外文翻譯--- max232-5v的供電多通道rs-232接口驅(qū)動器接收器-全文預(yù)覽
【正文】 IA232E的要求，在最壞的情況下它要求驅(qū)動器輸出的電壓為177。當(dāng)這部分被關(guān)閉時，V下降到0V，V+下降到+5V，10V的外部電源應(yīng)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。V+和V不固定，因此，輸出電壓下降而負(fù)載電流就相應(yīng)的增加。雙電荷泵電壓轉(zhuǎn)換器該MAX220MAX249有兩個內(nèi)部電荷泵能將RS232驅(qū)動從+5V轉(zhuǎn)換為177。30電壓。15V. The power supply current typically drops to 8μA in shutdown mode. The MAX220 does not have pullup resistors to force the outputs of the unused drivers low. Connect unused inputs to GND or VCC.The MAX239 has a receiver threestate control line, and the MAX223, MAX225, MAX235, MAX236, MAX240, and MAX241 have both a receiver threestate controlline and a lowpower shutdown control. Table 2 shows the effects of the shutdown control and receiver three state control on the receiver outputs. The receiver TTL/CMOS outputs are in a highimpedance, threestate mode whenever the threestate enable line is high (for the MAX225/MAX235/MAX236/MAX239–MAX241), and are also highimpedance whenever the shutdown control line is high.When in lowpower shutdown mode, the driver outputs are turned off and their leakage current 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 , the transmitter is diode 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 than 30V/μs as required by the EIA/TIA232E and specifications. Typical slew rates are 24V/μs unloaded and 10V/μs loaded with 3Ω and 2500pF.RS232 ReceiversEIA/TIA232E and specifications define a voltage level greater than 3V as a logic 0, so all receivers invert. Input thresholds are set at and , so receiversrespond to TTL level inputs as well as EIA/TIA232E and levels. The receiver inputs withstand an input overvoltage up to 177。10V (unloaded) for RS232 driver operation. The first converter uses capacitor C1 to 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.A small amount of power may be drawn from the +10V (V+) and 10V (V) outputs to power external circuitry (see the Typical Operating Characteristics section), except on the MAX225 and
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