MAX3491规格书,MAX3490技术资料,MAX3483，MAX3485，MAX3486，MAX3488，datasheet,pdf

_______________General Description

The MAX3483, MAX3485, MAX3486, MAX3488,MAX3490, and MAX3491 are 3.3V, low-power trans-ceivers for RS-485 and RS-422 communication. Each part contains one driver and one receiver. The MAX3483 and MAX3488 feature slew-rate-limited dri-vers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free data transmission at data rates up to 250kbps. The par-tially slew-rate-limited MAX3486 transmits up to 2.5Mbps. The MAX3485, MAX3490, and MAX3491transmit at up to 10Mbps.

Drivers are short-circuit current limited and are protect-ed against excessive power dissipation by thermal shutdown circuitry that places the driver outputs into a high-impedance state. The receiver input has a fail-safe feature that guarantees a logic-high output if both inputs are open circuit.

The MAX3488, MAX3490, and MAX3491 feature full-duplex communication, while the MAX3483, MAX3485,and MAX3486 are designed for half-duplex communi-cation.

________________________Applications

Low-Power RS-485/RS-422 Transceivers Telecommunications

Transceivers for EMI-Sensitive Applications Industrial-Control Local Area Networks

____________________________Features

o Operate from a Single 3.3V Supply—No Charge Pump!o Interoperable with +5V Logic

o 8ns Max Skew (MAX3485/MAX3490/MAX3491)o Slew-Rate Limited for Errorless Data Transmission (MAX3483/MAX3488) o 2nA Low-Current Shutdown Mode

(MAX3483/MAX3485/MAX3486/MAX3491)o -7V to +12V Common-Mode Input Voltage Range o Allows up to 32 Transceivers on the Bus o Full-Duplex and Half-Duplex Versions Available o Industry Standard 75176 Pinout (MAX3483/MAX3485/MAX3486)

o Current-Limiting and Thermal Shutdown for Driver Overload Protection

______________Ordering Information

* Contact factory for for dice specifications.

MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/MAX3491

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

True RS-485/RS-422 Transceivers

________________________________________________________________Maxim Integrated Products

1

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

19-0333; Rev 0; 12/94

PART NUMBER GUARANTEED DATA RATE (Mbps)

SUPPLY VOLTAGE

(V)

HALF/FULL DUPLEX

SLEW-RATE LIMITED

DRIVER/RECEIVER ENABLE

SHUTDOWN CURRENT (nA)

PIN COUNT MAX34830.25Half Yes Yes 28MAX348510Half No Yes 28MAX3486 2.5Half Yes Yes 28MAX34880.25Full Yes No —8MAX349010Full No No —8MAX3491

10

3.0 to 3.6Full

No

Yes

2

14

______________________________________________________________Selection Table

M A X 3483/M A X 3485/M A X 3486/M A X 3488/M A X 3490/M A X 3491

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

2_______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

DC ELECTRICAL CHARACTERISTICS

(V CC = 3.3V ±0.3V, T A = T MIN to T MAX , unless otherwise noted. Typical values are at T A = +25°C)

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 (V CC )...............................................................7V Control Input Voltage (RE, DE)...................................-0.3V to 7V Driver Input Voltage (DI).............................................-0.3V to 7V Driver Output Voltage (A, B, Y, Z)..........................-7.5V to 12.5V Receiver Input Voltage (A, B)................................-7.5V to 12.5V Receiver Output Voltage (RO)....................-0.3V to (V CC + 0.3V)Continuous Power Dissipation (T A = +70°C)

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

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

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

MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/MAX3491

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

True RS-485/RS-422 Transceivers

_______________________________________________________________________________________

3

DC ELECTRICAL CHARACTERISTICS (continued)

(V CC = 3.3V ±0.3V, T A = T MIN to T MAX , unless otherwise noted. Typical values are at T A = +25°C)

DRIVER SWITCHING CHARACTERISTICS—MAX3485, MAX3490, and MAX3491

(V CC = 3.3V, T A = +25°C)

DRIVER SWITCHING CHARACTERISTICS—MAX3486

(V CC = 3.3V, T A = +25°C)

M A X 3483/M A X 3485/M A X 3486/M A X 3488/M A X 3490/M A X 3491

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

4

_______________________________________________________________________________________

DRIVER SWITCHING CHARACTERISTICS—MAX3483 and MAX3488

(V CC = 3.3V, T A = +25°C)

RECEIVER SWITCHING CHARACTERISTICS

(V CC = 3.3V, T A = +25°C)

Note 1:?V OD and ?V OC are the changes in V OD and V OC , respectively, when the DI input changes state.Note 2:Measured on |t PLH (Y) - t PHL (Y)|and |t PLH (Z) - t PHL (Z)|.

Note 3:The transceivers are put into shutdown by bringing RE 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 to have entered shutdown. See Low-Power Shutdown Mode section.

MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/MAX3491

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

True RS-485/RS-422 Transceivers

_______________________________________________________________________________________5

__________________________________________Typical Operating Characteristics

(V CC = 3.3V, T A = +25°C, unless otherwise noted.)

