SHT40-AD1B-R2

Overview

Features

SHT4x is a digital sensor platform for measuring relative humidity and temperature at different accuracy classes. Its I2C interface provides several preconfigured I2C addresses and maintains an ultra-low power budget. The power-trimmed internal heater can be used at three heating levels thus enabling sensor operation in demanding environments. The four-pin dual-flat-no- leads package is suitable for surface mount technology (SMT) processing and comprises an optional on-package patented PTFE [1] membrane or a removable protection cap.

Products Details

SHT40-AD1B base RH&T accur., 0x44 I2C addr.

SHT40-BD1B base RH&T accur., 0x45 I2C addr.

SHT40-AD1F add. patented on-package PTFE

membrane

SHT40-AD1P add. removable protection cap

SHT41-AD1B Intermed. RH&T accur., 0x44 I2C addr. SHT45-AD1B ±1.0 %RH, ±0.1°C accur., 0x44 I2C addr.

Full

1 Quick Start – Hello World ..................................................................................................................................... 3

2 Humidity and Temperature Sensor Specifications ....................................................................................... 4

2.1 Relative Humidity ............................................................................................................................................ 4

2.2 Temperature ..................................................................................................................................................... 6

2.3 Recommended Operating Conditions ...................................................................................................... 7

3 Electrical Specifications ........................................................................................................................................ 8

3.1 Electrical Characteristics .............................................................................................................................. 8

3.2 Timings ............................................................................................................................................................... 9

3.3 Absolute Maximum Ratings ......................................................................................................................... 9

4 Sensor Operation .................................................................................................................................................. 10

4.1 I2C communication ....................................................................................................................................... 10

4.2 I2C Communication Timing ....................................................................................................................... 10

4.3 Data type & length ........................................................................................................................................ 10

4.4 Checksum Calculation ................................................................................................................................. 10

4.5 Command Overview .................................................................................................................................... 11

4.6 Conversion of Signal Output ..................................................................................................................... 11

4.7 Serial number ................................................................................................................................................. 12

4.8 Reset & Abort ................................................................................................................................................. 12

4.9 Heater Operation ........................................................................................................................................... 12

5 Physical Specification .......................................................................................................................................... 13

5.1 Package Description .................................................................................................................................... 13

5.2 Package Outline ............................................................................................................................................ 13

5.3 Land Pattern ................................................................................................................................................... 13

5.4 Pin Assignment & Laser Marking ............................................................................................................. 14

5.5 Thermal Information ..................................................................................................................................... 15

6 Quality and Material Contents ........................................................................................................................... 15

7 Tape and Reel Packaging .................................................................................................................................. 15

8 Product Name Nomenclature ............................................................................................................................ 16

9 Ordering Information ............................................................................................................................................ 16

10 Bibliography .......................................................................................................................................................... 17

11 Revision History .................................................................................................................................................. 17

• Relative humidity accuracy: up to ±1.0 %RH
• Operating range: 0…100 %RH, -40…125 °C
• Temperature accuracy: up to ±0.1 °C
• Fully functional in condensing environment
• Supply voltage: 1.08 V … 3.6 V
• Variable power heater
• Average current: 0.4 µA (at meas. rate 1 Hz)
• NIST traceability
• Idle current: 80 nA
• JEDEC JESD47 qualification
• I2C FM+, CRC checksum, multip. I2C addr.
• Mature technology from global market leader
• Patented on-package PTFE membrane [1]
• Removable protection cap

Applications

i2c_write(i2c_addr=0x44, tx_bytes=[0xFD]) wait_seconds(0.01) rx_bytes = i2c_read(i2c_addr=0x44, number_of_bytes=6) t_ticks = rx_bytes[0] * 256 + rx_bytes[1] checksum_t = rx_bytes[2] rh_ticks = rx_bytes[3] * 256 + rx_bytes[4] checksum_rh = rx_bytes[5] t_degC = -45 + 175 * t_ticks/65535 rh_pRH = -6 + 125 * rh_ticks/65535 if (rh_pRH > 100): rh_pRH = 100 if (rh_pRH < 0): rh_pRH = 0

Find code resources and embedded drivers on: https://github.com/Sensirion/embedded- sht/releases

CAD files can be downloaded from SnapEDA: https://www.snapeda.com/search/?q=sht4%3F- &search-type=parts

Long-term drift 8 typ. <0.2 %RH/y

Table 1: General relative humidity sensor specifications.

1 For definition of typ. and max. accuracy, please refer to the document “Sensirion Humidity Sensor Specification Statement”. 2 The stated repeatability is 3 times the standard deviation (3σ) of multiple consecutive measurement values at constant conditions and is a measure for the noise

on the physical sensor output. Different repeatability commands are listed in Table 7.

