Data Sheet

Smart Machine Smart Decision
SIM800F_Hardware Design_V1.00 32 2015-07-31
VDD_EXT
4.7K
47K
4.7K
DTE
RXD
Module
VDD_EXT
TXD
VDD
Figure 24: RX level converting by transistor
4.6.3 USB Interface
USB interface supports software debug function. When power on the module, connect VBUS, USB_DP,
USB_DN and GND to PC, install the driver successfully, a com port could be recognized by PC, then customer
could debug via this com port. The reference circuit is shown as below:
Moudle
USB
GND
GND
22R
USB_VBUS
VBUS
1uF
USB_DN
USB_DP
USB_DN
22R
USB_DP
Figure 25: USB reference circuit
The maximum capacitance of TVS on USB data line should be less than 5pF (e.g. ESD9L5.0ST5G and
ESD9M5.0ST5G). The USB_DP and USB_DN should be routed in differential traces.
Note: please reserve USB interface or test point for debugging.
Table 10: VBUS characteristics
Pin Min Typ Max Unit
VBUS 4.3 5.0 7.0 V
4.6.4 Software Upgrading and Debugging
Customer could upgrade module’s firmware through USB or UART interface.