2520

1510

5

00

0.5

1.0

1.5

2.0

2.5

3.5

3.0

OUTPUT CURRENT vs.

RECEIVER OUTPUT LOW VOLTAGE

M A X 3483-01

OUTPUT LOW VOLTAGE (V)

O U T P U T C U R R E N T (m A )

-20-18-16-14-12-10-8-6-4-2

00

0.5

1.0

1.5

2.0

2.5

3.5

3.0

OUTPUT CURRENT vs.

RECEIVER OUTPUT HIGH VOLTAGE

M A X 3483-02

OUTPUT HIGH VOLTAGE (V)

O U T P U T C U R R E N T (m A )

3.00

3.053.103.153.203.253.30-40-200204060100

80RECEIVER OUTPUT HIGH VOLTAGE

vs. TEMPERATURE

TEMPERATURE (°C)

O U T P U T H I G H V O L T A G E (V )

00.10.20.30.40.50.60.70.8-40

-20

20

40

6010080RECEIVER OUTPUT LOW VOLTAGE

vs. TEMPERATURE

TEMPERATURE (°C)O U T P U T L O W V O L T A G E (V )

25050751001251501750

2

4

6

8

10

12

OUTPUT CURRENT vs. DRIVER OUTPUT LOW VOLTAGE

M A X 3483-07

OUTPUT LOW VOLTAGE (V)

O U T P U T C U R R E N T (m A )

1009080706050403020100

00.5 1.0 1.5 2.0 2.5 3.5

3.0DRIVER OUTPUT CURRENT vs. DIFFERENTIAL OUTPUT VOLTAGE

M A X 3483-05

DIFFERENTIAL OUTPUT VOLTAGE (V)O U T P U T C U R R E N T (m A )

1.6

1.71.81.9

2.02.12.22.32.42.62.5-40

-20

20

40

60

100

80

DRIVER DIFFERENTIAL OUTPUT VOLTAGE vs.TEMPERATURE

TEMPERATURE (°C)

D I F F

E R E N T I A L O U T P U T V O L T A G E (V )

-100

-80

-60

-40

-205

4

3

210-7-6-3-4-5-2-1OUTPUT CURRENT vs. DRIVER OUTPUT HIGH VOLTAGE

M A X 348

3-08

OUTPUT HIGH VOLTAGE (V)

O U T P U T C U R R E N T (m A )

M A X 3483/M A X 3485/M A X 3486/M A X 3488/M A X 3490/M A X 3491

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

0.80.7

0.9

1.0

1.1

1.2-40

-20

20

40

60

100

80

SUPPLY CURRENT vs. TEMPERATURE

TEMPERATURE (°C)

S U P P L Y C U R R E N T (m A )

_____________________________Typical Operating Characteristics (continued)

010

20304050607080100

90-40

-20

20

40

60

100

80

SHUTDOWN CURRENT vs. TEMPERATURE

M A X 3483-10

TEMPERATURE (°C)

S H U T D O W N C U R R E N T (n A )

______________________________________________________________Pin Description

MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/MAX3491

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

True RS-485/RS-422 Transceivers

_______________________________________________________________________________________

7

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

Figure 3. MAX3491 Pin Configuration and Typical Operating Circuit

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

M A X 3483/M A X 3485/M A X 3486/M A X 3488/M A X 3490/M A X 3491

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

8_______________________________________________________________________________________

Figure 4. Driver V OD and V OC Figure 7.Driver Differential Output Delay and Transition Times

Figure 6.Receiver V OH and V OL

Figure 5. Driver V OD with Varying Common-Mode Voltage

MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/MAX3491

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

True RS-485/RS-422 Transceivers

_______________________________________________________________________________________9

Figure 8.Driver Propagation Times

Figure 9.Driver Enable and Disable Times (t PZH , t PSH , t PHZ )

Figure 10.Driver Enable and Disable Times (t PZL , t PSL , t PLZ )

M A X 3483/M A X 3485/M A X 3486/M A X 3488/M A X 3490/M A X 3491

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

10

______________________________________________________________________________________

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, t r ≤6.0ns, Z O = 50?.Note 5: C L includes probe and stray capacitance.

____________________Function Tables

Devices with Receiver/Driver Enable (MAX3483/MAX3485/MAX3486/MAX3491)

Table 1. Transmitting

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

X = Don’t care; High-Z = High impedance

Table 2. Receiving

* DE is a “don’t care” (x) for the full-duplex part (MAX3491).X = Don’t care; High-Z = High impedance

Devices without Receiver/Driver Enable

(MAX3488/MAX3490)

Table 3. Transmitting

Table 4. Receiving

__________Applications Information

The MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/MAX3491 are low-power transceivers for RS-485 and RS-422 communications. The MAX3483 and MAX3488can 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, while the MAX3483/MAX3485/MAX3486 are half-duplex.Driver Enable (DE) and Receiver Enable (RE) pins are included on the MAX3483/MAX3485/MAX3486/MAX3491. When disabled, the driver and receiver out-puts are high impedance.

