SGS Thomson Microelectronics ST485ADR, ST485CN, ST485CDR, ST485CD, ST485BN Datasheet

1/12March 2002

■ LOW QUIESCENT CURRENT: 300µA

■ DESIGNED FOR RS-485 INTERFACE

APPLICATIONS

■ -7V TO 12V COMMON MODE INPUT

VOLTAGERANGE

■ DRIVER MAINTAINS HIGH IMPEDANCE IN

3-STATE OR WITH THE POWER OFF

■ 70mV TYPICAL INPUT HYSTERESIS

■ 30ns PROPAGATION DELAYS, 5ns SKEW

■ OPERATE FROM A SINGLE 5V SUPPLY

■ CURRENT LIMITING AND THERMAL

SHUTDOWN FOR DRIVER OVERLOAD
PROTECTION

■ ALLOWS UP TO 64 TRANSCEIVERS ON

THE BUS

DESCRIPTION

The ST485 is al low power transceiver for RS-485
and RS-422 communication. Each part contains
one driver and one receiver.
This transceiver draw 300µA (typ.) of supply
current when unloaded or fully loaded with
disabled drivers.

It operates from a single 5V supply.
Driver is short-circuit current limited and is
protected against excessive power dissipation by
thermal shutdown circuitry that placed the driver
outputs into a high-impedance state. .
The ST485 is designed for bi-directional data
communications on multipoint bus transmission
line (half-duplex applciations).

ORDERING CODES

Type

Temperature

Range

Package Comments

ST485CN 0 to 70 °C DIP-8 50parts per tube / 40tube per box
ST485BN -40 to 85 °C DIP-8 50parts per tube / 40tube per box
ST485AN -55 to 125 °C DIP-8 50parts per tube / 40tube per box
ST485CD 0 to 70 °C SO-8 (Tube) 100parts per tube / 20tube per box
ST485BN -40 to 85 °C DIP-8 50parts per tube / 40tube per box

ST485AD -55 to 125 °C SO-8 (Tube) 100parts per tube / 20tube per box
ST485CDR 0 to 70 °C SO-8 (Tape & Reel) 2500 parts per reel
ST485BDR -40 to 85 °C SO-8 (Tape & Reel) 2500 parts per reel
ST485ADR -55 to 125 °C SO-8 (Tape & Reel) 2500 parts per reel

ST485

LOW POWER

RS-485/RS-422 TRANSCEIVER

DIP SOP

ST485

2/12

PIN CONFIGURATION

PIN DESCRIPTION

TRUTH TABLE (DRIVER)

X= Don’t Care; Z=High Impedance

TRUTH TABLE (RECEIVER)

X= Don’t Care; Z=High Impedance

ABSOLUTE MAXIMUM RATINGS

Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional operation under these condition is
not implied.

PlN N° SYMBOL NAME AND FUNCTION

1 RO Receiver Output
2 RE Receiver Output Enable
3 DE Driver Output Enable
4 DI Driver Input
5 GND Ground
6 A Non-inverting Receiver Input and Non-inverting Driver Output
7 B Inverting Receiver Input and Inverting Driver Output
8

V

CC

Supply Voltage

INPUTS OUTPUTS

RE DE DI B A

XHHLH
XHLHL
XLXZZ

INPUTS OUTPUT

RE DE A-B RO

LL≥ +0.2V H
LL≤ -0.2V L
L L INPUTS OPEN H

HL X Z

Symbol Parameter Value Unit

V

CC

Supply Voltage

12 V

V

I

Control Input Voltage (RE, DE) -0.5 to (VCC+ 0.5)

V

V

DI

Driver Input Voltage (DI) -0.5 to (VCC+ 0.5)

V

V

DO

Driver Output Voltage (A, B)

± 14 V

V

RI

Receiver Input Voltage (A, B)

± 14 V

V

RO

Receiver Output Voltage (RO) -0.5 to (VCC+ 0.5)

V

ST485

3/12

DC ELECTRICAL CHARACTERISTICS

(VCC=5V± 5%, TA=T

MIN

toT

MAX

,unlessotherwise specified. Typicalvalues arereferredto TA=25°C)

(See Note 1)

Note 1: All currents into device pins are positive; all cuttents out of device pins are negative; all voltages are referenced to device ground
unless specified.

Note 2: Supply current specification is valid for loaded transmitters when V

DE

=0V

Note 3: Applies to peak current. See typical Operating Characteristics.

