1-100071-04 - SENSIRION - Datasheet.Live

www.sensirion.com

Version 5 – December 2011 1/12

Datasheet SHT7x (SHT71, SHT75)

Humidity and Temperature Sensor IC

 Fully calibrated

 Digital output

 Low power consumption

 Excellent long term stability

 Pin type package – easy integration

Dimensions

Figure 1: Drawing of SHT7x (applies to SHT71 and SHT75)

sensor packaging, dimensions in mm (1mm = 0.039inch).

Contact assignment: 1: SCK, 2: VDD, 3: GND, 4: DATA.

Hatched item on backside of PCB is a 100nF capacitor – see

Section 2.1 for more information.

Sensor Chip

SHT7x V4 – for which this datasheet applies – features a

version 4 Silicon sensor chip. Besides a humidity and a

temperature sensor the chip contains an amplifier, A/D

converter, OTP memory and a digital interface. V4 sensors

can be identified by the alpha-numeric traceability code on

the sensor cap – see example “B2G” code on Figure 1.

Material Contents

While the sensor is made of a CMOS chip the sensor

housing consists of an LCP cap with epoxy glob top on an

FR4 substrate. Pins are made of a Cu/Be alloy coated with

Ni and Au. The device is fully RoHS and WEEE compliant,

thus it is free of Pb, Cd, Hg, Cr(6+), PBB and PBDE.

Evaluation Kits

For sensor trial measurements, for qualification of the

sensor or even experimental application (data logging) of

the sensor there is an evaluation kit EK-H4 available

including SHT71 (same sensor chip as SHT1x) and 4

sensor channels, hard and software to interface with a

computer. For other evaluation kits please check

www.sensirion.com/humidity.

Ø 0.4

3.1

2.2

0.6

2.0

0.2

3.7

19.5

6.0

3.4

3.7

13.5

6.4

1.2

0.46

1.27

5.08

71

B2G

1

2

3

4

Product Summary

SHT7x (including SHT71 and SHT75) is Sensirion’s family

of relative humidity and temperature sensors with pins.

The sensors integrate sensor elements plus signal

processing in compact format and provide a fully

calibrated digital output. A unique capacitive sensor

element is used for measuring relative humidity while

temperature is measured by a band-gap sensor. The

applied CMOSens® technology guarantees excellent

reliability and long term stability. Both sensors are

seamlessly coupled to a 14bit analog to digital converter

and a serial interface circuit. This results in superior signal

quality, a fast response time and insensitivity to external

disturbances (EMC).

Each SHT7x is individually calibrated in a precision

humidity chamber. The calibration coefficients are

programmed into an OTP memory on the chip. These

coefficients are used to internally calibrate the signals

from the sensors.

The 2-

wire serial interface and internal

voltage regulation allows for easy and

fast system

integration. The small size and low power consumption

makes SHT7x the ultimate choice for even the most

demanding applications.

SHT7x is supplied on FR4 with pins which allows for easy

integration or replacement. The same sensor is also

available as

surface mountable packaging (SHT1x) or on

flex print (SHTA1).

Datasheet SHT7x

www.sensirion.com Version 5 – December 2011 2/12

Sensor Performance

Relative Humidity

12

Parameter

Condition

min

typ

max

Units

Resolution

1

0.4

0.05

%RH

8

12

bit

Accuracy

2

SHT71

typ ±3.0 %RH

max

see Figure 2

Accuracy

2

SHT75

typ ±1.8 %RH

max

see Figure 2

Repeatability ±0.1 %RH

Hysteresis ±1 %RH

Nonlinearity raw data ±3 %RH

linearized

<<

1

%RH

Response time

3

tau 63%

8

s

Operating Range

0

100

%RH

Long term drift

4

normal

< 0.5

%RH/yr

Figure 2: Maximal RH-tolerance at 25°C per sensor type.

Electrical and General Items

Parameter

Condition

min

typ

max

Units

Source Voltage

2.4

3.3

5.5

V

Power

Consumption

5

sleep

2

5

µW

measuring

3

mW

average

90

µW

Communication

digital 2

-

wire interface, see Communication

Storage

10

–

50°C (0

–

80°C peak), 20

–

60%RH

1

The default measurement resolution of is 14bit for temperature and 12bit for

humidity. It can be reduced to 12/8bit by command to status register.

