sp3223ebcy-tr Exar Corporation, sp3223ebcy-tr Datasheet - Page 12

• Manufacturer Part Number: sp3223ebcy-tr
• Description: Sp3223eb -intelligent +3.0v To +5.5v Rs-232 Transceivers
• Manufacturer: Exar Corporation

Date: 10/06/06
The AUTO ON-LINE
The first stage, shown in Figure 20, detects an
inactive input. A logic HIGH is asserted on
R
external transmitters are disabled. Otherwise,
R
is duplicated for each of the other receivers.
The clock rate for the charge pump typically
operates at above 250kHz. The external capaci-
tors can be as low as 0.1µF with a 16V break-
down voltage rating.
The second stage of the AUTO ON-LINE
circuitry, shown in Figure 21, processes all the
receiver's R
lated delay that disables the device to a 1µA
supply current.
The STATUS pin goes to a logic LOW when the
cable is disconnected, the external transmitters
are disabled, or the SHUTDOWN pin is
invoked. The typical accumulated delay is around
20µs.
When the SP3223 drivers or internal charge
pump are disabled, the supply current is reduced
to 1µA. This can commonly occur in handheld
Figure 16. AUTO ON-LINE
X
X
INACT if the cable is disconnected or the
INACT will be at a logic LOW. This circuit
1) Inactive Detection
2) Accumulated Delay
X
INACT signals with an accumu-
RS-232 OUTPUT
RS-232 INPUT
VOLTAGES
RECEIVER
VOLTAGES
STATUS
®
®
DRIVER
circuit has two stages:
Timing Waveforms
+2.7V
-2.7V
V
+5V
-5V
CC
0V
0V
0V
SP3223 +3.0V to +5.5V RS-232 Transceivers
t
STSL
®
12
t
ONLINE
t
STSH
is disconnected or the RS-232 drivers of the
connected peripheral are turned off.
The AUTO ON-LINE
by the SHUTDOWN pin. If this pin is a logic
LOW, the AUTO ON-LINE
operate regardless of the logic state of the
ONLINE pin. Table 3 summarizes the logic of the
AUTO ON-LINE
table logic of the SP3223 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 en-
abled and the cable is connected.
When the SP3223 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 DTR or a Ring Indicator signal.
Tying
together will bypass the AUTO ON-LINE
circuitry so this connection acts like a shutdown
input pin
W
H
U
D
O
N
S
T
or portable applications where the RS-232 cable
ONLINE
®
CC
operating modes. The truth
,the V- output decays to
®
and
© Copyright 2006 Sipex Corporation
mode can be disabled
®
function will not
SHUTDOWN
®