SHT3X datasheet(6/13 Pages) ETC2

6 / 13 page

Datasheet SHT3x-ARP

www.sensirion.com

May 2015 - Version 0.93

6/13

Pin Assignment

The SHT3x-ARP comes in a tiny 8-pin DFN package –

see Table 6.

Name

Comments

Analog voltage out; output

No electrical function; recommended to

connect to VSS

No electrical function; recommended to

connect to VSS

Analog voltage out; output

VDD

Supply voltage; input

nRESET

Reset pin active low; Input; if not used it

is recommended to connect to VDD

No electrical function; recommended to

connect to VSS

VSS

Ground

Table 6 SHT3x-ARP pin assignment (Transparent top view).

Dashed lines are only visible from the bottom. The die pad is

internally connected to VSS.

3.1

Power Pins (VDD, VSS)

The electrical specifications of the SHT3x-ARP are

shown in Table 3. The power supply pins must be

decoupled with a 100 nF capacitor that shall be placed

as close to the sensor as possible – see Figure 7 for a

typical application circuit.

3.2

Temperature and Humidity Pin

The physical output of temperature and humidity can be

read out at separated pins, as shown in Table 6. Data is

supplied as ratiometric voltage output. The specification

of the Analog voltage signal and its conversion to

physical values is explained in Section 4.

3.3

nRESET Pin

The nReset pin may be used to generate a reset of the

sensor. A minimum pulse duration of 350 ns is required

to reliably trigger a reset of the sensor. If not used it is

recommended to connect to VDD.

Figure 7 Typical application circuit. Please note that the

positioning of the pins does not reflect the position on the

real sensor. This is shown in Table 6.

3.4

Die Pad (center pad)

The die pad or center pad is visible from below and

located in the center of the package. It is electrically

connected to VSS. Hence electrical considerations do

not impose constraints on the wiring of the die pad.

However, due to mechanical reasons it is recommended

to solder the center pad to the PCB. For more

information on design-in, please refer to the document

“SHTxx Design Guide”.

4 Operation and Communication

4.1

Start-up of the sensor

As a first step, the sensor needs to be powered up to

VDD (between 2.4 and 5.5 V). After power-up, the

sensor needs at most 17 ms for providing data as voltage

output on the respective output pins. During that time the

temperature and humidity pins have an undefined state.

4.2

Conversion of the Signal Output

The physical values as measured by the sensor are

mapped to a ratiometric voltage output (VX, x=T, RH as

10 to 90% of VDD). Prior to conversion into a voltage

signal, the physical values are linearized and

compensated for temperature and supply voltage effects

by the sensor. Additionally, the voltage output is

calibrated for each sensor. Hence the relationship

between temperature and humidity and the voltage

output is the same for each sensor, within the limits given

by the accuracy.

This allows to describe the relationship between physical

values (RH and T) and the voltage output for

temperature and humidity (VX, x=T, RH) through a

generic linear formula shown in Equation 1 (for RH) and

Equation 2 (for T), its graphical representation can be

found in Figure 8 & Figure 9.

R(2,3,7)

RH(1)

T(4)

VDD(5)

VSS(8)

die

pad

100nF

nRESET(6)

0.1nF

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