Datasheet MAX1481, MAX1484, MAX1485, MAX1486 Datasheet (MAXIM)

For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 408-737-7600 ext. 3468.

_______________General Description

The MAX1481/MAX1484/MAX1485/MAX1486 provide software-selectable, half-/full-duplex, low-power, slewrate-limited, and high-speed (12Mbps) RS-485/RS-422 operation in a 10-pin µMAX® package—the smallest 10-pin package available.

The software-selectable, half-/full-duplex MAX1485/ MAX1486 make obsolete the normally larger and more expensive solutions required for selectable half-/fullduplex RS-485/RS-422 operation: 1) a 14-pin, fullduplex transceiver configured via jumpers between receiver and transmitter lines, or 2) two 8-pin, halfduplex transceivers, which require an additional inverter logic gate for software selectability.

The MAX1481/MAX1484 are functionally equivalent to the industry-standard MAX491 and 75180, and are designed for space-constrained, full-duplex RS-422 applications.

All parts contain one driver and one receiver and feature a 1/8-unit-load receiver input impedance, allowing up to 256 transceivers on the bus. The MAX1481/ MAX1485 feature reduced-slew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free data transmission up to 250kbps. The MAX1484/MAX1486 driver slew rates are not limited, allowing them to transmit up to 12Mbps.

The MAX1481/MAX1484/MAX1485/MAX1486 draw only 300µA of supply current. The MAX1481 has a low-power shutdown mode that reduces supply current to only

0.1µA. All devices operate from a single 5V supply. Drivers are output short-circuit current limited and are

protected against excessive power dissipation by thermal-shutdown circuitry that places the driver outputs into a high-impedance state. The receiver input has a failsafe feature that guarantees a logic-high output if the input is open circuit.

____________________________Features

♦ 10-Pin µMAX Package: Smallest 10-Pin Package ♦ Software-Selectable Half-/Full-Duplex Operation

(MAX1485/MAX1486)

♦ 0.1µA Low-Current Shutdown Mode (MAX1481) ♦ Slew-Rate Limiting Allows Error-Free Data

Transmission (MAX1481/MAX1485)

♦ 12Mbps High-Speed Operation

(MAX1484/MAX1486)

♦ Allow up to 256 Transceivers on the Bus

________________________Applications

Low-Power RS-422/RS-485 Communications Level Translators Hand-Held Equipment Battery-Powered Equipment Transceiver for EMI-Sensitive Applications Industrial-Control Local Area Networks

MAX1481/MAX1484/MAX1485/MAX1486

Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited,

12Mbps, RS-485/RS-422 Transceivers in µMAX Package

________________________________________________________________

Maxim Integrated Products

1

19-1312; Rev 1; 3/06

PART

MAX1481CUB

MAX1481EUB MAX1484CUB

0°C to +70°C

-40°C to +85°C

0°C to +70°C

TEMP RANGE PIN-PACKAGE

10 µMAX 10 µMAX 10 µMAX

______________Ordering Information

______________________________________________________________Selection Table

Half/Full

Duplex

Data Rate

(Mbps)

MAX1481 Full 0.250 MAX1484 Full 12

Part

MAX1485 Selectable 0.250 MAX1486 Selectable 12

Slew-

Rate

Limited

Yes

No

Yes

No

Low-

Power

Shutdown

Driver

Enable

Yes Yes

No Yes No Yes No Yes

Quiescent

Current

(µA)

300 300 300 300

Transceivers

on Bus

256 256 256 256

Pin-

Package

10 µMAX 10 µMAX 10 µMAX 10 µMAX

MAX1484EUB -40°C to +85°C 10 µMAX

Receiver

Enable

Yes Yes

No No

MAX1485CUB MAX1485EUB MAX1486CUB

0°C to +70°C

-40°C to +85°C

0°C to +70°C 10 µMAX

10 µMAX 10 µMAX

MAX1486EUB -40°C to +85°C 10 µMAX

________________________________________________________________ Maxim Integrated Products 1

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

µMAX is a registered trademark of Maxim Integrated Products, Inc.

