UM1481 datasheet(10/55 Pages) STMICROELECTRONICS

10 / 55 page

System overview

UM1481

10/55

Doc ID 022389 Rev 1

System overview

3.1

General description of product architecture

Figure 4.

System architecture details

●

The STM32 communicates with the STC3105 using I2C communication protocol to

obtain information regarding battery capacity, relaxation time, current, voltage, etc.

●

The board is able to run on a battery source. When the battery reaches its critical

voltage, the board goes into shutdown mode. To keep track of the battery status, the

STC3105 is always powered up by the battery.

●

The L6920 is configured to step up input voltage to 5 V. Then, LD1117AS33TR

produces a constant output voltage of 3.3 V to power on the LCD and the STM32.

●

LCD and switches are used for user interface.

●

Onboard charger is provided to charge the battery.

●

Two manual slide switches are provided on the board. The SW7 slide switch is used to

allow the user to choose only one external power supply at a time i.e. either USB or an

external wall adapter.

●

The second manual slide switch (SW8) is used to select the battery charger, either

internal or external.

●

A MOSFET is provided between the battery and the L6920 which connects the board

(and is acting as a load to the battery) to the battery in the absence of any external

power source (USB/wall adapter) and similarly disconnects boards from the battery in

the presence of any external power source.

UM1481 Datasheet(PDF) 10 Page - STMicroelectronics