NSC DS36C278TN, DS36C278TMX, DS36C278TM, DS36C278N, DS36C278MX Datasheet

DS36C278
Low Power Multipoint EIA-RS-485 Transceiver

General Description

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

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

CC

is specified at

500 µA maximum.
The driver and receiver outputs feature TRI-STATE

®

capabil­ity.The driver outputs operate over the entire common mode
range of −7V to +12V. Bus contention or fault situations 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. (Note 1)

The DS36C278T is fully specified over the industrial tem­perature range (−40˚C to +85˚C).

Features

n 100%RS-485 compliant

— Guaranteed RS-485 device interoperation

n Low power CMOS design: I

CC

500 µA max

n Built-in power up/down glitch-free circuitry

— Permits live transceiver insertion/displacement

n DIP and SOIC packages available
n Industrial temperature range: −40˚C to +85˚C
n On-board thermal shutdown circuitry

— Prevents damage to the device in the event of

excessive power dissipation

n Wide common mode range: −7V to +12V
n Receiver open input fail-safe (Note 1)

n

1

⁄4unit load (DS36C278): ≥128 nodes

n

1

⁄2unit load (DS36C278T): ≥64 nodes

n ESD (human body model): ≥2kV
n Drop in replacement for:

— LTC485, MAX485, DS75176, DS3695

Connection and Logic Diagram 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

LL ≥+0.2V H
LL ≤−0.2V L
HL X Z
L L OPEN (Note 1) H

Note 1: Non-terminated, open input only

TRI-STATE®is a registered trademark of National Semiconductor Corporation.

DS012040-1

Order Number DS36C278TM, DS36C278TN,

DS36C278M, DS36C278N

See NS Package Number M08A or N08E

July 1998

DS36C278 Low Power Multipoint EIA-RS-485 Transceiver

© 1999 National Semiconductor Corporation DS012040 www.national.com

Absolute Maximum Ratings (Note 2)

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

Supply Voltage (V

CC

) +12V

Input Voltage (DE, RE*, & DI) −0.5V to (V

CC

+0.5V)

Common Mode (V

CM

)

Driver Output/Receiver Input

±

15V

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

±

14V

Receiver Output Voltage −0.5V to (V

CC

+0.5V)

Maximum Package Power Dissipation

@

+25˚C
M Package 1190 mW, derate 9.5 mW/˚C above +25˚C
N Package 744 mW, derate 6.0 mW/˚C above +25˚C

Storage Temperature Range −65˚C to +150˚C
Lead Temperature

(Soldering 4 sec) +260˚C

Recommended Operating
Conditions

Min Typ Max Units

Supply Voltage (V

CC

) +4.75 +5.0 +5.25 V
Bus Voltage −7 +12 V
Operating Free Air Temperature (Ta)
DS36C278T −40 25 +85 ˚C
DS36C278 0 25 +70 ˚C

Electrical Characteristics (Notes 3, 4)

Over Supply Voltage and Operating Temperature ranges, unless otherwise specified

Symbol Parameter Conditions Reference Min Typ Max Units

DIFFERENTIAL DRIVER CHARACTERISTICS

V

OD1

Differential Output Voltage IO= 0 mA (No Load)

(422)
(485)

1.5 5.0 V

V

OD0

Output Voltage IO= 0 mA 0 5.0 V

V

OD0*

Output Voltage (Output to GND) 0 5.0 V

V

OD2

Differential Output Voltage RL=50Ω (422)

Figure 1

2.0 2.8 V

(Termination Load) R

L

=27Ω (485) 1.5 2.3 5.0 V

∆V

OD2

Balance of V

OD2

RL=27Ωor 50Ω (Note 5) −0.2 0.1 +0.2 V

|V

OD2−V0D2*

| (422, 485)

V

OD3

Differential Output Voltage
(Full Load)

R1=54Ω,R2=375Ω
V

TEST

= −7V to +12V

Figure 2

1.5 2.0 5.0 V

V

OC

Driver Common Mode
Output Voltage

RL=27Ω (485)

Figure 1

0 3.0 V

R

L

=50Ω (422) 0 3.0 V

∆V

OC

Balance of V

OC

|VOC−V

OC*

|

R

L

=27Ωor

R

L

=50Ω

(Note 5)

(422, 485)

−0.2 +0.2 V

I

OSD

Driver Output Short-Circuit
Current

VO= +12V (485)

Figure 4

200 +250 mA

V

O

= −7V (485) −190 −250 mA

RECEIVER CHARACTERISTICS

V

TH

Differential Input High
Threshold Voltage

VO=VOH,IO= −0.4V

−7V ≤ V

CM

≤ +12V

(Note 6)

