外文翻譯--- max232-5v的供電，多通道rs-232接口驅(qū)動器接收器

1、<p><b>　　附錄A</b></p><p>　　MAX232-5V-Powered,Multichannel RS-232 Drivers/Receivers </p><p>　　The MAX232 is a dual driver/receiver that includes a capacitive voltage generator to

2、supply TIA/EIA-232-F voltage levels from a single 5-V supply. Each receiver converts TIA/EIA-232-F inputs to 5-V TTL/CMOS levels. These receivers have a typical threshold of 1.3 V, a typical hysteresis of 0.5 V, and can

3、accept ±30-V inputs. Each driver converts TTL/CMOS input levels into TIA/EIA-232-F levels. The driver, receiver, and voltage-generator functions are available as cells in the Texas Instruments Li</p><p>

4、;　　Dual Charge-Pump Voltage Converter</p><p>　　The MAX220–MAX249 have two internal charge-pumps that convert +5V to ±10V (unloaded) for RS-232 driver operation. The first converter uses capacitor C1 to

5、double the +5V input to +10V on C3 at the V+ output. The second converter uses capacitor C2 to invert +10V to -10V on C4 at the V- output.</p><p>　　A small amount of power may be drawn from the +10V (V+) and

6、 -10V (V-) outputs to power external circuitry (see the Typical Operating Characteristics section), except on the MAX225 and MAX245–MAX247, where these pins are not available. V+ and V- are not regulated, so the output v

7、oltage drops with increasing load current. Do not load V+ and V- to a point that violates the minimum ±5V EIA/TIA-232E driver output voltage when sourcing current from V+ and V- to external circuitry.</p><

8、;p>　　When using the shutdown feature in the MAX222,MAX225, MAX230, MAX235, MAX236, MAX240,MAX241, and MAX245–MAX249, avoid using V+ and V- to power external circuitry. When these parts are shut down, V- falls to 0V, a

9、nd V+ falls to +5V. For applications where a +10V external supply is applied to the V+ pin (instead of using the internal charge pump to generate +10V), the C1 capacitor must not be installed and the SHDN pin must be tie

10、d to VCC. This is because V+ is internally connected to VCC in shutd</p><p>　　RS-232 Drivers</p><p>　　The typical driver output voltage swing is ±8V when loaded with a nominal 5kΩ RS-232 re

11、ceiver and VCC =+5V. Output swing is guaranteed to meet the EIA/TIA-232E and V.28 specification, which calls for ±5V minimum driver output levels under worst-case conditions. These include a minimum 3kΩ load, VCC =

12、+4.5V, and maximum operating temperature. Unloaded driver output voltage ranges from (V+ -1.3V) to (V- +0.5V).</p><p>　　Input thresholds are both TTL and CMOS compatible.The inputs of unused drivers can be l

13、eft unconnected since 400kΩ input pull-up resistors to VCC are built in (except for the MAX220). The pull-up resistors force theoutputs of unused drivers low because all drivers invert.The internal input pull-up resistor

14、s typically source 12μA, except in shutdown mode where the pull-ups are disabled.Driver outputs turn off and enter a high-impedance state—where leakage current is typically microamperes (maximu</p><p>　　The

15、MAX239 has a receiver three-state control line, and the MAX223, MAX225, MAX235, MAX236, MAX240, and MAX241 have both a receiver three-state control</p><p>　　line and a low-power shutdown control. Table 2 sho

16、ws the effects of the shutdown control and receiver three state control on the receiver outputs. The receiver TTL/CMOS outputs are in a high-impedance, three-state mode whenever the three-state enable line is high (for t

17、he MAX225/MAX235/MAX236/MAX239–MAX241), and are also high-impedance whenever the shutdown control line is high.</p><p>　　When in low-power shutdown mode, the driver outputs are turned off and their leakage c

18、urrent is less than 1μA with the driver output pulled to ground. The driver output leakage remains less than 1μA, even if the transmitter output is backdriven between 0V and (VCC + 6V). Below -0.5V, the transmitter is di

19、ode clamped to ground with 1kΩ series impedance. The transmitter is also zener clamped to approximately VCC + 6V, with a series impedance of 1kΩ. The driver output slew rate is limited to less t</p><p>　　RS-

20、232 Receivers</p><p>　　EIA/TIA-232E and V.28 specifications define a voltage level greater than 3V as a logic 0, so all receivers invert. Input thresholds are set at 0.8V and 2.4V, so receivers</p>&l