MAX1481/MAX1484/MAX1485/MAX1486

Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in µMAX Package

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VCC= +5V ±5%, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at VCC= +5V and TA= +25°C.) (Note 1)

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

Supply Voltage (VCC) ............................................................+7V

Control Input Voltage (

RE, DE, H/F)...........-0.3V to (VCC+ 0.3V)

Driver Input Voltage (DI).............................-0.3V to (V

CC

+ 0.3V)

Driver Output Voltage (A, B, Y, Z)..........................-8V to +12.5V

Receiver Input Voltage, Half Duplex (Y, Z) ............-8V to +12.5V

Receiver Input Voltage, Full Duplex (A, B).............-8V to +12.5V

Receiver Output Voltage (RO)....................-0.3V to (V

CC

+ 0.3V)

Continuous Power Dissipation

10-Pin µMAX (derate 5.6mW/°C above +70°C)............444mW

Operating Temperature Ranges

MAX148_C_ _ ......................................................0°C to +70°C

MAX148_E_ _....................................................-40°C to +85°C

Storage Temperature Range.............................-65°C to +160°C

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

R = 50Ω (RS-422), Figure 5

No load, Figure 5

-7V ≤ V

OUT

≤ 12V

DE = GND

DE, DI, RE, H/F

R = 50Ω or 27Ω, Figure 5

DE = GND, VCC= GND or 5.25V

DE, DI, RE, H/F

CONDITIONS

mA35 250I

OSD

Driver Output Short-Circuit Current (Note 3)

µA

-10

I

O

10

Output Leakage (Y and Z) (MAX1481/MAX1484 Only)

mA

0.125

I

IN2

Input Current (Y and Z for Half Duplex, A and B for Full Duplex)

µA±2I

IN1

Input Current

2.0

V

OD1

Differential Driver Output

5

V0.8V

IL1

Input Low Voltage

V2.0V

IH1

Input High Voltage

V0.2∆V

OC

Change in Magnitude of Common-Mode Voltage (Note 2)

V0.2∆V

OD

Change in Magnitude of Differential Output Voltage (Note 2)

V3V

OC

Driver Common-Mode Output Voltage

UNITSMIN TYP MAXSYMBOLPARAMETER

DE = GND

-100

I

O

µA

125

Output Leakage (Y and Z) (MAX1485/MAX1486 Only)

V

OD2

R = 27Ω (RS-485), Figure 5

V

1.5 5

VIN= 12V VIN= -7V VIN= 12V VIN= -7V VIN= 12V VIN= -7V

-0.1

DRIVER

Driver Input to Output

MAX1481/MAX1484/MAX1485/MAX1486

Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited,

12Mbps, RS-485/RS-422 Transceivers in µMAX Package

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(V

CC

= +5V ±5%, TA = T

MIN

to T

MAX

, unless otherwise noted. Typical values are at V

CC

= +5V and TA = +25°C.) (Note 1)

SWITCHING CHARACTERISTICS (MAX1484/MAX1486)

(V

CC

= 5V ±5%, TA = T

MIN

to T

MAX

, unless otherwise noted. Typical values are at V

CC

= +5V and TA = +25°C.)

-7V ≤ VCM≤ 12V

IO= 4mA, VID= -200mV

IO= -4mA, VID= 200mV

0.4V ≤ VO≤ 2.4V

CONDITIONS

kΩ96R

IN

Receiver Input Resistance

µA±1I

OZR

Three-State Output Current at Receiver

mV70∆V

TH

Receiver Input Hysteresis

mV-200 200V

TH

Receiver Differential Threshold Voltage

V0.4V

OL

Receiver Output Low Voltage

V3.5V

OH

Receiver Output High Voltage

UNITSMIN TYP MAXSYMBOLPARAMETER

0V ≤ VRO≤ V

CC

RE = GND, DE = V

CC

mA±95I

OSR

Receiver Output Short-Circuit Current

µA300 600I

CC

No-Load Supply Current

DE = GND, RE = V

CC

µA0.1 10I

SHDN

Supply Current in Shutdown Mode (MAX1481 Only)

