SunFounder PCA9685 16 Channel 12 Bit PWM Servo Driver for Arduino and Raspberry Pi Contain an I2C-controlled PWM driver with a built-in clock. It means, unlike the TLC5940 family, you do not need to continuously send it signals tying up your microcontroller; it's completely free running! 5V compliant, which means you can control it from a 3.3V microcontroller and still safely drive up to 6V outputs (this is good when you want to control white or blue LEDs with 3.4+ forward voltages) Support using only two pins to control 16 free-running PWM outputs  you can even chain up 62 breakouts to control up to 992 PWM outputs 3 pin connectors in groups of 4, so you can plug in 16 servos at one time (Servo plugs are slightly wider than 0.1" so you can only stack 4 next to each other on 0.1" header 12-bit resolution for each output - for servos, that means about 4us resolution at 60Hz update rate