21、t;p>　　respond to TTL level inputs as well as EIA/TIA-232E and V.28 levels. The receiver inputs withstand an input overvoltage up to ±25V and provide input terminating resistors with nominal 5kΩ values. The receiv

22、ers implement Type 1 interpretation of the fault conditions of V.28 and EIA/TIA-232E. The receiver input hysteresis is typically 0.5V with a guaranteed minimum of 0.2V. This produces clear output transitions with slow-mo

23、ving input signals, even with moderate amounts of noise and ringing. The r</p><p>　　Low-Power Receive Mode</p><p>　　The low-power receive-mode feature of the MAX223, MAX242, and MAX245–MAX249 pu

24、ts the IC into shutdown mode but still allows it to receive information. This is important for applications where systems are periodically awakened to look for activity. Using low-power receive mode, the system can still

25、 receive a signal that will activate it on command and prepare it for communication at faster data rates. This operation conserves system power.</p><p>　　Receiver and Transmitter Enable</p><p>　

26、　The MAX225 and MAX245–MAX249 feature transmitter and receiver enable controls.</p><p>　　The receivers have three modes of operation: full-speed receive (normal active)? three-state (disabled)? and low power

27、 receive (enabled receivers continue to function</p><p>　　at lower data rates). The receiver enable inputs control the full-speed receive and three-state modes. The transmitters have two modes of operation:

28、full-speed transmit (normal active) and three-state (disabled). The transmitter enable inputs also control the shutdown mode. The device enters shutdown mode when all transmitters are disabled. Enabled receivers function

29、 in the low-power receive mode when in shutdown.</p><p>　　Shutdown—MAX222–MAX242</p><p>　　On the MAX222? MAX235? MAX236? MAX240? and MAX241? all receivers are disabled during shutdown. On the MA

30、X223 and MAX242? two receivers continue to operate in a reduced power mode when the chip is in shutdown. Under these conditions? the propagation delay increases to about 2.5μs for a high-to-low input transition. When in

31、shutdown, the receiver acts as a CMOS inverter with no hysteresis. The MAX223 and MAX242 also have a receiver output enable input (EN for the MAX242 and EN for the MAX223) that</p><p>　　The MAX225 provides f

32、ive transmitters and five receivers? while the MAX245 provides ten receivers and eight transmitters. Both devices have separate receiver and transmitter-enable controls. The charge pumps turn off and the devices shut dow

33、n when a logic high is applied to the ENT input. In this state, the supply current drops to less than 25μA and the receivers continue to operate in a low-power receive mode. Driver outputs enter a high-impedance state (t

34、hree-state mode). On the MAX225?all fiv</p><p>　　The MAX247 provides nine receivers and eight drivers with four control pins. The ENRA and ENRB receiver enable inputs each control four receiver outputs. The

35、ENTA and ENTB transmitter enable inputs each control four drivers. The ninth receiver (RB5) is always active. The device enters shutdown mode with a logic high on both ENTA and ENTB.</p><p>　　The MAX248 prov

36、ides eight receivers and eight drivers with four control pins. The ENRA and ENRB receiver enable inputs each control four receiver outputs. The ENTA and ENTB transmitter enable inputs control four drivers each. This part

37、 does not have an always-active receiver. The device enters shutdown mode and transmitters go into a three-state mode with a logic high on both ENTA and ENTB.</p><p><b>　　附錄B</b></p><p

38、>　　MAX232-5V的供電，多通道RS-232接口</p><p><b>　　驅(qū)動器/接收器</b></p><p>　　該MAX232是一種雙驅(qū)動器/接收器，其中包括一個電容式電壓發(fā)電機，供應TIA/EIA-232-F一個單一的5 V電源。每個接收器轉(zhuǎn)換TIA/EIA-232-F需要工作電壓5V的TTL/CMOS。這些接收器有一個典型的閾值為1.3伏，一

39、個典型的滯后為0.5伏，并且可以接受±30電壓。每個TTL/CMOS驅(qū)動轉(zhuǎn)換的輸入和TIA/EIA-232-F同一水平。在德州儀器LinASIC庫該驅(qū)動器，接收器和電壓發(fā)生器起到了主要作用。</p><p>　　該MAX220-MAX249包含四個部分：雙電荷泵型DC-DC電壓轉(zhuǎn)換器，RS-232接口的驅(qū)動程序，RS-232接口接收器和能控制輸入的發(fā)射器。</p><p><

