Microchip Technology SAM Series

Figure 10-3. VBAT Bypassing and Battery Monitoring Diagram
External Battery Monitoring
MCU VBAT Input Pin Bypassing
+
VBAT
MCU
BATT
4.7µf
0.1uf
+
ADC IN_0
MCU
VDDx
VDDx
0.22µf
500k
250k
BATT
LDO
9v
+
ADC IN_0
MCU
VDDx
VDDx
500k
250k
BATT
LDO
9v
R1
R2
R1
R2
ADC
I/O PIN
3 pf
+
0.22µf
500k
250k
BATT
9v
Capacitor charge ratio =
= 0.22uf / 3pf
= 73,333:1
Equivalent Circuit
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PCB MCU Connections
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Manual
DS70005439B-page 32