ANALOG DEVICES ADM3485E Service Manual

±15 kV ESD-Protected, 3.3 V,12 Mbps,

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FEATURES

TIA/EIA RS-485/RS-422 compliant ±15 kV ESD protection on RS-485 input/output pins 12 Mbps data rate Half-duplex transceiver Up to 32 nodes on the bus Receiver open-circuit, fail-safe design Low power shutdown current Outputs high-Z when disabled or powered off Common-mode input range: −7 V to +12 V Thermal shutdown and short-circuit protection Industry-standard 75176 pinout 8-lead narrow SOIC package

APPLICATIONS

Power/energy metering Telecommunications EMI-sensitive systems Industrial control Local area networks

EIA RS-485/RS-422 Transceiver

ADM3485E

FUNCTIONAL BLOCK DIAGRAM

ADM3485E

RO

RE

DE

DI

R

D

Figure 1.

B

A

03338-001

GENERAL DESCRIPTION

The ADM3485E is a 3.3 V, low power data transceiver with ±15 kV ESD protection, suitable for half-duplex communication on multipoint bus transmission lines. The ADM3485E is designed for balanced data transmission and complies with TIA/EIA standards RS485 and RS-422. The ADM3485E is a half-duplex transceiver that shares differential lines and has separate enable inputs for the driver and the receiver.

The devices have a 12 kΩ receiver input impedance,

h allows up to 32 transceivers on a bus. Because only

whic one driver should be enabled at any time, the output of a

disabled or powered-down driver is tristated to avoid overloading the bus.

The receiver has a fail-safe feature that ensures a logic high o

utput when the inputs are floating. Excessive power dissipation caused by bus contention or by output shorting is prevented with a thermal shutdown circuit.

The part is fully specified over the industrial temperature range a

nd is available in an 8-lead narrow SOIC package.

Rev. C

Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Anal og Devices for its use, nor for any infringements of patents or ot her rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners.

ADM3485E

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REVISION HISTORY

12/06—Rev. B to Rev. C

Updated Format..................................................................Universal

Removed PDIP Model ....................................................... Universal

Changes to Features, Applications, and General Description .... 1

Changes to Specifications................................................................ 3

Changes to Timing Specifications.................................................. 4

Changes to Absolute Maximum Ratings....................................... 5

Reorganized Test Circuits and Switching C

haracteristics Section..................................................................... 7

Replaced Figure 3 to Figure 11 ....................................................... 7

Deleted Figure 12 to Figure 14........................................................ 8

Changes to Figure 15 to Figure 20.................................................. 9

Changes to Figure 21 and Figure 22............................................. 10

Changes to Table 9.......................................................................... 11

Deleted Figure 24............................................................................ 11

Removed Fast Transient Burst Immunity (IEC1000-4-4) S

Updated Outline Dimensions....................................................... 13

Changes to Ordering Guide.......................................................... 13

10/04—Rev. A to Rev. B

Updated Format..................................................................Universal

Changes to Power-Supply Current, Table 1 .................................. 3

Updated Outline Dimensions....................................................... 14

Changes to Ordering Guide.......................................................... 14

5/00—Rev. 0 to Rev. A

ection ................................................................... 12

Test Circuits and Switching Characteristics...................................7

Typical Perf or m an c e Charac t e r istics ..............................................9

Standards and Testing .................................................................... 11

ESD Testing ................................................................................. 11

Applications Information.............................................................. 12

Differential Data Transmission ................................................ 12

Cable and Data Rate................................................................... 12

Receiver Open-Circuit Fail-Safe............................................... 12

Outline Dimensions ....................................................................... 13

Ordering Guide .......................................................................... 13

Rev. C | Page 2 of 16

ADM3485E

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SPECIFICATIONS

VCC = +3.3 V ± 0.3 V. All specifications T

Table 1.

