SP3243E EXAR [Exar Corporation], SP3243E Datasheet - Page 12

• Manufacturer Part Number: SP3243E
• Description: 3 Driver/5 Receiver Intelligent +3.0V to +5.5V RS-232 Transceivers
• Manufacturer: EXAR [Exar Corporation]

Figure 14. AUTO ON-LINE
The second stage of the AUTO ON-LINE
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 AUTO ON-LINE
the SHUTDOWN pin. If this pin is a logic LOW,
the AUTO ON-LINE
regardless of the logic state of the ONLINE pin.
Table 3 summarizes the logic of the AUTO ON-
LINE
the SP3243E driver and receiver outputs can be
found in Table 2.
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.
X
X
X
INACT signals with an accumulated delay that
INACT if the cable is disconnected or the
INACT will be at a logic LOW. This circuit is
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operating modes. The truth table logic of
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com
RS-232 OUTPUT
RS-232 INPUT
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VOLTAGES
RECEIVER
mode can be disabled by
function will not operate
VOLTAGES
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STATUS
Timing Waveforms
DRIVER
+2.7V
-2.7V
+5V
V
-5V
0V
CC
0V
0V
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circuitry,
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STSL
12
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
will bypass the AUTO ON-LINE
connection acts like a shutdown input pin.
t
ONLINE
t
STSH
W
O
S
H
U
D
N
T
CC
, the V- output decays to
SP3243E_100_072309
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circuitry so this