2

Accuracies are tested at Outgoing Quality Control at 25°C (77°F) and 3.3V.

Values exclude hysteresis and are only applicable to non-condensing

environments.

3

Time for reaching 63% of a step function, valid at 25°C and 1 m/s airflow.

Temperature

45

Parameter

Condition

min

typ

max

Units

Resolution

1

0.04

0.01

°

C

12

14

bit

Accuracy

2

SHT71

typ ±0.4 °C

max

see Figure 3

Accuracy

2

SHT75

typ ±0.3 °C

max see Figure 3

Repeatability ±0.1 °C

Operating Range

-

40

123.8

°

C

-

40

254.9

°F

Response Time

6

tau 63%

5

30

s

Long term drift

< 0.04

°C/yr

Figure 3: Maximal T-tolerance per sensor type.

Packaging Information

Sensor Type

Packaging

Quantity

Order Number

SHT71

Tape

Stripes

50

1

-

100092

-

04

SHT75

Tape Stripes

50

1

-

100071

-

04

This datasheet is subject to change and may be

amended without prior notice.

4

Value may be higher in environments with high contents of volatile organic

compounds. See Section 1.3 of Users Guide.

5

Values for VDD=3.3V at 25°C, average value at one 12bit measurement

per second.

6

Response time depends on heat capacity of and thermal resistance to

sensor substrate.

SHT71

SHT75

± 0

± 2

± 4

± 6

0 10 20 30 40 50 60 70 80 90 100

DRH (%RH)

Relative Humidity (%RH)

SHT71

SHT75

± 0.0

± 0.5

± 1.0

± 1.5

± 2.0

± 2.5

± 3.0

-40 -20 0 20 40 60 80 100

DT (°

°

°C)

Temperature (°C)

www.sensirion.com

Version 5 – December 2011 3/12

Users Guide SHT7x

1 Application Information

1.1 Operating Conditions

Sensor works stable within recommended normal range –

see Figure 4. Long term exposures to conditions outside

normal range, especially at humidity >80%RH, may

temporarily offset the RH signal (+3 %RH after 60h). After

return to normal range it will slowly return towards

calibration state by itself. See Section 1.4 “Reconditioning

Procedure” to accelerate eliminating the offset. Prolonged

exposure to extreme conditions may accelerate ageing.

Figure 4: Operating Conditions

1.2 Sockets and Soldering

For maintain high accuracy specifications the sensor shall

not be soldered. Sockets may be used such as “Preci-dip /

Mill-Max R851-83-004-20-001” or similar.

Standard wave soldering ovens may be used at maximum

235°C for 20 seconds. For manual soldering contact time

must be limited to 5 seconds at up to 350°C

7

.

After wave soldering the devices should be stored at

>75%RH for at least 12h to allow the polymer to re-

hydrate.

Alternatively the re-hydration process may be

performed at ambient conditions (>40%RH) during more

than 5 days.

In no case, neither after manual nor wave soldering, a

board wash shall be applied. In case of application with

exposure of the sensor to corrosive gases the soldering

pads of pins and PCB shall be sealed to prevent loose

contacts or short cuts.

1.3 Storage Conditions and Handling Instructions

It is of great importance to understand that a humidity

sensor is not a normal electronic component and needs to

be handled with care. Chemical vapors at high

concentration in combination with long exposure times

may offset the sensor reading.

7

235°C corresponds to 455°F, 350°C corresponds to 662°F

For these reasons it is recommended to store the sensors

in original packaging including the sealed ESD bag at

following conditions: Temperature shall be in the range of

10°C – 50°C (0 – 80°C for limited time) and humidity at 20

– 60%RH (sensors that are not stored in ESD bags). For

sensors that have been removed from the original

packaging we recommend to store them in ESD bags

made of metal-in PE-HD

8

.

In manufacturing and transport the sensors shall be

prevented of high concentration of chemical solvents and

long exposure times. Out-gassing of glues, adhesive tapes

and stickers or out-gassing packaging material such as

bubble foils, foams, etc. shall be avoided. Manufacturing

area shall be well ventilated.

