Analog Devices ADM1485JR, ADM1485JN, ADM1485AR, ADM1485AQ, ADM1485AN Datasheet

+5 V Low Power

a

FEATURES
Meets EIA RS-485 Standard
30 Mb/s Data Rate
Single +5 V Supply
–7 V to +12 V Bus Common-Mode Range
High Speed, Low Power BiCMOS
Thermal Shutdown Protection
Short Circuit Protection
Zero Skew Driver
Driver Propagation Delay: 10 ns
Receiver Propagation Delay: 25 ns
High Z Outputs with Power Off
Superior Upgrade for LTC1485

APPLICATIONS
Low Power RS-485 Systems
DTE-DCE Interface
Packet Switching
Local Area Networks
Data Concentration
Data Multiplexers
Integrated Services Digital Network (ISDN)

EIA RS-485 Transceiver

ADM1485

FUNCTIONAL BLOCK DIAGRAM

8-Lead

ADM1485

RO

RE

DE

R

DI

D

V

CC

B

A

GND

GENERAL DESCRIPTION

The ADM1485 is a differential line transceiver suitable for high
speed bidirectional data communication on multipoint bus
transmission lines. It is designed for balanced data transmission
and complies with both EIA Standards RS-485 and RS-422.
The part contains a differential line driver and a differential line
receiver. Both the driver and the receiver may be enabled inde­pendently. When disabled, the outputs are tristated.

The ADM1485 operates from a single +5 V power supply.
Excessive power dissipation caused by bus contention or by
output shorting is prevented by a thermal shutdown circuit.
This feature forces the driver output into a high impedance state
if during fault conditions a significant temperature increase is
detected in the internal driver circuitry.

Up to 32 transceivers may be connected simultaneously on a
bus, but only one driver should be enabled at any time. It is
important therefore that the remaining disabled drivers do not
load the bus. To ensure this, the ADM1485 driver features high
output impedance when disabled and also when powered down.

This minimizes the loading effect when the transceiver is not
being utilized. The high impedance driver output is maintained
over the entire common-mode voltage range from –7 V to +12 V.

The receiver contains a fail safe feature which results in a logic
high output state if the inputs are unconnected (floating).

The ADM1485 is fabricated on BiCMOS, an advanced mixed
technology process combining low power CMOS with fast
switching bipolar technology. All inputs and outputs contain
protection against ESD; all driver outputs feature high source
and sink current capability. An epitaxial layer is used to guard
against latch-up.

The ADM1485 features extremely fast switching speeds. Mini­mal driver propagation delays permit transmission at data rates
up to 30 Mbits/s while low skew minimizes EMI interference.

The part is fully specified over the commercial and industrial
temperature range and is available in an 8-lead DIL/SOIC
package.

REV. A

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ADM1485–SPECIFICATIONS

(VCC = +5 V  5%. All specifications T

MIN

to T

unless otherwise noted.)

MAX

Parameter Min Typ Max Unit Test Conditions/Comments

DRIVER

Differential Output Voltage, V

OD

2.0 5.0 V V

5.0 V R = ∞, Figure 1
= 5 V, R = 50 Ω (RS-422), Figure 1

CC

1.5 5.0 V R = 27 Ω (RS-485), Figure 1

V

OD3

∆|V

| for Complementary Output States 0.2 V R = 27 Ω or 50 Ω, Figure 1

OD

Common-Mode Output Voltage V

| for Complementary Output States 0.2 V R = 27 Ω or 50 Ω

∆|V

OD

Output Short Circuit Current (V
Output Short Circuit Current (V
CMOS Input Logic Threshold Low, V
CMOS Input Logic Threshold High, V

OC

= High) 35 250 mA –7 V ≤ VO ≤ +12 V

OUT

= Low) 35 250 mA –7 V ≤ VO ≤ +12 V

OUT

INL

INH

1.5 5.0 V V

3 V R = 27 Ω or 50 Ω, Figure 1

0.8 V

2.0 V

= –7 V to +12 V, Figure 2

TST

Logic Input Current (DE, DI) ± 1.0 µA

RECEIVER

Differential Input Threshold Voltage, V
Input Voltage Hysteresis, ∆V

TH

TH

Input Resistance 12 kΩ –7 V ≤ V
Input Current (A, B) + 1 mA V

–0.2 +0.2 V –7 V ≤ VCM ≤ +12 V

70 mV VCM = 0 V

≤ +12 V

CM

= 12 V

IN

–0.8 mA V

= –7 V

IN

Logic Enable Input Current (RE) ± 1 µA
CMOS Output Voltage Low, V
CMOS Output Voltage High, V

OL

OH

4.0 V I
Short Circuit Output Current 7 85 mA V
Tristate Output Leakage Current ± 1.0 µA 0.4 V ≤ V

0.4 V I

= +4.0 mA

OUT

= –4.0 mA

OUT

= GND or V

OUT

≤ +2.4 V

OUT

CC

POWER SUPPLY CURRENT

(Outputs Enabled) 1.35 2.2 mA Outputs Unloaded, Digital Inputs = GND or V

I

CC

ICC (Outputs Disabled) 0.7 1 mA Outputs Unloaded, Digital Inputs = GND or V

Specifications subject to change without notice.

