UMTS/HSPA Module Series
UC20 Hardware Design
UC20_Hardware_Design Confidential / Released 40 / 84
VCCA
VCCB
OE
A1
A2
A3
A4
A5
A6
A7
A8
GND
B1
B2
B3
B4
B5
B6
B7
B8
VDD_EXT
RI
DCD
RTS
RXD
DTR
CTS
TXD
51K
51K
0.1uF
0.1uF
RI_3.3V
DCD_3.3V
RTS_3.3V
RXD_3.3V
DTR_3.3V
CTS_3.3V
TXD_3.3V
VDD_3.3V
TXB0108PWR
Figure 18: Reference Circuit with
Translator
Chip
Please visit http://www.ti.com for more information.
Another example with transistor translation circuit is shown as below. The construction of dotted line can
refer to the construction of solid line. Please pay attention to direction of connection. Input dotted line of
module should refer to input solid line of the module. Output dotted line of module should refer to output
solid line of the module.
MCU/ARM
/TXD
/RXD
VDD_EXT
4.7K
VCC_MCU
4.7K
4.7K
4.7K
VDD_EXT
TXD
RXD
RTS
CTS
DTR
RI
/RTS
/CTS
GND
GPIO
DCD
Module
GPIO
EINT
VCC_MCU
4.7K
GND
Figure 19: Reference Circuit with
Transistor Circuit
The following figure is an example of connection between UC20 and PC. A voltage level translator and a
RS-232 level translator chip must be inserted between module and PC, since these two UART interfaces
do not support the RS-232 level, while support the 1.8V CMOS level only.