UM1481 datasheet(32/55 Pages) STMICROELECTRONICS

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Hardware design description

UM1481

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Doc ID 022389 Rev 1

Hardware design description

The board supports both USB and a wall adapter (external supply). A switch (SW7) is used

to choose between these two. When an external supply is absent the whole board

consumes power from the battery. In this case the step-up converter device L6920 steps up

battery voltage to 5 V. The voltage from these sources (external or L6920) is connected to a

low drop-out regulator (LD1117V) which gives 3.3 V output. This output is used for powering

up devices such as the LCD, microcontroller, etc.

The STC3105 battery monitoring device always receives power from the battery. In order to

avoid the loss of data stored in the RAM registers of the STC3105 during power-off.

7.1

Microcontroller (STM32)

The STM32 is a 32-bit MCU based on the popular ARM 32-bit Cortex™-M3 CPU. The

STM32 device (STM32F102C8T6A) used in this demonstration board runs at 48 MHz. The

microcontroller has single-cycle multiplication and hardware division. The device supports

low power mode such as sleep, stop, and also standby. This device (microcontroller) has up

to 5 communication interfaces which includes two I2Cs (400 kHz), three USARTs, two SPIs

(12 Mbit/s), and USB 2.0 full-speed interface. For more details refer to the STM32F102x8

datasheet and RM0008 reference manual. For this application, a minimum of one I2C to

interface with the STC3105 is needed, a USB to support a USB based charger and USB

data transfer, and some general purpose IOs for the user interface, are required. The part

numbers used to develop this application are shown in Table 2.

The microcontroller is used to communicate with and control the STC3105 device, USB

communication to display data on the PC, LCD driving, interfacing menu keys and menu

operation.

Table 2.

Microcontroller details

Feature

Description

Sales type

STM32F102C8T6A:USB access line, USB 2.0 full-speed interface

Package

LQFP-48 (7 x 7) mm

Flash - Kbytes

SRAM - Kbytes

Operating voltage

2.0 to 3.6 V

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