This is the brain and heart of our calculator. This chip combines an ARMv7-M Cortex-M4 core clocked at 100 MHz, 1 MB of Flash memory and 256K of Static RAM.
The LCD panel integrates an LCD controller that receives bitmap data from the MCU and drives the pixel matrix accordingly. This LCD controller has an integrated SRAM framebuffer and is driven using a 16-bit wide bus.
This part regulates the voltage from the Lithium-Polymer battery. It's a low-dropout regulator that takes any voltage between 3.0V and 5.5V and outputs a constant 2.8V. Its efficiency depends on the voltage gap and is fixed by the fact that the input current is equal to the output current.
Our Lithium-Polymer battery is recharged over USB. This chips draws current from the USB port and charges the lithium cell, using a CC-CV (constant current, constant voltage) charging curve.
This surface-mounted component includes three LEDs (red, green and blue) in a small package. These LEDs are able to glow an arbitrary through the casing of the device.
The USB port can receive electrostatic discharges. Those very high voltage surge can permanently damage electronic components. This part evacuates the surge entering from the USB port and protects the whole circuit.