40、;b>　　雙電荷泵電壓轉(zhuǎn)換器</b></p><p>　　該MAX220-MAX249有兩個內(nèi)部電荷泵能將RS-232驅(qū)動從+5V轉(zhuǎn)換為±10V。第一個轉(zhuǎn)換器使用電容器C1將+5V變?yōu)?10V在C3上的V+上輸出，而第二個轉(zhuǎn)換器使用電容C2將+10V轉(zhuǎn)變?yōu)?10V在C4在V-輸出。</p><p>　　少量的功率可能來自電源外部電路10V(V+）和-10V（V-

41、）的輸出（見典型工作特性部分），除非MAX225和MAX245-MAX247，這些引腳不可用。V+和V-不固定，因此，輸出電壓下降而負載電流就相應的增加。當在外部電路時電源從V+到V-時不要將V+和V-接到一點，違反了EIA/TIA-232E接口的最小輸出電壓±5V。</p><p>　　當在MAX222，MAX225，MAX230，MAX235，MAX236，MAX240，MAX241和MAX245，

42、MAX249中使用停機功能，應避免在電源外部電路使用V+和V-。當這部分被關閉時，V-下降到0V，V+下降到+5V，10V的外部電源應接到V+引腳上（而不是使用內(nèi)部電荷泵產(chǎn)生的10V），C1電容不需要接并且SHDN引腳必須接到VCC上。這是因為V+接到VCC是在關斷模式狀態(tài)下。</p><p><b>　　RS-232接口卡</b></p><p>　　當一個5kΩR

43、S-232接收器接電源5V時，典型的驅(qū)動器輸出電壓幅值變化為±8V。輸出幅值保證滿足EIA/TIA-232E的要求，在最壞的情況下它要求驅(qū)動器輸出的電壓為±5V。這些條件有阻值最小為3kΩ負載，外接電源4.5伏，最高工作溫度。卸載驅(qū)動器的輸出電壓范圍為1.3V至-0.5V。</p><p>　　TTL和CMOS的輸入閥值是相互兼容的。未被使用的驅(qū)動器不工作這是因為400kΩ輸入上拉電阻接到VC

44、C（除MAX220）。上拉電阻使得未使用的驅(qū)動器輸出電壓變低，因為所有的驅(qū)動器倒置了。內(nèi)部輸入上拉電阻電流通常12μ，除了在關斷模式下都不能被使用。驅(qū)動器輸出端關閉了并且進入了高阻抗狀態(tài)下—泄漏電流通常是微安（最大25μA），在停機模式，三態(tài)模式，或者設備電源被移除時。驅(qū)動電壓輸出可達到±15V。在關斷模式電源電流通常降至8μA。該MAX220沒有上拉電阻使未使用的驅(qū)動器輸出電壓降低。將未使用的輸入端連接到GND或Vcc上。&

45、lt;/p><p>　　該MAX239接收器有三態(tài)控制線，并且MAX223，MAX225，MAX235，MAX236，MAX240，和MAX241都同時擁有三態(tài)控制線和一個低功耗的關斷控制器。表2說明了關斷控制和三態(tài)門控制接收器輸出的影響。無論三態(tài)門使能端是不是接高電平，TTL/CMOS接收器輸出端都處于高阻抗，三態(tài)模式（為MAX225/MAX235/MAX236/MAX239-MAX241），并且關斷控制端是否高電

46、平也同樣處于高阻抗模式。</p><p>　　當在低功耗關斷模式下，驅(qū)動器輸出端將被關閉并且漏電流低于1uA，同時驅(qū)動器輸出端接地。該驅(qū)動器輸出漏極電流仍然低于1uA，即使發(fā)射極輸出電壓在0V和6V之間（電源電壓為+6V）。當?shù)陀?0.5V，發(fā)射極端的二極管和1kΩ的電阻串聯(lián)之后接地。發(fā)射極與1kΩ的電阻串聯(lián)之后接到6V的外部電壓上。該驅(qū)動器輸出轉(zhuǎn)換速率是有限的，按EIA/TIA-232E和V.28的規(guī)格以低于3

