MAX3485CPA中文资料

19-0333; Rev 0; 12/94

3.3V-Powered, 10Mbps and Slew-Rate-Limited

True RS-485/RS-422 Transceivers

_______________General Description

____________________________Features

The MAX3483, MAX3485, MAX3486, MAX3488,MAX3490, and MAX3491 are 3.3V, low-power trans-oOperate from a Single 3.3V Supply—ceivers for RS-485 and RS-422 communication. EachNo Charge Pump!part contains one driver and one receiver. TheoInteroperable with +5V Logic

MAX3483 and MAX3488 feature slew-rate-limited dri-vers that minimize EMI and reduce reflections causedo8ns Max Skew (MAX3485/MAX3490/MAX3491)by improperly terminated cables, allowing error-freeoSlew-Rate Limited for Errorless Data Transmissiondata transmission at data rates up to 250kbps. The par-(MAX3483/MAX3488) tially slew-rate-limited MAX3486 transmits up to2.5Mbps. The MAX3485, MAX3490, and MAX3491o2nA Low-Current Shutdown Mode

transmit at up to 10Mbps.

(MAX3483/MAX3485/MAX3486/MAX3491)Drivers are short-circuit current limited and are protect-o-7V to +12V Common-Mode Input Voltage Rangeed against excessive power dissipation by thermalshutdown circuitry that places the driver outputs into aoAllows up to 32 Transceivers on the Bushigh-impedance state. The receiver input has a fail-safeoFull-Duplex and Half-Duplex Versions Availablefeature that guarantees a logic-high output if bothinputs are open circuit.

oIndustry Standard 75176 PinoutThe MAX3488, MAX3490, and MAX3491 feature full-(MAX3483/MAX3485/MAX3486)

duplex communication, while the MAX3483, MAX3485,oCurrent-Limiting and Thermal Shutdown forand MAX3486 are designed for half-duplex communi-Driver Overload Protection

cation.

________________________Applications

______________Ordering Information

Low-Power RS-485/RS-422 TransceiversTelecommunications

Transceivers for EMI-Sensitive ApplicationsIndustrial-Control Local Area Networks

* Contact factory for for dice specifications.

______________________________________________________________Selection Table

PARTGUARANTEEDSUPPLY SLEW-RATEDRIVER/SHUTDOWNNUMBERDATA RATEVOLTAGE

HALF/FULL(Mbps)

(V)

DUPLEX

LIMITED

RECEIVERCURRENTPINENABLE

(nA)

COUNTMAX34830.25HalfYesYes28MAX348510HalfNoYes28MAX34862.5YesYes28MAX34880.253.0 to 3.6HalfFullYesNo—8MAX349010FullNoNo—8MAX3491

10

Full

No

Yes

2

14

________________________________________________________________Maxim Integrated Products

1

Call toll free 1-800-998-8800 for free samples or literature.

MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/MAX3491

3.3V-Powered, 10Mbps and Slew-Rate-LimitedTrue RS-485/RS-422 Transceivers

MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/MAX3491

ABSOLUTE MAXIMUM RATINGS

Supply Voltage (VCC)...............................................................7VDriver Input Voltage (DI).............................................-0.3V to 7VDriver Output Voltage (A, B, Y, Z)..........................-7.5V to 12.5VReceiver Input Voltage (A, B)................................-7.5V to 12.5VReceiver Output Voltage (RO)....................-0.3V to (VCC+ 0.3V)Continuous Power Dissipation (TA= +70°C)

8-Pin Plastic DIP (derate 9.09mW/°C above +70°C).....727mW8-Pin SO (derate 5.88mW/°C above +70°C)..................471mW

14-Pin Plastic DIP (derate 10mW/°C above +70°C)......800mW14-Pin SO (derate 8.33mW/°C above +70°C)................667mWOperating Temperature Ranges

MAX34_ _C_ _.......................................................0°C to +70°CMAX34_ _E_ _....................................................-40°C to +85°CStorage Temperature Range.............................-65°C to +160°CLead Temperature (soldering, 10sec).............................+300°C

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

DC ELECTRICAL CHARACTERISTICS

(VCC= 3.3V ±0.3V, TA= TMINto TMAX, unless otherwise noted. Typical values are at TA= +25°C)

2_______________________________________________________________________________________

3.3V-Powered, 10Mbps and Slew-Rate-Limited

True RS-485/RS-422 Transceivers

DC ELECTRICAL CHARACTERISTICS (continued)

