TITLE
PROJECT
Lorry XU
Woody WU
CHECKED BY
DRAWN BY
OF
A
6
5
4
3
2
1
SHEET
A
B
C
D
1
2
3
4
5
6
D
C
B
Quectel Wireless Solutions
SIZE
VER
14
6
1.0
DATE
2019/12/5
EG21-G
A2
Reference Design
(U)SIM and UART Designs
UART Translation - Transistor Solution
UART Translation - IC Solution
Notes:
(U)SIM Interface
1. There are two translation solutions: transistor solution and IC solution,
3. The transistor circuit solution is not suitable for applications with high baud rates exceeding 460Kbps.
The 1nF capacitors C0402 and C0403 can improve the signal quality.
2. The power supply voltage of VCCA should not exceed that of VCCB.
Notes:
1. U401 is recommended to be used to offer good ESD protection,
2. It is recommended to connect the (U)SIM card connector's GND to the module's USIM_GND.
3. The pull-up resistor R0401 can improve anti-jamming capability,
4. R0407
～
R0409 are used for debugging,
5. C0401 capacitance should be less than 1μF.
4. The RTS and DTR transistor circuits are similar to that of RXD interface.
If the ground is complete on customers' PCB, USIM_GND can be connected to PCB ground directly.
and the parasitic capacitance should not be more than 15pF.
and should be placed close to the (U)SIM card connector.
6. For more information about the layout, please refer to
For more information about TXS0108E, please refer to the datasheet from TI.
The CTS, RI and DCD transistor circuits are similar to that of TXD interface.
and C0404
～
C0406 are used for filtering interference of EGSM900.
and should be placed close to the (U)SIM card connector.
and IC solution is recommended to be selected.
Quectel_EG21-G_Hardware_Design.
Q0401
2SC4617TLQ
Q0402
2SC4617TLQ
R0406
10K
R0405
10K
R0403
10K
R0404
10K
C0401 100nF
1
GND
2
VPP
3
I/O
4 CLK
5 RST
6 VCC
7
8 PRESENCE
J0401
(U)SIM card connector
1
2
3
4
5
6
U0401
ESDA6V8AV6
R0402
51K
C0405
33pF
C0406
33pF
C0404
33pF
R0407
0R
R0408
0R
R0409
0R
R0401
15K
C0407
100nF
R0411
120K
R0410
10K
C0408 100nF
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
U0402
TXS0108E
C0403
1nF
C0402
1nF
[4,6] RXD
[3,6]
RXD_EG21-G
VDD_EXT
VDD_EXT
[4,6] TXD
[3,6]
TXD_EG21-G
VDD_EXT
VDD_MCU
[3]
USIM_GND
VDD_EXT
USIM_VDD
[3]
USIM_RST
[3]
USIM_CLK
[3]
USIM_DATA
USIM_VDD
[3]
USIM_PRESENCE
VDD_EXT
VDD_EXT
VDD_MCU
[3,6] TXD_EG21-G
[3,6]
RXD_EG21-G
[3] RI_EG21-G
[3] DTR_EG21-G
[4,6]
TXD
[4,6]
RXD
[4]
DTR
[4]
RI
[4]
CTS
[4]
RTS
[3] CTS_EG21-G
[3]
RTS_EG21-G
[3] DCD_EG21-G
[4]
DCD
