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Key Specifications
Product 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 INVALID 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 ±8kV for human body mode and ±8kV for IEC61000-4-2 contact discharge mode.
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
- Latch-Up Performance Exceeds 200mA
- Enhanced ESD Specifications for RS-232 Pins:
±8kV Human Body Mode
±8kV IEC61000-4-2 Contact Discharge Mode
- Available in SSOP28, TSSOP28, SOP28 and QFN32 Packages Typical Application Circuit
 Applications
- Industrial Controllers and Instruments
- Notebooks, Palmtop PCs and Laptops
- Networking Routers and Switches
- Peripherals
- Printers, PDAs and POS
Pin Configurations
 TSSOP28
Function Tables Table 1. Each Transmitter (Note 1)
Table 2. Each Receiver (Note 2)
Table 3. ROUT2B and Outputs INVALID (Note 2)
Ordering Information
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Application Notes
Product Selection Guide
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