16 MHz 8-bit MCU with 4 KB Flash — entry-level control for cost-sensitive boards
It packs 4 KB of Flash program memory, 1 KB of RAM, and 640 bytes of EEPROM — enough for small control loops, sensor polling, and simple communication stacks. The 20-UFQFN package keeps board area tight, and the wide supply range from 2.95 V to 5.5 V lets it run off an unregulated battery or a 3.3 V / 5 V rail without an extra regulator. This is a value-line part meant for high-volume, cost-sensitive applications like appliance controllers, industrial sensor interfaces, and basic motor commutation.
With 4 KB of Flash and 1 KB of RAM, the firmware footprint is the first constraint a designer hits. This part suits a single-purpose control task — a fan speed controller, a thermostat, a keypad scanner — where the code compiles under 3.5 KB and the data buffers fit in the remaining RAM. The 640 bytes of EEPROM give non-volatile storage for calibration constants or configuration parameters without wearing the Flash. The 16 I/O pins in the 20-UFQFN package are enough for a handful of sensor inputs, a few relay or LED outputs, and a serial bus. The 5-channel 10-bit ADC handles analog inputs like a potentiometer or a thermistor directly.
20-UFQFN — rework and layout notes
Orientation is marked by a chamfered corner — find pin 1 before placing, because a misaligned UFQFN is a pain to lift without lifting the pad.
The brown-out detect and POR circuits keep the core from running into undefined states during a cold-crank or a brown-out event.