App note: Using the A/D Amplifier on AT90PWM

Here’s an application note from Atmel for using the 10-bit ADC amplified conversion on AT90PWM (PDF!):

ADC features on Atmel® AVR® AT90PWM devices:
– 10-bit ADC amplified conversion with differential inputs
– Programmable gain
– Internal voltage reference

The AT90PWM devices feature a 10-bit successive approximation ADC. The ADC
is connected to an analog multiplexer which provides:
• Eight or eleven single-ended inputs which are referenced to 0V (GND)
• One or two amplified ADC channels with differential inputs (AMPx)