prescaler

Prescaler in microcontroller 

ADC Introduction 

ADC Prescaler  

ADC Reference voltage

ADC Channel

ADC Resolution

ADC Interrupt

What is the function of Prescaler ?

Prescaler is electronic counter used to decreases frequency of the electrical signal to a lower frequency using integer division . The Prescaler takes the basic timer clock frequency or CPU clock frequency or some higher or lower frequency and divides it by some value before feeding it to you hardware (like timer or ADC CAN), that value depends on how the Prescaler register(s) are configured. The Prescaler values configured might be limited to a few fixed values (powers of 2), or they may be any integer value from 1 to 2^P, where P is the number of Prescaler bits.

example :ADC Prescaler in Atmel controller 

By default, the successive approximation circuitry requires an input clock frequency between 50 kHz and 200 kHz to get maximum resolution. If a lower resolution than 10 bits is needed, the input clock frequency to the ADC can be higher than 200 kHz to get a higher sample rate.

The ADC module contains a prescaler, which generates an acceptable ADC clock frequency
from any CPU frequency above 100 kHz. The prescaling is set by the ADPS bits in ADCSRA.
The prescaler starts counting from the moment the ADC is switched on by setting the ADEN bit in ADCSRA. The prescaler keeps running for as long as the ADEN bit is set, and is continuously reset when ADEN is low.