I'm currently using an Atmega328p board to control an RGBW LED strip over 4 PWM outputs.
The commsands are received/sent over an RS485 serial interface.
I want to replace it with something cheaper, physically smaller that has 4 PWM outputs and hardware serial capability and is compatible with Arduino IDE.
The program is minimal, it just waits for incoming data then sets the 4 PWM registers according to the received data. It just has to be executed really fast so I'd prefer something capable of running on 16MHz clock as the desired data rate is 2Mb/s.
At 4x4 mm and 1 mm thick the smallest package for the ATmega328p is pretty darn small already.
But no worries, Atmel has you covered. The ATtiny841 is actually available in an even smaller package: the VQFN package is a mere 3x3mm and just 0.85mm thick. It has 6 PWM, 2-UART, 1-SPI, 1-I2C. For 16 MHz you'll need to add an external resonator or crystal, though.
FeriHUN:
The only problem is that the Attiny1634 is more expensive than the 328p.
The prices given on the Atmel site (5k pricing - didn't bother to look further) are USD 1.46 up for the ATmega328p, and USD 0.69 up for the ATtiny1634. That makes the ATtiny1634 less than half price of the ATmega328p. It even beats the ATtiny841, which starts at USD 0.73.
Maybe a show stopper: the ATtiny1634 is rated 12 MHz only. That's why it's cheaper, of course.