Integration Manual

Table Of Contents
TOBY-L3 series - System Integration Manual
TSD-19090601 - R13 System Integration Manual Page 98 of 143
35 um
35 um
35 um
35 um
270 um
270 um
760 um
L1 Copper
L3 Copper
L2 Copper
L4 Copper
FR-4 dielectric
FR-4 dielectric
FR-4 dielectric
350 um 400 um400 um350 um400 um
Figure 41: Example of USB line design, with Z
0
close to 90 and Z
CM
close to 30 , for the described 4-layer board layup
35 um
35 um
1510 um
L2 Copper
L1 Copper
FR-4 dielectric
740 um 410 um410 um740 um410 um
Figure 42: Example of USB line design, with Z
0
close to 90 and Z
CM
close to 30 , for the described 2-layer board layup
2.6.2 UART interfaces
2.6.2.1 Guidelines for UART circuit design
4-wire UART
If RS-232 compatible signal levels are needed, the Maxim MAX13234E voltage level translator can be used.
This chip translates voltage levels from 1.8 V (module side) to the RS-232 standard.
If a 1.8 V external Processor / Device is used, the circuit should be implemented as shown in Figure 43.
TxD
1.8V Processor / Device
RxD
RTS
CTS
GND
TOBY-L3 series
TXDx
RXDx
RTSx
CTSx
GND
0 Ohm
TP
0 Ohm
TP
Figure 43: 4-wire UART interface application circuit to connect an external 1.8 V processor / device
If a 3.0 V external Processor / Device is used, then it is recommended to connect the 1.8 V UART interface
of the module by means of appropriate unidirectional voltage translators using the module V_INT output
as a 1.8 V supply for the voltage translators on the module side, as shown in Figure 44.