CC

CC

TIMING SPECIFICATIONS

(VCC = +5 V  5%. All specifications T

MIN

to T

unless otherwise noted.)

MAX

Parameter Min Typ Max Unit Test Conditions/Comments

DRIVER

Propagation Delay Input to Output T
Driver O/P to O/P T
Driver Rise/Fall Time T

SKEW

R

, T

F

PLH

, T

PHL

21015nsR

05nsR
210nsR

Diff = 54 Ω CL1 = CL2 = 100 pF, Figure 3

L

Diff = 54 Ω CL1 = CL2 = 100 pF, Figure 3

L

Diff = 54 Ω CL1 = CL2 = 100 pF, Figure 3

L

Driver Enable to Output Valid 10 25 ns
Driver Disable Timing 10 25 ns

RECEIVER

Propagation Delay Input to Output T
Skew |T

PLH–TPHL

Receiver Enable T
Receiver Disable T

Specifications subject to change without notice.

|05ns

EN1

EN2

PLH

, T

PHL

18 25 40 ns CL = 15 pF, Figure 5

15 25 ns Figure 6
15 25 ns Figure 6

–2–

REV. A

ADM1485

TOP VIEW

(Not to Scale)

8

7

6

5

1

2

3

4

RO

RE

DE

V

CC

B

A

GNDDI

ADM1485

WARNING!

ESD SENSITIVE DEVICE

ABSOLUTE MAXIMUM RATINGS*

(TA = +25°C unless otherwise noted)

VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +7 V

Inputs

Driver Input (DI) . . . . . . . . . . . . . . . .–0.3 V to V

Control Inputs (DE, RE) . . . . . . . . . .–0.3 V to V

+ 0.3 V

CC

+ 0.3 V

CC

Receiver Inputs (A, B) . . . . . . . . . . . . . . . . . –14 V to +14 V

Outputs

Driver Outputs . . . . . . . . . . . . . . . . . . . . . . . –14 V to +14 V

Receiver Output . . . . . . . . . . . . . . . . .–0.5 V to V

+ 0.5 V

CC

Power Dissipation 8-Lead DIP . . . . . . . . . . . . . . . . . 500 mW

θ

, Thermal Impedance . . . . . . . . . . . . . . . . . . +130°C/W

JA

Power Dissipation 8-Lead SOIC . . . . . . . . . . . . . . . . 450 mW

, Thermal Impedance . . . . . . . . . . . . . . . . . . +170°C/W

θ

JA

Power Dissipation 8-Lead Cerdip . . . . . . . . . . . . . . . 500 mW

, Thermal Impedance . . . . . . . . . . . . . . . . . . +125°C/W

θ

JA

Operating Temperature Range

Commercial (J Version) . . . . . . . . . . . . . . . . . 0°C to +70°C

Industrial (A Version) . . . . . . . . . . . . . . . . –40° C to +85°C

Storage Temperature Range . . . . . . . . . . . –65°C to +150°C

Lead Temperature (Soldering, 10 sec) . . . . . . . . . . . .+300°C

Vapor Phase (60 sec) . . . . . . . . . . . . . . . . . . . . . . . .+215°C

Infrared (15 sec) . . . . . . . . . . . . . . . . . . . . . . . . . . . .+220°C

*Stresses above those listed under Absolute Maximum Ratings may cause perma-

nent damage to the device. This is a stress rating only; functional operation of the
device at these or any other conditions above those listed in the operational
sections of this specification is not implied. Exposure to absolute maximum ratings
for extended periods of time may affect device reliability.

PIN FUNCTION DESCRIPTION

Pin Mnemonic Function

1 RO Receiver Output. When enabled if A > B

by 200 mV, then RO = High. If A < B by
200 mV, then RO = Low.

2 RE Receiver Output Enable. A low level enables

the receiver output, RO. A high level places
it in a high impedance state.

3 DE Driver Output Enable. A high level enables

the driver differential outputs, A and B. A
low level places it in a high impedance state.

4 DI Driver Input. When the driver is enabled a

logic Low on DI forces A low and B high
while a logic High on DI forces A high and

B low.
5 GND Ground Connection, 0 V.
6 A Noninverting Receiver Input A/Driver

Output A.
7 B Inverting Receiver Input B/Driver Output B.
8V

CC

Power Supply, 5 V ± 5%.

PIN CONFIGURATION

Table I. Transmitting

INPUTS OUTPUTS

RE DE DI B A

X1101
X1010
X0 XZ Z

ORDERING GUIDE

Temperature Package

Model Range Option

Table II. Receiving

INPUTS OUTPUT

RE DE A-B RO

00 ≥ +0.2 V 1

ADM1485JN 0°C to +70°C N-8
ADM1485JR 0°C to +70°C SO-8
ADM1485AN –40°C to +85°C N-8
ADM1485AR –40°C to +85°C SO-8
ADM1485AQ –40°C to +85°C Q-8

00 ≤ –0.2 V 0
0 0 Inputs Open 1
10 X Z

CAUTION

ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection. Although
the ADM1485 features proprietary ESD protection circuitry, permanent damage may occur on
devices subjected to high-energy electrostatic discharges. Therefore, proper ESD precautions are
recommended to avoid performance degradation or loss of functionality.

REV. A

–3–