For more detailed information please consult the

document “Handling Instructions” or contact Sensirion.

1.4 Reconditioning Procedure

As stated above extreme conditions or exposure to solvent

vapors may offset the sensor. The following reconditioning

procedure may bring the sensor back to calibration state:

Baking: 100 – 105°C at < 5%RH for 10h

Re-Hydration: 20 – 30°C at ~ 75%RH for 12h

9

.

1.5 Temperature Effects

Relative humidity reading strongly depends on

temperature. Therefore, it is essential to keep humidity

sensors at the same temperature as the air of which the

relative humidity is to be measured. In case of testing or

qualification the reference sensor and test sensor must

show equal temperature to allow for comparing humidity

readings.

The packaging of SHT7x is designed for minimal heat

transfer from the pins to the sensor. Still, if the SHT7x

shares a PCB with electronic components that produce

heat it should be mounted in a way that prevents heat

transfer or keeps it as low as possible.

Furthermore, there are self-heating effects in case the

measurement frequency is too high. Please refer to

Section 3.3 for detailed information.

8

For example, 3M antistatic bag, product “1910” with zipper .

9

75%RH can conveniently be generated with saturated NaCl solution.

100 – 105°C correspond to 212 – 221°F, 20 – 30°C correspond to 68 – 86°F

Max. Range

Normal

Range

0

20

40

60

80

100

-40 -20 0 20 40 60 80 100 120

Relative Humidity (%)

Temperature (°C)

Datasheet SHT7x

www.sensirion.com Version 5 – December 2011 4/12

1.6 Light

The SHT7x is not light sensitive. Prolonged direct

exposure to sunshine or strong UV radiation may age the

housing.

1.7 Materials Used for Sealing / Mounting

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 Wiring Considerations and Signal Integrity

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 (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 Interface Specifications

Name

Comment

1

SCK

Serial Clock, input only

2

VDD

Source Voltage

3

GND

Ground

4

DATA

Serial Data, bidirectional

Table 1: SHT7x pin assignment.

2.1 Power Pins (VDD, GND)

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

2

C protocol, however, the sensor

can be connected to an I

2

C bus without interference with

other devices connected to the bus. Microcontroller must

switch between protocols.

Figure 5: Typical application circuit, including pull up resistor R

P

.

2.2 Serial clock input (SCK)

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 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 6. 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. 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

VDD

GND

DATA

SCK

71

B2G

1

2

3

4

Micro-

Controller

(Master)

SHT7x

(Slave)

R

P

10kΩ

B2G

71

1

2

3

4

Datasheet SHT7x

www.sensirion.com Version 5 – December 2011 5/12

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 SHT7x with the assumption of 5V supply voltage if not

stated otherwise. For proper communication with the

sensor it is essential to make sure that signal design is

strictly within the limits given in Table 3 and Figure 6.

Absolute maximum ratings for VDD versus GND are +7V

and -0.3V.

Exposure to absolute maximum rating

conditions for extended periods may affect the sensor

reliability (e.g. hot carrier degradation, oxide breakdown).

Parameter

Conditions

min

typ

max

Units

Power supply DC

10

2.4

3.3

5.5

V

Supply current

measuring

0.55

1

mA

average

11

2

28

µA

sleep

0.3

1.5

µA

Low level output

voltage I

OL

< 4 mA 0 250 mV

High level output

voltage R

P

< 25 kΩ 90% 100%

VDD

Low level input

voltage Negative going

0% 20% VDD

High level input

voltage Positive going 80% 100%

VDD

Input current on

pads 1 µA

Output current

on

4

mA

Tri

-

stated (off)

10

20

µA

Table 2: SHT7x DC characteristics. R

P

stands for pull up

resistor, while I

OL

is low level output current.

Figure 6: Timing Diagram, abbreviations are explained in

Table 3. Bold DATA line is controlled by the sensor, plain DATA

line is controlled by the micro-controller. Note that DATA valid

read time is triggered by falling edge of anterior toggle.

10

Recommended voltage supply for highest accuracy is 3.3V, due to sensor

calibration.

