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SP310ECT-L/TR 参数 Datasheet PDF下载

SP310ECT-L/TR图片预览
型号: SP310ECT-L/TR
PDF下载: 下载PDF文件 查看货源
内容描述: 高性能RS - 232线路驱动器/接收器 [High Performance RS-232 Line Drivers/Receivers]
分类和应用: 线路驱动器或接收器驱动程序和接口接口集成电路光电二极管
文件页数/大小: 17 页 / 1059 K
品牌: EXAR [ EXAR CORPORATION ]
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DESCRꢁPTꢁꢀꢂ  
Receivers  
DETAꢁLED DESCRꢁPTꢁꢀꢂ  
The receivers convert EIA/TIA-232 signal lev-  
els to inverted TTL or CMOS logic output lev-  
els. Since the input is usually from a transmis-  
sion line, where long cable length 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 2.8V maximum, again  
well within the +/-3V RS-232 requirements.  
Should an input be left unconnected, an internal  
5kohm pull-down resistor to ground will commit  
the output of the receiver to a HIGH state.  
The SP202E, SP232E, SP233E, SP3ꢀ0E and  
SP3ꢀ2A devices are a family of line driver and  
receiver pairs that meet the EIA/TIA-232 and  
V.28 serial communication protocols. The ESD  
tolerance has been improved on these devices  
to over +/-ꢀ5kV for Human Body Model. These  
devices are pin-to-pin compatible with Exar's  
232A, 233A, 3ꢀ0A and 3ꢀ2A as well as popular  
industry standards. This family of parts offer a  
ꢀ20kbps data rate, ꢀ0V/μs slew rate and an on-  
board charge pump that operates from a single  
5V supply using 0.ꢀμF ceramic capacitors.  
The SP202E, 232E, 233E, 3ꢀ0E and 3ꢀ2E de-  
vices have internal charge pump voltage con-  
verters which allow them to operate from a sin-  
gle +5V supply. The charge pumps will operate  
with polarized or non-polarized capacitors rang-  
ing from 0.ꢀ to ꢀ0µF and will generate the +/-6V  
needed to generate the RS-232 output levels.  
In actual system applications, it is quite pos-  
sible for signals to be applied to receiver inputs  
before power is applied to the receiver circuitry.  
This occurs, for example, when a PC user at-  
tempts to print, only to realize that the printer  
wasn't turned on. In this case an RS-232 signal  
from the PC will appear on the receiver input  
at the printer. When the printer power is turned  
on, the receiver will operate normally. All of  
these devices are fully protected.  
The SP233E design offers internal charge pump  
capacitors. The SP3ꢀ0E provides an ON/OFF  
input that simultaneously disables the internal  
charge pump circuit and puts all transmitter and  
receiver outputs into a high impedance state.  
The SP3ꢀ2E is identical to the SP3ꢀ0E but with  
seperate tri-state and shutdown inputs  
Charge pump  
The charge pump is an Exar patented design  
and uses a unique approach compared to  
older less efficiant designs. The charge pump  
requires 4 external capacitors and uses a four  
phase voltage shifting technique. The internal  
power supply consists of a dual charge pump  
that provides a driver output voltage swing of  
+/-6V. The internal oscillator controls the four  
phases of the voltage shifting. A description of  
each phase follows:  
Theory ꢀf ꢀperation  
The SP202E, SP232E, SP233E, SP3ꢀ0E and  
SP3ꢀ2E devices are made up of three basic  
circuit blocks: 1. Drivers, 2. Receivers, and 3.  
charge pump. Each block is described below.  
Drivers  
The drivers are inverting level transmitters that  
convert TTL or CMOS logic levels to EIA/TIA-  
232 levels with an inverted sense relative to  
the input logic levels. The typical driver output  
voltage swing is +/-6V. Even under worst case  
loading conditions of 3k ohms and 2500pF, the  
driver output is guaranteed to be +/-5.0V mini-  
mum, thus satisfying the RS-232 specification.  
The driver outputs are protected against infinite  
short-circuits to ground without degradation in  
reliability.  
Phase 1  
Vss charge store and double: The positive ter-  
minals of capacitors Cꢀ and C2 are charged  
from Vcc with their negative terminals initially  
connected to ground. Cꢀ+ is then connected  
to ground and the stored charge from Cꢀ- is  
superimposed onto C2-. Since C2+ is still con-  
nected to Vcc the voltage potential across C2  
is now 2 x Vcc.  
Phase 2  
Vss transfer and invert: Phase two connects  
the negative terminal of C2 to the Vss storage  
capacitor and the positive terminal of C2 to  
ground. This transfers the doubled and invert-  
ed (V-) voltage onto C4. Meanwhile, capacitor  
The slew rate of the driver output is internally  
limited to 30V/μs in order to meet the EIA stan-  
dards (EIA-232F). Additionally, the driver out-  
puts LOW to HIGH transition meets the mon-  
tonic output requirements of the standard.  
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • (5ꢀ0)668-7000 • www.exar.com SP202E,232E,233E, 3ꢀ0E, 3ꢀ2E_ꢀ00_ꢀꢀ0608  
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