SHT40 typ

SHT41 typ

SHT40 max

SHT41 max

SHT45 typ

SHT45 max

Relative Humidity (%RH)

Figure 4: SHT45 typical and maximal relative humidity accuracy at 25 °C

SHT41 |typ. Delta %RH|

SHT40 |typ. Delta %RH|

humidity and temperature for SHT41.

SHT45 |typ. Delta %RH|

Temperature (°C)

Figure 7: Typical RH accuracy tolerance over humidity and temperature for SHT45.

max. see Figure 9 -

SHT45 T Accuracy 1 typ.  0.1 °C

Table 2: General temperature sensor specifications.

±1.0

SHT40 typ SHT40 max

SHT41 typ SHT41 max

±0.8

±0.6

±0.4

±0.2

±0.0

Figure 10: SHT45 typical and maximal temperature accuracy.

The sensor shows best performance when operated within the recommended normal temperature and humidity range of 5 °C … 60 °C and 20 %RH … 80 %RH, respectively. Long term exposure to conditions outside recommended normal range, especially at high relative humidity, may temporarily offset the RH signal (e.g. +3 %RH after 60 h at > 80 %RH). After returning into the recommended normal temperature and humidity range the sensor will recover to within specifications by itself. Prolonged exposure to extreme conditions may accelerate ageing. To ensure stable operation of the humidity sensor, the conditions described in the document [2] regarding exposure to volatile organic compounds must be met. Please note as well that this does apply not only to transportation and manufacturing, but also to operation of the SHT4x.

Part Numbering

I2C interface with 0x44 address I2C interface with 0x45 address

B package without membrane

Packaging article contains 2’500 pieces

Packaging article contains 10’000 pieces

Table 9 SHT4x product name nomenclature.

Specifications

Stress levels beyond those listed in Table 5 may cause permanent damage or affect the reliability of the device. These are stress ratings only and functional operation of the device at these conditions is not guaranteed. Ratings are only tested each at a time.

Parameter Rating

Storage temperature range 11 -40 °C …150 °C

ESD HBM 2 kV

Latch up, JESD78 Class II, 125°C +-100 mA

Table 5: Absolute maximum ratings.

Interface & Communication

Parameter Symbol Conditions Min Typ Max Unit Comments

Supply

voltage V DD 1.08 3.3 3.6 V -

Power-

V POR Static power supply 0.6 - 1.08 V -

up/down level

Voltage changes on the

Slew rate of

supply between V DD, min

the supply

V DD, slew - - 20 V/ms

and V DD, max. Faster slew

voltage

rates may lead to a reset

µA At 25°C

Measurement - 320 500 µA Current while sensor is

Supply current

measuring

(no heater) I DD

Aver., high repeatability

Aver. current consumption (continuous operation with

Aver., med. repeatability

one meas. per second)

Aver. power consumption

consumpt. at

(continuous operation with

(no heater)

Aver., low repeatability

input voltage V IL - 0 - 0.3*

Low level

High level

resistors R p

R pullup > 390 Ω - - 0.4 V -

Capacitive bus load can be

R P ≤ 820 Ω: fast mode - - 400 pF

determined from

C b < t rise /(0.8473*R p ).

for fast mode and

VDD > 1.62 V: fast

- - 340 pF

t rise = 120 ns for fast mode

mode plus

plus

Max. values are measured at -40°C and 1.08 V supply voltage (based on characterization).

Parameter Symbol Conditions Min. Typ. Max. Units Comments

Time between V DD reaching V POR and

Power-up time t PU After hard reset,

V DD ≥ V POR - 0.3 1 ms

sensor entering idle

state

Time between ACK of

soft reset command and

Soft reset time t SR After soft reset - - 1 ms

state. Also valid for I2C

general call reset.

t MEAS,l Low

repeatability - 1.3 1.6 ms Including t PU :

The three repeatability

Measurement

t MEAS,m Med.

modes differ with

repeatability - 3.7 4.5 ms

duration

respect to measurement duration, noise level and

t MEAS,h High

repeatability - 6.9 8.3 ms

energy consumption

After that time the heater is automatically switched off

Long pulse 0.9 1 1.1 s

Heater-on duration t Heater

Short pulse 0.09 0.1 0.11 s

Table 4 System timing specifications.

I2C bus operates with 8-bit data packages. Information from the sensor to the master has a checksum after every second 8-bit data package. Humidity and temperature data will always be transmitted in the following way: The first value is the temperature signal (2 * 8-bit data + 8-bit CRC), the second is the humidity signal (2 * 8-bit data + 8-bit CRC).

