Datasheet

15
32059L–AVR32–01/2012
AT32UC3B
Figure 5-1. Power Supply
5.6.2 Voltage Regulator
5.6.2.1 Single Power Supply
The AT32UC3B embeds a voltage regulator that converts from 3.3V to 1.8V. The regulator takes
its input voltage from VDDIN, and supplies the output voltage on VDDOUT that should be exter-
nally connected to the 1.8V domains.
Adequate input supply decoupling is mandatory for VDDIN in order to improve startup stability
and reduce source voltage drop. Two input decoupling capacitors must be placed close to the
chip.
Adequate output supply decoupling is mandatory for VDDOUT to reduce ripple and avoid oscil-
lations. The best way to achieve this is to use two capacitors in parallel between VDDOUT and
GND as close to the chip as possible
Figure 5-2. Supply Decoupling
3.3V
VDDANA
VDDIO
VDDIN
VDDCORE
VDDOUT
VDDPLL
ADVREF
3.3V
1.8
V
VDDANA
VDDIO
VDDIN
VDDCORE
VDDOUT
VDDPLL
ADVREF
Single Power Supply
Dual Power Supply
1.8V
Regulator
1.8V
Regulator
3.3V
1.8V
VDDIN
VDDOUT
1.8V
Regulator
C
IN1
C
OUT1
C
OUT2
C
IN2