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4.3 Pin assignment

The pin assignments of the STC31-C, bottom view.

Pin no.

Name

Description

1

VSS

Connect to ground

2

-

Reserved. Do not connect

3

ADDR

I2C Address Selection

4

SCL

Serial Clock (I2C Interface)

5

VSS

Connect to ground

6

VDD

VDD Supply

7

SDA

Bidirectional Serial Data (I2C Interface)

8

-

Reserved. Do not connect

9

VSS

Connect to ground

10

-

Reserved. Do not connect

11

VSS

Connect to ground

12

-

Reserved. Do not connect

4.3.1 Power pins (VDD, GND)

The power supply pin must be decoupled with a 100 nF capacitor that shall be placed as close to the sensor as

possible.

4.3.2 Serial clock and serial data (SCL, SDA)

The SCL and SDA are bidirectional pins of the I2C slave interface. The SCL is the Serial Clock pin and the SDA is

the Serial Data pin. For more details about the I2C interface refer to section 3.

Both SCL and SDA lines are open-drain I/Os with diodes to VDD und VSS. They should be connected to external

pull-up resistors (please refer to Figure 3). A device on the I2C bus must only drive a line to ground. The

external pull-up resistors (e.g. Rp = 10 kΩ) are required to pull the signal high. For dimensioning resistor sizes

please take bus capacity and communication frequency into account (see for example Section 7.1 of NXPs I2C

Manual for more details14). It should be noted that pull-up resistors may be included in I/O circuits of

microcontrollers. It is recommended to wire the sensor according to the application circuit in Figure 3.

Figure 3 Typical application circuit. Please note that the positioning of the pins does not reflect the position of

the sensor’s orientation in the reel. This is shown in section 5. The pin numbers corresponding to the schematic

in section 4.3 are indicated.

14

http://www.nxp.com/documents/user_manual/UM10204.pdf