Figure 3-3. USB Input Power Schematic
USBA_N
USBA_P
20pF
50V
0402
C194
20k
0402
1%
R188
GND
GND
USBA_VBUSDETECT_PD11
GND_USBA
USBA_VBUS_5V
EN
1
FLG 2
GND
3
NC
4
NC 5
OUT 6
IN
7
OUT 8
USB Power Switch
MIC2025-1YM
U16
USBA_VBUS_5V
USBA_OVCUR_PC7
USBA_EN_5V_PB2
5V_MAIN
VDD_3V3
GND
GND
GND
10uF
25V
1206
C195
10uF
25V
1206
C197
0475890001
1
2
3
4
5
0
ID
D
+
D
-
+5
V
G
N
D
M
in
i-B
Re
ce
pt
ac
le
J7
USB Micro-AB type connector to the USBA port (HOST/DEVICE)
0.1uF
10V
0402
C198
100uF
10V
1210
C200
22uF
10V
1206
C199
0.1uF
10V
0402
C196
10k
0402
1%
R189
10k
0402
1%
R187
10k
0402
1%
R186
120R
BLM18PG121SN1D
FB9
120R
BLM18PG121SN1D
FB10
DIFF90
DIFF90
0R
0603
R185
USB_VBUS_5V
GND
GND_USBA
90
Ω
±15% differential trace impedance
Routing top or bottom
Note:
USB-powered operation eliminates the need for additional wires and batteries. It is the preferred mode of
operation for any project that requires only a 5V source at up to 500 mA.
3.1.1.3
Automatic Power Switch
The switch between the two powering options is made by four transistors that ensure the separation between the two
when both are plugged. The switch prioritizes powering from the wall adapter to maximize power transfer.
The following figure shows the automatic power switch topology.
Figure 3-4. Automatic Power Switch Schematic
0603
LT
ST
-C
19
1K
RK
T
D3
3k
0603
1%
R7
GND
5V_MAIN
5V_DC
2
7
1
6
SIA923AEDJ-T1-GE3
Q1A
5
8
4
3
SIA923AEDJ-T1-GE3
Q1B
2
7
1
6
SIA923AEDJ-T1-GE3
Q2A
5
8
4
3
SIA923AEDJ-T1-GE3
Q2B
GND
GND
GND
GND
GND
External Power Switch
0.1uF
10V
0402
C7
0.1uF
10V
0402
C14
100k
0402
5%
R8
100k
0402
5%
R9
100uF
10V
1210
C8
22uF
10V
1206
C9
0.1uF
10V
0402
C10
10uF
25V
1206
C13
GND
120R
BLM18PG121SN1D
FB1
USB_VBUS_5V
TP4
SAMA7G54-EK
Function Blocks
©
2022 Microchip Technology Inc.
and its subsidiaries
User Guide
DS50003273A-page 10