11

Minimum value with one measurement of 8 bit resolution without OTP reload

per second, typical value with one measurement of 12bit resolution per

second.

Parameter Conditions min typ max

Units

F

SCK

SCK Frequency VDD > 4.5V

0 0.1 5 MHz

VDD < 4.5V

0 0.1 1 MHz

T

SCKx

SCK hi/low time 100

ns

T

R

/T

F

SCK rise/fall time 1 200

* ns

T

FO

DATA fall time OL = 5pF 3.5 10 20 ns

OL = 100pF

30 40 200

ns

T

RO

DATA rise time ** ** ** ns

T

V

DATA valid time 200

250

*** ns

T

SU

DATA setup time 100

150

*** ns

T

HO

DATA hold time 10 15 **** ns

*

T

R_max

+ T

F_max

= (F

SCK

)

-1

–

T

SCKH

–

T

SCKL

**

T

R0

is

determined by the R

P

*C

bus

time

-

constant at DATA line

***

T

V_max

and T

SU_max

depend on external pull

-

up resistor (R

P

) and total bus

line capacitance (Cbus) at DATA line

****

T

H0_max

< T

V

–

max (T

R0

, T

F0

)

Table 3: SHT7x I/O signal characteristics, OL stands for Output

Load, entities are displayed in Figure 6.

3 Communication with Sensor

3.1 Start up Sensor

As a first step the sensor is powered up to chosen supply

voltage VDD. The slew rate during power up shall not fall

below 1V/ms. After power-up the sensor needs 11ms to

get to Sleep State. No commands must be sent before

that time.

3.2 Sending a Command

To initiate a transmission, a Transmission Start sequence

has to be issued. It consists of a lowering of the DATA line

while SCK is high, followed by a low pulse on SCK and

raising DATA again while SCK is still high – see Figure 7.

Figure 7: "Transmission Start" sequence

The subsequent command consists of three address bits

(only ‘000’ is supported) and five command bits. The

SHT7x indicates the proper reception of a command by

pulling the DATA pin low (ACK bit) after the falling edge of

the 8th SCK clock. The DATA line is released (and goes

high) after the falling edge of the 9th SCK clock.

DATA

SCK

80%

2

0%

80%

2

0%

DATA valid read

DATA valid write

DATA

SCK

80%

2

0%

80%

2

0%

T

V

T

SCKL

T

SU

T

HO

T

SCK

T

SCKH

T

R

T

F

T

RO

T

FO

Datasheet SHT7x

www.sensirion.com Version 5 – December 2011 6/12

Command

Code

Reserved

0000x

Measure

Temperature

00011

Measure Relative Humidity

00101

Read Status Register

00111

Write Status Register

00110

Reserved

0101x

-

1110x

Soft reset,

resets the interface, clears the

status register to default values. Wait minimum

11 ms before next command

11110

Table 4: SHT7x list of commands

3.3 Measurement of RH and T

After issuing a measurement command (‘00000101’ for

relative humidity, ‘00000011’ for temperature) the

controller has to wait for the measurement to complete.

This takes a maximum of 20/80/320 ms for a 8/12/14bit

measurement. The time varies with the speed of the

internal oscillator and can be lower by up to 30%. To

signal the completion of a measurement, the SHT7x pulls

data line low and enters Idle Mode. The controller must

wait for this Data Ready signal before restarting SCK to

readout the data. Measurement data is stored until

readout, therefore the controller can continue with other

tasks and readout at its convenience.

Two bytes of measurement data and one byte of CRC

checksum (optional) will then be transmitted. The micro

controller must acknowledge each byte by pulling the

DATA line low. All values are MSB first, right justified (e.g.

the 5

th

SCK is MSB for a 12bit value, for a 8bit result the

first byte is not used).

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, SHT7x

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 Connection reset sequence

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 8.

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 8: Connection Reset Sequence

3.5 CRC-8 Checksum calculation

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.

3.6 Status Register

Some of the advanced functions of the SHT7x 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 9 and Figure 10 – the

assignation of the bits is displayed in Table 5.

TS

ACK

Bit 7

ACK

0

1

0

Status Register

Figure 9: Status Register Write

Figure 10: Status Register Read

Examples of full communication cycle are displayed in

Figure 11 and Figure 12.

