

3

4

Micro-

Controller

(Master)

GND

2.4 – 5.5V

DATA

SCK

VDD

VDD

GND

SHT1x

(Slave)

A5Z

11

100nF