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UM3243

Low Supply Current, 3V to 5.5V, 250kbps, 3-Driver/5-Receiver,

Enhanced ESD Protection Smart RS-232 Transceivers

UM3243EEAS/UM3243EEUS/UM3243EESS/UM3243EEQA

General Description

The UM3243 series are 3-driver/5-receiver 3V-5.5V powered RS-232 transceivers featuring Auto

Power-Off and low supply current, when no valid RS-232 level signal is sensed on any receiver inputs,

the charge pump circuit and drivers will be powered off. Disconnection of the RS-232 cable or

poweroff of the transmitters of the attaching peripherals will lead to Power-Off mode. When a valid

level is applied to any RS-232 receiver inputs, the chip will turn on again. The Auto Power-Off mode

helps to save power without changing the existing system.

The UM3243 transceivers have a regulated discontinuous mode dual charge pump power supply and

low-dropout transmitters, which combine to deliver true RS-232 performance from a single +3V to

+5.5V supply. Data rate of 250kbps is guaranteed.

The UM3243 needs only four 0.1μF capacitors in 3.3V operation, and can operate from input voltages

ranging from +2.7V to +5.5V. They are ideal for 3.3V-only systems, mixed 3.3V and 5.0V systems,

or 5.0V-only systems that require true RS-232 performance or EIA/TIA-562 levels of ±3.7V with

supply voltages as low as 2.7V.

The UM3243 includes one complementary always-active receiver. This receiver can monitor an

external device (such as a modem) in Power-Off. The UM3243 also includes an always-active

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output which indicates valid RS-232 signal levels on any receiver inputs. It is usually used

in UART wakeup. The UM3243 also features enhanced ESD protection with ±15kV for human body

mode and ±8kV for IEC61000-4-2 contact discharge mode.

Applications



Industrial Controllers and Instruments



Notebooks, Palmtop PCs and Laptops



Networking Routers and Switches



Peripherals



Printers, PDAs and POS

Features



Meets True EIA/TIA-232-F Standards from a +3.0V to +5.5V Power Supply



Meets EIA/TIA-562 Levels of ±3.7V with Supply Voltages as Low as 2.7V



Auto Power-Off Feature to Disable Driver Outputs when No Valid RS-232 Signal is Sensed



250kbps Minimum Transmission Rate



0.1μA (Typ) Low Power-Off Current



Accepts 5V Logic Input with 3.3V Supply



Enhanced ESD Specifications for RS-232 Pins:

±15kV Human Body Mode

±8kV IEC61000-4-2 Contact Discharge Mode



Available in SSOP28, TSSOP28, SOP28 and QFN32 Packages