资料介绍
The introduction of single-voltage EPROMS and dynamic RAMs
has permitted designers to produce complete digital systems
powered by a single 5V supply. One area which has not yielded
to single-supply operation, however, is the RS-232 interface. If a
system must communicate with an RS-232 serial device, such as
a printer or another computer, a separate power supply is
required. AN782
TC7660 Powers RS-232 Data Loop Low Cost Adapter
The RS-232 input voltage spec is ±3V. The minimum input resis-
Author: Wes Freeman, tance of the TC232, a typical RS-232 transceiver, is about 3k.
Microchip Technology, Inc. Therefore, 1mA of current must be supplied, and R1 must be:
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