Digital temperature sensor

AN2680

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1.2

Interfacing of sensor with the microcontroller

thus can support up to 8 different addresses. All 3 address lines are grounded in the present

application and hence the address of sensor is made 0x90.

interface (SDA and SCL).

1.3

Configuring the sensor

The sensor has 3 internal registers which are used to configure its behavior:

1.

Configuration register: Tconfig (8-bit)

2.

3.

Hysteresis register: Thys (16-bit)

Based on the value configured in the configuration register the behavior of sensor is

achieved. In our application these settings are made as 0x40. This setting configures the

mode of operation of the sensor and the nature of the output alarm signal. For details,

please refer to the STDS75 datasheet.

The value set in the oversaturation register defines the threshold value at which fan starts. In

our application the fan starts as the temperature rises above 29 degrees Celsius. Thus the

setting for this register is made as 0x1D00. Also as the temperature rises above this

oversaturation value the alarm signal turns ON. This alarm is shown as an LED in the

system.

A setting in the hysteresis register is used to control the output of the alarm output signal of

sensor. It is set at 27 degrees Celsius in our application which means that as the

temperature falls below 27 degrees Celsius the alarm goes OFF. Thus the settings for this

register are made 0x1B00.

1.4

Alarm signal behavior

The alarm signal of the sensor is configured to go ON when the measured temperature

exceeds 29 degrees Celsius and goes OFF when the temperature falls below 27 degrees

Celsius.