(VCC= 3.3V ±0.3V, TA= TMINto TMAX, unless otherwise noted. Typical values are at TA= +25°C)

DRIVER SWITCHING CHARACTERISTICS—MAX3485, MAX3490, and MAX3491

(VCC= 3.3V, TA= +25°C)

DRIVER SWITCHING CHARACTERISTICS—MAX3486

(VCC= 3.3V, TA= +25°C)

_______________________________________________________________________________________

3

MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/MAX3491

3.3V-Powered, 10Mbps and Slew-Rate-LimitedTrue RS-485/RS-422 Transceivers

MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/MAX3491

DRIVER SWITCHING CHARACTERISTICS—MAX3483 and MAX3488

(VCC= 3.3V, TA= +25°C)

RECEIVER SWITCHING CHARACTERISTICS

(VCC= 3.3V, TA= +25°C)

Note 1: VODand VOCare the changes in VODand VOC, respectively, when the DI input changes state.Note 2:Measured on |tPLH(Y) - tPHL(Y)|and |tPLH(Z) - tPHL(Z)|.

Note 3:high and DE low. If the inputs are in this state for less than 80ns, the

parts are guaranteed not to enter shutdown. If the inputs are in this state for at least 300ns, the parts are guaranteed tohave entered shutdown. See Low-Power Shutdown Modesection.4

_______________________________________________________________________________________

3.3V-Powered, 10Mbps and Slew-Rate-Limited

True RS-485/RS-422 Transceivers

__________________________________________Typical Operating Characteristics

(VCC= 3.3V, TA= +25°C, unless otherwise noted.)

OUTPUT CURRENT vs.

OUTPUT CURRENT vs.

RECEIVER OUTPUT HIGH VOLTAGE

RECEIVER OUTPUT LOW VOLTAGE

RECEIVER OUTPUT HIGH VOLTAGE

vs. TEMPERATURE

251

-202

3.3000--33884-18433XXAAMM)

)

)

V3.25A20

A-16( mm(( -14EGTTAN15NT3.20EERR-12LORRVUUCC-10 HG3.15 ITTU10

U-8H PPTTTUUU3.10OO-6PTU5

-4O-2

3.05003.00

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0.5

1.0

1.5

2.0

2.5

3.0

3.5

-40-20020406080100

OUTPUT LOW VOLTAGE (V)

OUTPUT HIGH VOLTAGE (V)

TEMPERATURE (°C)

RECEIVER OUTPUT LOW VOLTAGE

DRIVER OUTPUT CURRENT vs. DRIVER DIFFERENTIAL OUTPUT vs. TEMPERATURE

DIFFERENTIAL OUTPUT VOLTAGE

VOLTAGE vs.TEMPERATURE

0.81005

0-2.638904)

30.7XVA(2.5M )

EVG(0.6)

A80A2.4 EmTGLA( 70O2.3T0.5TVN LOETU2.2VR60P W0.4RUTU2.1OC50L O TT0.3U40LA2.0UPIPTTTNE1.9UO0.2UO30R20EF1.80.1FI10D1.700

1.6

-40

-20

20

40

608010000.51.01.52.02.53.03.5

-40

-20

20

40

60

80

100

TEMPERATURE (°C)DIFFERENTIAL OUTPUT VOLTAGE (V)TEMPERATURE (°C)

OUTPUT CURRENT vs. OUTPUT CURRENT vs. DRIVER OUTPUT LOW VOLTAGE

DRIVER OUTPUT HIGH VOLTAGE

1757

-100

8

00--33884433XXAA150MM)

)

-80

AAmm(125( TTNNERR100E-60

RRUUC TU75C TU-40

PPTTUO50UO-202500

2

4

6

8

10

12

-7-6-5-4-3-2-10123

4

5

OUTPUT LOW VOLTAGE (V)

OUTPUT HIGH VOLTAGE (V)

_______________________________________________________________________________________5

MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/MAX3491

3.3V-Powered, 10Mbps and Slew-Rate-LimitedTrue RS-485/RS-422 Transceivers

MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/MAX3491

_____________________________Typical Operating Characteristics (continued)

SUPPLY CURRENT vs. TEMPERATURE

SUPPLY CURRENT (mA)

1.1

0.9

SHUTDOWN CURRENT vs. TEMPERATURE

90SHUTDOWN CURRENT (nA)

