Datasheet ST485B, ST485C Datasheet (ST)

Low power RS-485/RS-422 transceiver

Features

■ Low quiescent current: 300 µA

■ Designed for RS-485 interface application

■ - 7 V to 12 V common mode input voltage range

■ Driver maintains high impedance in 3-state or

with the power OFF

■ 70 mV typical input hysteresis

■ 30 ns propagation delay, 5 ns skew

■ Operate from a single 5 V supply

■ Current limiting and thermal shutdown for

driver overload protection

■ Allows up to 64 transceivers on the bus

ST485B
ST485C

DIP-8 SO-8

The ST485 is available in three temperature
range: commercial (0 °C to 70 °C), industrial (- 40
°C to 85 °C) and automotive (- 55 °C to 125 °C).

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 300 µA (typ.) of supply
current when unloaded or fully loaded with
disabled drivers.

It operates from a single 5 V 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 applications).

Table 1. Device summary

Order code Temperature range Package Packaging

ST485CN 0 to 70 °C DIP-8 50 parts per tube / 40 tube per box

ST485BN - 40 to 85 °C DIP-8 50 parts per tube / 40 tube per box

ST485CDR 0 to 70 °C SO-8 (tape and reel) 2500 parts per reel

ST485BDR - 40 to 85 °C SO-8 (tape and reel) 2500 parts per reel

February 2009 Rev 16 1/19

www.st.com

19

Contents ST485B - ST485C

Contents

1 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.1 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 Truth tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4.1 Driver switching characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

4.2 Receiver switching characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

5 Test circuit and typical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . 9

6 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

7 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

2/19

ST485B - ST485C Pin configuration

1 Pin configuration

Figure 1. Pin connections

Table 2. Pin description

Pin n° Symbol Name and function

1 RO Receiver output

2 RE Receiver output enable

3 DE Driver output enable

4DIDriver input

5 GND Ground

6 A Non-inverting receiver input and non-inverting driver output

7 B Inverting receiver input and inverting driver output

8V

CC

Supply voltage

3/19

Truth tables ST485B - ST485C

2 Truth tables

Table 3. Truth table (driver)

Inputs Outputs

RE DE DI B A

XHHLH

XHLHL

XLXZZ

Note: X = Don’t care; Z = High impedance

Table 4. Truth table (receiver)

Inputs Outputs

RE DE A-B RO

LL

LL

L L Inputs open H

HLX Z

Note: X = Don’t care; Z = High impedance

≥ +0.2V H

≤ -0.2V L

4/19

ST485B - ST485C Maximum ratings

3 Maximum ratings

Table 5. Absolute maximum ratings

Symbol Parameter Value Unit

V

V

V

V

V

V

CC

DI

DO

RI

RO

Supply voltage 7 V

Control input voltage (RE, DE) -0.5 to (VCC + 0.5) V

I

Driver input voltage (DI) -0.5 to (VCC + 0.5) V

Driver output voltage (A, B) ± 14 V

Receiver input voltage (A, B) ± 14 V

Receiver output voltage (RO) -0.5 to (VCC + 0.5) V

Note: Absolute maximum ratings are those values beyond which damage to the device may occur.

Functional operation under these condition is not implied.

5/19

Electrical characteristics ST485B - ST485C

4 Electrical characteristics

VCC = 5 V ± 5 %, TA = T

= 25 °C

to T

A

Table 6. DC electrical characteristics

MIN

to T

, unless otherwise specified. Typical values are referred

MAX

Symbol Parameter Test conditions

V

V

Differential driver output

OD1

(no load)

Differential driver output

OD2

(with load)