R

DIFF

= 54Ω, CL1= CL2= 100pF,

Figures 7 and 9

R

DIFF

= 54Ω, CL1= CL2= 100pF,

Figures 7 and 9

CONDITIONS

ns5 10t

DSKEW

Driver Output Skew

| t

DPLH

- t

DPHL

|

30 60t

DPLH

ns

30 60t

DPHL

Driver Input to Output

UNITSMIN TYP MAXSYMBOLPARAMETER

CL= 15pF, S1 closed, Figures 8 and 10

CL= 100pF, S2 closed, Figures 8 and 10

CL= 100pF, S1 closed, Figures 8 and 10

ns40 70t

DLZ

Driver Disable Time from Low

ns40 70t

DZH

Driver Enable to Output High

ns40 70t

DZL

Driver Enable to Output Low

Mbps12f

MAX

Maximum Data Rate

CL= 15pF, S2 closed, Figures 8 and 10

CL= 100pF, S2 closed, Figures 6 and 12

CL= 100pF, S1 closed, Figures 6 and 12

ns20 50t

RZH

Receiver Enable to Output High

ns20 50t

RZL

Receiver Enable to Output Low

ns40 70t

DHZ

Driver Disable Time from High

CL= 100pF, S2 closed, Figures 6 and 12

CL= 100pF, S1 closed, Figures 6 and 12

ns20 50t

RHZ

Receiver Disable Time from High

ns20 50t

RLZ

Receiver Disable Time from Low

Figures 11 and 13 ns5t

RSKD

| t

RPLH

- t

RPHL

| Differential

Receiver Skew

Figures 11 and 13 ns90 150

t

RPLH

,

t

RPHL

Receiver Input to Output

R

DIFF

= 54Ω, CL1= CL2= 100pF,

Figures 7 and 9

ns5 15 35tDR, t

DF

Driver Rise or Fall Time

RECEIVER

SUPPLY CURRENT

MAX1481/MAX1484/MAX1485/MAX1486

Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in µMAX Package

4 _______________________________________________________________________________________

SWITCHING CHARACTERISTICS (MAX1481/MAX1485) (continued)

(VCC= 5V ±5%, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at VCC= +5V and TA= +25°C.)

Note 1: All currents into the device are positive; all currents out of the device are negative. All voltages are referenced to device

ground unless otherwise noted.

Note 2: ∆V

OD

and ∆VOCare the changes in VODand VOC, respectively, when the DI input changes state.

Note 3: Maximum current level applies to peak current just prior to foldback-current limiting; minimum current level applies during

current limiting.

Note 4: Shutdown is enabled by bringing RE high and DE low. If the enable inputs are in this state for less than 50ns, the MAX1481

is guaranteed not to enter shutdown. If the enable inputs are in this state for at least 600ns, the MAX1481 is guaranteed to have entered shutdown.

CL= 15pF, S1 closed, Figures 8 and 10

CL= 100pF, S2 closed, Figures 8 and 10

R

DIFF

= 54Ω, CL1= CL2= 100pF,

Figures 7 and 9

CL= 100pF, S1 closed, Figures 8 and 10

R

DIFF

= 54Ω, CL1= CL2= 100pF,

Figures 7 and 9

ns200t

DLZ

CL= 100pF, S2 closed, Figures 6 and 12

Driver Disable Time from Low

CL= 100pF, S1 closed, Figures 6 and 12

R

DIFF

= 54Ω, CL1= CL2= 100pF,

Figures 7 and 9

ns3000t

DZH

Driver Enable to Output High

ns3000

CONDITIONS

t

DZL

Driver Enable to Output Low

kbps250f

MAX

Maximum Data Rate

CL= 15pF, S2 closed, Figures 8 and 10

CL= 100pF, S2 closed, Figures 6 and 12

CL= 100pF, S1 closed, Figures 6 and 12

ns10 200t

DSKEW

Driver Output Skew

| t

DPLH

- t

DPHL

|

Figures 11 and 13

ns

ns20 50t

RZH

Receiver Enable to Output High

ns20 50t

RZL

Receiver Enable to Output Low

ns200t

DHZ

Driver Disable Time from High

ns

ns20 50t

RHZ

Receiver Disable Time from High

90 150

t

RPLH

,

t

RPHL

Receiver Input to Output

250 1000tDR, t

DF

Driver Rise or Fall Time

ns20 50t

RLZ

Receiver Disable Time from Low

Figures 11 and 13 ns15t

RSKD

| t

RPLH

- t

RPHL

| Differential

Receiver Skew

600 1000t

DPLH

ns

600 1000t

DPHL

Driver Input to Output

UNITSMIN TYP MAXSYMBOLPARAMETER

MAX1481 only (Note 4) ns50 200 600t

SHDN

Time to Shutdown

MAX1481 only, CL= 15pF, S2 closed, Figures 8 and 10

ns3000t

DZH(SHDN)

Driver Enable from Shutdown to Output High

MAX1481 only, CL= 15pF, S1 closed, Figures 8 and 10

ns3000t

DZL(SHDN)

Driver Enable from Shutdown to Output Low

MAX1481 only, CL= 100pF, S1 closed, Figures 6 and 12

ns1000t

RZL(SHDN)

