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Key Specifications
Part Number Description Status Drivers Per Package Receivers Per Package Logic Voltage (Min)(V) ICC (Max)(mA) Shutdown Control Data Rate(kbps) Main Supply Voltage (Nom)(V) ESD HBM (kV) ESD Contact (kV) ESD Air (kV) Operating Temperature Range(℃) Pin/Package EV Kit Available?
UM3243EEAS Low Supply Current, 3V to 5.5V, 250kbps, 3-Driver/5-Receiver, Enhanced ESD Protection Smart RS-232 Transceivers Active 3 5 3 1 Yes 250 0 ±15 (for RS-232 Pins); ±2 (for Other Pins) ±8 -40 ~ +85 28/SSOP Y
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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 ±15kV 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:
  ±15kV 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  

 
                       SSOP28

Function Tables

                                                                                     Table 1. Each Transmitter (Note 1)
INPUTS
OUTPUT
TRANSMITTER STATUS
TIN
FORCEON
FORCEOFF(____________________)
VALID RIN
RS-232 LEVEL
TOUT
X
X
L
X
Z
Forced Power-Off
L
H
H
X
H
Normal Operation
with Forced Power-On
H
H
H
X
L
L
L
H
Yes
H
Normal Operation
with Auto Power-On
H
L
H
Yes
L
X
L
H
No
Z
Auto Power-Off
Note 1: H=high level, L=low level, X=irrelevant, Z=high impedance
 
                                                                                        Table 2. Each Receiver (Note 2)
INPUTS
OUTPUT
RECEIVER STATUS
RIN
FORCEON
FORCEOFF(_____________________)
ROUT
X
X
L
Z
Forced Power-Off
L
X
H
H
Normal Operation
H
X
H
L
Open
X
H
H

                                                                         Table 3. ROUT2B and Outputs
INVALID(________________) (Note 2)

INPUTS
OUTPUTS
OUTPUT STATUS
VALID RIN
RS-232 LEVEL
RIN2
FORCEON
FORCEOFF(____________________)
INVALID(_______________)
ROUT2B
Yes
L
X
X
H
L
Always Active
Yes
H
X
X
H
H
Yes
Open
X
X
H
L
No
Open
X
X
L
L
Note 2:
H=high level, L=low level, X=irrelevant, Z=high impedance (off), Open=input disconnected or connected driver off.
 
Ordering Information

Part Number
Temp. Range
Package Type
Shipping Qty
UM3243EEAS
-40°C to +85°C
SSOP28
48pcs/Tube
 
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