(422, 485)

+0.035 +0.2 V

V

TL

Differential Input Low
Threshold Voltage

VO=VOL,IO= 0.4 mA

−7V ≤ V

CM

≤ +12V

−0.2 −0.035 V

V

HST

Hysteresis VCM= 0V (Note 7) 70 mV

R

IN

Input Resistance −7V ≤ VCM≤ +12V DS36C278T 24 68 kΩ

R

IN

Input Resistance −7V ≤ VCM≤ +12V DS36C278 48 68 kΩ

I

IN

Line Input Current Other Input = 0V, DS36C278 VIN= +12V 0 0.19 0.25 mA
(Note 8) DE = V

IL

,RE*=VIL,V

IN

= −7V 0 −0.1 −0.2 mA

V

CC

= 4.75 to 5.25 DS36C278T VIN= +12V 0 0.19 0.5 mA

or 0V V

IN

= −7V 0 −0.1 −0.4 mA

I

ING

Line Input Current Glitch Other Input = 0V, DS36C278 VIN= +12V 0 0.19 0.25 mA
(Note 8) DE = V

IL

,RE*=VIL,V

IN

= −7V 0 −0.1 −0.2 mA

V

CC

= +3.0V or 0V, DS36C278T VIN= +12V 0 0.19 0.5 mA

T

A

= 25˚C VIN= −7V 0 −0.1 −0.4 mA

I

B

Input Balance Test RS = 500Ω (422) (Note 10)

±

400 mV

V

OH

High Level Output Voltage IOH= −4 mA, VID= +0.2V

RO

Figure 11

3.5 4.6 V

V

OL

Low Level Output Voltage IOL= +4 mA, VID= −0.2V 0.3 0.5 V

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Electrical Characteristics (Notes 3, 4) (Continued)

Over Supply Voltage and Operating Temperature ranges, unless otherwise specified

Symbol Parameter Conditions Reference Min Typ Max Units

RECEIVER CHARACTERISTICS

I

OSR

Short Circuit Current VO= GND

RO

73585mA

I

OZR

TRI-STATE Leakage
Current

VO= 0.4V to 2.4V

±

1µA

DEVICE CHARACTERISTICS

V

IH

High Level Input Voltage

DE,

RE*,

DI

2.0 V

CC

V

V

IL

Low Level Input Voltage GND 0.8 V

I

IH

High Level Input Current VIH=V

CC

2µA

I

IL

Low Level Input Current VCC=5V

V

IL

=0V

−2 µA

V

CC

= +3.0V −2 µA

I

CC

Power Supply Current Driver and Receiver ON

V

CC

200 500 µA

I

CCR

(No Load) Driver OFF, Receiver ON 200 500 µA

I

CCD

Driver ON, Receiver OFF 200 500 µA

I

CCZ

Driver and Receiver OFF 200 500 µA

Switching Characteristics (Notes 4, 9)

Over Supply Voltage and Operating Temperature ranges, unless otherwise specified

Symbol Parameter Conditions Reference Min Typ Max Units

DRIVER CHARACTERISTICS

t

PHLD

Differential Propagation
Delay High to Low

RL=54Ω,CL= 100 pF

Figures 5, 6

10 39 80 ns

t

PLHD

Differential Propagation
Delay Low to High

10 40 80 ns

t

SKD

Differential Skew
|t

PHLD−tPLHD

|

0 1 10 ns

t

r

Rise Time 32550 ns

t

f

Fall Time 32550 ns

t

PHZ

Disable Time High to Z CL=15pF

Figures 7, 8

— 80 200 ns

t

PLZ

Disable Time Low to Z RE*=L

Figures 9, 10

— 80 200 ns

t

PZH

Enable Time Z to High CL= 100 pF

Figures 7, 8

— 50 200 ns

t

PZL

Enable Time Z to Low RE*=L

Figures 9, 10

— 65 200 ns

RECEIVER CHARACTERISTICS

t

PHL

Propagation Delay
High to Low

CL=15pF

Figures 12, 13

30 210 400 ns

t

PLH

Propagation Delay
Low to High

30 190 400 ns

t

SK

Skew, |t

PHL−tPLH

| 0 20 50 ns

t

PLZ

Output Disable Time CL=15pF

Figures 14, 15, 16

— 50 150 ns

t

PHZ

— 55 150 ns

t

PZL

Output Enable Time — 40 150 ns

t

PZH

— 45 150 ns

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