Receiver Enable from Shutdown to Output Low

MAX1481 only, CL= 100pF, S2 closed, Figures 6 and 12

ns500t

RZH(SHDN)

Receiver Enable from Shutdown to Output High

MAX1481/MAX1484/MAX1485/MAX1486

Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited,

12Mbps, RS-485/RS-422 Transceivers in µMAX Package

_______________________________________________________________________________________

5

220

260

240

300

280

340

320

360

-60 -20 0-40 20 40 60 80 100

NO-LOAD SUPPLY CURRENT

vs. TEMPERATURE

MAX1481/4/5/6-01

TEMPERATURE (°C)

SUPPLY CURRENT (µA)

MAX1481/MAX1485

MAX1484/MAX1486

0

10

30

20

50

40

60

0

1

2 3 4 5

OUTPUT CURRENT vs.

RECEIVER OUTPUT LOW VOLTAGE

MAX1481/4/5/6-02

OUTPUT LOW VOLTAGE (V)

OUTPUT CURRENT (mA)

0

5

15

10

25

20

30

0

1

2 3 4 5

OUTPUT CURRENT vs.

RECEIVER OUTPUT HIGH VOLTAGE

MAX1481/4/5/6-03

OUTPUT LOW VOLTAGE (V)

OUTPUT CURRENT (mA)

94

98

106

102

110

114

-60 -20 0-40 20 40 60 80 100

SHUTDOWN CURRENT

vs. TEMPERATURE

MAX1481/4/5/6-04

TEMPERATURE (°C)

SHUTDOWN CURRENT (nA)

75

80

90

85

100

95

105

-60 -20 0-40 20 40 60 80 100

MAX1481/MAX1485 RECEIVER

PROPAGATION DELAY vs. TEMPERATURE

MAX1481/4/5/6-07

TEMPERATURE (°C)

PROPAGATION DELAY (ns)

C

LOAD

= 15pF

0.10

0.20

0.15

0.35

0.30

0.25

0.45

0.40

0.50

-60 -20 0-40 20 40 60 80 100

RECEIVER OUTPUT LOW VOLTAGE

vs. TEMPERATURE

MAX1481/4/5/6-05

TEMPERATURE (°C)

OUTPUT LOW VOLTAGE (V)

IRO = 8mA

3.8

4.0

3.9

4.2

4.1

4.4

4.3

4.5

-60 -20 0-40 20 40 60 80 100

RECEIVER OUTPUT HIGH VOLTAGE

vs. TEMPERATURE

MAX1481/4/5/6-06

TEMPERATURE (°C)

OUTPUT VOLTAGE (V)

IRO = 8mA

86

87

90 89

88

93 92 91

94

-60 -20 0-40 20 40 60 80 100

MAX1484/MAX1486 RECEIVER

PROPAGATION DELAY vs. TEMPERATURE

MAX1481/4/5/6-08

TEMPERATURE (°C)

PROPAGATION DELAY (ns)

C

LOAD

= 15pF

540

580

560

620

600

660

640

680

-60 -20 0-40 20 40 60 80 100

MAX1481/MAX1485 DRIVER

PROPAGATION DELAY vs. TEMPERATURE

MAX1481/4/5/6-09

TEMPERATURE (°C)

PROPAGATION DELAY (ns)

R

DIFF

= 54Ω

C

L1 = CL2 = 100pF

__________________________________________Typical Operating Characteristics

(VCC= +5V, TA= +25°C, unless otherwise noted.)

MAX1481/MAX1484/MAX1485/MAX1486

Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in µMAX Package

6 _______________________________________________________________________________________

_________________________________Typical Operating Characteristics (continued)

(VCC= +5V, TA= +25°C, unless otherwise noted.)

18

26

22

30

34

38

-60 -20 0-40 20 40 60 80 100

MAX1484/MAX1486 DRIVER

PROPAGATION DELAY vs. TEMPERATURE

MAX1481/4/5/6-10

TEMPERATURE (°C)

PROPAGATION DELAY (ns)

R

DIFF

= 54Ω

C

L1 = CL2 = 100pF

0

60

40

20

80

120

100

140

0 42 6 8 10 12

OUTPUT CURRENT vs.

DRIVER OUTPUT LOW VOLTAGE

MAX1481/4/5/6-11

OUTPUT LOW VOLTAGE (V)

OUTPUT CURRENT (mA)

0

40

20

60

100

80

120

-8 -4 -2-6 0 2 4 6

OUTPUT CURRENT vs.

