Data Sheet

ManualsBrandsDFRobot Manualstemperature & humidity sensorsSHT20 I2C Temperature & Humidity Sensor (Waterproof Probe)

www.sensirion.com Version 3 – December 2011 1/14

Datasheet SHT20

Humidity and Temperature Sensor IC

 Fully calibrated

 Digital output, I

C interface

 Low power consumption

 Excellent long term stability

 DFN type package – reflow solderable

Dimensions

Figure 1: Drawing of SHT20 sensor package, dimensions are

given in mm (1mm = 0.039inch), tolerances are ±0.1mm. The

die pad (center pad) is internally connected to VSS. The NC

pads must be left floating. VSS = GND, SDA = DATA.

Numbering of E/O pads starts at lower right corner (indicated by

notch in die pad) and goes clockwise (compare Table 2).

Sensor Chip

SHT20 features a generation 4C CMOSens® chip.

Besides the capacitive relative humidity sensor and the

band gap temperature sensor, the chip contains an

amplifier, A/D converter, OTP memory and a digital

processing unit.

Material Contents

While the sensor itself is made of Silicon the sensors‟

housing consists of a plated Cu lead-frame and green

epoxy-based mold compound. The device is fully RoHS

and WEEE compliant, e.g. free of Pb, Cd and Hg.

Additional Information and Evaluation Kits

Additional information such as Application Notes is

available from the web page www.sensirion.com/SHT20.

For more information please contact Sensirion via

info@sensirion.com.

For SHT20 two Evaluation Kits are available: EK-H4, a

four-channel device with Viewer Software, that also serves

for data-logging, and a simple EK-H5 directly connecting

one sensor via USB port to a computer.

1.0

2.4

0.3

0.4

1.5

0.4

0.75

1.1

0.2

SCL

SDA

VSS

VDD

Bottom View

SHT20

D0AC4

3.0

2.2

0.8 typ

1.4 typ

3.0

0.3 typ

2.0 typ

Product Summary

SHT20, the new humidity and temperature sensor of

Sensirion is about to set new standards in terms of size

and intelligence: Embedded in a reflow solderable Dual

Flat No leads (DFN) package of 3 x 3mm foot print and

1.1mm height it provides calibrated, linearized signals in

digital, I

C format.

With a completely new designed CMOSens® chip, a

reworked capacitive type humidity sensor and an

improved band gap temperature sensor the performance

has been lifted even beyond the outstanding level of the

previous sensor generation (SHT1x and SHT7x). For

example, measures have been taken to stabilize the

behavior at high humidity levels.

Every sensor is individually calibrated and tested. Lot

identification is printed on the sensor and an electronic

identification code is stored on the chip – which can be

read out by command. Furthermore, the resolution of

SHT20 can be changed by command (8/12bit up to

12/14bit for RH/T), low battery can be detected and a

checksum helps to improve communication reliability.

With made improvements and the miniaturization of the

sensor the performance-to-price ratio has been improved

– and eventually, any device should benefit from the

cutting edge energy saving operation mode. For testing

SHT20 a new evaluation Kit EK-H4 is available.

Summary of content (14 pages)

