MAX3222CUP+T中文资料(7)

Transceivers Using Four 0.1µF External Capacitors

3.0V to 5.5V, Low-Power, up to 1Mbps, True RS-232_______________Detailed Description

The MAX3222/MAX3237/MAX3241’s output stage isDual Charge-Pump Voltage Converter

turned off (high impedance) when the device is in shut-The MAX3222/MAX3232/MAX3237/MAX3241’s internaldown mode. When the power is off, the MAX3222/power supply consists of a regulated dual charge pumpMAX3232/MAX3237/MAX3241 permit the outputs to bethat provides output voltages of +5.5V (doubling chargedriven up to ±12V.

pump) and -5.5V (inverting charge pump), regardless ofThe transmitter inputs do not have pullup resistors.the input voltage (VCC) over the 3.0V to 5.5V range. TheConnect unused inputs to GND or VCC.

charge pumps operate in a discontinuous mode; if theoutput voltages are less than 5.5V, the charge pumpsMAX3237 MegaBaud Operation

are enabled, and if the output voltages exceed 5.5V, theIn normal operating mode (MBAUD = GND), thecharge pumps are disabled. Each charge pumpMAX3237 transmitters guarantee a 250kbps data raterequires a flying capacitor (C1, C2) and a reservoirwith worst-case loads of 3k in parallel with 1000pF.capacitor (C3, C4) to generate the V+ and V- supplies.

This provides compatibility with PC-to-PC communica-tion software, such as Laplink.

RS-232 Transmitters

For higher speed serial communications, the MAX3237The transmitters are inverting level translators that con-features MegaBaud operation. In MegaBaud operatingvert CMOS-logic levels to 5.0V EIA/TIA-232 levels.

mode (MBAUD = VCC), the MAX3237 transmitters guar-The MAX3222/MAX3232/MAX3241 transmitters guaran-antee a 1Mbps data rate with worst-case loads of 3k intee a 120kbps data rate with worst-case loads of 3k inparallel with 250pF for 3.0V < VCC < 4.5V. For 5V ±10%parallel with 1000pF, providing compatibility with PC-to-operation, the MAX3237 transmitters guarantee a 1MbpsPC communication software (such as LapLink ).data rate into worst-case loads of 3k in parallel withTypically, these three devices can operate at data rates1000pF.

of 235kbps. Transmitters can be paralleled to drive multi-ple receivers or mice.

LapLink is a trademark of Traveling Software, Inc.

Figure 1. Slew-Rate Test Circuits

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MAX3222/MAX3232/MAX3237/MAX3241

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