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參數(shù)資料
| 型號： | SP3243BET |
| 元件分類： | RS-232 |
| 英文描述： | 5V High-Speed RS-232 Transceivers with 0.1uF Capacitors |
| 中文描述： | 5V的高速RS - 232收發(fā)器與0.1uF電容 |
| 文件頁數(shù)： | 17/24頁 |
| 文件大?。?/td> | 180K |
| 代理商： | SP3243BET |
17
Rev. 6/30/03
SP3223B/3243B +3.0V to +5.5V RS-232 Transceivers
Copyright 2003 Sipex Corporation
AUTO ON-LINE
Circuitry
The SP3223B and SP3243B devices have a
patent pending AUTO ON-LINE
circuitry on
board that saves power in applications such as
laptop computers, palmtop (PDA) computers,
and other portable systems.
The SP3223B and SP3243B devices incorporate
an AUTO ON-LINE
circuit that automatically
enables itself when the external transmitters are
enabled and the cable is connected. Conversely,
the AUTO ON-LINE
circuit also disables most
of the internal circuitry when the device is not
being used and goes into a standby mode where
the device typically draws 1
μ
A. This function
can also be externally controlled by the ONLINE
pin. When this pin is tied to a logic LOW, the
AUTO ON-LINE
function is active. Once
active, the device is enabled until there is no
activity on the receiver inputs. The receiver
input typically sees at least
±
3V, which are
generated from the transmitters at the other end
of the cable with a
±
5V minimum. When the
external transmitters are disabled or the cable is
disconnected, the receiver inputs will be pulled
down by their internal 5k
resistors to ground.
When this occurs over a period of time, the
internal transmitters will be disabled and the
device goes into a shutdown or standby mode.
When ONLINE is HIGH, the AUTO ON-LINE
mode is disabled.
The AUTO ON-LINE
circuit has two stages:
1) Inactive Detection
2) Accumulated Delay
The first stage, shown in
Figure 28
, detects an
inactive input. A logic HIGH is asserted on
R
X
INACT if the cable is disconnected or the
external transmitters are disabled. Otherwise,
R
X
INACT will be at a logic LOW. This circuit is
duplicated for each of the other receivers.
The second stage of the AUTO ON-LINE
cir-
cuitry, shown in
Figure 29
, processes all the
receiver's R
X
INACT signals with an accumu-
lated delay that disables the device to a 1
μ
A
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 20
μ
s.
When the SP3223B and SP3243B drivers or
internal charge pump are disabled, the supply
current is reduced to 1
μ
A. This can commonly
occur in hand-held or portable applications where
the RS-232 cable is disconnected or the RS-232
drivers of the connected peripheral are turned off.
The AUTO ON-LINE
mode can be disabled by
the SHUTDOWN pin. If this pin is a logic LOW,
the AUTO ON-LINE
function will not operate
regardless of the logic state of the ONLINE pin.
Table 3 summarizes the logic of the AUTO ON-
LINE
operating modes. The truth table logic of
the SP3223B and SP3243B 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 SP3223B and SP3243B devices
are shut down, the charge pumps are turned off.
V+ charge pump output decays to V
CC
, the
V- output decays to 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 200
μ
s.
For easy programming, the STATUS can be
used to indicate DTR or a Ring Indicator signal.
Tying ONLINE and SHUTDOWN together
will bypass the AUTO ON-LINE
circuitry so
this connection acts like a shutdown input pin.
相關PDF資料 |
PDF描述 |
|---|---|
| SP3243BEY | 5V High-Speed RS-232 Transceivers with 0.1uF Capacitors |
| SP3223B | 5V High-Speed RS-232 Transceivers with 0.1uF Capacitors |
| SP3243EBCA | 5V High-Speed RS-232 Transceivers with 0.1uF Capacitors |
| SP3243CA | 5V High-Speed RS-232 Transceivers with 0.1uF Capacitors |
| SP3243EB | 5V High-Speed RS-232 Transceivers with 0.1uF Capacitors |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| SP3243BEY | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Intelligent +3.0V to +5.5V RS-232 Transceivers |
| SP3243CA | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Intelligent +3.0V to +5.5V RS-232 Transceivers |
| SP3243CT | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Intelligent +3.0V to +5.5V RS-232 Transceivers |
| SP3243E | 制造商:EXAR 制造商全稱:EXAR 功能描述:3 Driver/5 Receiver Intelligent +3.0V to +5.5V RS-232 Transceivers |
| SP3243EA | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Intelligent +3.0V to +5.5V RS-232 Transceivers |
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