DRIVER OUTPUT HIGH VOLTAGE

MAX1481/4/5/6-12

OUTPUT HIGH VOLTAGE (V)

OUTPUT CURRENT (mA)

2.10

2.15

2.25

2.20

2.35

2.30

2.40

-60 -20 0-40 20 40 60 80 100

DRIVER DIFFERENTIAL OUTPUT

VOLTAGE vs. TEMPERATURE

MAX1481/4/5/6-13

TEMPERATURE (°C)

OUTPUT VOLTAGE (V)

R

DIFF

= 54Ω

VA - V

B

RO

(2V/div)

(5V/div)

1µs/div

MAX1481/MAX1485

RECEIVER PROPAGATION DELAY

MAX1481/4/5/6-16

100

0.01 0 2.5 3.0 3.5 4.0 4.50.5 1.0 1.5 2.0 5.0

DRIVER OUTPUT CURRENT

vs. DIFFERENTIAL OUTPUT VOLTAGE

0.1

MAX1481/4/5/6-14

DIFFERENTIAL OUTPUT VOLTAGE (V)

OUTPUT CURRENT (mA)

1

10

VA - V

B

RO

(2V/div)

(5V/div)

50ns/div

MAX1484/MAX1486

RECEIVER PROPAGATION DELAY

MAX1481/4/5/6-15

DI

V

Y

- V

Z

(5V/div)

(2V/div)

1µs/div

MAX1481/MAX1485

DRIVER PROPAGATION DELAY

MAX1481/4/5/6-17

DI

V

Y

- V

Z

5V/div

2V/div

50ns/div

MAX1484/MAX1486

DRIVER PROPAGATION DELAY

MAX1481/4/5/6-18

MAX1481/MAX1484/MAX1485/MAX1486

Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited,

12Mbps, RS-485/RS-422 Transceivers in µMAX Package

_______________________________________________________________________________________ 7

______________________________________________________________Pin Description

1 1

Receiver Output. When RE is low and if A - B ≥ 200mV, RO goes high; if A - B ≤

-200mV, RO goes low.

— 2

Half-/Full-Duplex Selector Input. Connect H/F to VCCfor half-duplex mode, and connect to GND for full-duplex mode.

2 —

Receiver Output Enable Input. Drive RE low to enable RO; RO is high impedance when RE is high. For MAX1481 only, drive RE high and DE low to enter the lowpower shutdown mode.

3 3

Driver Output Enable Input. Drive DE high to enable driver outputs. These outputs are high impedance when DE is low.

4 4

Driver Input. With DE high, a low on DI forces noninverting output low and inverting output high. Similarly, a high on DI forces noninverting output high and invert-

ing output low. 5 5 Ground 6 6 Inverting Receiver Input

— — Receiver Input Resistors*

7 7 Inverting Driver Output

— — Inverting Driver Output and Inverting Receiver Input

8 8 Noninverting Driver Output

— — Noninverting Driver Output and Noninverting Receiver Input

9 9 Noninverting Receiver Input

— — Receiver Input Resistors* 10 10 Positive Supply; +4.75V ≤ VCC≤ +5.25V

MAX1481/

MAX1484

1 RO

2

H/F

—

RE

3 DE

4 DI

5 GND

— B

6 B

— Z

7 Z

— Y

8 Y

— A

9 A

10 V

CC

MAX1485/MAX1486

H/F = 0

FUNCTIONNAME

H/F = 1

*

(MAX1485/MAX1486 only) In half-duplex mode, the driver outputs serve as receiver inputs. The full-duplex receiver inputs (A and B)

will still have a 1/8-unit load, but are not connected to the receiver.

OUTPUT

INPUTS

MAX1481/MAX1484/MAX1485/MAX1486

Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in µMAX Package

8 _______________________________________________________________________________________