Parameter Symbol Min Typ Max Unit Test Conditions/Comments

DRIVER

Differential Outputs

Differential Output Voltage V

1.5 V RL = 54 Ω (RS-485) (see Figure 3)

1.5 V RL = 60 Ω (RS-485) (see Figure 4) ∆|VOD| for Complementary Output States1∆V Common-Mode Output Voltage V ∆|VOC| for Complementary Output States1∆V Short-Circuit Output Current I 250 mA V

Logic Inputs

Input High Voltage V Input Low Voltage V Logic Input Current I

RECEIVER

Differential Inputs

Differential Input Threshold Voltage V Input Voltage Hysteresis ∆V Input Resistance (A, B) R Input Current (A, B) I –0.8 mA DE = 0 V, VCC = 0 V or 3.6 V, VIN = –7 V

RO Logic Output

Output Voltage High V Output Voltage Low V Short-Circuit Output Current I Tristate Output Leakage Current I

POWER SUPPLY CURRENT

Voltage Range V Supply Current I

Shutdown Current I

ESD PROTECTION

A, B Pins ±15 kV Human body model All Pins Except A, B ±4 kV Human body model

1

Δ|VOD| and Δ|VOC| are the changes in VOD and VOC, respectively, when DI input changes state.

MIN

to T

, unless otherwise noted.

MAX

OD

OC

OSD

IH

IL

IN1

TH

IN

IN2

OH

OL

OSR

OZR

CC

2.0 V RL = 100 Ω (RS-422) (see Figure 3)

0.2 V RL = 54 Ω or 100 Ω (see Figure 3) 3 V RL = 54 Ω or 100 Ω ( see Figure 3)

0.2 V RL = 54 Ω or 100 Ω (see Figure 3) –250 mA V

0.8 V

2.0 V ±2 μA

–0.2 +0.2 V –7 V < VCM < +12 V 50 mV VCM = 0 V 12 kΩ –7 V < VCM < +12 V

1.0 mA DE = 0 V, VCC = 0 V or 3.6 V, VIN = 12 V

VCC – 0.4 V V I

0.4 V I ±8 ±60 mA 0 V < VRO < V ±1 μA VCC = 3.6 V, 0 V < V

3.0 3.6 V

1.1 2.2 mA

0.95 1.9 mA

SHDN

0.002 1 μA

= –7 V

OUT

= 12 V

OUT

DE, DI, RE DE, DI, RE DE, DI, RE

= –1.5 mA, VID = 200 mV (see Figure 5)

OUT

= 2.5 mA, VID = 200 mV (see Figure 5)

OUT

CC

< V

OUT

CC

No load, DI = 0 V or V

= 0 V or V

RE

CC

No load, DI = 0 V or V

= 0 V

RE DE = 0 V, RE

= VCC, DI = 0 V or V

, DE = VCC,

CC

, DE = 0 V,

CC

Rev. C | Page 3 of 16

ADM3485E

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TIMING SPECIFICATIONS

VCC = 3.3 V, TA = 25°C.

Table 2.

Parameter Symbol Min Typ Max Unit Test Conditions/Comments

DRIVER

Maximum Data Rate 12 15 Differential Output Delay t Differential Output Transition Time t

DD

TD

Propagation Delay

From Low to High Level t From High to Low Level t

|t

− t

PLH

| Propagation Delay Skew t

PHL

PLH

PHL

PDS

Enable/Disable Timing

Enable Time to Low Level t Enable Time to High Level t Disable Time from Low Level t Disable Time from High Level t Enable Time from Shutdown to Low Level t Enable Time from Shutdown to High Level t

PZL

PZH

PLZ

PHZ

PSL

PSH

RECEIVER

Propagation Delay

From Low to High Level t From High to Low Level t

|t

− t

RPLH

| Propagation Delay Skew t

RPHL

RPLH

RPHL

RPDS

Enable/Disable Timing

Enable Time to Low Level t Enable Time to High Level t Disable Time from Low Level t Disable Time from High Level t Enable Time from Shutdown to Low Level t Enable Time from Shutdown to High Level t Time to Shutdown

1

The transceivers are put into shutdown mode by bringing the RE high and the DE low. If the inputs are in this state for less than 80 ns, the parts are guaranteed not to

enter shutdown. If the parts are in this state for 300 ns or more, the parts are guaranteed to enter shutdown.

