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ManualsBrandsMAXIM INTEGRATED ManualsInterface ICsInterface IC - transceivers RS422, RS485 1/1 PDIP 28

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_______________General Description

The MAX3480A/MAX3480B are electrically isolated

RS-485/RS-422 data-communications interfaces.

Transceivers, optocouplers, and a transformer are all

included in one low-cost, 28-pin DIP package. A single

+3.3V supply on the logic side powers both sides of the

interface.

The MAX3480B features reduced-slew-rate drivers that

minimize EMI and reduce reflections caused by

improperly terminated cables, allowing error-free data

transmission at data rates up to 250kbps. The

MAX3480A’s driver slew rate is not limited, allowing

transmission rates up to 2.5Mbps.

These devices typically draw 180mA of quiescent sup-

ply current. The MAX3480B provides a low-power shut-

down mode in which it consumes only 0.2µA.

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 the input

is open circuit.

The MAX3480A/MAX3480B typically withstand 1600V

RMS

(1 minute) or 2000V

RMS

(1 second). Their isolated inputs

and outputs meet RS-485/RS-422 specifications.

________________________Applications

Isolated RS-485/RS-422 Data Interface

Transceivers for EMI-Sensitive Applications

Industrial-Control Local Area Networks

Automatic Test Equipment

HVAC/Building Control Networks

____________________________Features

♦ Isolated Data Interface to 1600V

RMS

(1 minute)

♦ Slew-Rate-Limited Data Transmission (MAX3480B)

♦ High-Speed, Isolated, 2.5Mbps RS-485 Interface

(MAX3480A)

♦ -7V to +12V Common-Mode Input Voltage Range

with Respect to Isolated Ground

♦ Single +3.3V Supply

♦ Current Limiting and Thermal Shutdown for

Driver Overload Protection

♦ Standard 28-Pin DIP Package

MAX3480A/MAX3480B

Complete, Isolated, 3.3V

RS-485/RS-422 Data Interface

________________________________________________________________

Maxim Integrated Products

AC1

AC2

ISO V

CC1

CC2

CC1

ISO RO DRV

ISO DI IN

ISO DE INV

CC3

GND1

ISO COM1

ISO DI DRV

ISO V

CC2

ISO DE DRV

GND2

CC4

ISO COM2

ISO RO LED

CC5

MAX485

MAX487

MAX845

ISOLATION BARRIER

TOP VIEW

MAX3480A/B

DIP

__________________Pin Configuration

19-0453; Rev 0; 1/96

PART

MAX3480ACPI

MAX3480AEPI

MAX3480BCPI

0°C to +70°C

-40°C to +85°C

0°C to +70°C

TEMP. RANGE PIN-PACKAGE

28 Plastic DIP

MAX3480BEPI -40°C to +85°C 28 Plastic DIP

DATA

RATE

(kbps)

2500

250

______________Ordering Information

Summary of content (16 pages)

