UM1539 datasheet(7/46 Pages) STMICROELECTRONICS

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UM1539

Getting started

Doc ID 023106 Rev 1

7/46

1.2.1

Power supply unit

There are two power sections in this system:

Power for motherboard.

Power for temperature sensor daughter cards.

1.2.2

Power for motherboard

The motherboard input power is 5 V from a USB connection. This 5 V is converted to 3.3 V

using the LD39080DT33 voltage regulator. The STM32F102xx microcontroller is operated

at 3.3 V.

1.2.3

Power for temperature sensor and RTC daughter cards

Connector CN5 and CN6 are used to configure the supply voltage for the daughter cards.

Table 1 shows the pin connections and their respective voltages generated for daughter

cards.

1.2.4

Address selection of sensor daughter cards

This demo board supports different temperature sensors and RTCs present on different

daughter cards. For digital temperature sensors, the address lines are configured using the

switches (SW2, SW3, and SW4) present on the motherboard. Logic level is assigned to the

address line using the address selection switches. Figure 3 shows the position of the switch

and the respective logic level assigned by that switch.

Table 1.

Power selection for daughter cards

Connector CN5 on

motherboard

Connector CN6 on motherboard

Daughter card supply

voltage

Short Pin1(5 V) and

Pin2(VDD_D)

DON’T CARE

5.0 V

Short Pin2(VDD_D)

and Pin3(VCC_SEL)

Short Pin1 and Pin2 (2.3 V)

2.3 V

Short Pin2(VDD_D)

and Pin3(VCC_SEL)

Short Pin3 and Pin4 (2.7 V)

2.7 V

Short Pin2(VDD_D)

and Pin3(VCC_SEL)

Short Pin5 and Pin6 (3.0 V)

3.0 V

Short Pin2(VDD_D)

and Pin3(VCC_SEL)

Short Pin7 and Pin8 (2.3 V)

3.3 V

Short Pin2(VDD_D)

and Pin3(VCC_SEL)

Short Pin9 and Pin10 (2.3 V)

3.6 V

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