3- to 5.5-V single channel 1Mbps RS-232 line driver/receiver with +/-15-kV IEC-ESD protection

The SN65C3221E and SN75C3221E consist of one line

driver, one line receiver, and a dual charge-pump circuit with ±15-kV IEC ESD

protection pin to pin (serial-port connection pins, including GND). These devices

provide the electrical interface between an asynchronous communication controller

and the serial-port connector. The charge pump and four small external capacitors

allow operation from a single 3-V to 5.5-V supply.

These devices operate at data signaling rates up to 1 Mbit/s and a driver output

slew rate of 24 V/µs to 150 V/µs.

Flexible control options for power management are

available when the serial port is inactive. The auto-powerdown feature functions

when FORCEON is low and FORCEOFF is high. During this mode of

operation, if the devices do not sense a valid RS-232 signal on the receiver input,

the driver output is disabled. If FORCEOFF is set low and

EN is high, both the driver and receiver are shut off, and

the supply current is reduced to 1 µA. Disconnecting the serial port or turning off

the peripheral drivers causes the auto-powerdown condition to occur. Auto-powerdown

can be disabled when FORCEON and FORCEOFF are high. With

auto-powerdown enabled, the device is activated automatically when a valid signal is

applied to the receiver input. The INVALID output notifies the

user if an RS-232 signal is present at the receiver input.

INVALID is high (valid data) if the receiver input voltage

is greater than 2.7 V or less than –2.7 V, or has been between –0.3 V and 0.3 V for

less than 30 µs. INVALID is low (invalid data) if the receiver

input voltage is between –0.3 V and 0.3 V for more than 30 µs. See Figure 8-5 for receiver input levels.

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