SP3485 데이터 시트보기 (PDF) - Exar Corporation

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SP3485

+3.3V Low Power Half-Duplex RS-485 Transceiver with 10Mbps Data Rate

Exar Corporation 

The SP3485 is a member in the family of

+3.3V low power half-duplex transceivers

that meet the electrical specifications of the

RS-485 and RS-422 serial protocols. This

device is pin-to-pin compatible with the Exar

SP481, SP483 and SP485 devices as well

as popular industry standards. The SP3485

feature Exar's BiCMOS process allowing

low power operation without sacrificing

performance.

Driver

The driver outputs of the SP3485 are dif-

ferential outputs meeting the RS-485 and

RS-422 standards. The typical voltage

output swing with no load will be 0 volts to

+3.3 Volts. With a load of 54Ω across the

differential outputs, the drivers can maintain

greater than 1.5V voltage levels.

The driver of the SP3485 has a driver enable

control line which is active HIGH. A logic

HIGH on DE (pin 3) will enable the differential

driver outputs. A logic LOW on the DE (pin

3) will tri-state the driver outputs.

The driver of the SP3485 operates up to

10Mbps. The 250mA ISC maximum limit

on the driver output allows the SP3485 to

withstand an infinite short circuit over the

-7.0V to +12V common mode range without

catastrophic damage to the IC.

Receiver

DESCRIPTION

The SP3485 receiver has differential inputs

with an input sensitivity of ±200mV. Input

impedance of the receiver is typically 15kΩ

(12kΩ minimum). A wide common mode

range of -7V to +12V allows for large ground

potential differences between systems. The

receiver is equipped with a fail-safe feature

that guarantees the receiver output will be

in a HIGH state when the input is left uncon-

nected. The receiver of the SP3485 operates

up to 10Mbps.

The receiver of the SP3485 has an enable

control line which is active LOW. A logic

LOW on RE (pin 2) will enable the differential

receiver. A logic HIGH on RE (pin 2) of the

SP3485 will disable the receiver.

INPUTS

RE DE

Line

DI Condition

X

1

1

No Fault

X

1

0

No Fault

X

0

X

X

Table 1. Transmit Function Truth Table

OUTPUTS

BA

01

10

ZZ

INPUTS

RE

DE

A-B

0

0

+0.2V

0

0

-0.2V

0

0

Inputs Open

1

0

X

Table 2. Receive Function Truth Table

OUTPUTS

R

1

0

1

Z

Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com



SP3485_100_061912

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