47、0V/μs的速率轉(zhuǎn)換。通常卸載的轉(zhuǎn)換速率是24V/μs，當滿載3Ω和2500pF為10V/μs。</p><p>　　RS-232接口接收器</p><p>　　EIA/TIA-232E和V.28的規(guī)格為將電壓大于3V作為邏輯0，因此，所有接收顛倒。輸入閾值定為0.8V和2.4V，所以TTL接收器和EIA/TIA-232E和V.28是相同的。接收器輸入端的輸入電壓高達± 25V的

48、輸入，并供應5kΩ電阻。接收器解釋V.28和EIA/TIA-232E故障的原因 ，該接收器遲滯輸入電壓通常是0.5V，其中0.2V是最低電壓。這明顯的表明了轉(zhuǎn)換輸出帶有緩慢移動的輸入信號，即使有適量的噪聲和振鈴。接收器傳輸延遲通常是600ns和具有獨立的輸入擺動方向。</p><p><b>　　低功耗接收模式</b></p><p>　　MAX223，MAX242和

49、MAX245，MAX249低功耗接收模式的特點：當電路處于關斷模式時，仍然允許它接收信息。這個對定期喚醒系統(tǒng)去工作是很重要的。使用低功耗接收模式下，系統(tǒng)仍然可以接收的信號，這些信號以命令的方式啟動并且以更快的數(shù)據(jù)傳輸速率來進行通信。此作業(yè)可節(jié)省系統(tǒng)功耗。</p><p><b>　　接收機和發(fā)射機啟用</b></p><p>　　MAX225和MAX245-MAX24

50、9都具有發(fā)射與接收控制的功能。接收器有三個操作模式：全速接收（正常激活），三態(tài)門（使能端），低功耗接收端（接收器繼續(xù)以較低的數(shù)據(jù)傳輸速率繼續(xù)發(fā)揮作用）。該接收器能夠在全速接收和三態(tài)模式下進行輸入控制。發(fā)射器有兩種操作模式：全速傳輸（正常激活）和三態(tài)門（禁用端）。發(fā)射器能夠在關斷模式下進行輸入控制。當所有發(fā)射器都被禁用時，該設備進入關斷模式。當關斷時，在低功耗接收模式下啟動接收功能。</p><p>　　關斷-MA

51、X222-MAX242</p><p>　　關于MAX222，MAX235，MAX236，MAX240和MAX241，在關斷過程中，所有的接收器都被禁用。關于MAX223和MAX242，當芯片關斷時，兩個接收器繼續(xù)處在降低功耗模式。在這種情況下，在高低轉(zhuǎn)換期間傳輸延遲增加約2.5μs。當關斷時，接收器作為沒有滯后的CMOS逆變器。在MAX223和MAX242也有接收器輸出使能輸入（MAX242和MAX223的使能

52、端），使接收器輸出控制端具有獨立的SHDN（MAX241為關斷）。與所有其他設備一樣，SHDN（MAX241的SHDN）也禁用接收器輸出端。</p><p>　　MAX225提供5個發(fā)射器和5個接收器，而MAX245提供10接收器和8發(fā)射器。這兩款器件有不同的接收器與發(fā)射器控制器。當輸入端ENT為邏輯高電平時，該電荷泵和設備關閉。在這種狀態(tài)下，電源電流降到低于25μA和接收器繼續(xù)運行在低功耗接收模式。驅(qū)動器輸出端

53、進入高阻抗狀態(tài)（三態(tài)模式）。對于MAX225，所有的5個接收器都是有ENR輸入控制的，對于MAX245，其中的八個輸出端接收器是由ENR輸出端控制的，剩余的兩個（RA5和RB5）仍然是活動的。當ENR處于邏輯高電平時，RA1-RA4和RB1-RB4處于三態(tài)模式狀態(tài)下。</p><p>　　MAX247提供了9個接收器和帶有四個控制引腳的8個驅(qū)動器。該ENRA和ENRB接收器輸入端每個都能控制4個接收器輸出端。EN

54、TA和ENTB發(fā)射器輸入端每個都能控制四個驅(qū)動器。第九個接收器（RB5）始終都是活動的。當ENTA和ENTB都是邏輯高電平時該設備進入關斷模式。</p><p>　　MAX248提供了8個接收器和帶有四個控制引腳的8個驅(qū)動器。該ENRA和ENRB接收器每個輸入端都能控制4個接收器輸出端。ENTA和ENTB發(fā)射器每個輸入端都能控制四個驅(qū)動器。這部分沒有始終激活的接收器。ENTA，ENTB都處于邏輯高電平時該設備進入