National DS36C278 User Manual

DS36C278
Low Power Multipoint EIA-RS-485 Transceiver

DS36C278 Low Power Multipoint EIA-RS-485 Transceiver

December 1995

General Description

The DS36C278 is a low power differential bus/line trans­ceiver designed to meet the requirements of RS-485 stan­dard for multipoint data transmission. In addition it is com­patible with TIA/EIA-422-B.

The CMOS design offers significant power savings over its
bipolar and ALS counterparts without sacrificing ruggedness
against ESD damage. The device is ideal for use in battery
powered or power conscious applications. I
500 mA maximum.

The driver and receiver outputs feature TRI-STATE
bility. The driver outputs operate over the entire common
mode range of

b

7V toa12V. Bus contention or fault situa-

is specified at

CC

É

capa-

tions that cause excessive power dissipation within the de­vice are handled by a thermal shutdown circuit, which forces
the driver outputs into the high impedance state.

The receiver incorporates a fail safe circuit which guaran­tees a high output state when the inputs are left open.

The DS36C278T is fully specified over the industrial temper­ature range (

b

40§Ctoa85§C).

²

Connection and Logic Diagram

Order Number DS36C278TM, DS36C278TN,

DS36C278M, DS36C278N

See NS Package Number M08A or N08E

TL/F/12040– 1

Features

Y

100% RS-485 compliant
Ð Guaranteed RS-485 device interoperation

Y

Low power CMOS design ICC500 mA max

Y

Built-in power up/down glitch-free circuitry
Ð Permits live transceiver insertion/displacement

Y

DIP and SOIC packages available

Y

Industrial temperature range

Y

On-board thermal shutdown circuitry

b

40§Ctoa85§C

Ð Prevents damage to the device in the event of ex-

cessive power dissipation

Y

Wide common mode range

Y

Receiver open input fail-safe

Y

(/4 unit load (DS36C278)

Y

(/2 unit load (DS36C278T)

Y

ESD (human body model)

Y

Drop in replacement for:

²

b

7V toa12V

t

128 nodes

t

64 nodes

Ð LTC485, MAX485, DS75176, DS3695

Truth Table

DRIVER SECTION

RE* DE DI DO/RI DO*/RI*

XHH H L
XHL L H
XLX Z Z

RECEIVER SECTION

RE* DE RI-RI* RO

t

LL
LL
HL X Z
L L OPEN

²

Note: Non-terminated, open input only

a

0.2V H

s

b

0.2V L

²

H

t

2kV

TRI-STATEÉis a registered trademark of National Semiconductor Corporation.

C

1996 National Semiconductor Corporation RRD-B30M36/Printed in U. S. A.

TL/F/12040

http://www.national.com

Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales
Office/Distributors for availability and specifications.

Supply Voltage (V

Input Voltage (DE, RE*, & DI)

Common Mode (V

CC

CM

)

b

0.5V to (V

)

Driver Output/Receiver Input

Input Voltage (DO/RI, DO*/RI*)

Receiver Output Voltage

Maximum Package Power Dissipation

@

a

25§C
M Package 1190 mW, derate 9.5 mW/
N Package 744 mW, derate 6.0 mW/

Storage Temperature Range

b

0.5V to (V

C abovea25§C

§

C abovea25§C

§

b

65§Ctoa150§C

Lead Temperature (Soldering 4 sec)

CC

CC

a

a

a

a

12V

0.5V)

g

15V

g

14V

0.5V)

260§C

Recommended Operating
Conditions

Supply Voltage (V
Bus Voltage
Operating Free Air Temperature (Ta)
DS36C278T
DS36C278 0 25

Min Typ Max Units

)a4.75a5.0a5.25 V

CC

b

7

b

40 25

a

12 V

a

85§C

a

70§C

Electrical Characteristics

Over Supply Voltage and Operating Temperature ranges, unless otherwise specified (Notes 2 and 3)

Symbol Parameter Conditions Reference Min Typ Max Units

DIFFERENTIAL DRIVER CHARACTERISTICS

V

V

V

V

DV

V

V

DV

I

OSD

OD1

OD0

OD0*

OD2

OD3

OC

Differential Output Voltage I

Output Voltage I

Output Voltage (Output to GND) 0 5.0 V

Differential Output Voltage R
(Termination Load)

Balance of V

OD2

V

l

OD2

OD2

b

V

l

OD2*

Differential Output Voltage R1e54X,R2e375X
(Full Load) V

Driver Common Mode R
Output Voltage

Balance of V

OC

V

l

OC

OC

b

V

l

OC*

Driver Output Short-Circuit V
Current

RECEIVER CHARACTERISTICS

V

TH

V

TL

V

HST

R

IN

R

IN

Differential Input High V
Threshold Voltage

Differential Input Low V
Threshold Voltage

Hysteresis V

Input Resistance

Input Resistance

e

0 mA (No Load)

