Data Sheet

Smart Machine Smart Decision
SIM800F_Hardware Design_V1.00 31 2015-07-31
Figure 21: Level converting by resistor
If the voltage of UART is 3V or3.3V, users also can use following reference circuits:
Figure 22: Level converting by diodes
Note: when diode is used for level converting, customer should check the voltage drop on the diode to make sure the signal’s
voltage level could meet both module and DTE’s electrical character. The recommend diode is Schottky diode e.g.
RB551V-30TE-17 and SDM20U40.
If the voltage of UART is 5V on customer side, users can use the following reference circuits:
VDD_EXT
4.7K
47K
TXD
4.7K
Module
VDD_EXT
RXD
VDD
DTE
Figure 23: TX level converting by transistor