SENSIRION SHT4x Transition Guide for Analog Sensors User Guide

SENSIRION SHT4x Transition Guide for Analog Sensors

Product Information

Specifications

• Product Name: RH/T Sensor SHT4x
• Accuracy: Improved
• Robustness: Higher
• Driving Strength: Higher
• Heater: Powerful internal heater for self-decontamination and creep prevention
• Versatility: Superior
• Technology: Two decades of sensor development
• Additional Features:
  • SHT30: 2.5, 2.5, 0.9 with 8 pins and analog output characteristics
  • SHT40: 1.5, 1.5, 0.5 with 4 pins and analog output characteristics

FAQ

• Q: Can the heater duration be adjusted in the SHT4x sensor?
  • A: Yes, the SHT4x sensor allows for selectable heater-on durations of 0.1, 0.5, 1, or 2 seconds for specific applications.

Product Overview

Boarding the new flagship RH/T sensor generation

• Improved accuracy and robustness
• Higher driving strength
• Powerful internal heater for self-decontamination and creep prevention
• Superior versatility and technology from two decades of sensor development

Abstract

Introduced as a highly versatile humidity (RH) and temperature (T) sensor platform, the SHT3x family already enables outstanding sensing performance for several years. Sensirion now proudly features its all-new flagship sensors from the SHT4x family, which profit from about two decades of RH/T sensor development. Dedicated to best-in-class performance, smallest footprint, and attractive pricing, our new SHT4x sensors are the products of choice for many SHT3x applications.

In particular, the SHT4x outperforms the SHT3x in every aspect and offers versatile add-ons, such as a powerful heater for self-decontamination, conformal coating protection, or filter membranes. Moreover, the latest analog output circuitry enables reduced the PSRR (Power Supply Rejection Ratio) and further increase of the driving strength of the load.

Important changes

with D T ³60°C, Full condensation robustness

General

This document first highlights the new features and differences from the previous generation. It then aims to provide a high-level guideline to replace SHT3x with sensors from the SHT4x family and outlines important differences to be considered in design-in processes.

Performance Comparison

Relative Humidity and Temperature

Relative humidity
RH accuracy1| Typ.| ± 3| ± 2.5| %RH
Repeatability2| –| 0.1| 0.5| %RH
Resolution3| –| 0.01| 0.01| %RH
Hysteresis| –| ±0.8| ±0.8| %RH
Specified range4| extended5| 0 to 100| 0 to 100| %RH
Response time6| t 63%| 8| 4| s
Long-term drift7| Typ.| <0.25| <0.2| %RH/y
Sensitivity| V DD = 5.0 V| 40| 40| mV/%RH
Condensation behavior| Droplet formation| Slight signal drop| No signal drop| –
Temperature
T Accuracy1| Typ.| ± 0.3| ± 0.3| °C
Repeatability2| –| 0.06| 0.1| °C
Resolution3| –| 0.01| 0.01| °C
Specified range4| –| −40 to +125| −40 to +125| °C
Response time8| t 63%| > 2| 2| s
Long-term drift9| Typ.| < 0.03| < 0.03| °C/y
Sensitivity| V DD = 5.0 V| 22.9| 23| mV/°C

Table 1. Humidity and temperature specifications of the SHT3x and SHT4x, where bold values highlight important differences. For further details, kindly refer to the SHT3x and SHT4x datasheets.

1. For definition of typ. 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.
3. Resolution of A/D converter.
4. Specified range refers to the range for which the humidity or temperature sensor specification is guaranteed.
5. For details about recommended humidity and temperature operating range, please refer to the SHT4x Datasheet.
6. Time for achieving 63% of a humidity step function, valid at 25°C and 1 m/s airflow. Humidity response time in the application depends on the design-in of the sensor.
7. Typical value for operation in normal RH/T operating range. Max. value is < 0.5 %RH/y. Value may be higher in environments with vaporized solvents, out-gassing tapes, adhesives, packaging materials, etc. For more details, please refer to Handling Instructions.
8. Temperature response time depends on heat conductivity of sensor substrate and design-in of sensor in application.
9. Max. value is < 0.04°C/y.