PAGE 1
Datasheet SHT20 Humidity and Temperature Sensor IC Fully calibrated Digital output, I2C interface Low power consumption Excellent long term stability DFN type package – reflow solderable      Product Summary SHT20, the new humidity and temperature sensor of Sensirion is about to set new standards in terms of size and intelligence: Embedded in a reflow solderable Dual Flat No leads (DFN) package of 3 x 3mm foot print and 1.1mm height it provides calibrated, linearized signals in digital, I2C format.
PAGE 2
Sensor Performance Relative Humidity1234 Parameter Temperature567 Condition 12 bit 8 bit Resolution 1 min typ Accuracy tolerance 2 max typ 0.04 0.7 Units %RH %RH Parameter 3.0 see Figure 2 %RH %RH Accuracy tolerance 2 0.1 %RH Repeatability 1 <0.1 %RH Operating Range extended 4 %RH Response Time 8 s Long Term Drift Repeatability Hysteresis Nonlinearity Response time 63% Operating Range extended 4 Long Term Drift 5 normal 3 max 0 100 < 0.
PAGE 3
Datasheet SHT20 Users Guide SHT20 For details on how Sensirion is specifying and testing accuracy performance please consult Application Note “Statement on Sensor Specification”. Relative Humidity (%) 1.1 Operating Range The sensor works stable within recommended Normal Range – see Figure 4. Long term exposure to conditions outside Normal Range, especially at humidity >80%RH, may temporarily offset the RH signal (+3%RH after 60h).
PAGE 4
Datasheet SHT20 2.1 Soldering Instructions The DFN’s die pad (centre pad) and perimeter I/O pads are fabricated from a planar copper lead-frame by overmolding leaving the die pad and I/O pads exposed for mechanical and electrical connection. Both the I/O pads and die pad should be soldered to the PCB. In order to prevent oxidation and optimize soldering, the bottom side of the sensor pads is plated with Ni/Pd/Au. On the PCB the I/O lands8 should be 0.2mm longer than the package I/O pads.
PAGE 5
Datasheet SHT20 recommended to further process the sensors within 1 year after date of delivery. 10% of the time – e.g. maximum two measurements per second at 12bit accuracy shall be made. 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.
PAGE 6
Datasheet SHT20 noted that pull-up resistors may be included in I/O circuits of MCUs. See Table 4 and Table 5 for detailed I/O characteristic of the sensor. 3 Interface Specifications Pin Name Comment 1 SDA Serial Data, bidirectional 4 2 VSS Ground 5 5 VDD Supply Voltage 6 SCL Serial Clock, bidirectional 6 3,4 NC Not Connected 4 Electrical Characteristics 3 2 1 Table 2 SHT2x pin assignment, NC remain floating (top view) 3.1 Power Pins (VDD, VSS) The supply voltage of SHT2x must be in the range of 2.
PAGE 7
Datasheet SHT20 1/fSCL tSCLH tR tSCLL tF 70% SCL 30% tSU SDA valid write tHD DATA IN 70% SDA 30% SDA valid read tR tF tVD DATA OUT 70% SDA 5.2 Start / Stop Sequence Each transmission sequence begins with Start condition (S) and ends with Stop condition (P) as displayed in Figure 13 and Figure 14. 30% Figure 12 Timing Diagram for Digital Input/Output Pads, abbreviations are explained in Table 5. SDA directions are seen from the sensor.
PAGE 8
Datasheet SHT20 2 3 4 5 6 7 8 S 1 0 0 0 0 0 0 0 In the hold master mode, the SHT2x pulls down the SCL line while measuring to force the master into a wait state. By releasing the SCL line the sensor indicates that internal processing is terminated and that transmission may be continued.
PAGE 9
Datasheet SHT20 29 15 9 4 T max 85 43 22 11 Units ms ms ms ms ms ms Table 7 Measurement times for RH and T measurements at different resolutions. Typical values are recommended for calculating energy consumption while maximum values shall be applied for calculating waiting times in communication. Please note: I2C communication allows for repeated Start conditions (S) without closing prior sequence with Stop condition (P) – compare Figures 15, 16 and 18.
PAGE 10
Datasheet SHT20 5.8 Serial Number SHT20 provides an electronic identification code. For instructions on how to read the identification code please refer to the Application Note “Electronic Identification Code” – to be downloaded from the web page www.sensirion.com/SHT20. 6 Conversion of Signal Output Default resolution is set to 12 bit relative humidity and 14 bit temperature reading. Measured data are transferred in two byte packages, i.e.
PAGE 11
Datasheet SHT20 8.2 Filter Cap and Sockets For SHT2x a filter cap SF2 will is available. It is designed for fast response times and compact size. Please find the datasheet on Sensirion‟s web page. For testing of SHT2x sensors sockets, such as from Plastronics, part number 10LQ50S13030 are recommended (see e.g. www.locknest.com). 8.3 Traceability Information All SHT2x are laser marked with an alphanumeric, fivedigit code on the sensor – see Figure 19.
PAGE 12
Datasheet SHT20 alternative to OTP Reload the soft reset may be used. Please note that even if SHT1x/7x protocol is applied the timing values of Table 5 and Table 7 in this SHT2x datasheet apply. and for temperature T For the calculation of physical values the following equation must be applied: RES is the chosen respective resolution, e.g. 12 (12bit) for relative humidity and 14 (14bit) for temperature. T 46.85 175.72 ST 2 RES For relative humidity RH RH 6 125 www.sensirion.
PAGE 13
Revision History Date 6 May 2009 21 January 2010 5 May 2010 Version 0.3 1.0 1.1 Page(s) 1–9 1 – 4, 7 – 10 1 – 12 31 May 2011 2 1 – 7, 10 – 13 December 2011 3 1, 7-10 www.sensirion.com Changes Initial preliminary release Complete revision. For complete revision list please require respective document. Typical specification for temperature sensor. Elimination of errors. For detailed information, please require complete change list at info@sensirion.com.
PAGE 14
Datasheet SHT20 Warning, Personal Injury Important Notices 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.