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| 型号： | SP238AET-L |
| 厂商： | Exar Corporation |
| 文件页数： | 7/12页 |
| 文件大小： | 0K |
| 描述： | IC DVR/RCVR RS232 MULTI 24WSOIC |
| 标准包装： | 31 |
| 类型： | 收发器 |
| 驱动器/接收器数： | 4/4 |
| 规程： | RS232 |
| 电源电压： | 4.5 V ~ 5.5 V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 24-SOIC（0.295"，7.50mm 宽） |
| 供应商设备封装： | 24-SOIC W |
| 包装： | 管件 |
| 其它名称： | 1016-1687 SP238AET-L-ND |
Exar Corporation 48720 Kato Road, Fremont CA, 94538 (50)668-707 www.exar.com
SP238A_00_0740
4
FeatUReS…
The SP238A multi-channel RS-232 line trans-
ceiverprovides4driversand4receiverstofit
most communication needs, especially those
applications where ±2V is not available. The
device features low power CMOS operation,
whichisparticularlybeneficialinbattery-powered
systems.
The device includes two charge pump voltage
converters which allows it to operate from a
single +5V supply. These converters convert the
+5V input power to the minimum loaded voltage
of ±5.0V for compliant RS-232 output levels. All
drivers and receivers meet all EIA RS-232D and
CCITTV.28specifications.
The device is available for use over the com-
mercial and industrial temperature ranges. It is
packaged in a WSOIC package.
tHeoRY oF oPeRation
The SP238A is made up of three basic circuit
blocks - ) transmitter, 2) receiver and 3) charge
pump.
Driver/transmitter
The drivers are inverting transmitters, which ac-
cept TTL or CMOS inputs and output the RS-232
signals with an inverted sense relative to the input
logic levels.The transmitter outputs are protected
againstinfiniteshort-circuitstogroundwithout
degradation in reliability. Should the input of the
driver be left open, an internal 400k pull-up
resistor to Vcc forces the input HIGH, thus com-
mitting the output to a low state.
The slew rate of the transmitter output is internally
limited to a maximum of 30V/s in order to meet
the standards [EIA RS-232-D 2..7, Paragraph
(5)]. The transition of the loaded output from V
OL to
V
OH clearly meets the monotonicity requirements
of the standard [EIA RS-232-D 2..7, Paragraphs
() & (2)].
Receivers
The receivers convert RS-232 input signals to
inverted TTL signals. Since the input is usually
fromatransmissionline,wherelongcablelengths
and system interference can degrade the signal,
the inputs have a typical hysteresis margin of
500mV. This ensures that the receiver is virtually
immune to noisy transmission lines.
The input thresholds are 0.8V minimum and
2.4V maximum, again well within the ±3V RS-
232 requirements. The receiver inputs are also
protected against voltages up to ±30V. Should
aninputbeleftunconnected,a5kpull-down
resistor to ground will commit the output of the
receiver to a high state.
In actual system applications, it is quite pos-
sible for signals to be applied to the receiver
inputs before power is applied to the receiver
circuitry. This occurs, for example, when a
PC user attempts to print, only to realize
the printer wasn’t turned on. In this case an
RS-232 signal from the PC will appear on the re-
ceiver input at the printer. When the printer power
is turned on, the receiver will operate normally.
All series devices are fully protected.
charge Pump
The charge pump is a patented design and
uses a unique approach compared to older less
efficientdesigns.Thechargepumprequires4
external capacitors and uses a four phase volt-
age shifting technique. The internal power sup-
ply consists of a regulated dual charge pump
that provides output voltages of +/-5.5V. This
is important to maintain compliant RS-232 lev-
els regardless of power supply fluctuations.
The charge pump operates in a discontinuous
mode using an internal oscillator. If the voltages
are less than a magnitude of 5.5V, the charge
pump is enabled. If the output voltage exceed
a magnitude of 5.5V then the charge pump is
disabled. The internal oscillator controls the four
phases of the voltage shifting. A description of
each phase follows:
DeScRiPtion
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相关代理商/技术参数 |
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| SP238AET-L/TR | 功能描述:RS-232接口集成电路 5V 4-DRVR/4-RCVR RS-232 -40-85C RoHS:否 制造商:Exar 数据速率:52 Mbps 工作电源电压:5 V 电源电流:300 mA 工作温度范围:- 40 C to + 85 C 安装风格:SMD/SMT 封装 / 箱体:LQFP-100 封装: |
| SP2394 | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Thermoelectric Cooler |
| SP2394-01AB | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Thermoelectric Cooler |
| SP2394-02AB | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Thermoelectric Cooler |
| SP2394-03AB | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Thermoelectric Cooler |
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