Reduced EMI and Reflections (MAX3483/MAX3486/MAX3488)

The MAX3483/MAX3488 are slew-rate limited, minimiz-ing EMI and reducing reflections caused by improperly terminated cables. Figure 13 shows both the driver output waveform of a MAX3485/MAX3490/MAX3491transmitting a 125kHz signal and the Fourier analysis of that waveform. High-frequency harmonics with large amplitudes are evident. Figure 14 shows the same infor-mation, but for the slew-rate-limited MAX3483/MAX3488transmitting the same signal. The high-frequency har-monics have much lower amplitudes, and the potential for EMI is significantly reduced.

Low-Power Shutdown Mode

(MAX3483/MAX3485/MAX3486/MAX3491)

A low-power shutdown mode is initiated by bringing both RE high and DE low. The devices will not shut down unless both the driver and receiver are disabled (high impedance). In shutdown, the devices typically draw only 2nA of supply current.

For these devices, the t PSH and t PSL enable times assume the part was in the low-power shutdown mode;the t PZH and t PZL enable times assume the receiver or driver was disabled, but the part was not shut down.

MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/MAX3491

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

True RS-485/RS-422 Transceivers

______________________________________________________________________________________

11

INPUTS OUTPUT A, B RO ≥+0.2V 1≤-0.2V 0Inputs Open

1

INPUT OUTPUTS DI Z Y 1010

1

5MHz

500kHz/div 0Hz 5MHz

500kHz/div 0Hz Figure 13. Driver Output Waveform and FFT Plot of MAX3485/MAX3490/MAX3491 Transmitting a 125kHz Signal Figure 14. Driver Output Waveform and FFT Plot of MAX3483/MAX3488 Transmitting a 125kHz Signal

M A X 3483/M A X 3485/M A X 3486/M A X 3488/M A X 3490/M A X 3491

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

12______________________________________________________________________________________

B 1V/div

A 1V/div

RO 2V/div

20ns/div

DI 5V/div V Y - V Z 2V/div

RO 5V/div

2μs/div

B 1V/div

A 1V/div

RO 2V/div

1μs/div

DI 2V/div 20ns/div

Z 1V/div

Y 1V/div

DI 2V/div Z 1V/div Y 1V/div

1μs/div

DI 5V/div V Y - V Z 2V/div

RO 5V/div

2μs/div

Figure 15.MAX3485/MAX3490/MAX3491 Driver Propagation Delay Figure 17.MAX3483/MAX3488 Driver Propagation Delay Figure 16.

MAX3485/MAX3490/MAX3491 Receiver Propagation Delay Driven by External RS-485 Device

Figure 18.MAX3483/MAX3488 Receiver Propagation Delay

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

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 shut-down circuit forces the driver outputs into a high-imped-ance state if the die temperature rises excessively.

Propagation Delay Figures 15–18 show the typical propagation delays. Skew time is simply the difference between the low-to-high and high-to-low propagation delay. Small driver/receiver skew times help maintain a symmetrical mark-space ratio (50% duty cycle).

The receiver skew time, |t PRLH- t PRHL|, is under 10ns (20ns for the MAX3483/MAX3488). The driver skew times are 8ns for the MAX3485/MAX3490/MAX3491, 11ns for the MAX3486, and typically under 100ns for the MAX3483/MAX3488.

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, see Figure 23.

Figures 19 and 20 show the system differential voltage for parts driving 4000 feet of 26AWG twisted-pair wire at 125kHz into 120?loads.

Typical Applications The MAX3483, MAX3485, MAX3486, MAX3488, MAX3490, and MAX3491 transceivers are designed for bidirectional data communications on multipoint bus transmission lines. Figures 21 and 22 show typical net-work applications circuits. These parts can also be used as line repeaters, with cable lengths longer than 4000 feet, as shown in Figure 23.

To minimize reflections, the line should be terminated at both ends in its characteristic impedance, and stub lengths off the main line should be kept as short as possible. The slew-rate-limited MAX3483/MAX3488 and the partially slew-rate-limited MAX3486 are more tolerant of imperfect termination.

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

MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/MAX34913.3V-Powered, 10Mbps and Slew-Rate-Limited True RS-485/RS-422 Transceivers ______________________________________________________________________________________13

M A X 3483/M A X 3485/M A X 3486/M A X 3488/M A X 3490/M A X 3491

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

14______________________________________________________________________________________

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

Figure 23.Line Repeater for MAX3488/MAX3490/MAX3491

MAX3483/MAX3485/MAX3486/MAX3488/MAX3490/MAX3491

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

True RS-485/RS-422 Transceivers

______________________________________________________________________________________15

TRANSISTOR COUNT: 810

SUBSTRATE CONNECTED TO GROUND

__________________Chip Topography

_Ordering Information (continued)

* Contact factory for for dice specifications.

0.146" (3.71mm)

0.086" (2.18mm)

Z/B

B A

Y/A

GND

DI

DE RE

RO

V

CC

GND

M A X 3483/M A X 3485/M A X 3486/M A X 3488/M A X 3490/M A X 3491

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

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.

________________________________________________________Package Information