TS

Wait for

DATA ready

0

Command

0

MSB

LSb

ACK

LSB

Checksum

Figure 11: Overview of Measurement Sequence. TS = Trans-

mission Start, MSB = Most Significant Byte, LSB = Last

Significant Byte, LSb = Last Significant Bit.

TS

ACK

Bit 7

ACK

Bit 7

ACK

0

1

Status Register

Checksum

DATA

SCK

80%

2

0%

80%

2

0%

1

2

3

2

4 - 8

9

Transmission Start

Datasheet SHT7x

www.sensirion.com Version 5 – December 2011 7/12

Figure 12: 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.

Bit

Type

Description

Default

7

reserved

0

6 R

End of Battery (low voltage

detection)

‘0’ for VDD > 2.47

‘1’ for VDD < 2.47

X

No default value,

bit is only updated

after a

measurement

5

reserved

0

4

reserved

0

3

For Testing only, do not use

0

2

R/W

Heater

0

off

1

R/W

no reload from OTP

0

reload

0 R/W

’1’ = 8bit RH / 12bit Temp.

resolution

’0’ = 12bit RH / 14bit Temp.

resolution

0 12bit RH

14bit Temp.

Table 5: Status Register Bits

Measurement resolution: The default measurement

resolution of 14bit (temperature) and 12bit (humidity) can

be reduced to 12 and 8bit. This is especially useful in high

speed or extreme low power applications.

End of Battery function detects and notifies VDD voltages

below 2.47 V. Accuracy is ±0.05 V.

Heater: An on chip heating element can be addressed by

writing a command into status register. The heater may

increase the temperature of the sensor by 5 – 10°C

12

beyond ambient temperature. The heater draws roughly

8mA @ 5V supply voltage.

12

Corresponds to 9 – 18°F

For example the heater can be helpful for functionality

analysis: Humidity and temperature readings before and

after applying the heater are compared. Temperature shall

increase while relative humidity decreases at the same

time. Dew point shall remain the same.

Please note: The temperature reading will display the

temperature of the heated sensor element and not

ambient temperature. Furthermore, the sensor is not

qualified for continuous application of the heater.

OTP reload: With this operation the calibration data is

uploaded to the register before each measurement. This

may be deactivated for reducing measurement time by

about 10ms.

4 Conversion of Signal Output

4.1 Relative Humidity

For compensating non-linearity of the humidity sensor –

see Figure 13 – and for obtaining the full accuracy of the

sensor it is recommended to convert the humidity readout

(SO

RH

) with the following formula with coefficients given in

Table 6:

2

RH3RH21linear

SOcSOccRH ⋅+⋅+=

(%RH)

SO

RH

c

1

c

2

c

3

12 bit

-

2.0468

0.0367

-

1.5955E

-

6

8 bit

-

2.0468

0.5872

-

4.0845E

-

4

Table 6: Humidity conversion coefficients

DATA

SCK

DATA

A2 A1

A0

C4 C3 C2 C1 C0 ACK

15 14 13 12 11 10 9 8 ACK 7 6 5

4 3 2 1 0 ACK

7 6 5 4 3 2

1 0 ACK

Transmission Start

Address = ‘000

’

Command = ‘00101

’

12bit Humidity Data

CRC-8 Checksum

Transmission Start

Measurement (80ms for 12bit)

Sleep

(wait for next

measurement)

Idle Bits

Skip ACK to end trans

-

mission (if no CRC is used)

Sensor pulls DATA line low after

completion of measurement

MSb

LSb

MSb

LSb

15 14 13 12 11 10 9 8 ACK

7 6 5 4 3 2 1 0

A2

A1

A0

C4

C3

C2

C1

C0

ACK

7 6 5 4 3 2 1 0 ACK

ACK

Datasheet SHT7x

www.sensirion.com Version 5 – December 2011 8/12

Values higher than 99%RH indicate fully saturated air and

must be processed and displayed as 100%RH

13

. Please

note that the humidity sensor has no significant voltage

dependency.