1

t

RPZL

RPZH

RPLZ

RPHZ

RPSL

RPSH

SHDN

1 22 35 ns RL = 60 Ω, CL1 = CL2 = 15 pF (see Figure 6) 3 11 25 ns RL = 60 Ω, CL1 = CL2 = 15 pF (see Figure 6)

7 23 35 ns RL = 27 Ω (see Figure 7) 7 23 35 ns RL = 27 Ω (see Figure 7) –1.4 ±8 ns RL = 27 Ω (see Figure 7)

42 90 ns RL = 110 Ω (see Figure 9) 42 90 ns RL = 110 Ω (see Figure 8) 35 80 ns RL = 110 Ω (see Figure 9) 35 80 ns RL = 110 Ω (see Figure 8) 650 900 ns RL = 110 Ω (see Figure 9) 650 900 ns RL = 110 Ω (see Figure 8)

25 62 90 ns VID = 0 V to 3.0 V, CL = 15 pF (see Figure 10) 25 62 90 ns VID = 0 V to 3.0 V, CL = 15 pF (see Figure 10) 6 ±10 ns VID = 0 V to 3.0 V, CL = 15 pF (see Figure 10)

25 50 ns CL = 15 pF (see Figure 11) 25 50 ns CL = 15 pF (see Figure 11) 25 45 ns CL = 15 pF (see Figure 11) 25 45 ns CL = 15 pF (see Figure 11) 720 1400 ns CL = 15 pF (see Figure 11) 720 1400 ns CL = 15 pF (see Figure 11) 80 190 300 ns

Rev. C | Page 4 of 16

ADM3485E

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ABSOLUTE MAXIMUM RATINGS

TA = 25°C, unless otherwise noted.

Table 3.

Parameter Values

VCC to GND –0.3 V to +6 V Digital Input/Output Voltage (DE, RE, DI) Receiver Output Voltage (RO) –0.3 V to (VCC + 0.3 V) Driver Output (A, B)/

Receiver Input (A, B) Voltage −8 V to +13 V Driver Output Current ±250 mA Power Dissipation (8-Lead SOIC_N) 650 mW Operating Temperature Range –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 ESD Rating

Human Body Model (A, B) ±15 kV

Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

–0.3 V to +6 V

THERMAL RESISTANCE

θJA is specified for the worst-case conditions, that is, a device soldered in a circuit board for surface-mount packages.

Table 4. Thermal Resistance

Package Type θ

8-Lead SOIC_N 158 °C/W

JA

Unit

ESD CAUTION

Rev. C | Page 5 of 16

ADM3485E

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PIN CONFIGURATION AND PIN FUNCTION DESCRIPTIONS

RO

1

ADM3485E

RE

2

TOP VIEW

DE

3

(Not to Scale)

4

DI

Figure 2. SOIC_N Pin Configuration (R-8)

Table 5. Pin Function Descriptions

Mnemonic

Number

Description

RO 1 Receiver Output. When enabled, if A > B by 200 mV, then RO = high. If A < B by 200 mV, then RO = low. RE

2

Receiver Output Enable. With RE

low, the receiver output (RO) is enabled. With RE high, the output goes into a

high impedance state. If RE is high and DE is low, the ADM3485E enters a shutdown state.

DE 3

Driver Output Enable. A high level enables the driver differen impedance state.

DI 4

Driver Input. When the driver is enabled, a logic low on DI forces A low and B high, while a logic high on DI

orces A high and B low.

f GND 5 Ground Connection, 0 V. A 6 Noninverting Receiver Input A/Driver Output A. B 7 Inverting Receiver Input B/Driver Output B. V

CC

8 Power Supply, 3.3 V ± 0.3 V.

V

8

CC

B

7

A

6

5

GND

03338-002

tial outputs A and B. A low level places it in a high

Rev. C | Page 6 of 16

ADM3485E

V

2

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TEST CIRCUITS AND SWITCHING CHARACTERISTICS

A

/2

R

V

B

L

OD

RL/2

V

Figure 3. Driver Differential Output Voltage and

Co

mmon-Mode Output Voltage

375

D

V

CC

R

V

L

OD

375

Figure 4. Driver Differential Output Voltage with

V

arying Common-Mode Voltage

R

ID

0

V

OL

Figure 5. Receiver Output Voltag

I

OL (+)

e High and Output Voltage Low

OC

03338-037

VCM = –7V TO +12V

V

OH

S1

D

GENERATOR

1

PPR = 250kHz, 50% DUT Y CYCLE,

2

CL INCLUDES PROBE AND STRAY CAPACITANCE.

