AT90PWM2 datasheet(236/365 Pages) ATMEL

236 / 365 page

236

AT90PWM2/3

4317B–AVR–02/05

Analog Comparator

The Analog Comparator compares the input values on the positive pin ACMPx and neg-

ative pin ACMPM.

Overview

The AT90PWM2/3 features three fast analog comparators.

Each comparator has a dedicated input on the positive input, and the negative input can

be configured as:

•

a steady value among the 4 internal reference levels defined by the Vref selected

thanks to the REFS1:0 bits in ADMUX register.

•

a value generated from the internal DAC

•

an external analog input ACMPM.

When the voltage on the positive ACMPn pin is higher than the voltage selected by the

ACnM multiplexer on the negative input, the Analog Comparator output, ACnO, is set.

The comparator is a clocked comparator. A new comparison is done on the falling edge

of CLK

I/O or CLKI/O/2 ( Depending on ACCKDIV fit of ACSR register, See “Analog Com-

parator Status Register – ACSR” on page 240.).

Each comparator can trigger a separate interrupt, exclusive to the Analog Comparator.

In addition, the user can select Interrupt triggering on comparator output rise, fall or

toggle.

The interrupt flags can also be used to synchronize ADC or DAC conversions.

Moreover, the comparator’s output of the comparator 1 can be set to trigger the

Timer/Counter1 Input Capture function.

A block diagram of the three comparators and their surrounding logic is shown in Figure

114.

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