For read transfers each 16-bit data is followed by a checksum with the following properties

Property Value

Name CRC-8

Message Length 16-bit

0xFD 6 measure T & RH with high precision (high repeatability)

[2 * 8-bit T-data; 8-bit CRC; 2 * 8-bit RH-data; 8-bit CRC]

0xF6 6 measure T & RH with medium precision (medium repeatability)

0xE0 6 measure T & RH with lowest precision (low repeatability) [2 * 8-bit T-data; 8-bit CRC; 2 * 8-bit RH-data; 8-bit CRC]

0x89 6 read serial number

[2 * 8-bit data; 8-bit CRC; 2 * 8-bit data; 8-bit CRC]

activate heater with 200mW for 1s, including a high precision

measurement just before deactivation

activate heater with 200mW for 0.1s including a high precision

activate heater with 110mW for 1s including a high precision

activate heater with 110mW for 0.1s including a high precision

activate heater with 20mW for 1s including a high precision

activate heater with 20mW for 0.1s including a high precision

Table 7 Overview of I2C commands. If the sensor is not ready to process a command, e.g. because it is still measuring, it will response with NACK to the I2C read header. Given heater power values are typical and valid for VDD=3.3V.

Signal Conversion

The digital sensor signals correspond to following humidity and temperature values:

A reset of the sensor can be achieved in three ways:

1. The heater is enabled, and the timer starts its count-down. 2. On timer expiration a temperature and humidity measurement with the highest repeatability

is started, the heater remains enabled.

3. After the measurement is finished the heater is turned off.

4. Temperature and humidity values are now available for readout.

The maximum on-time of the heater commands is 1 second in order to prevent overheating of the sensor by unintended usage of the heater. Thus, there is no dedicated command to turn off the heater. For extended heating periods it is required to send periodic heater-on commands, keeping in mind that the heater is designed for a maximal duty cycle of less than 10%. To obtain a fast increase in temperature the idle time between consecutive heating pulses shall be kept minimal.

There will be dedicated Sensirion application notes elaborating on various use cases of the heater. In general, the applications of the on-package heater range around:

1. Removal of condensed / spray water on the sensor surface. Although condensed water is

not a reliability / quality problem to the sensor, it will however make the sensor non- responsive to RH changes in the air as long as there is liquid water on the surface.

2. Creep-free operation in high humid environments. Periodic heating pulses allow for creep-

free high-humidity measurements for extended times.

1. The heater is designed for a maximum duty cycle of 10%, meaning the total heater-on-time

should not be longer than 10% of the sensor’s lifetime.

2. During operation of the heater, sensor specifications are not valid. 3. The temperature sensor can additionally be affected by the thermally induced mechanical

stress, offsetting the temperature reading from the actual temperature.

4. The sensor’s temperature (base temperature + temperature increase from heater) must not

exceed T max = 125 °C in order to have proper electrical functionality of the chip.

6. If higher heating temperatures are desired, consecutive heating commands have to be sent

to the sensor. The heater shall only be operated in ambient temperatures below 65°C else it could drive the sensor outside of its maximal operating temperature.

Figure 12 Dimensional drawing of SHT4x including package tolerances (units mm).

Figure 13: Recommended land pattern

(in mm). Details can vary and depend on used PCBs and solder processes. There

shall be no copper under the sensor

other than at the pin pads.

Heater off, die

Heater on, die

pad

Symbol Description

pad soldered

not soldered

𝑅 𝜃𝐽𝐴 Junction-to-ambient

thermal resistance 246 308 297 357

𝑅 𝜃𝐽𝐶 Junction-to-case

thermal resistance 189 255 191 257

𝑅 𝜃𝐽𝐵 Junction-to-board

thermal resistance 159 225 193 258

Junction-to-board

characterization

param.

Junction-to-top

Table 8 Typical values for thermal metrics. In the “heater on” columns a heater power of 200 mW was assumed. Soldering of the die pad is not recommended, therefore the two right hand side columns are bold. Values are based on simulation.

Qualification of SHT4x is performed based on the JEDEC JESD47 qualification test method, qualification report available on request. The device is fully RoHS and WEEE compliant, e.g. free of Pb, Cd, and Hg. For general remarks of best practice in processing humidity sensor please refer to the handling instructions [2].

• Soft reset: send the reset command described in Table 7 .
• I2C general call reset: all devices on I2C bus are reset by sending the command 0x06 to
• the I2C address 0x00.
• Power down (incl. pulling SCL and SDA low)

Ordering Information

base RH&T acc., 0x44 I2C addr.,

SHT40-AD1F-R3 tbd

including patented PTFE membrane

available Q3/22

SHT40-AD1P-R3 tbd

removable protection cap

Table 10 SHT4x ordering options.

[1] K. Ehrhorn, "A Humidity Sensor and a Methode for Manufacturing the Same.". UK, DE, FR, NL, DM, BE, US, CN

Patent EP1810013, US7741950, CN101040181, 2005.

[2] Sensirion, "Handling Instructions for Humidity Sensors," 2020.

Included checksum in Figure 1

Included description of NIST traceability in section 2

Specified serial number in 4.7

Updated qualification status in section 6

Updated ordering information in Table 10

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

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 © 2022, by SENSIRION. CMOSens ® is a trademark of Sensirion. All rights reserved

• 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.