03338-038

OUT

I

OH (–)

03338-039

OUT

1

50

V

CC

+ V

V

OH

=

V

OM

t

 6.0ns, ZO = 50.

R

IN

A

B

1.5V 1.5V

t

PLH

V

OM

t

PHL

V

OM

Figure 7. Driver Propagation Delays

OM

RL = 27

OUT

2

C

= 15pF

L

OL

 1.5V

2

3V

0V

t

PHL

V

OM

V

OM

OH

V

OL

t

PLH

V

OH

V

OL

03338-041

C

L

RL =

D

GENERATOR

1

PPR = 250kHz, 50% DUTY CYCLE,

2

CL INCLUDES PROBE AND STRAY CAPACITANCE.

IN

OUT

1

50

V

CC

+1.5V +1.5V

t

DD

t

TD

t

 6.0ns, ZO = 50.

R

90%90%

50%50%

10%10%

CL = 15pF

t

DD

t

TD

60

+3V

0V

 +2V

 –2V

2

OUT

03338-040

Figure 6. Driver Differential Output Delay and Transition Times

OM

D

t

PHZ

S1

C

= 50pF

L

+ V

V

OH

V

=

OM

t

 6.0ns, ZO = 50.

R

1.5V1.5V

2

0V OR 3V

OUT

1

50

IN

t

PZH

V

GENERATOR

1

PPR = 250kHz, 50% DUTY CYCLE , CL INCLUDES PRO BE AND STRAY CAPACI TANCE.

Figure 8. Driver Enable and Disable Times (t

OL

0.25V

 1.5V

PZH

, t

OUT

RL = 110

3V

0V

V

OH

0V

, t

PSH

PHZ

03338-042

)

Rev. C | Page 7 of 16

ADM3485E

V

2

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CC

0V OR 3V

OUT

1

50

IN

1.5V 1.5V

V

OM

GENERATOR

1

PPR = 250kHz, 50% DUT Y CYCLE,

2

CL INCLUDES PROBE AND STRAY CAPACIT ANCE.

S1

D

2

C

= 50pF

L

t

 6.0ns, ZO = 50.

R

t

PSL

t

Figure 9. Driver Enable and Disable Times (t

+1.5V

–1.5V

GENERATOR

PLZ

0.25V

RL = 110

, t

PZL

S3

OUT

GENERATOR

1

PPR = 250kHz, 50% DUTY CYCLE, CL INCLUDES PROBE AND STRAY CAPACITANCE.

3V

0V

V

CC

V

OL

PSL

03338-043

, t

)

PLZ

V

R

ID

1

50

1k

2

C

L

OUT

1

1.5V

0V

IN

t

RPLH

Figure 10. Receiver Propagation Delays

S1

S2

50

V

ID

t

R

1.5V1.5V

OM

CC

OUT

R

C

VOM =

 6.0ns, ZO = 50.

t

RPHL

V

OM

= 15pF

L

V

CC

2

3V

0V

V

CC

0V

2

03338-044

1

OUT

IN

+0.25V

PPR = 250kHz, 50% DUTY CYCLE,

2

CL INCLUDES PROBE AND STRAY CAPACIT ANCE.

+3V

+1.5V

0V

V

0V

+3V

0V

V

0V

OH

+1.5V

t

RPZH

t

RPSH

t

+1.5V

RPHZ

t

R

S1 OPEN S2 CLOSED S3 = +1.5V

 6.0ns, ZO = 50.

IN

OUT

IN

OUT

+0.25V

+1.5V

t

RPLZ

t t

RPZL

RPSL

+1.5V

+3V

0V

V

+3V

0V

V

CC

OL

CC

OL

S1 CLOSED S2 OPEN S3 = –1.5V

03338-045

Figure 11. Receiver Enable and Disable Times

Rev. C | Page 8 of 16

ADM3485E

–

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TYPICAL PERFORMANCE CHARACTERISTICS

25

20

0.8

0.7

0.6

IRO = 2.5mA

15

10

OUTPUT CURRENT ( mA)

5

0

03

0.5 1.0 1. 5 2 .0 2.5 3. 0

OUTPUT LOW VOLTAGE (V)

