Demonstration board application schematic

AN2786

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Demonstration board application schematic

The demonstration board power supply is designed using a L5970D step-down switching

regulator. The input supply voltage may vary in the range of 5 V to 30 VDC, allowing the

user to connect a standard AC notebook computer power supply. The input is reverse-

polarity protected (D6), and over-voltage protected (TR1).

The power supply output voltage is set at 5 VDC by mean of 2 resistors (R2, R3).

The ST7LITE49M MCU (U2) runs at 8 MHz by means of an internal oscillator, avoiding the

need for any external components. Pull-up resistors R10 and R11 are used for the I²C bus,

while R12 and R13 prevent the MCU from entering the programming mode unintentionally.

Finally, R14 and R15 set the working mode (MD1, MD2 at logic 1 is "standalone mode").

The LEDs, display and keyboard are entirely managed through U3, (STLED316S). 8

segment lines are multiplexed with 7 digit lines, allowing a total of 56 LEDs (in a common

anode configuration) to be controlled by a single STLED316S device. R4 sets the LED peak

current.

Communication between the MCU and the STLED316S is achieved by means of 3 pins:

data input/output (DIO), clock (CLK) and strobe (STB). An extra IRQ pin generates an

interrupt request any time a key on the keyboard is pressed.

The demonstration board is equipped with connectors J3 and J4 to allow connection to the

STEVAL-IHI002V1 daughter demonstration board. The board is also equipped with ICC

programming connector J2 to program the MCU in-circuit. An extra I²C bus connector (J5) is

foreseen to eventually connect other boards or devices via I²C bus.