Figure 14.
Clock and reset
OSC-MOD
EXTAL-SMA
ESR0
PORST
RST-SW
RST-MCU
D2
Red
D1 Yellow
GND
GND
VSS_OSC
GND
GND
GND
GND
GND
GND
Loop Controlled Pierce
Oscillator Circuit
Note -
Internal
Pull-Up on
Pin 1
SMA style
Connector
Note - External 3.3V
regulator MUST be
enabled when using
oscillator module
Reset-In
Disable
USR RESET LED
MCU RESET LED
Reset circuit
REMOVE XTAL jumper when driving EXTAL from
Oscillator Module or External Source
Connect XTAL jumper to GND when driving EXTAL from
Oscillator Module or External Source
C82
8pF
50V
NORMAL TRACE
LEGEND
AS SHORT AS POSSIBLE TRACE
50 OHM SAME LENGHT TRACE
50 OHM TRACE
J17
STRIP3PMD-2MM
1
2
3
EXTAL
PB4-XTAL32
PE14-EXTAL32
EVB_EXTAL
J19
STRIP3PMD-2MM
1
2
3
XTAL
R40
0R
Y1
40MHz
1
2
C79 100nF
50V
J18
STRIP2PMD-2MM-O
1
2
U5
8MHz
EN
1
GND
2
OUT
3
+Vs
4
1
2
P1
SMA-FEM-180
J22
STRIP3PMD-2MM
1
2
3
EVB_EXTAL
SW1
Pushbutton
R45
10K
R46
560R
RST-SW
GND
Vcc
U6A
74LVC125AMTR
2
3
7
14
1
J24
STRIP2PMD-2MM
1
2
R47
4K7
GND
Vcc
U6B
74LVC125AMTR
5
6
7
14
4
3.3V_SR
GND
Vcc
U6C
74LVC125AMTR
9
8
7
14
10
J23
STRIP2PMD-2MM
1
2
J25
STRIP2PMD-2MM
1
2
GND
VCC
U7
74V1G08STR
1
2
4
5
3
R43
4K7
R48
4K7
R44
560R
ESR0
PORST
VSS_OSC
External clock input
External oscillator
32 kHz oscillator
C81
10pF
50V
R38
0R
Y2
32.768 KHz
1
2
C83
10pF
50V
VSS_OSC
R39
DNM
R36 0R
J20
STRIP2PMD-2MM-O
1
2
J21
STRIP2PMD-2MM-O
1
2
C80
8pF
50V
VDD_HV_IO_MAIN
VDD_HV_IO_MAIN
VDD_HV_IO_MAIN
VDD_HV_IO_MAIN
R41
DNM
R37
DNM
PB4
PE14
R42 50R
UM2725
-
Rev 1
page 30
/38
UM2725
Schematic
