CH340 Datasheet (I)
9
TPR
Reset time of power-up
20
35
50
mS
7. Applications
7.1. USB to 9-line RS232 UART
(figure below)
The figure below shows that CH340T (or CH340C/B) converts USB to RS232 UART. CH340 provides
common
UART and MODEM signals, and converts TTL to RS232 through level converter chip U8. The
P11 port is DB9
connector, the pins and their functions are the same as common PC DB9 connector, the
chips similar with U8 is MAX213/ADM213/SP213/MAX211 etc.
U8 and C46/C47/C48/C49/C40 could be removed when realize USB to TTL converter only. For the signal
lines shown in the figure, only RXD, TXD and public
ground need to be connected, the
other signal lines
should not connect when not used.
P2 is a USB port. USB bus contains a pair of 5V power lines and a pair of data signal lines. Usually, the
color of +5V power lines is red, the black one is ground. D+ signal line is green and the D- signal line is
white. The max supply current of USB bus is up to 500mA. Generally, CH340 and low-power USB products
can use the 5V power supplied by USB bus directly.
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