O

e

0 mA 0 5.0 V

O

e

50X (422)

L

e

R

27X (485) 1.5 2.3 5.0 V

L

e

R

27X or 50X (Note 4)

L

eb

TEST

L

R

L

R

L

R

L

O

V

O

O

b

7VsV

O

b

7VsV

CM

b

7VsV

b

7VsV

7V toa12V

e

27X (485)

e

50X (422) 0 3.0 V

e

27X or (Note 4)

e

50X (422, 485)

ea

12V (485)

eb

7V (485)

e

e

eb

VOH,I

CM

VOL,I

CM

e

0V (Note 6) 70 mV

CM

CM

0.4V

O

s

a

12V

e

0.4 mA

O

s

a

12V

s

a

12V DS36C278T 24 68 kX

s

a

12V DS36C278 48 68 kX

(422)
(485)

Figure 1

(422, 485)

Figure 2

Figure 1

Figure 4

(Note 5)

(422, 485)

1.5 5.0 V

2.0 2.8 V

b

0.2 0.1

1.5 2.0 5.0 V

0 3.0 V

b

0.2

200

b

190

a

0.035

b

0.2b0.035 V

a

0.2 V

a

0.2 V

a

250 mA

b

250 mA

a

0.2 V

http://www.national.com 2

Electrical Characteristics (Continued)

Over Supply Voltage and Operating Temperature ranges, unless otherwise specified (Notes 2 and 3)

Symbol Parameter Conditions Reference Min Typ Max Units

I

I

I

V

V

I

I

Line Input Current Other Inpute0V, DS36C278 V

IN

Line Input Current Glitch Other Inpute0V, DS36C278 V

ING

Input Balance Test RSe500X (422) (Note 9)

B

High Level Output Voltage I

OH

Low Level Output Voltage I

OL

Short Circuit Current V

OSR

TRI-STATE Leakage Current V

OZR

DEVICE CHARACTERISTICS

V

V

I

I

I

I

I

I

High Level Input Voltage

IH

Low Level Input Voltage GND 0.8 V

IL

High Level Input Current V

IH

Low Level Input Current V

IL

Power Supply Current Driver and Receiver ON

CC

(No Load)

CCR

CCD

CCZ

DEeVIL,RE*eVIL,(Note 7)

e

V

4.75 to 5.25

CC

or 0V

DS36C278T

DEeVIL,RE*eVIL,(Note 7)

ea

V
T

V

OH

OL

CC

A

O

O

IH

CC

CC

e

eb

ea

e

e

e

3.0V or 0V,

25§C

4 mA, V

4 mA, V

GND

0.4V to 2.4V

V

CC

e

5V

ea

3.0V

DS36C278T V

ea

0.2V

ID

eb

0.2V 0.3 0.5 V

ID

e

0V

V

IL

Driver OFF, Receiver ON 200 500 mA

Driver ON, Receiver OFF 200 500 mA

Driver and Receiver OFF 200 500 mA

ea

12V 0 0.19 0.25 mA

IN

eb

V

7V 0b0.1b0.2 mA

IN

ea

V

12V 0 0.19 0.5 mA

IN

eb

V

7V 0b0.1b0.4 mA

IN

ea

12V 0 0.19 0.25 mA

IN

eb

V

7V 0b0.1b0.2 mA

IN

ea

12V 0 0.19 0.5 mA

IN

eb

V

7V 0b0.1b0.4 mA

IN

RO

3.5 4.6 V

Figure 11

RO

73585mA

2.0 V

DE,

RE*,

DI

V

CC

g

400 mV

g

1 mA

CC

2 mA

b

2 mA

b

2 mA

200 500 mA

V

Switching Characteristics

Over Supply Voltage and Operating Temperature ranges, unless otherwise specified (Notes 3 and 8)

Symbol Parameter Conditions Reference Min Typ Max Units

DRIVER CHARACTERISTICS

t

PHLD

t

PLHD

t

SKD

t

r

t

f

t

PHZ

t

PLZ

t

PZH

t

PZL

Differential Propagation R
Delay High to Low

e

L

Differential Propagation
Delay Low to High

Differential Skew

b

t

PHLD

t

PLHD

l

l

Rise Time 3 25 50 ns

Fall Time 3 25 50 ns

Disable Time High to Z C

e

L

Disable Time Low to Z RE *eL

Enable Time Z to High C

e

L

Enable Time Z to Low RE *eL

54X,C

15 pF

100 pF

e

100 pF

L

10 39 80 ns

10 40 80 ns

Figures 5, 6

0 1 10 ns

Figures 7, 8

Figures 9, 10

Figures 7, 8

Figures 9, 10

Ð 80 200 ns

Ð 80 200 ns

Ð 50 200 ns

Ð 65 200 ns

http://www.national.com3