Electrical Characteristics

Parameter| Symbol| Conditions| SHT3x| SHT4x| Units
---|---|---|---|---|---
Min| Typ.| Max| Min| Typ.| Max
Supply voltage| V DD|  | 2.4| 3.3| 5.5| 4.5| 5| 5.5| V
Power-up/down level| V POR| Static power supply| 1.8| 2.3| 2.4| 0.75| 0.9| 1.0| V
Slew rate change of the supply voltage| V DD,slew|  | –| –| 20| –| –| 20| V/ms
Supply current| I DD| Measurement| –| 220| 300| –| 520| 850| µA
Resistive load to VSS| R L|  | 50| > 1000| –| 50| –| –| kΩ
Capacitive load| C L|  | 1| 3.9| 5| –| –| 100| nF
Application circuit design| –| –| Largely advantageous for SHT4x, see Section 6| –

Table 2. Key electrical specifications of the SHT3x and SHT4x, where bold values highlight important differences. For further details, kindly refer to the SHT3x and SHT4x datasheets.

Timing Specifications

Parameter| Symbol| Conditions| SHT3x| SHT4x| Units
---|---|---|---|---|---
Min| Typ.| Max| Min| Typ.| Max
Power-up time| t PU| After hard reset,

V DD ≥ V POR

| –| –| 17| –| 7| 15| ms
Analog out settling time|  | For a step of

V DD /2

| –| 0.3|  |  | 200|  | ms
Measurement interval| t Measint| Heater disabled|  |  |  |  | 0.5|  | s
Heater-on duration10| t Heat|  | –| –| –| 0|  | 2| s

Table 3. Key timing specifications of the SHT3x and SHT4x, where bold values highlight important differences. For further details, kindly refer to the SHT3x and SHT4x datasheets.

Flagship SHT4x Feature

Flagship SHT4x Feature: Built-In Heater

The SHT4x analog sensor incorporates an optional powerful on-chip heater on request, which can be used for self-decontamination, e.g., in environments with solvents present, and periodical creep compensation in prolonged application in highest humidity. It provides an over-temperature up to about 60 °C and different heater powers (up to 200 mW) and durations (up to 2 s) can be selected. There is no dedicated command to turn off the heater since it has an internal timer after which it is switched off automatically. However, it is important to note that in case the active heater option is chosen by the user, the sensor will be continuously running periodic heating pulses in specific measurement intervals defined at factory level.

Package Differences

The SHT4x comes in a new open-cavity dual flat no lead (DFN) package design in order to enable additional features, such as conformal coating, protection cover, and filter membrane compatibility. In comparison to the SHT3x, the package is considerably smaller, enabling power-efficient, accurate, and robust RH/T sensing with fast reaction times. Instead of featuring eight pins, the bottom side of the SHT4x DFN package exposes four metallic contacts, which are Ni/Pd/Au coated.

Figure 2.
Sensor opening| –| Top| Top|

Protection compatibility

|

–

| Compatible with conformal coating,

Compatible with filter membranes

| Compatible with conformal coating,

Compatible with filter membranes

|
Pin Layout| –| 2 x 4 pins| 2 x 2 pins|
Necessity for fine-print PCB| –| no| no|

Pin Assignment

|

–

| | | Drawings not to scale VDD: Supply voltage SCL: Serial clock

SDA: Serial data bidirectional VSS: Ground

R: no electrical function

Pin Size| mm| 0.25 x 0.35| 0.3 x 0.3|
Pin Pitch| mm| 0.5| 0.8|
Pin Material| –| Ni/Pd/Au coated Cu| Ni/Pd/Au coated Cu|
Housing Material| –| Epoxy housing| Epoxy housing|

Table 4. Key package differences between the SHT3x and SHT4x. For further details, kindly refer to the SHT3x and SHT4x datasheets.

Communication and Signal Output

The start-up of the sensor and the conversion of the signal output have not undergone major changes, apart from the power-up/down levels reported in Table 2. In addition, all the voltage output characteristics have been maintained, only the names have been changed following the scheme reported in Table 5.