RE

DE X 1 X 1 0 0 1 0

DI Z

1 0 0 1 X High-Z X

INPUTS

_____________________________________________________________Function Tables

TRANSMITTING

Y

1 0

High-Z

High-Z and Shutdown

OUTPUTS

MAX1481

MAX1484

MAX1485/MAX1486

RE

DE 0 X 0 X 1 1

1 0

High-Z and

Shutdown

OUTPUT

A-B RO

≥ 0.2V 1

≤ -0.2V 0

X High-Z X

INPUTS

RECEIVING

TRANSMITTING

RE

DE Y X 1 1 X 1 0 X 0 High-Z

OUTPUTS

DI Z

1 0 0 1 X High-Z

INPUTS

RE

DE 0 X 0 X 1 X

OUTPUT

A-B RO

≥ 0.2V 1

≤ -0.2V 0

X High-Z

INPUTS

RECEIVING

DE DI

TRANSMITTING

1 1 1 0 0 X

Z Y 0 1 1 0

High-Z High-Z

OUTPUTS

RECEIVING

H/F

DE RO 0 X 1 0 X 0 1 0 1

OUTPUT

A-B Y-Z

≥ 0.2V X

≤ -0.2V X

X ≥ 0.2V

INPUTS

1 0 0X ≤ -0.2V

X = Don’t care

Note: In shutdown mode, driver and receiver outputs are high impedance.

INPUTS

MAX1481/MAX1484/MAX1485/MAX1486

Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited,

12Mbps, RS-485/RS-422 Transceivers in µMAX Package

_______________________________________________________________________________________ 9

1 2 3 4 5

1

9 A

R

t

R

t

10

0.1µF

5

GND

6 B

Z

7

8

Y

RO

RE

DE

DI

2 3 4

10

9 8 7 6

V

CC

A Y ZDI

DE

RE

RO

MAX1481 MAX1484

µMAX

TOP VIEW

BGND

8

4

10

0.1µF

5

GND

3 2

DI DE

RE

RO

1

Y Z

B

A

7

6 9

V

CC

V

CC

Figure 1. MAX1481/MAX1484 Pin Configuration and Typical Full-Duplex Operating Circuit

1 2 3 4 5

1

9 A

R

t

R

t

10

0.1µF

V

CC

5

GND

6 B

Z

7

8

Y

RO

H/F

DE

DI

2 3 4

10

9 8 7 6

V

CC

A Y ZDI

DE

H/F

RO

MAX1485 MAX1486

µMAX

TOP VIEW

BGND

8

4

10

0.1µF

V

CC

5

GND

3 2

DI DE

H/F

RO

1

Y Z

B

A

7

6 9

V

CC

V

CC

Figure 2. MAX1485/MAX1486 Pin Configuration and Equivalent Typical Full-Duplex Operating Circuit

1 2 3 4 5

1

8

Y

R

t

10

0.1µF

5

GND

7 Z

A

9

6

B

RO

H/F

DE

DI

2 3 4

10

9 8 7 6

V

CC

A Y ZDI

DE

H/F

RO

MAX1485 MAX1486

µMAX

TOP VIEW

BGND

R

t

8

4

10

0.1µF

5

GND

3 2

DI DE

H/F

RO

1

Y Z

7 9

A

B

6

V

CC

V

CC

Figure 3. MAX1485/MAX1486 Pin Configuration and Equivalent Typical Half-Duplex Operating Circuit

MAX1481/MAX1484/MAX1485/MAX1486

Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in µMAX Package

10 ______________________________________________________________________________________

_______________Detailed Description

The MAX1481/MAX1484/MAX1485/MAX1486 highspeed transceivers for RS-485/RS-422 communication contain one driver and one receiver. The MAX1481/ MAX1485 feature reduced-slew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free data transmission up to 250kbps. The MAX1484/MAX1486 driver slew rates are not limited, making transmission speeds up to 12Mbps possible.

These transceivers are designed to operate on a +5V single supply and typically draw 300µA of supply current when unloaded or fully loaded with the drivers disabled. The MAX1481 has a shutdown mode in which supply current is typically reduced to 0.1µA.

Drivers are output short-circuit current limited and are protected against excessive power dissipation by thermal-shutdown circuitry that places the driver outputs into a high-impedance state.

All devices have a 1/8-unit-load receiver input impedance that allows up to 256 transceivers on the bus. The MAX1481/MAX1484 are designed for full-duplex communications. The H/F pin on the MAX1485/MAX1486 allows the user to select between half-duplex or fullduplex operation (Figure 4).

MAX1485/MAX1486

Half-/Full-Duplex Mode Operation

The MAX1484/MAX1485 can operate in full- or halfduplex mode. Drive the H/F pin low or connect it to GND for full-duplex operation, or drive it high for halfduplex operation. In full-duplex mode, the pin configuration of the driver and receiver is the same as a MAX1481 (Figure 1).

