SP3490EN-L/TR View Datasheet(PDF) - Exar Corporation

Part Name

Description

Manufacturer

SP3490EN-L/TR

+3.3V low power full duplex RS-485 transceivers with 10Mbps data rate

Exar Corporation 

SP3490 / SP3491

Description

The SP3490 and SP3491 are two members in the family

of 3.3V low power full-duplex transceivers that meet the

electrical specifications of the RS-485 and RS-422 serial

protocols. These devices are pin-to-pin compatible with the

MaxLinear SP490 and SP491 devices as well as popular

industry standards. The SP3490 and SP3491 feature

MaxLinear’s BiCMOS process allowing low power operation

without sacrificing performance.

The RS-485 standard is ideal for multi-drop applications and

for long-distance interfaces. RS-485 allows up to 32 drivers

and 32 receivers to be connected to a data bus, making

it an ideal choice for multi-drop applications. Since the

cabling can be as long as 4,000 feet, RS-485 transceivers

are equipped with a wide (-7V to 12V) common mode range

to accommodate ground potential differences. Because

RS-485 is a differential interface, data is virtually immune to

noise in the transmission line.

Receivers

The receivers of the SP3490 and SP3491 have differential

inputs with an input sensitivity of ±200mV. Input impedance

of the receivers is typically 15kΩ (12kΩ minimum). A wide

common mode range of -7V to 12V allows for large ground

potential differences between systems. The receivers for

both the SP3490 and SP3491 are equipped with a fail-

safe feature that guarantees the receiver output will be in a

HIGH state when the input is left unconnected.

The receiver of the SP3491 has a enable control line which

is active LOW. A logic LOW on REB (pin 3) of the SP3491

will enable the differential receiver. A logic HIGH on REB

(pin 3) of the SP3491 will tri-state the receiver.

Drivers

The drivers for both the SP3490 and SP3491 have

differential outputs. The typical voltage output swing with

no load will be 0 volts to Vcc. With worst case loading of

54Ω across the differential outputs, the drivers can maintain

greater than 1.5V voltage levels.

The driver of the SP3491 has a driver enable control line

which is active HIGH. A logic HIGH on DE (pin 4) of the

SP3491 will enable the differential driver outputs. A logic

LOW on the DE (pin 4) will tri-state the driver outputs. The

SP3490 does not have a driver enable.

REV 1.0.3

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