Smart Machine Smart Decision
SIM800_Hardware Design_V1.10
32
2018-08-13
Module
USB
USB_DP
USB_ DN
USB_ DN
GND
GND
USB_ DP
USB_VBUS
VBUS
22
Ω
22
Ω
1uF
Figure 24: USB reference circuit
The maximum allowable cap load 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 the USB interface or test point for debug.
Table 10: USB_VBUS operation voltage
Pin
Min
Typ
Max
Unit
USB_VBUS
4.3
5.0
7.0
V
Note: USB_VBUS is only used for USB inserting detection, can not be used as a power source.
4.5.4
Software Upgrade and Debug
USB and UART interfaces can be used for firmware upgrade.
If customer upgrading firmware via the USB port, SIM800 must be powered first, then connect USB_VBUS,
USB_DP, USB_DN and GND to PC. There is no need to operate PWRKEY pin in the whole procedure, when
SIM800 detects USB_VBUS and could communicate normally by USB_DP and USB_DN, module will enter
USB download mode automatically.
Note: When only USB_DP and USB_DN connected, no USB_VBUS, customer need to pull down KBC0
before power on the module, then press the PWRKEY button, the module will enter download mode;
If customer upgrading firmware via the UART port, it is strongly recommended that reserve the TXD,
RXD,GND and PWRKEY pins to IO connector for the upgrade, and PWRKEY pin should connect to GND
while upgrading. Refer to the following figure for upgrading software.