__________Applications Information

256 Transceivers on the Bus

The standard RS-485 receiver input impedance is 12kΩ (1-unit load), and the standard driver can drive up to 32-unit loads. The MAX1481/MAX1484/MAX1485/ MAX1486 transceivers have a 1/8-unit-load receiver input impedance (96kΩ), allowing up to 256 transceivers to be connected in parallel on one communication line. Connect any combination of these devices and/or other RS-485 transceivers totaling 32-unit loads or less.

Reduced EMI and Reflections

The MAX1481/MAX1485 are slew-rate limited, minimizing EMI and reducing reflections caused by improperly terminated cables. Figure 14 shows the driver output waveform and its Fourier analysis of a 20kHz signal transmitted by a MAX1484. High-frequency harmonic components with large amplitudes are evident. Figure 15 shows the same signal displayed for a MAX1481 transmitting under the same conditions. Figure 15’s high-frequency harmonic components are much lower in amplitude compared to Figure 14’s, significantly reducing potential EMI.

In general, a transmitter’s rise time relates directly to the length of an unterminated stub, which can be driven with only minor waveform reflections. The following equation expresses this relationship conservatively:

Length = t

RISE

/ (10 x 1.5ns/ft)

where t

RISE

is the transmitter’s rise time.

For example, the MAX1481’s rise time is typically 500ns, which results in excellent waveforms with a stub length up to 33 feet. A system may work well with longer unterminated stubs, even with severe reflections, if the waveform settles out before the UART samples them.

Figure 4. MAX1485/MAX1486 Functional Diagram

V

CC

MAX1485 MAX1486

DI

DE

RO

H/F

GND

Z

Y

B

A

MAX1481/MAX1484/MAX1485/MAX1486

Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited,

12Mbps, RS-485/RS-422 Transceivers in µMAX Package

______________________________________________________________________________________ 11

R

Y

Z

V

OD

V

OC

Figure 5. Driver DC Test Load

RECEIVER

OUTPUT

TEST POINT

1k

S1

S2

V

CC

C

L

Figure 6. Receiver Enable/Disable Timing Test Load

DI

DE

3V

Y

Z

C

L1

C

L2

R

DIFF

V

ID

Figure 7. Driver Timing Test Circuit

OUTPUT

UNDER TEST

500Ω

S1

S2

V

CC

C

L

Figure 8. Driver Enable/Disable Timing Test Load

DI

3V 0V

Z Y

V

O

0V

-V

O

V

O

1.5V t

DPLH

1/2 V

O

10%

t

R

90%

t

DPHL

1.5V 1/2 V

O

10%

t

F

V

DIFF

= VY - V

Z

V

DIFF

t

SKEW = | tPLH

- t

PHL

|

Figure 9. Driver Propagation Delays

OUTPUT NORMALLY LOW

OUTPUT NORMALLY HIGH

3V 0V

Y, Z V

OL

Y, Z

0V

1.5V 1.5V

V

OL

+0.5V

V

OH

-0.5V

2.3V

t

DZL(SHDN)

, t

DPL

t

DLZ

D

ZH(SHDN)

, D

ZH

D

HZ

DE

Figure 10. Driver Enable and Disable Times

MAX1481/MAX1484/MAX1485/MAX1486

Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in µMAX Package

12 ______________________________________________________________________________________

Low-Power Shutdown Mode

(MAX1481 only)

Low-power shutdown mode is initiated by bringing both RE high and DE low. In shutdown, the MAX1481 typically draws only 0.1µA of supply current.

RE and DE may be driven simultaneously; the parts are guaranteed not to enter shutdown if RE is high and DE is low for less than 50ns. If the inputs are in this state for at least 600ns, the parts are guaranteed to enter shutdown.

Enable times t_ZHand t_

Z

L

in the

Switching Character-

istics

tables assume the part was not in low-power shut-

down. Enable times t_

ZH

(SHDN)

and t_

ZL

(SHDN)

assume

the parts were shut down. It takes drivers and receivers

longer to become enabled from the low-power shutdown mode (t_

ZH

(SHDN)

, t_

Z

L(SHDN)

) than from the

driver/receiver disable mode (t_ZH, t_

Z

L

).

Driver Output Protection

Excessive output current and power dissipation caused by faults or by bus contention are prevented by two mechanisms. A foldback current limit on the output stage provides immediate protection against short circuits over the whole common-mode voltage range (see

Typical Operating Characteristics

). In addition, a thermal shutdown circuit forces the driver outputs into a high-impedance state if the die temperature becomes excessive.