Symbol Parameter Test Conditions Min. Typ. Max. Unit

V

OD1

Differential Driver Output
(No Load)

5V

V

OD2

Differential Driver Output
(With Load)

RL=27Ω (RS-485) (See Fig. 1)
R

L

=50Ω (RS-422) (See Fig. 1)

1.4 5
5

V
V

∆V

OD

Change in Magnitude of
Driver Differential Output
Voltage for Complementary
Output States

RL=27Ω or 50Ω (See Fig. 1) 0.2 V

V

OC

Driver Common-Mode
Output Voltage

RL=27Ω or 50Ω (See Fig. 1) 3 V

∆V

OC

Change in Magnitude of
Driver Common-Mode
Output Voltage for
Complementary Output
States

RL=27Ω or 50Ω (See Fig. 1) 0.2 V

V

IH

Input High Voltage RE, DE, DI 2.0 V

V

IL

Input Low Voltage RE, DE, DI 0.8 V

I

IN1

Input Current RE, DE, DI ± 2 µA

I

IN2

Input Current (A, B) VCM= 0V or 5.25V VDE=0V

V

IN

= 12V

V

IN

= -7V

1

-0.8

mA
mA

V

TH

Receiver Differential
Threshold Voltage

VCM= -7 to 12V -0.2 0.2 V

∆V

TH

Receiver Input Hysteresis VCM=0V 70 mV

V

OH

Receiver Output High
Voltage

IO= -4mA VID= 200mV 3.4 V

V

OL

Receiver Output Low
Voltage

IO=4mA VID= -200mV 0.5 V

I

OZR

3-State (High Impedance)
Output Current at Receiver

VO= 0.4 to 2.4V ± 1 µA

R

IN

Receiver Input Resistance VCM= -7 to 12V 24 KΩ

I

CC

No Load Supply Current
(Note 2)

VRE=0VorV

CC

VDE=V

CC

VDE=0V

400
300

900
500

µA
µA

I

OSD1

Driver Short-Circuit Current,
V

O

=High

V

O

= -7 to 12V (Note 3) 35 250 mA

I

OSD2

Driver Short-Circuit Current,
V

O

=Low

V

O

= -7 to 12V (Note 3) 35 250 mA

I

OSR

Receiver Short-Circuit
Current

VO=0VtoV

CC

795mA

ST485

4/12

DRIVER SWITCHING CHARACTERISTICS

(VCC=5V ± 5%, TA=T

MIN

toT

MAX

,unless otherwise specified.Typical values are referred to TA=25°C)

(See Note 1)

Note 1: All currents into device pins are positive; all cuttents out of device pins are negative; all voltages are referenced to device ground
unless specified.

RECEIVER SWITCHING CHARACTERISTICS

(VCC=5V± 5%, TA=T

MIN

toT

MAX

,unlessotherwise specified. Typicalvalues arereferredto TA=25°C)

(See Note 1)

Note 1: All currents into device pins are positive; all cuttents out of device pins are negative; all voltages are referenced to device ground
unless specified.

Symbol Parameter Test Conditions Min. Typ. Max. Unit

t

PLH

t

PHL

Propagation Delay Input to
Output

R

DIFF

=54Ω CL1=CL2= 100pF

(See Fig. 3 and 5)

10 30 70 ns

t

SK

Output Skew to Output R

DIFF

=54Ω CL1=CL2= 100pF

(See Fig. 3 and 5)

510ns

t

TLH

t

THL

Rise or Fall Time R

DIFF

=54Ω CL1=CL2= 100pF

(See Fig. 3 and 5)

31545ns

t

PZH

Output Enable Time CL= 100pF S2 = Closed

(See Fig. 4 and 6)

70 90 ns

t

PZL

Output Enable Time CL= 100pF S1 = Closed

(See Fig. 4 and 6)

70 90 ns

t

PLZ

Output Disable Time CL= 15pF S1 = Closed

(See Fig. 4 and 6)

70 90 ns

t

PHZ

Output Disable Time CL= 15pF S2 = Closed

(See Fig. 4 and 6)

70 90 ns

Symbol Parameter Test Conditions Min. Typ. Max. Unit

t

PLH

t

PHL

Propagation Delay Input to
Output

R

DIFF

=54Ω CL1=CL2= 100pF

(See Fig. 3 and 7)

20 130 230 ns

t

SKD

Differential Receiver Skew R

DIFF

=54Ω CL1=CL2= 100pF

(See Fig. 3 and 7)

13 ns

t

PZH

Output Enable Time CRL= 15pF S1 = Closed

(See Fig. 2 and 8)

20 55 ns

t

PZL

Output Enable Time CRL= 15pF S2 = Closed

(See Fig. 2 and 8)

20 55 ns

t

PLZ

Output Disable Time CRL= 15pF S1 = Closed

(See Fig. 2 and 8)

20 55 ns

t

PHZ

Output Disable Time CRL= 15pF S2 = Closed

(See Fig. 2 and 8)

20 55 ns

f

MAX

Maximum Data Rate 2.5 Mbps