Figure 12. Output Current vs. R

18

–16

–14

–12

–10

–8

–6

OUTPUT CURRENT ( mA)

–4

–2

0

03

0.5 1.0 1. 5 2 .0 2.5 3. 0

OUTPUT HIGH VOLT AGE (V)

Figure 13. Output Current vs. R

3.30

3.25

3.20

3.15

3.10

OUTPUT HIGH VOLT AGE (V)

3.05

3.00 –50 –25 0 25 50 75

eceiver Output Low Voltage

eceiver Output High Voltage

IRO = –1.5mA

TEMPERATURE ( °C)

.5

03338-051

.5

03338-052

03338-053

Figure 14. Receiver Output High Voltage vs. Temperature

0.5

0.4

0.3

0.2

OUTPUT LOW VOLTAGE (V)

0.1

0

–40 10 60 85

Figure 15. Receiver Output Low Voltage vs. Temperature

100

90

80

70

60

50

40

30

OUTPUT CURRENT ( mA)

20

10

0

03.5

0.5 1.0 1. 5 2 .0 2.5 3. 0

Figure 16. Driver Output Current vs. Differential Output Voltage

2.6

2.5

2.4

2.3

2.2

2.1

2.0

1.9

1.8

DIFFERENT IAL OUTPUT VOLT AGE (V)

1.7

1.6 –50

–25 0 25 50 75

Figure 17. Driver Differential Output Voltage vs. Temperature

TEMPERATURE (°C)

DIFFERENT IAL OUT PUT VOL TAGE (V)

TEMPERATURE (° C)

RL = 54

03338-054

03338-055

03338-056

Rev. C | Page 9 of 16

ADM3485E

CH1C

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120

100

80

60

40

OUTPUT CURRENT (mA)

20

0

024681012

OUTPUT LOW VOLTAGE (V)

Figure 18. Output Current vs. Driv

120

100

80

er Output Low Voltage

03338-057

0.9

0.8

0.7

0.6

0.5

0.4

0.3

SHUTDOWN CURRENT (µA)

0.2

0.1

0 –50

–25 0 25 50 75

TEMPERATURE (° C)

03338-060

Figure 21. Shutdown Current vs. Temperature

DI

3

60

40

OUTPUT CURRENT (mA)

20

0

–7–6–5–4–3–2–101234

OUTPUT HIG H VOLTAG E (V)

Figure 19. Output Current vs. Driv

1.2

1.1

1.0

0.9

0.8

0.7

SUPPLY CURRENT (mA)

0.6

0.5 –40

–10 20 50 80

TEMPERATURE (° C)

er Output High Voltage

Figure 20. Supply Current vs. Temperature

03338-058

03338-059

A

B

H2

CH1 1.0V  CH2 1.0V  IT 400ps/pt CH3 2.0V  M20ns 1. 25GS/s

Figure 22. Driver Propagation Delay

VA– V

B

M1

RO

3

CH3 2.0V 4ns/ pt

MATH1 2.01V 200ns

M200ns 250MS/ s A CH2 1.24V



Figure 23. Receiver Propagation Delay,

en by External RS-485 Device

Driv

A CH3 1.44V

03338-061

03338-062

Rev. C | Page 10 of 16

ADM3485E

3

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STANDARDS AND TESTING

Tabl e 6 compares RS-422 and RS-485 interface standards, and Tabl e 7 and Ta b le 8 show transmitting and receiving truth tables.

Table 6.

Specification RS-422 RS-485

Transmission Type Differential Differential Maximum Data Rate 10 Mbps 10 Mbps Maximum Cable Length 4000 ft 4000 ft Minimum Driver Output Voltage ±2 V ±1.5 V Driver Load Impedance 100 Ω 54 Ω Receiver Input Resistance 4 kΩ min 12 kΩ min Receiver Input Sensitivity ±200 mV ±200 mV Receiver Input Voltage Range −7 V to +7 V −7 V to +12 V Number of Drivers/Receivers per Line 1/10 32/32

Table 7. Transmitting Truth Table

Transmitting Inputs Transmitting Outputs

RE

1

X

1

X 0 0 X 1 0 X

1

X = don't care.

2

High-Z = high impedance.