Figure 13: Conversion from SO

RH

to relative humidity

4.2 Temperature compensation of Humidity Signal

For temperatures significantly different from 25°C (~77°F)

the humidity signal requires temperature compensation.

The temperature correction corresponds roughly to

0.12%RH/°C @ 50%RH. Coefficients for the temperature

compensation are given in Table 8.

(

)

(

)

linearRH21Ctrue

RHSOtt25TRH

+

⋅

+

⋅

−

=

°

SO

RH

t

1

t

2

12 bit

0.01

0.00008

8 bit

0.01

0.00128

Table 7: Temperature compensation coefficients

4.3 Temperature

The band-gap PTAT (Proportional To Absolute

Temperature) temperature sensor is very linear by design.

Use the following formula to convert digital readout (SO

T

)

to temperature value, with coefficients given in Table 9:

T21

SOddT ⋅+=

VDD

d

1

(°C)

d

1

(°F)

SO

T

d

2

(°C)

d

2

(°F)

5V

-

40.1

-

40.2

14bit

0.01

0.018

4V

-

39.8

-

39.6

12bit

0.04

0.072

3.5V

-

39.7

-

39.5

3V

-

39.6

-

39.3

2.5V

-

39.4

-

38.9

Table 8: Temperature conversion coefficients.

13

If wetted excessively (strong condensation of water on sensor surface),

sensor output signal can drop below 100%RH (even below 0%RH in some

cases), but the sensor will recover completely when water droplets

evaporate. The sensor is not damaged by water immersion or condensation.

4.4 Dew Point

SHT7x is not measuring dew point directly, however dew

point can be derived from humidity and temperature

readings. Since humidity and temperature are both

measured on the same monolithic chip, the SHT7x allows

superb dew point measurements.

For dew point (T

d

) calculations there are various formulas

to be applied, most of them quite complicated. For the

temperature range of -40 – 50°C the following

approximation provides good accuracy with parameters

given in Table 10:

( )

TT

Tm

100%

RH

lnm

TT

Tm

100%

RH

ln

TTRH,T

n

nd

+

⋅

−













−

+

⋅

+













⋅=

Temperature Range

Tn (°C)

m

Above water, 0

–

50°C

243.12

17.62

Above ice,

-

40

–

0°C

272.62

22.46

Table 9: Parameters for dew point (T

d

) calculation.

Please note that “ln(…)” denotes the natural logarithm. For

RH and T the linearized and compensated values for

relative humidity and temperature shall be applied.

For more information on dew point calculation see

Application Note “Introduction to Humidity”.

5 Environmental Stability

If sensors are qualified for assemblies or devices, please

make sure that they experience same conditions as the

reference sensor. It should be taken into account that

response times in assemblies may be longer, hence

enough dwell time for the measurement shall be granted.

For detailed information please consult Application Note

“Testing Guide”.

SHT7x have been tested according to the test conditions

given in Table 11. Sensor performance under other test

conditions cannot be guaranteed and is not part of the

sensor specifications. Especially, no guarantee can be

given for sensor performance in the field or for customer’s

specific application.

Please contact Sensirion for detailed information.

0%

20%

40%

60%

80%

100%

0 500 1000 1500 2000 2500 3000 3500

Relative Humidity

SORH sensor readout (12bit)

Datasheet SHT7x

www.sensirion.com Version 5 – December 2011 9/12

E

nvironment

Standard

Results

14

HTOL

125°C, 1000 h

Within

specifications

TC

-

40°C

-

125°C, 500 cycles

Acc. JESD22-A104-C

Within

specifications

THU

85°C / 85%RH, 1000h

Within

specifications

ESD immunity

MIL STD 883E, method 3015

(Human Body Model at ±2kV)

Qualified

Latch

-

up

force current of ±100mA with

T

amb

= 80°C, acc. JEDEC 17

Qualif

ied

Table 10: Qualification tests: HTSL = High Temperature Storage

Lifetime, TC = Temperature Cycles, UHST = Unbiased Highly

accelerated temperature and humidity Test, THU = Temperature

humidity unbiased

6 Packaging

6.1 Packaging type

The device is supplied in a single-in-line pin type package.

