• Figure 25: USB reference circuit The TVS on USB data line should be less than 5pf, and traced by differential forms.
  • Note: When only USB_DP and USB_DN are connected, no VBUS, customers need to pull down KBC0 (pin20) before power on
    		•

    Note: When Figure22, Figure 23 and Figure 24 are used for electrical level isolation, if customers use serial port to upgrade SW




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    SIM800L

    Note: When Figure22, Figure 23 and Figure 24 are used for electrical level isolation, if customers use serial port to upgrade SW, 
    please note VDD_EXT has no voltage output during the upgrading process, LDO output could be used as VDD_EXT in the 
    figure, upgrading through USB port is recommended. 
     
    4.5.3 Debug Interface 
    SIM800H&SIM800L could achieve software debug function through USB interface. When powering on the 
    module, connect VBUS, USB_DP, USB_DN, and GND to PC, then install the driver following the prompts, a 
    UART port could be recognized by PC, customer could achieve the software Debug with this UART port. 
    SIMCom recommended the following connected diagram: 
    Figure 25: USB reference circuit 
    The TVS on USB data line should be less than 5pf, and traced by differential forms. 
     
    Note: please reserve the USB interface or test point for the further debugging 
    Table 11: VBUS operation voltage 
    Pin
    Min 
    Typ 
    Max 
    Unit 
    VBUS 
    4.3 
    5.0 
    7.0 
    V 
    SIM800H&SIM800L_Hardware Design_V2.02 32 2015-07-27 

    Smart Machine Smart Decision 
    4.5.4 Software Upgrade 
    Customer could upgrade module’s firmware through USB or UART interface. 
    If upgrading through USB interface, it is necessary to power on SIM800H&SIM800L first, then connect VBUS, 
    USB_DP, USB_DN, and GND to PC. There is no need to operate PWRKEY pin in the whole procedure, when 
    SIM800H&SIM800L detects VBUS and could communicate normally with USB_DP and USB_DN, it will enter 
    USB download mode automatically. 
    Note: When only USB_DP and USB_DN are connected, no VBUS, customers need to pull down KBC0 (pin20) before power on 

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    Note: When Figure22, Figure 23 and Figure 24 are used for electrical level isolation, if customers use serial port to upgrade SW

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