Table 5. New nomenclature of the SHT4x version and corresponding SHT3x version.

New Features and Design-in Advantages

The new SHT4x generation shows two main improvements in the analog output circuitry with respect to the previous SHT3x version. First, the new design introduces several enhancements (reference filtering, output buffer optimized bandwidth…) to improve the Power Supply Rejection Ratio (PSRR), which yields less noise on the output signals. Second, the new design of the output buffers strongly increases the driving capability of resistive and capacitive loads (down to 1 kΩ and up to 100 nF respectively). Moreover, it is worth comparing the SHT4x sensor to the existing solutions available in the analog market. Table 6 reports some examples of Sensirion solutions and other SMD sensors.

 | Haechitech

MXH1100

| TE-Connectivity

HTU31V

| Sensirion

SHT3x

| Sensirion

SHT4x

---|---|---|---|---
Capacitive load up to| 400 pF| 5 nF| 5 nF| 100 nF

Table 6. Capacitive load comparison considering chip size analog sensors

In terms of design-in advantages, the new SHT4x improved PSRR and the higher output current allow major overall cost savings. In fact, any active filtering circuitry at the sensor’s output is no longer needed to improve PSRR or to drive long cables.

The following figures highlight the improvements just mentioned compared to the previous sensor generation. The first schematic (Figure 3) shows a standard application of the SHT3x in which loads are directly connected to the output pins. This configuration has two main limitations: the output signals are subject to significant noise and it cannot drive significant loads.

To improve these limitations, some additional components may be introduced between the SHT3x sensor and the load, as shown in Figure 4. In this example, the first external stage is a passive RC filter to reduce the noise while the second external stage is an OpAmp (Operational Amplifier) to increase the driving capability. If this solution improves the overall performance, it also significantly increases the total production costs.

On the other hand, the implementation of the new SHT4xI sensor brings evident design-in advantages and improves performances as well. Thanks to the new chip design, significant loads can now be connected directly to the output pins while no additional noise-filtering stage is needed. This dramatically simplifies the final product, as reported in Figure 5, and results in significant cost saving.

Please note that potential self-heating may affect the sensors performance. The self heating depends on the sensors load, the measurement intensity and the thermal mass and conductivity of the surrounding. To avoid any problems with self heating follow the design-in guidelines provided by Sensiron.

Quality and Material Contents

• Qualification of the SHT3x and SHT4x is performed based on the JEDEC JESD47 qualification test method.
• W devices are fully RoHS and REACH compliant, the SHT4x is also WEEE compliant.

Further Information

This transition guide aims at providing an overview of the key differences between the SHT3x and the SHT4x, yet it might not be fully inclusive. For further reading on the SHT4x specifications, communication, operation, and application, please consult the dedicated SHT3x and SHT4x documents provided on the Sensirion webpage www.sensirion.com. In case you are in need of specific details, or would like to request assistance in transitioning from the SHT3x to the SHT4x or any other Sensirion product, please consult us directly at www.sensirion.com/en/about- us/contact/.

Revision History

remark about self heating

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.

Contacts

Headquarters and Subsidiaries

Sensirion AG

• Laubisruetistr. 50 CH-8712 Staefa ZH Switzerland
• phone: +41 44 306 40 00
• fax: +41 44 306 40 30
• [email protected]
• www.sensirion.com

Sensirion Taiwan Co. Ltd

• phone: +886 2 2218-6779
• [email protected]
• www.sensirion.com

Sensirion Inc., USA

• phone: +1 312 690 5858
• [email protected]
• www.sensirion.com

Sensirion Japan Co. Ltd.

• phone: +81 45 270 4506
• [email protected]
• www.sensirion.com/jp

Sensirion Korea Co. Ltd.

• phone: +82 31 337 7700~3
• [email protected]
• www.sensirion.com/kr

Sensirion China Co. Ltd.

• phone: +86 755 8252 1501
• [email protected]
• www.sensirion.com/cn

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

www.sensirion.com

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References

• Product catalog

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