DE DI B A

1 1 0 1 1 0 1 0

1

High-Z High-Z

2

High-Z High-Z

2

Table 8. Receiving Truth Table

Receiving Inputs Receiving Outputs

RE

0 X 0 X 0 X 1 X

1

X = don't care.

2

High-Z = high impedance.

DE A – B RO

1

> +0.2 V 1 < –0.2 V 0 Inputs open 1

1

X

High-Z

2

influenced by humidity, temperature, barometric pressure, distance, and rate of closure of the discharge gun. The contact discharge method, while less realistic, is more repeatable and is gaining acceptance and preference over the air-gap method.

Although very little energy is contained within an ESD pulse, t

he extremely fast rise time, coupled with high voltages, can cause failures in unprotected semiconductors. Catastrophic destruction can occur immediately as a result of arcing or heating. Even if catastrophic failure does not occur immediately, the device can suffer from parametric degradation, which can result in degraded performance. The cumulative effects of continuous exposure can eventually lead to complete failure.

I/O lines are particularly vulnerable to ESD damage. Simply tou

ching or plugging in an I/O cable can result in a static discharge that can damage or completely destroy the interface product connected to the I/O port. It is extremely important, therefore, to have high levels of ESD protection on the I/O lines.

The ESD discharge could induce latch-up in the device under

st, so it is important that ESD testing on the I/O pins be

te carried out while device power is applied. This type of testing is more representative of a real-world I/O discharge, where the equipment is operating normally when the discharge occurs.

Table 9. ESD Test Results

ESD Test Method I/O Pins

Human Body Model ±15 kV

100%

90%

PEAK

I

ESD TESTING

Two coupling me t hods are us e d for ESD testi n g , cont act discharge and air-gap discharge. Contact discharge calls for a direct connection to the unit being tested. Air-gap discharge uses a higher test voltage but does not make direct contact with the unit under test. With air-gap discharge, the discharge gun is moved toward the unit under test, developing an arc across the air gap, hence the term air-gap discharge. This method is

Rev. C | Page 11 of 16

6.8%

10%

t

RL

Figure 24. Human Body Model Current Waveform

t

DL

TIME

t

03338-023

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APPLICATIONS INFORMATION

DIFFERENTIAL DATA TRANSMISSION

Differential data transmission is used to reliably transmit data at high rates over long distances and through noisy environments. Differential transmission nullifies the effects of ground shifts and noise signals that appear as common-mode voltages on the line.

Two main standards that specify the electrical characteristics of

nsceivers used in differential data transmission are approved

tra by the Electronics Industries Association (EIA). The RS-422 standard specifies data rates up to 10 Mbps and line lengths up to 4000 feet. A single driver can drive a transmission line with up to 10 receivers. The RS-485 standard was defined to cater to true multipoint communications. This standard meets or exceeds all the requirements of RS-422 but also allows multiple drivers and receivers to be connected to a single bus. An extended common-mode range of −7 V to +12 V is defined.

The most significant difference between RS-422 and RS-485 is

e fact that under the RS-485 standard the drivers may be

th disabled, thereby allowing more than one to be connected to a single line. Only one driver should be enabled at a time, but the RS-485 standard contains additional specifications to guarantee device safety in the event of line contention.

CABLE AND DATA RATE

The transmission line of choice for RS-485 communications is a twisted pair. Twisted-pair cable tends to cancel common-mode noise and also causes cancellation of the magnetic fields generated by the current flowing through each wire, thereby reducing the effective inductance of the pair.

The ADM3485E is designed for bidirectional data communi-

ations on multipoint transmission lines. A typical application

c showing a multipoint transmission network is illustrated in Figure 25. Only one driver can transmit at a particular time, b

ut multiple receivers may be enabled simultaneously.

As with any transmission line, it is important that reflections are minimize

d. This can be achieved by terminating the extreme ends of the line using resistors equal to the characteristic impedance of the line. Stub lengths off the main line must also be kept as short as possible. A properly terminated transmission line appears purely resistive to the driver.

RECEIVER OPEN-CIRCUIT FAIL-SAFE

The receiver input includes a fail-safe feature that guarantees a logic high on the receiver when the inputs are open circuit or floating.

