STC232E Datasheet, PDF (5/6 Pages) List of Unclassifed Manufacturers – High ESD-Protected, Fail-Safe , Single Supply RS-232 Transceivers

STC International Limited
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RS-232 Receivers
The receivers convert RS-232 input signals to inverted TTL signals. Since the input is usually from a transmission line,
where long cable lengths and system interference can degrade the signal, the inputs have a typical hysteresis margin of
500mV. This ensures that the receiver is virtually immune to noisy transmission lines. The input thresholds are 0.8V
minimum and 2.4V maximum, again well within the 3V RS-232 requirements. The receiver inputs are also protected
against voltage up to 25V. Should an input be left unconnected, a 5kO pull down resistor to ground will commit the
output of the receiver to a high state. In actual system applications, it is quite possible for signals to be applied to the
receiver inputs before power is applied the receiver circuitry. This occurs, for example, when a PC user attempts to print,
only to realize the printer wasn’t turned on. In this case an RS-232 signal from the PC will appear on the receiver input
at the printer. When the printer power is turned on, the receiver will operate normally. All of these enhanced devices are
fully protected.
ESD Protection
STC232E devices have standard ESD protection structures incorporated on the pins to protect against electrostatic
discharges encountered during assembly and handling. In addition, the RS232 bus pins (driver outputs and receiver
input) of these devices have an extra level of ESD protection. Advanced ESD structures were designed to successfully
protect these pins against ESD discharge of 15kV when powered down.
Pin Configurations and Typical Operating Circuits
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STC232E Datasheet Rev.0.1, Dec.2005
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