TITLE
Yeoman CHEN
CHECKED BY
Eden LIU
DRAWN BY
C
A
6
5
4
3
2
1
A
B
C
D
1
2
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6
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C
B
4
2016/11/11
A2
PROJECT
Quectel Wireless Solutions
SIZE
SHEET
VER
OF 10
DATE
EC25
1. R401~R403 are applied to suppress the EMI spurious transmission
Notes:
3. R404 can improve anti-jamming capability of the USIM circuit, and
USIM and UART Design
and enhance the ESD protection.
it should be placed close to the USIM connector.
UART Translation - IC Solution (Recommended)
UART Translation - Transistor Solution
4. VCCA should not exceed VCCB. For more information about TXS0108E,
please refer to the datasheet from TI.
5. If you need to enable high baud rate, it is highly recommended to install
a 1nF capacitor (C407/C408/C409/C410) on transistor circiut.
6. The DTR transistor circuit is similar to RTS interface. The RI and DCD
transistor circuits are similar to CTS interface.
2. It is recommended to take electrostatic discharge (ESD) protection measures
near the USIM card socket. The TVS diode with junction capacitance
less than 50 pF must be placed as close as possible to the USIM socket.
USIM Interface
2. EC25 module provides an input pin (USIM_PRESENCE) to detect whether the USIM card exists or not.
It supports both low level and high level detections. For more details, please refer to
1. The decouple capacitor of USIM_VDD should be less than 1uF and must be near to USIM socket.
Notes:
Note:
It is recommended to use an IC conversion chip for UART translation.
Note:
Transistor circuit solution is not suitable for applications with high baud rates exceeding 460Kbps.
Reference Design
Quectel_EC25_Hardware_Design.
C401 100nF
1
2
3
4
5
6
U401
ESDA6V8AV6
C403
33pF
C404
33pF
C402
33pF
R401
22R
R402
22R
R403
22R
R404
15K
C405
100nF
R406
120K
R405
10K
C406 100nF
Q401
2SC4617TLQ
Q402
2SC4617TLQ
R408
4.7K
R407
4.7K
C407
1nF
R409
4.7K
R410
4.7K
C408
1nF
Q403
2SC4617TLQ
R412
4.7K
R411
4.7K
Q404 2SC4617TLQ
R413
4.7K
R414
4.7K
6 A5
7 A6
8 A7
9 A8
10 OE
5 A4
4 A3
19
VCCB
20
B1
18
B2
14
B6
13
B7
12
B8
11
GND
3 A2
2 VCCA
1 A1
17
B3
16
B4
15
B5
U402
TXS0108E
GND
VPP
I/O
CLK
RST
VCC
PRESENCE
J401
SIM Holder
R415
51K
C409
1nF
C410
1nF
USIM_VDD
[1] USIM_RST
[1] USIM_CLK
[1] USIM_DATA
USIM_VDD
[1]
USIM_GND
VDD_EXT
VDD_EXT
VDD_MCU
[1,4] TXD_MODULE
[1,4] RXD_MODULE
[1] RI_MODULE
[1] DTR_MODULE
[2,4]
RXD_MCU
[2,4]
TXD_MCU
[2]
DTR_MCU
[2]
RI_MCU
[2,4] TXD_MCU
[1,4]
RXD_MODULE
VDD_EXT
VDD_EXT
[2,4] RXD_MCU
[1,4]
TXD_MODULE
VDD_EXT
VDD_MCU
VDD_EXT
[1,4]
RTS_MODULE
[2,4] RTS_MCU
VDD_EXT
VDD_MCU
[2,4] CTS_MCU
[1,4]
CTS_MODULE
VDD_EXT
[2,4]
CTS_MCU
[2,4]
RTS_MCU
[1,4] CTS_MODULE
[1,4] RTS_MODULE
[1] DCD_MODULE
[2]
DCD_MCU
VDD_EXT
[1] USIM_PRESENCE
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