Table 10. RS-422 and RS-485 Interface Standards

Specification RS-422 RS-485

Transmission Type Differential Differential Maximum Cable Length 4000 ft 4000 ft Minimum Driver Output Voltage ±2 V ±1.5 V Driver Load Impedance 100 Ω 54 Ω Receiver Input Resistance 4 kΩ min 12 kΩ min Receiver Input Sensitivity ±200 mV ±200 mV Receiver Input Voltage Range

−7 V to +7 V −7 V to +12 V

ADM3485E

A

B

R

RO

RE

DE

D

DI

03338-027

RO

RE

DE

DI

ADM3485E

R

D

A

B

ADM3485E

R

RO

A

B

D

DE

RE DI

MAXIMUM NUMBER OF TRANSCEIVERS ON BUS: 50

Figure 25. Multipoint Transmission Network

RO

A

R

RE

B

ADM3485E

D

DI

DE

Rev. C | Page 12 of 16

ADM3485E

www.BDTIC.com/ADI

OUTLINE DIMENSIONS

5.00 (0.1968)

4.80 (0.1890)

4.00 (0.1574)

3.80 (0.1497)

0.25 (0.0098)

0.10 (0.0040)

COPLANARIT Y

0.10

CONTROLL ING DIM ENSIONS ARE IN MILL IMETERS; INCH DIME NSIONS (IN PARENTHESES) ARE ROUNDE D-OFF M ILLIMETER EQUIVALENTS FOR REFERENCE ON LY AND ARE NOT APPRO PRIATE FOR US E IN DESIG N.

85

1

1.27 (0.0500)

SEATING

PLANE

COMPLI ANT TO JEDEC STANDARDS MS-012-A A

Figure 26. 8-Lead Standard Small Outline Package [SOIC_N]

BSC

6.20 (0.2440)

5.80 (0.2284)

4

1.75 (0.0688)

1.35 (0.0532)

0.51 (0.0201)

0.31 (0.0122)

Nar

row Body

8° 0°

0.25 (0.0098)

0.17 (0.0067)

0.50 (0.0196)

0.25 (0.0099)

1.27 (0.0500)

0.40 (0.0157)

45°

060506-A

(R-8)

Dimensions shown in millimeters and (inches)

ORDERING GUIDE

Model Temperature Range Package Description Package Option

ADM3485EAR –40°C to +85°C 8-Lead Standard Small Outline Package [SOIC_N] R-8 ADM3485EAR-REEL7 –40°C to +85°C 8-Lead Standard Small Outline Package [SOIC_N] R-8 ADM3485EAR-REEL –40°C to +85°C 8-Lead Standard Small Outline Package [SOIC_N] R-8 ADM3485EARZ ADM3485EARZ-REEL7 ADM3485EARZ-REEL

1

Z = Pb-free part.

1

–40°C to +85°C 8-Lead Standard Small Outline Package [SOIC_N] R-8 –40°C to +85°C 8-Lead Standard Small Outline Package [SOIC_N] R-8 –40°C to +85°C 8-Lead Standard Small Outline Package [SOIC_N] R-8

Rev. C | Page 13 of 16

ADM3485E

www.BDTIC.com/ADI

NOTES

Rev. C | Page 14 of 16

ADM3485E

www.BDTIC.com/ADI

NOTES

Rev. C | Page 15 of 16

ADM3485E

www.BDTIC.com/ADI

NOTES

T

Rev. C | Page 16 of 16

TTT

ANALOG DEVICES ADM3485E Service Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

FEATURES

APPLICATIONS

FUNCTIONAL BLOCK DIAGRAM

GENERAL DESCRIPTION

TABLE OF CONTENTS

REVISION HISTORY

SPECIFICATIONS

TIMING SPECIFICATIONS

ABSOLUTE MAXIMUM RATINGS

THERMAL RESISTANCE

ESD CAUTION

PIN CONFIGURATION AND PIN FUNCTION DESCRIPTIONS

TEST CIRCUITS AND SWITCHING CHARACTERISTICS

TYPICAL PERFORMANCE CHARACTERISTICS

STANDARDS AND TESTING

ESD TESTING

APPLICATIONS INFORMATION

DIFFERENTIAL DATA TRANSMISSION

CABLE AND DATA RATE

RECEIVER OPEN-CIRCUIT FAIL-SAFE

OUTLINE DIMENSIONS

ORDERING GUIDE