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32099I–01/2012
AT32UC3L016/32/64
6.
Supply and Startup Considerations
6.1
Supply Considerations
6.1.1
Power Supplies
The AT32UC3L016/32/64 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, VDDIO, and VDDIN. The ground pin for
VDDANA is GNDANA.
When VDDCORE is not connected to VDDIN, the VDDIN voltage must be higher than 1.98V.
For decoupling recommendations for the different power supplies, please refer to the schematic
checklist.
6.1.2
Voltage Regulator
The AT32UC3L016/32/64 embeds a voltage regulator that converts from 3.3V nominal to 1.8V
with a load of up to 60mA. The regulator supplies the output voltage on VDDCORE. The regula-
tor may only be used to drive internal circuitry in the device. VDDCORE should be externally
connected to the 1.8V domains. See
Section 6.1.3 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
784 for decoupling capacitors values and regulator characteristics.
Figure 6-1.
Supply Decoupling
6.1.3
Regulator Connection
The AT32UC3L016/32/64 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