36
32099DS–06/2010
AT32UC3L016/32/64
6.
Supply and Startup Considerations
6.1
Supply Considerations
6.1.1
Power Supplies
The AT32UC3L has several types of power supply pins:
•VDDIO: Powers I/O lines. Voltage is 1.8 to 3.3V nominal.
•VDDIN: Powers I/O lines and the internal regulator. Voltage is 1.8 to 3.3V nominal.
•VDDANA: Powers the ADC. Voltage is 1.8V nominal.
•VDDCORE: Powers the core, memories, and peripherals. Voltage is 1.8V nominal.
The ground pins GND are common to VDDCORE and VDDIO. The ground pin for VDDANA is
GNDANA.
for power consumption on the various supply pins.
6.1.2
Voltage Regulator
The AT32UC3L embeds a voltage regulator that converts from 3.3V nominal to 1.8V with a load
of up to 60 mA. The regulator supplies the output voltage on VDDCORE. The regulator may only
be used to drive internal circuitry in the device. VDDCORE should be externally connected to the
1.8V domains. See
for regulator connection figures.
Adequate output supply decoupling is mandatory for VDDCORE to reduce ripple and avoid
oscillations. The best way to achieve this is to use two capacitors in parallell between
VDDCORE and GND as close to the chip as possible. Please refer to
for decoupling capacitors values and regulator characteristics.
Figure 6-1.
Supply Decoupling
6.1.3
Regulator Connection
The AT32UC3L supports three power supply configurations:
• 3.3V single supply mode
• 1.8V single supply mode
• 3.3V supply mode, with 1.8V regulated I/O lines
3.3V
1.8V
VDDIN
VDDCORE
1.8V
Regulator
C
IN1
C
OUT1
C
OUT2
C
IN2
IN3
C
