ST491ABN ,LOW POWER HIGH SPEED RS-485/RS422 TRANSCEIVERAPPLICATIONS■ -7 TO 12 COMMON MODE INPUT VOLTAGERANGE■ 70mV TYPICAL INPUT HYSTERESIS■ DESIGNED FOR ..
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ST491ABN
LOW POWER HIGH SPEED RS-485/RS422 TRANSCEIVER
1/11November 2002 LOW SUPPLY CURRENT: 5mA MAX DESIGNED FOR RS485 INTERFACE
APPLICATIONS -7 TO12 COMMON MODE INPUT VOLTAGE
RANGE 70mV TYPICAL INPUT HYSTERESIS DESIGNED FOR 25Mbps OPERATION OPERATE FROM SINGLE5 SUPPLY ±4kV ESD PROTECTION CURRENT LIMITING AND THERMAL
SHUTDOWN FOR DRIVER OVERLOAD
PROTECTION
DESCRIPTIONThe ST491Aisa low power transceiver for
RS-485 and RS-422 communications. The device
contains one driver and one receiverin full duplex
configuration. The ST491A draws 5mA (typ.)of
supply current when unloaded and operates from single 5V supply.
Driver is short-circuit current limited and is
protected against excessive power dissipationby
thermal shutdown circuitry that place the driver
outputs intoa high-impedance state. The receiver
input hasa fail-safe feature that guaranteesa
logic high outputif both inputs are open circuit.
ORDERING CODES
ST491ALOW POWER HIGH SPEED RS-485/RS-422 TRANSCEIVER
PRELIMINARY DATA
ST491A2/11
PIN CONFIGURATION
PIN DESCRIPTION
TRUTH TABLE (DRIVER) Don’t Care; Z=High Impedance
TRUTH TABLE (RECEIVER) Irrelevant;X= Don’t Care; Z=High Impedance
ST491A3/11
ABSOLUTE MAXIMUM RATINGSAbsoluteMaximum Ratingsare those values beyond which damagetothe device may occur. Functional operation under these conditionis
not implied.
ELECTRICAL CHARACTERISTICSVCC =4.5V to5.5V,TA= -40to 85°C, unless otherwise specified. Typicalvalues are referredtoTA =25°C)
TRANSMITTER ELECTRICAL CHARACTERISTICSCC= 4.5Vto 5.5V,TA= -40 to85°C, unless otherwise specified. Typical values are referredtoTa= 25°C)
ST491A4/11
RECEIVER ELECTRICAL CHARACTERISTICSVCC= 4.5Vto 5.5V,TA= -40 to85°C, unless otherwise specified. Typical values are referredtoTa= 25°C)
DRIVER SWITCHING CHARACTERISTICSVCC =4.5Vto 5.5V, TA= -40to 85°C, unless otherwise specified. Typical values are referredtoTa =25°C)
RECEIVER SWITCHING CHARACTERISTICSCC =4.5V to5.5V,TA= -40to 85°C, unless otherwise specified.Typical values are referredtoTa= 25°C)
ST491A5/11
TEST CIRCUITS AND TYPICAL CHARACTERISTICS
Figure1: Driver DC Test Load
Figure2: Receiver Timing Test Load
Figure3: Driver/Receiver Timing Test Circuit
ST491A6/11
Figure4: Driver Timing Test Load
Figure5: Driver Propagation Delay