The sensor housing consists of a Liquid Crystal Polymer

(LCP) cap with epoxy glob top on a standard 0.6 mm FR4

substrate. The sensor head is connected to the pins, by a

small bridge to minimize heat conduction and response

times. The pins are made of Cu/Be alloy coated with

1.3µm Ni and 0.5µm Au, which are soldered to the FR4

substrate by lead-free solder paste. The gold plated back

side of the sensor head is connected to the GND pin. A

100nF capacitor is mounted on the back side between

VDD and GND. The device is fully RoHS and WEEE

compliant – thus it is free of of Pb, Cd, Hg, Cr(6+), PBB

and PBDE.

Size including pins is 19.5 x 5.08 x 3.1mm. Total weight:

168 mg, weight of sensor head: 73 mg.

All pins are Au plated to avoid corrosion. They can be

soldered or mate with most 1.27 mm (0.05’’) sockets, for

example: Preci-dip / Mill-Max R851-83-004-20-001 or

similar.

6.2 Traceability Information

All SHT7x are marked with an alphanumeric, three digit

code on the chip cap – see “B2G” on Figure 1. The lot

numbers allow full traceability through production,

calibration and testing. No information can be derived from

the code directly, respective data is stored at Sensirion.

Labels on the reels are displayed in Figure 14 and Figure

15, they both give traceability information.

14

According to accuracy and long term drift specification given on Page 2.

Figure 14: First label on reel: XX = Sensor Type (71 for SHT71),

NN = Chip Version (04 for V4), Y = last digit of year, RRR =

number of sensors on reel divided by 10 (200 for 2000 units),

TTTTT = Traceability Code.

Figure 15: Second label on reel: For Device Type and Part

Order Number please refer to Table 12, Delivery Date (also

Date Code) is date of packaging of sensors (DD = day, MM =

month, YYYY = year), CCCC = number of order.

6.3 Shipping Package

SHT7x are shipped in 32mm tape at 50pcs each – for

details see Figure 16 and Table 12. Reels are individually

labeled with barcode and human readable labels, see

section 6.2.

Sensor Type

Packaging

Quantity

Order

Number

SHT71

Tape Stripes

50

1

-

100092

-

04

SHT75

Tape Stripes

50

1

-

100071

-

04

Table 11: Packaging types per sensor type.

Dimensions of packaging tape are given in Figure 16. All

tapes have a 7 pockets empty leader tape (first pockets of

the tape) and a 7 pockets empty trailer tape (last pockets

of the tape).

Device Type: 1-100PPP-NN

Description: Humidity & Temperature Sensor

SHTxx

Part Order No. 1-100PPP-NN or Customer Number

Date of Delivery: DD.MM.YYYY

Order Code: 45CCCC / 0

Lot No.: XX0-NN-YRRRTTTTT

Quantity: RRRR

RoHS: Compliant

Lot No.

Datasheet SHT7x

www.sensirion.com Version 5 – December 2011 10/12

Figure 16: Tape configuration and unit orientation within tape,

dimensions in mm (1mm = 0.039inch). Leader tape is to the right

of the figure, trailer tape to the left.

Ø1.5 MIN

Ø2.0 MIN

R0.5 TYP

R0.75 TYP

1.75 ± 0.10

0.20± 0.05

14.2

12.00

2.00 ± 0.10

4.00

28.4 ± 0.1

32.0 ± 0.3

20.5

6.4

14.1

5.6

3.6

2.7

0.30

R0.30 MAX

71

B2G

Datasheet SHT7x

www.sensirion.com Version 5 – December 2011 11/12

Revision History

Date

Version

Page(s)

Changes

March 2007

3.0

1

–

10

Data sheet valid for SHTxx

-

V4 and SHTxx

-

V3

July 2008

4.0

1

–

10

New release, rework of datasheet

April 2009

4.2

2, 7

Amended foot note 2, communication

diagram changed (Figure 12)

May 2010

4.3

1

–

11

Errors eliminated, information added

–

for details please ask for change protocol.

December 2011

5

1

, 7

-

9

References to V3 sensors eliminated.