V

OH

V

OL

A B

1V

-1V

1.5V 1.5V

OUTPUT

INPUT

RO

R

PLH

R

PHL

Figure 11. Receiver Propagation Delays

OUTPUT NORMALLY LOW

OUTPUT NORMALLY HIGH

3V 0V

V

CC

RO

0V

1.5V 1.5V

V

OL

+ 0.5V

V

OH

- 0.5V

1.5V

R

ZL(SHDN)

, R

ZL

R

LZ

R

ZH(SHDN)

, R

ZH

R

HZ

RE

Figure 12. Receiver Enable and Disable Times (MAX1481/MAX1484 only)

R

B

RECEIVER OUTPUT

ATE

A

V

ID

R

Figure 13. Receiver Propagation Delay Test Circuit

20dB/div

250kHz/div 2.5MHz0Hz

MAX1481/4/5/6-fig14

Figure 14. Driver Output Waveform and FFT Plot of MAX1484/MAX1486 Transmitting a 20kHz signal

MAX1481/MAX1484/MAX1485/MAX1486

Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited,

12Mbps, RS-485/RS-422 Transceivers in µMAX Package

______________________________________________________________________________________ 13

Line Length vs. Data Rate

The RS-485/RS-422 standard covers line lengths up to 4000 feet. For line lengths greater than 4000 feet, use the repeater application shown in Figure 16.

Figures 17 and 18 show the system differential voltage for the parts driving 4000 feet of 26AWG twisted-pair wire into 120Ω loads.

Typical Applications

The MAX1485/MAX1486 are designed for bidirectional data communications on multipoint bus transmission

lines. Figures 19 and 20 show typical network applications circuits. These parts can also be used as line repeaters with cable lengths longer than 4000 feet (Figure 16).

To minimize reflections, terminate the line at both ends in its characteristic impedance, and keep stub lengths off the main line as short as possible. The slew-rate-limited MAX1481/MAX1485 are more tolerant of imperfect termination than the MAX1484/MAX1486.

20dB/div

250kHz/div 2.5MHz0Hz

MAX1481/4/5/6-fig15

Figure 15. Driver Output Waveform and FFT Plot of MAX1481/MAX1485 Transmitting a 20kHz Signal

120Ω

DATA IN

DATA OUT

R

D

RO

RE DE

DI

H/F

A B

Z Y

MAX1481 MAX1484 MAX1485 MAX1486

NOTE: RE ON MAX1481 AND MAX1484 ONLY. H/F ON MAX1485 AND MAX1486 ONLY.

Figure 16. Line Repeater

VA - V

B

DI

RO

5V/div

4V/div

5µs/div

MAX1481/4/5/6-fig17

Figure 17. MAX1481/MAX1485 System Differential Voltage at 50kHz Driving 4000 ft. of Unterminated Cable

VA - V

B

DI

RO

5V/div

4V/div

1µs/div

MAX1481/4/5/6-fig18

Figure 18. MAX1484/MAX1486 System Differential Voltage at 200kHz Driving 4000 ft. of Unterminated Cable

MAX1481/MAX1484/MAX1485/MAX1486

Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited, 12Mbps, RS-485/RS-422 Transceivers in µMAX Package

14 ______________________________________________________________________________________

Figure 19. Typical Half-Duplex RS-485 Network

DI RO DE

Z

RO

DI

DE

D

R

Z

(Z)

(Y)

Y

120Ω

D

R

MAX1485 MAX1486

V

CC

5V

H/F

V

CC

5V

H/F

V

CC

5V

V

CC

V

CC

H/F

MAX1481/MAX1484/MAX1485/MAX1486

Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited,

12Mbps, RS-485/RS-422 Transceivers in µMAX Package

______________________________________________________________________________________ 15

120Ω

R

D

RO

DE

DI

A

B

Y

RE* RE*

120Ω

DI

DI DIRO RO

RO

DE DE

DE

RE

RE*

Z

Y

A A

A

B B

B

D

R

MAX1481 MAX1484 MAX1485 MAX1486

*RE ON MAX1481 AND MAX1484 ONLY. **H/F ON MAX1485 AND MAX1486 ONLY.

H/F**

Figure 20. Typical Full-Duplex RS-485 Network

___________________Chip Information

TRANSISTOR COUNT: 396

Software-Selectable, Half-/Full-Duplex, Slew-Rate-Limited,

Package Information

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages

.)

12Mbps, RS-485/RS-422 Transceivers in µMAX Package

________________________________________________________Package Information

10LUMAXB.EPS

MAX1481/MAX1484/MAX1485/MAX1486

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

16

____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

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