8070605040302010

MAX3483-10

1.2100

1.0

0.80.7

-40

-20

20

40

60

80

100

TEMPERATURE (°C)

0-40

-20

20

40

60

80

100

TEMPERATURE (°C)

______________________________________________________________Pin Description

3.3V-Powered, 10Mbps and Slew-Rate-Limited

True RS-485/RS-422 Transceivers

Figure 1. MAX3483/MAX3485/MAX3486 Pin Configuration and Typical Operating Circuit

Figure 2. MAX3488/MAX3490 Pin Configuration and Typical Operating Circuit

Figure 3. MAX3491 Pin Configuration and Typical Operating Circuit

_______________________________________________________________________________________

7

MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/MAX3491

3.3V-Powered, 10Mbps and Slew-Rate-LimitedTrue RS-485/RS-422 Transceivers

MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/MAX3491

Figure 4. Driver VODand VOCFigure 5. Driver VODwith Varying Common-Mode Voltage

Figure 6.Receiver VOHand VOL

Figure 7.Driver Differential Output Delay and Transition Times

8_______________________________________________________________________________________

3.3V-Powered, 10Mbps and Slew-Rate-Limited

True RS-485/RS-422 Transceivers

Figure 8.Driver Propagation Times

Figure 9.Driver Enable and Disable Times (tPZH, tPSH, tPHZ)

Figure 10.Driver Enable and Disable Times (tPZL, tPSL, tPLZ)

_______________________________________________________________________________________9

MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/MAX3491

3.3V-Powered, 10Mbps and Slew-Rate-LimitedTrue RS-485/RS-422 Transceivers

MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/MAX3491

Figure 11.Receiver Propagation Delay

Figure 12.Receiver Enable and Disable Times

Note 4: The input pulse is supplied by a generator with the following characteristics: PRR = 250kHz, 50% duty cycle, tr≤6.0ns, ZO= 50 .Note 5: CLincludes probe and stray capacitance.10

______________________________________________________________________________________

3.3V-Powered, 10Mbps and Slew-Rate-Limited

True RS-485/RS-422 Transceivers

____________________Function Tables

__________Applications Information

Devices with Receiver/Driver EnableThe MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/(MAX3483/MAX3485/MAX3486/MAX3491)

MAX3491 are low-power transceivers for RS-485 andRS-422 communications. The MAX3483 and MAX3488Table 1. Transmitting

can transmit and receive at data rates up to 250kbps,the MAX3486 at up to 2.5Mbps, and the MAX3485/MAX3490/MAX3491 at up to 10Mbps. The MAX3488/MAX3490/MAX3491 are full-duplex transceivers, whilethe MAX3483/MAX3485/MAX3486 are half-duplex.included on the MAX3483/MAX3485/MAX3486/MAX3491. When disabled, the driver and receiver out-puts are high impedance.

* B and A outputs are Z and Y, respectively, for full-duplex part(MAX3491).

Reduced EMI and ReflectionsX = Don’t care; High-Z = High impedance

(MAX3483/MAX3486/MAX3488)

The MAX3483/MAX3488 are slew-rate limited, minimiz-Table 2. Receiving

ing EMI and reducing reflections caused by improperlyterminated cables. Figure 13 shows both the driveroutput waveform of a MAX3485/MAX3490/MAX3491transmitting a 125kHz signal and the Fourier analysis ofthat waveform. High-frequency harmonics with largeamplitudes are evident. Figure 14 shows the same infor-mation, but for the slew-rate-limited MAX3483/MAX3488transmitting the same signal. The high-frequency har-* DE is a “don’t care” (x) for the full-duplex part (MAX3491).monics have much lower amplitudes, and the potential forX = Don’t care; High-Z = High impedance

EMI is significantly reduced.

Devices without Receiver/Driver Enable

Low-Power Shutdown Mode

(MAX3488/MAX3490)

(MAX3483/MAX3485/MAX3486/MAX3491)

A low-power shutdown mode is initiated by bringing bothTable 3. Transmitting

Table 4. Receiving

high and DE low. The devices will not shut downunless both the driver and receiver are disabled (highINPUTOUTPUTSINPUTSOUTPUTimpedance). In shutdown, the devices typically drawDIZYA, BROonly 2nA of supply current.

101≥+0.2V1For these devices, the t0

1

≤-0.2V0assume the part was in the low-power shutdown mode;PSHand tPSLenable timesInputs Open

1

the tPZHand tPZLenable times assume the receiver ordriver was disabled, but the part was not shut down.

