The UNO R4 Minima features a microcontroller based on the Renesas RA4M1 (Arm® Cortex®-M4) with an operating voltage of 5 V.
It has 14 digital I/O, 6 analog inputs with up to 14-bit resolution, a clock speed of 48 MHz, and 32 kB SRAM, 256 kB flash memory & 8 kB of EEPROM.
It features a DAC for audio projects, RTC for accurate time tracking and HID for emulating a keyboard/mouse.
The barrel jack plug (VIN) supports voltages at up to 24V, making it compatible with common higher voltage adapters.
 
Key Differences between UNO R3 & R4 MINIMA 
Processor: 
The Uno R4 uses a 32-bit ARM Cortex-M4 processor, while the Uno R3 uses an 8-bit ATmega328 chip. 
Performance: 
The R4's 48 MHz clock speed is three times faster than the R3's 16 MHz clock speed, providing significantly faster processing. 
Memory: 
The R4 has vastly more memory, with 256 KB of Flash and 32 KB of SRAM, compared to the R3's 32 KB Flash and 2 KB of SRAM. 
Connectivity: 
The Uno R4 features a modern USB-C connector, replacing the Uno R3's USB Type-B port. 
Built-in Features: 
The Uno R4 includes an onboard Real-Time Clock (RTC) and a Digital-to-Analog Converter (DAC), features absent in the Uno R3. 
Current per I/O Pin: 
The R4's current per I/O pin is reduced to 8mA, while the R3's is 20mA, requiring more caution with power requirements for the R4. 
Input Voltage: 
The R4 supports a wider input voltage range (6-24V) compared to the R3 (7-12V). 
Protocol Support: 
The R4 adds a CAN bus controller, not present on the R3. 
Compatibility: 
Both boards are 5V compatible, and the R4 retains a similar form factor to the R3, ensuring broad compatibility with existing shields and projects.