Datasheet SHT7x

www.sensirion.com Version 5 – December 2011 12/12

Important Notices

Warning, Personal Injury

Do not use this product as safety or emergency stop devices or in

any other application where failure of the product could result in

personal injury. Do not use this product for applications other

than its intended and authorized use. Before installing, handling,

using or servicing this product, please consult the data sheet and

application notes. Failure to comply with these instructions could

result in death or serious injury.

If the Buyer shall purchase or use SENSIRION products for any

unintended or unauthorized application, Buyer shall defend, indemnify

and hold harmless SENSIRION and its officers, employees,

subsidiaries, affiliates and distributors against all claims, costs,

damages and expenses, and reasonable attorney fees arising out of,

directly or indirectly, any claim of personal injury or death associated

with such unintended or unauthorized use, even if SENSIRION shall be

allegedly negligent with respect to the design or the manufacture of the

product.

ESD Precautions

The inherent design of this component causes it to be sensitive to

electrostatic discharge (ESD). To prevent ESD-induced damage and/or

degradation, take customary and statutory ESD precautions when

handling this product.

See application note “ESD, Latchup and EMC” for more information.

Warranty

SENSIRION warrants solely to the original purchaser of this product for

a period of 12 months (one year) from the date of delivery that this

product shall be of the quality, material and workmanship defined in

SENSIRION’s published specifications of the product. Within such

period, if proven to be defective, SENSIRION shall repair and/or

replace this product, in SENSIRION’s discretion, free of charge to the

Buyer, provided that:

• notice in writing describing the defects shall be given to

SENSIRION within fourteen (14) days after their appearance;

• such defects shall be found, to SENSIRION’s reasonable

satisfaction, to have arisen from SENSIRION’s faulty design,

material, or workmanship;

• the defective product shall be returned to SENSIRION’s factory at

the Buyer’s expense; and

• the warranty period for any repaired or replaced product shall be

limited to the unexpired portion of the original period.

This warranty does not apply to any equipment which has not been

installed and used within the specifications recommended by

SENSIRION for the intended and proper use of the equipment.

EXCEPT FOR THE WARRANTIES EXPRESSLY SET FORTH

HEREIN, SENSIRION MAKES NO WARRANTIES, EITHER EXPRESS

OR IMPLIED, WITH RESPECT TO THE PRODUCT. ANY AND ALL

WARRANTIES, INCLUDING WITHOUT LIMITATION, WARRANTIES

OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR

PURPOSE, ARE EXPRESSLY EXCLUDED AND DECLINED.

SENSIRION is only liable for defects of this product arising under the

conditions of operation provided for in the data sheet and proper use of

the goods. SENSIRION explicitly disclaims all warranties, express or

implied, for any period during which the goods are operated or stored

not in accordance with the technical specifications.

SENSIRION does not assume any liability arising out of any application

or use of any product or circuit and specifically disclaims any and all

liability, including without limitation consequential or incidental

damages. All operating parameters, including without limitation

recommended parameters, must be validated for each customer’s

applications by customer’s technical experts. Recommended

parameters can and do vary in different applications.

SENSIRION reserves the right, without further notice, (i) to change the

product specifications and/or the information in this document and (ii) to

improve reliability, functions and design of this product.

Copyright

©

2011, SENSIRION.

CMOSens

®

is a trademark of Sensirion

Headquarters and Subsidiaries

SENSIRION AG

Laubisruetistr. 50

CH-8712 Staefa ZH

Switzerland

phone: +41 44 306 40 00

fax: +41 44 306 40 30

info@sensirion.com

www.sensirion.com

Sensirion Inc., USA

phone: +1 805 409 4900

info_us@sensirion.com

www.sensirion.com

Sensirion Japan Co. Ltd.

phone: +81 3 3444 4940

info@sensirion.co.jp

www.sensirion.co.jp

Sensirion Korea Co. Ltd.

phone: +82 31 345 0031 3

info@sensirion.co.kr

www.sensirion.co.kr

Sensirion China Co. Ltd.

phone: +86 755 8252 1501

info@sensirion.com.cn

www.sensirion.com.cn

Sensirion AG

(Germany)

phone: +41 44 927 11 66

info@sensirion.com

www.sensirion.com To find your local representative, please visit www.sensirion.com/contact