Signal
Name
Recommended Pin Connection
Description
V
LCD
LCD Bias Voltage
Analog input/output
When V
LCD
is generated internally, the output voltage
range is 2.5V to 3.5V.
When V
LCD
is provided externally, the input voltage
range is 2.4V to 3.6V.
External VLCD capacitor 1µF
(1)(5)
Powers the LCD voltage pump
GND
Common ground
Ground
GND
ANA
Ground for VDDANA
Ground for the analog power
domain
1.
These values are only given as a typical example.
2.
Decoupling capacitors should be placed close to the device for each supply pin pair in the signal
group, low ESR capacitors should be used for better decoupling.
3.
An inductor should be added between the external power and the V
DD
for power filtering.
4.
A ferrite bead has better filtering performance compared to standard inductor at high frequencies. A
ferrite bead can be added between the main power supply (V
DDIO
) and V
DDANA
to prevent digital
noise from entering the analog power domain. The bead should provide enough impedance (e.g.
50Ω at 20MHz and 220Ω at 100MHz) to separate the digital and analog power domains. Make sure
to select a ferrite bead designed for filtering applications with a low DC resistance to avoid a large
voltage drop across the ferrite bead.
5.
The external capacitor 1µF on the V
LCD
pin is only required if V
LCD
is generated internally
(SLCD.CTRLA.XVLCD=0). When the SLCD controller is not used at all, the VLCD pin can remain
unconnected - in this case, no external capacitor required, too.
6.
When the V
BAT
pin is used for battery supply, PB03 (V
BAT
) cannot be used as PORT I/O pin or for
any other multiplexed peripheral signal.
48.2.2. Special Considerations for QFN Packages
The QFN package has an exposed paddle that must be connected to GND.
48.3. External Analog Reference Connections
The following schematic checklist is only necessary if the application is using one or more of the external
analog references. If the internal references are used instead, the following two circuits are not
necessary.
Atmel SAM L22G / L22J / L22N [DATASHEET]
Atmel-42402E-SAM L22G / L22J / L22N_Datasheet_Complete-07/2016
1195
