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Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com

SP3243E_100_072309

The first stage, shown in Figure 21, detects an

inactive input. A logic HIGH is asserted on

R

external transmitters are disabled. Otherwise,

R

duplicated for each of the other receivers.

shown in Figure 22, processes all the receiver's

R

disables the device to a 1µA supply current.

The STATUS pin goes to a logic LOW when the

cable is disconnected, the external transmit-

ters are disabled, or the SHUTDOWN pin is

invoked.The typical accumulated delay is around

20µs.

When the SP3243E drivers or internal charge

pump are disabled, the supply current is reduced

to 1µA. This can commonly occur in hand-held

or portable applications where the RS-232 cable

is disconnected or the RS-232 drivers of the con-

nected peripheral are turned off.

the SHUTDOWN pin. If this pin is a logic LOW,

regardless of the logic state of the ONLINE pin.

Table 3 summarizes the logic of the AUTO ON-

the SP3243E driver and receiver outputs can be

found in Table 2.

The STATUS pin outputs a logic LOW signal

if the device is shutdown. This pin goes to a

logic HIGH when the external transmitters are

enabled and the cable is connected.

When the SP3243E devices are shut down, the

charge pumps are turned off. V+ charge pump

output decays to V

GND. The decay time will depend on the size

of capacitors used for the charge pump. Once

in shutdown, the time required to exit the shut

down state and have valid V+ and V- levels is

typically 200µs.

For easy programming, the STATUS can be

used to indicate DSR or a Ring Indicator sig-

nal. Tying ONLINE and SHUTDOWN together

connection acts like a shutdown input pin.

RECEIVER

RS-232 INPUT

VOLTAGES

STATUS

+5V

0V

-5V

0V

DRIVER

RS-232 OUTPUT

VOLTAGES

0V

+2.7V

-2.7V

S

H

U

T

D

O

W

N