RL = 27Ω (RS-485) Figure 2
RL = 50Ω (RS-422) Figure 2

Change in magnitude of

ΔV

driver differential output

OD

voltage for complementary

= 27Ω or 50Ω Figure 2 0.2 0.2 V

R

L

output states

V

Driver common-mode

OC

output voltage

= 27Ω or 50Ω Figure 2 33V

R

L

Change in magnitude of
driver common-mode

ΔV

output voltage for

OC

= 27Ω or 50Ω Figure 2 0.2 0.2 V

R

L

complementary output
states

V

Input high voltage RE, DE, DI 2.0 2.0 V

IH

Input low voltage RE, DE, DI 0.8 0.8 V

V

IL

I

Input current RE, DE, DI ± 2 ± 2µA

IN1

VCM = 0V or 5.25V, VDE = 0V

Input current (A, B)

I

IN2

V

Receiver differential

TH

threshold voltage

VIN = 12V

= -7V

V

IN

V

= -7 to 12V -0.2 0.2 -0.2 0.2 V

CM

(1)

Val ue

Min. Typ. Max. Min. Max.

55V

1.5

5
5

1

-0.8

1.4

5
5

1

-0.8mAmA

Unit-40 to 85 °C -55 to 125 °C

V
V

ΔV

V

V

I

Receiver input hysteresis VCM = 0V 70 mV

TH

Receiver output high

OH

voltage

Receiver output low

OL

voltage

3-state (high impedance)

OZR

output current at receiver

R

Receiver input resistance VCM = -7 to 12V 24 24 kΩ

IN

I

No load supply current

CC

= -4mA, VID = 200mV 3.5 3.4 V

I

O

I

= 4mA, VID = -200mV 0.4 0.55 V

O

= 0.4 to 2.4V ± 1 ± 1µA

V

O

VRE = 0V or V

(2)

VDE = V

CC

CC

VDE = 0V

6/19

400
300

900
500

900
500µAµA

ST485B - ST485C Electrical characteristics

Table 6. DC electrical characteristics (continued)

Val ue

Symbol Parameter Test conditions

(1)

Min. Typ. Max. Min. Max.

I

OSD1

I

OSD2

I

1. All currents into device pins are positive; all cuttents out of device pins are negative; all voltages are referenced to device

2. Supply current specification is valid for loaded transmitters when V

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

Driver short-circuit
current, V

=High

O

Driver short-circuit
current, VO=Low

Receiver short-circuit

OSR

current

ground unless specified.

VCC = 5 V ± 5 %, TA = T
to T

= 25 °C

A

Table 7. Driver switching characteristics

V

= -7 to 12V

O

= -7 to 12V

V

O

= 0V to V

V

O

to T

MIN

(3)

(3)

CC

= 0V

DE

, unless otherwise specified. Typical values are referred

MAX

35 25035250mA

35 25035250mA

7 95795mA

Val u e

Symbol Parameter Test conditions

(1)

Min. Typ. Max. Min. Max.

Unit-40 to 85 °C -55 to 125 °C

Unit-40 to 85 °C -55 to 125°C

t

PLH

t

t

t
t

t

PZH

t

t

t

PHZ

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.

Propagation delay
input to output

PHL

Output skew to output

SK

TLH

Rise or fall time

THL

Output enable time

Output enable time

PZL

Output disable time

PLZ

Output disable time

R

= 54Ω, CL1 = CL2 = 100pF

DIFF

(See Figure 4 and Figure 6)

R

= 54Ω, CL1 = CL2 = 100pF

DIFF

(See Figure 4 and Figure 6)

= 54Ω, CL1 = CL2 = 100pF

R

DIFF

(See Figure 4 and Figure 6)

= 100pF, S2 = Closed

C

L

(See Figure 5 and Figure 7)

C

= 100pF, S1 = Closed

L

(See Figure 5 and Figure 7)

= 15pF, S1 = Closed

C

L

(See Figure 5 and Figure 7)

= 15pF, S2 = Closed

C

L

(See Figure 5 and Figure 7)

10 30 60 70 ns

510 10ns

3 15 40 3 45 ns

70 90 90 ns

70 90 90 ns

70 90 90 ns

70 90 90 ns

7/19

Electrical characteristics ST485B - ST485C

VCC = 5 V ± 5%, TA = T
to T

= 25 °C

A

Table 8. Receiver switching characteristics

MIN

to T

, unless otherwise specified. Typical values are referred

MAX

Val ue

Symbol Parameter Test conditions

(1)