11

MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/MAX3491

3.3V-Powered, 10Mbps and Slew-Rate-LimitedTrue RS-485/RS-422 Transceivers

MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/MAX3491

B 1V/div

DI 2V/divZ 1V/div

A 1V/div

Y 1V/div

20ns/div

RO 2V/div

20ns/div

Figure 15.MAX3485/MAX3490/MAX3491 Driver PropagationDelayFigure 16.MAX3485/MAX3490/MAX3491 ReceiverPropagation Delay Driven by External RS-485 Device

B 1V/div

DI 2V/divZ 1V/divY 1V/div

1µs/div

A 1V/div

RO 2V/div

1µs/div

Figure 17.MAX3483/MAX3488 Driver Propagation DelayFigure 18.MAX3483/MAX3488 Receiver Propagation Delay

DI 5V/divVY - VZ 2V/div

DI 5V/divVY - VZ 2V/div

RO 5V/div

RO 5V/div

2µs/div

2µs/div

Figure 19. MAX3483/MAX3488 System Differential Voltage at125kHz Driving 4000 ft of CableFigure 20. MAX3485/MAX3490/MAX3491 System DifferentialVoltage at 125kHz Driving 4000 ft of Cable

12______________________________________________________________________________________

3.3V-Powered, 10Mbps and Slew-Rate-Limited

True RS-485/RS-422 Transceivers

Figure 21.MAX3483/MAX3485/MAX3486 Typical RS-485 Network

Driver Output Protection

Line Length vs. Data Rate

Excessive output current and power dissipation causedThe RS-485/RS-422 standard covers line lengths up toby faults or by bus contention are prevented by two4000 feet. For line lengths greater than 4000 feet, seemechanisms. A foldback current limit on the output stageFigure 23.

provides immediate protection against short circuits overthe whole common-mode voltage range (see TypicalFigures 19 and 20 show the system differential voltageOperating Characteristics). In addition, a thermal shut-for parts driving 4000 feet of 26AWG twisted-pair wiredown circuit forces the driver outputs into a high-imped-at 125kHz into 120 loads.

ance state if the die temperature rises excessively.

Typical Applications

Propagation Delay

The MAX3483, MAX3485, MAX3486, MAX3488,Figures 15–18 show the typical propagation delays. SkewMAX3490, and MAX3491 transceivers are designed fortime is simply the difference between the low-to-high andbidirectional data communications on multipoint bushigh-to-low propagation delay. Small driver/receivertransmission lines. Figures 21 and 22 show typical net-skew times help maintain a symmetrical mark-spacework applications circuits. These parts can also beratio (50% duty cycle).

used as line repeaters, with cable lengths longer than4000 feet, as shown in Figure 23.

The receiver skew time, |tPRLH- tPRHL|, is under 10ns(20ns for the MAX3483/MAX3488). The driver skewTo minimize reflections, the line should be terminated attimes are 8ns for the MAX3485/MAX3490/MAX3491,both ends in its characteristic impedance, and stub11ns for the MAX3486, and typically under 100ns forlengths off the main line should be kept as short asthe MAX3483/MAX3488.

possible. The slew-rate-limited MAX3483/MAX3488and the partially slew-rate-limited MAX3486 are moretolerant of imperfect termination.

______________________________________________________________________________________13

MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/MAX3491

3.3V-Powered, 10Mbps and Slew-Rate-LimitedTrue RS-485/RS-422 Transceivers

MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/MAX3491

Figure 22.MAX3488/MAX3490/MAX3491 Full-Duplex RS-485 Network

Figure 23.Line Repeater for MAX3488/MAX3490/MAX3491

14______________________________________________________________________________________

3.3V-Powered, 10Mbps and Slew-Rate-Limited

True RS-485/RS-422 Transceivers

_Ordering Information (continued)

__________________Chip Topography

* Contact factory for for dice specifications.

TRANSISTOR COUNT: 810

SUBSTRATE CONNECTED TO GROUND

______________________________________________________________________________________15

MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/MAX3491

3.3V-Powered, 10Mbps and Slew-Rate-LimitedTrue RS-485/RS-422 Transceivers

MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/MAX3491

________________________________________________________Package Information

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©1994 Maxim Integrated Products

Printed USA

is a registered trademark of Maxim Integrated Products.

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