Evaluation Kit Hardware
SAM3S-EK Development Board User Guide
4-11
11031A–ATARM–14-Dec-09
4.3.12
Analog Interface
4.3.12.1 Analog Reference
The 2V5 voltage reference is based on an LM4040 (Precision Micropower Shunt Voltage Reference).
This ADVREF level can be set as 2.5V or 3.3V via the jumper JP2.
Figure 4-15.
Analog Vref
4.3.12.2 Analog Input
The BNC connector CN1 is connected to the ADC port PB1 as an external analog input. An on-board 50-
Ohm resistor termination can be applied by closing jumper JP16. A low pass filter can be implemented
for the BNC connector CN1 by replacing R94 and C78 with custom resistor and capacitor values,
depending on your application requirements.
A 10-KOhm potentiometer (VR1) is also connected to this channel to implement an easy access to ADC
programming and debugging (or implement an analog user control like display brightness, volume, etc.).
Either of these two functions can be selected by jumper JP18.
Figure 4-16.
ADC Input
4.3.12.3 Analog Output
The BNC connector CN2 is connected to the DAC port PB13 and provides an external analog output. An
on-board 50-Ohm resistor termination can be enabled by closing jumper JP21. A filter can be imple-
mented on this output channel by replacing R106 and C90 with appropriate resistor and capacitor
values, depending on the application requirements.
ADVREF
DGND
DGND
VCC
33
+5V
JP2
JP2
1
2
3
C5
100nF
C5
100nF
AT91
S
AM
3S
AT91
S
AM
3S
ADVREF
1
R1
3
2.2K
R1
3
2.2K
MN2
LM4040-2.5
MN2
LM4040-2.5
Potentiometer
AD12B5
ADC
DGND
DGND
VCC
33
PB1
JP1
8
JP1
8
1
2
3
CN1
BNC
CN1
BNC
1
2
3
4
5
JP16
JP16
VR1
10K
VR1
10K
1
3
2
R96
49.9R 1%
R96
49.9R 1%
C
8
9
10nF
C
8
9
10nF
R94
0R
R94
0R
C7
8
10nF
C7
8
10nF