Min. Typ. Max. Min. Max.

t

PLH

t

t

SKD

t

PZH

t

PZL

t

PLZ

t

PHZ

f

MAX

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

Propagation delay input
to output

PHL

Differential receiver
skew

Output enable time

Output enable time

Output disable time

Output disable time

R

=54Ω, CL1 = CL2 = 100pF

DIFF

(See Figure 4 and Figure 8)

R

=54Ω, CL1 = CL2 = 100pF

DIFF

(See Figure 4 and Figure 8)

= 15pF, S1 = Closed

C

RL

(See Fig. 2 and Figure 9)

= 15pF, S2 = Closed

C

RL

(See Fig. 2 and Figure 9)

C

= 15pF, S1 = Closed

RL

(See Fig. 2 and Figure 9)

= 15pF, S2 = Closed

C

RL

(See Fig. 2 and Figure 9)

20 130 210 230 ns

13 ns

20 50 56 ns

20 50 56 ns

20 50 56 ns

20 50 56 ns

Maximum data rate 2.5 2.5 Mbps

Unit-40 to 85 °C -55 to 125°C

8/19

ST485B - ST485C Test circuit and typical characteristics

5 Test circuit and typical characteristics

Figure 2. Driver DC test load Figure 3. Receiver timing test load

Figure 4. Drive/receiver timing test circuit Figure 5. Driver timing test load

9/19

Test circuit and typical characteristics ST485B - ST485C

Figure 6. Driver propagation delay

Figure 7. Driver enable and disable time

10/19

ST485B - ST485C Test circuit and typical characteristics

Figure 8. Receiver propagation delay

Figure 9. Receiver enable and disable time

11/19

Test circuit and typical characteristics ST485B - ST485C

Figure 10. Receiver output current vs. output

low voltage

Figure 12. Driver output current vs. output low

voltage

Figure 11. Receiver output current vs. output

high voltage

Figure 13. Driver output current vs. output

high voltage

Figure 14. Supply current vs. temperature Figure 15. Receiver high level output voltage

12/19

vs. temperature

ST485B - ST485C Test circuit and typical characteristics

Figure 16. Receiver low level output voltage

vs. temperature

Figure 17. Differential driver output voltage vs.

temperature

13/19

Package mechanical data ST485B - ST485C

6 Package mechanical data

In order to meet environmental requirements, ST offers these devices in different grades of
ECOPACK
specifications, grade definitions and product status are available at: www.st.com. ECOPACK
is an ST trademark.

®

packages, depending on their level of environmental compliance. ECOPACK®

14/19

ST485B - ST485C Package mechanical data

Plastic DIP-8 mechanical data

Dim.

Min. Typ. Max. Min. Typ. Max.

A 3.3 0.130

a1 0.7 0.028

B1.39 1.65 0.055 0.065

B1 0.91 1.04 0.036 0.041

b 0.5 0.020

b10.38 0.5 0.015 0.020

D 9.8 0.386

E 8.8 0.346

e 2.54 0.100

e3 7.62 0.300

e4 7.62 0.300

F 7.1 0.280

I4.8 0.189

L 3.3 0.130

Z 0.44 1.6 0.017 0.063

mm. inch.

P001F

15/19

Package mechanical data ST485B - ST485C

SO-8 mechanical data

Dim.

A1.35 1.75 0.053 0.069

A1 0.10 0.25 0.04 0.010

A2 1.10 1.65 0.043 0.065

B0.33 0.51 0.013 0.020

C0.19 0.25 0.007 0.010

D4.80 5.00 0.189 0.197

E 3.80 4.00 0.150 0.157

e 1.27 0.050

H5.80 6.20 0.228 0.244

h 0.25 0.50 0.010 0.020

L 0.40 1.27 0.016 0.050

k 8° (max.)

ddd 0.1 0.04

Min. Typ. Max. Min. Typ. Max.

mm. inch.