PAGE 1
9-0453; Rev 0; 1/96 Complete, Isolated, 3.3V RS-485/RS-422 Data Interface The MAX3480A/MAX3480B are electrically isolated RS-485/RS-422 data-communications interfaces. Transceivers, optocouplers, and a transformer are all included in one low-cost, 28-pin DIP package. A single +3.3V supply on the logic side powers both sides of the interface.
PAGE 2
MAX3480A/MAX3480B Complete, Isolated, 3.3V RS-485/RS-422 Data Interface ABSOLUTE MAXIMUM RATINGS LED Forward Current (DI, DE, ISO RO LED) ......................50mA Continuous Power Dissipation (TA = +70°C) Plastic DIP (derate 9.09mW/°C above +70°C) ...............727mW Operating Temperature Ranges MAX3480_CPI ......................................................0°C to +70°C MAX3480_EPI ...................................................-40°C to +85°C Storage Temperature Range ............................
PAGE 3
Complete, Isolated, 3.3V RS-485/RS-422 Data Interface (VCC = VCC1 = VCC2 = VCC4 = VCC5 = 3.0V to 3.6V, FS = 0V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = VCC1 = VCC2 = VCC4 = VCC5 = 3.3V and TA = +25°C.) (Notes 1, 2, 3) PARAMETER Input Current (A, B) SYMBOL ISO IIN Receiver Input Resistance Receiver Differential Threshold CONDITIONS DE´ = 0V, VCC = 0V or 3.6V RIN -7V ≤ VCM ≤ 12V VTH -7V ≤ VCM ≤ 12V MIN TYP MAX VIN = 12V VIN = 12V MAX3480A VIN = -7V 0.8 -0.
PAGE 4
MAX3480A/MAX3480B Complete, Isolated, 3.3V RS-485/RS-422 Data Interface SWITCHING CHARACTERISTICS—MAX3480B (VCC = VCC1 = VCC2 = VCC4 = VCC5 = 3.0V to 3.6V, FS = 0V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = VCC1 = VCC2 = VCC4 = VCC5 = 3.3V and TA = +25°C.) PARAMETER Driver Input to Output Propagation Delay SYMBOL tPLH tPHL CONDITIONS MIN Figures 4, 6; RDIFF = 54Ω, CL1 = CL2 = 100pF TYP MAX 1.0 2.0 1.0 2.
PAGE 5
Complete, Isolated, 3.3V RS-485/RS-422 Data Interface 2.7 2.6 2.5 2.4 2.3 160 OUTPUT CURRENT (mA) -80 -70 -60 -50 -40 -30 140 120 100 80 60 2.2 -20 40 2.1 -10 20 2.0 0 20 40 60 0 -6 80 -4 TEMPERATURE (°C) -2 0 2 4 4 6 8 10 12 RECEIVER OUTPUT HIGH VOLTAGE vs. TEMPERATURE 0.6 0.5 0.4 0.3 0.2 5.00 MEASURED AT ISO RO DRV IRO = 8mA 4.75 OUTPUT HIGH VOLTAGE (V) MAX3480 A/B-04 MEASURED AT ISO RO DRV IRO = 8mA 0.
PAGE 6
____________________________Typical Operating Characteristics (continued) (VCC_ = 3.3V, TA = +25°C, unless otherwise noted.) MAX3480A DRIVER ENABLE (AB) AND RECEIVER OUTPUT (RO) MAX3480A DRIVER INPUT (AB) AND RECEIVER OUTPUT (RO) MAX3480A SUPPLY CURRENT vs.
PAGE 7
Complete, Isolated, 3.3V RS-485/RS-422 Data Interface PIN NAME FUNCTION PINS ON THE NON-ISOLATED SIDE 1 VCC1 Logic-Side (non-isolated side) +3.3V Supply Voltage Input. Connect to pins 2, 10, and 14. 2 VCC2 Logic-Side (non-isolated side) +3.3V Supply Voltage Input. Connect to pins 1, 10, and 14. 3, 4 D1, D2 Boost-Voltage Generator Outputs. See Figures 1 and 2. 5, 12 GND1, GND2 Logic-Side Ground Inputs. Must be connected; not internally connected. 6 FS Frequency Switch Input.
PAGE 8
MAX3480A/MAX3480B Complete, Isolated, 3.3V RS-485/RS-422 Data Interface _________________________________________________Pin Description (continued) PIN NAME FUNCTION PINS ON THE ISOLATED RS-485/RS-422 SIDE 15 ISO RO LED Isolated Receiver-Output LED Anode (input). If A > B by 200mV, ISO RO LED will be high; if A < B by 200mV, ISO RO LED will be low. 16 ISO COM2 17 ISO DE DRV 18 ISO VCC2 19 ISO DI DRV Isolated Driver-Input Drive.
PAGE 9
Complete, Isolated, 3.3V RS-485/RS-422 Data Interface The MAX3480B features reduced-slew-rate drivers that minimize EMI and reduce reflections caused by improperly terminated cables, allowing error-free transmission at data rates up to 250kbps. The MAX3480A’s driver slew rates are not limited, allowing transmission rates up to 2.5Mbps. The MAX3480A/MAX3480B are electrically isolated, RS-485/RS-422 data-communications interface solutions.
PAGE 10
MAX3480A/MAX3480B Complete, Isolated, 3.3V RS-485/RS-422 Data Interface shutdown circuitry that puts the driver outputs into a high-impedance state. The receiver input has a fail-safe feature that guarantees a logic-high output if the input is open circuit. The driver outputs are enabled by bringing DE´ high. Driver-enable times are typically 200ns for the MAX3480A and 50µs for the MAX3480B. Allow time for the devices to be enabled before sending data. When enabled, driver outputs function as line drivers.
PAGE 11
Complete, Isolated, 3.3V RS-485/RS-422 Data Interface ISOLATION BARRIER A ISOLATION BARRIER 3.3V 3.3V ´ DE R CL1 A VOD D ´ DI R VID R RO B B VOC R3 A RDIFF CL2 B Figure 3. Driver DC Test Load Figure 4. Driver/Receiver Timing Test Circuit S1 500Ω ISO VCC1, ISO VCC2 OUTPUT UNDER TEST CL S2 Figure 5. Driver Timing Test Load _______________________________________________________Switching Waveforms VCC_ - 0.4V ´ DI 0V VCC_ - 0.4V VCC_ - 0.4V 2 VCC_ - 0.
PAGE 12
MAX3480A/MAX3480B Complete, Isolated, 3.3V RS-485/RS-422 Data Interface __Switching Waveforms (continued) VOH RO 1.5V VOL tPHL VID VB - VA -VID OUTPUT 0V 1.5V Driver Output Protection tPLH There are two mechanisms to prevent excessive output current and power dissipation caused by faults or by bus contention. 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).
PAGE 13
Complete, Isolated, 3.3V RS-485/RS-422 Data Interface MAX3480A/MAX3480B __________Applications Information The MAX3480A/MAX3480B are designed for bidirectional data communications on multipoint bus-transmission lines. Figure 9 shows a typical network application circuit. To minimize reflections, terminate the line at both ends with its characteristic impedance, and keep stub lengths off the main line as short as possible.
PAGE 14
MAX3480A/MAX3480B Complete, Isolated, 3.3V RS-485/RS-422 Data Interface TERMINATING RESISTOR (ONE RESISTOR ON EACH END) B DI D 120Ω DE A A B A B RO R RE R RE RE R D RO DE D DI RO DE VIN DI VCC1 3.0V to 3.6V C1 22µF 6V C2 0.
PAGE 15
Complete, Isolated, 3.3V RS-485/RS-422 Data Interface MAX3480A/MAX3480B Table 4. Maxim’s Isolated RS-485 Product Family PART No. OF Tx/Rx GUARANTEED DATA RATE (Mbps) FULL/HALF DUPLEX MAX1480A 1/1 2.50 MAX1480B 1/1 0.25 MAX1490A 1/1 2.50 MAX1490B 1/1 0.25 MAX3480A 1/1 2.50 Half MAX3480B 1/1 0.25 Half SUPPLY VOLTAGE (V) SLEW-RATE LIMITED No. OF Tx/Rx ON BUS Half No 32 5.0 Half Yes 32 5.0 Full No 32 5.0 Full Yes 32 5.0 No 32 3.3 Yes 128 3.
PAGE 16
MAX3480A/MAX3480B Complete, Isolated, 3.3V RS-485/RS-422 Data Interface 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.