8

AVR32768

32157A-AVR-12/10

6 Clocks and crystal oscillators

There are three clock inputs available:

• XIN0 / XOUT0

• XIN1 / XOUT1

• XIN32 / XOUT32

The recommendations below refer to XIN / XOUT, but apply to all the clock inputs.

6.1 External clock source

Figure 6-1.

External clock source schematic.

Table 6-1.

External clock source checklist.

Signal name

Recommended pin connection

Description

XIN

Connected to clock output from external clock source

Up to VDDIO-volt square wave signal up to 50MHz

XOUT

Can be left unconnected or used as GPIO

6.2 Crystal oscillator

Figure 6-2.

Crystal oscillator example schematic.

Table 6-2.

Crystal oscillator checklist.

Signal name

Recommended pin connection

Description

XIN

Biasing capacitor, 22pF

(1)(2)

External crystal between 450kHz and 16MHz

XOUT

Biasing capacitor, 22pF

(1)(2)

Notes:

1. These values are given only as a typical example. The capacitance, C, of the biasing capacitors can be computed

2. Decoupling capacitor should be placed as close as possible to each pin in the signal group, and vias should be

avoided