16/19

0016023/C

ST485B - ST485C Package mechanical data

Tape & reel SO-8 mechanical data

mm. inch.

Dim.

Min. Typ. Max. Min. Typ. Max.

A 330 12.992

C 12.8 13.2 0.504 0.519

D 20.2 0.795

N60 2.362

T 22.4 0.882

Ao 8.1 8.5 0.319 0.335

Bo 5.5 5.9 0.216 0.232

Ko 2.1 2.3 0.082 0.090

Po 3.9 4.1 0.153 0.161

P7.98.1 0.311 0.319

17/19

Revision history ST485B - ST485C

7 Revision history

Table 9. Document revision history

Date Revision Changes

21-Mar-2006 12 Order codes has been updated and new template.

02-Aug-2006 13 Mistake in cover page first row mA ==> µA.

08-Nov-2006 14 Added: Ta bl e 1 .

07-Feb-2008 15 Modified: Table 1 on page 1.

16-Feb-2009 16 Modified Note: on page 5.

18/19

ST485B - ST485C

Please Read Carefully:

Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the
right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any
time, without notice.

All ST products are sold pursuant to ST’s terms and conditions of sale.

Purchasers are solely responsible for the choice, selection and use of the ST products and services described herein, and ST assumes no
liability whatsoever relating to the choice, selection or use of the ST products and services described herein.

No license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted under this document. If any part of this
document refers to any third party products or services it shall not be deemed a license grant by ST for the use of such third party products
or services, or any intellectual property contained therein or considered as a warranty covering the use in any manner whatsoever of such
third party products or services or any intellectual property contained therein.

UNLESS OTHERWISE SET FORTH IN ST’S TERMS AND CONDITIONS OF SALE ST DISCLAIMS ANY EXPRESS OR IMPLIED
WARRANTY WITH RESPECT TO THE USE AND/OR SALE OF ST PRODUCTS INCLUDING WITHOUT LIMITATION IMPLIED
WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE (AND THEIR EQUIVALENTS UNDER THE LAWS
OF ANY JURISDICTION), OR INFRINGEMENT OF ANY PATENT, COPYRIGHT OR OTHER INTELLECTUAL PROPERTY RIGHT.

UNLESS EXPRESSLY APPROVED IN WRITING BY AN AUTHORIZED ST REPRESENTATIVE, ST PRODUCTS ARE NOT
RECOMMENDED, AUTHORIZED OR WARRANTED FOR USE IN MILITARY, AIR CRAFT, SPACE, LIFE SAVING, OR LIFE SUSTAINING
APPLICATIONS, NOR IN PRODUCTS OR SYSTEMS WHERE FAILURE OR MALFUNCTION MAY RESULT IN PERSONAL INJURY,
DEATH, OR SEVERE PROPERTY OR ENVIRONMENTAL DAMAGE. ST PRODUCTS WHICH ARE NOT SPECIFIED AS "AUTOMOTIVE
GRADE" MAY ONLY BE USED IN AUTOMOTIVE APPLICATIONS AT USER’S OWN RISK.

Resale of ST products with provisions different from the statements and/or technical features set forth in this document shall immediately void
any warranty granted by ST for the ST product or service described herein and shall not create or extend in any manner whatsoever, any
liability of ST.

ST and the ST logo are trademarks or registered trademarks of ST in various countries.

Information in this document supersedes and replaces all information previously supplied.

The ST logo is a registered trademark of STMicroelectronics. All other names are the property of their respective owners.

© 2009 STMicroelectronics - All rights reserved

STMicroelectronics group of companies

Australia - Belgium - Brazil - Canada - China - Czech Republic - Finland - France - Germany - Hong Kong - India - Israel - Italy - Japan -

Malaysia - Malta - Morocco - Singapore - Spain - Sweden - Switzerland - United Kingdom - United States of America

www.st.com

19/19