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參數(shù)資料
| 型號： | SP3238E |
| 英文描述： | Intelligent +3.0V to +5.5V RS-232 Transceivers(智能+3.0V 至 +5.5V RS-232收發(fā)器（5發(fā)3收）) |
| 中文描述： | 智能3.0V至5.5V的RS - 232收發(fā)器（智能3.0V至5.5V的RS - 232接口收發(fā)器（5發(fā)3收）） |
| 文件頁數(shù)： | 15/20頁 |
| 文件大?。?/td> | 224K |
| 代理商： | SP3238E |
15
SP3238EDS/04
SP3238E +3.0V to +5.5V RS-232 Transceivers
Copyright 1999 Sipex Corporation
Auto-Online Circuitry
The
SP3238E
device has a patent pending
Auto-Online
circuitry on board that saves power
in applications such as laptop computers, palmtop
(PDA) computers, and other portable systems.
The
SP3238E
device incorporates an
Auto-Online
circuit that automatically
enables itself when the external transmitters are
enabled and the cable is connected. Conversely,
the
Auto-Online
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-Online
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 standy mode. When ONLINE
is HIGH, the
Auto-Online
mode is disabled.
The
Auto-Online
circuit has two stages:
1) Inactive Detection
2) Accumulated Delay
The first stage, shown in
Figure 18
, detects an
inactive input. A logic HIGH is asserted on
R
INACT if the cable is disconnected or the
external transmitters are disabled. Otherwise,
R
INACT will be at a logic LOW. This circuit is
duplicated for each of the other receivers.
The second stage of the
Auto-Online
circuitry,
shown in
Figure 19
, processes all the receiver's
R
INACT signals with an accumulated 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 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-Online
mode can be disabled by the
SHUTDOWN pin. If this pin is a logic LOW,
the
Auto-Online
function will not operate
regardless of the logic state of the ONLINE pin.
Table 3
summarizes the logic of the
Auto-Online
operating modes. The truth table logic of the
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
SP3238E
device is shut down, the
charge pump is turned off. V+ charge pump
output decays to V
, 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-Online
circuitry so this
connection acts like a shutdown input pin.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SP3238EA | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Intelligent +3.0V to +5.5V RS-232 Transceiver |
| SP3238EA/TR | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:Intelligent +3.0V to +5.5V RS-232 Transceiver |
| SP3238ECA | 制造商:Rochester Electronics LLC 功能描述: 制造商:Exar Corporation 功能描述: |
| SP3238ECA/TR | 制造商:Rochester Electronics LLC 功能描述: 制造商:Exar Corporation 功能描述: |
| SP3238ECA-L | 功能描述:RS-232接口集成電路 RS232 250 kbps 5Tx temp 0C to 70C RoHS:否 制造商:Exar 數(shù)據(jù)速率:52 Mbps 工作電源電壓:5 V 電源電流:300 mA 工作溫度范圍:- 40 C to + 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:LQFP-100 封裝: |
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