Datasheet

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

_________________General Description

The MAX1480A/MAX1480B/MAX1480C/MAX1490A/

MAX1490B are complete, electrically isolated, RS-485/

RS-422 data-communications interface solutions in a

hybrid microcircuit. Transceivers, optocouplers, and a

transformer provide a complete interface in a standard

DIP package. A single +5V supply on the logic side pow-

ers both sides of the interface.

The MAX1480B/MAX1480C/MAX1490B feature reduced-

slew-rate drivers that minimize EMI and reduce reflec-

tions caused by improperly terminated cables, allowing

error-free data transmission at data rates up to 250kbps.

The MAX1480A/MAX1490A driver slew rate is not limited,

allowing transmission rates up to 2.5Mbps. The

MAX1480A/B/C are designed for half-duplex communi-

cation, while the MAX1490A/B feature full-duplex com-

munication.

Drivers are short-circuit current limited and protected

against excessive power dissipation by thermal shut-

down circuitry that places the driver outputs into a high-

impedance state. The receiver input has a fail-safe

feature that guarantees a known output (RO low for the

MAX1480A/B/C, RO high for the MAX1490A/B) if the

input is open circuit.

The MAX1480A/MAX1480B/MAX1480C/MAX1490A/

MAX1490B typically withstand 1600V

RMS

(1 minute) or

2000V

RMS

(1 second). Their isolated outputs meet all

RS-485/RS-422 specifications. The MAX1480A/B/C are

available in a 28-pin DIP package, and the MAX1490A/B

are available in a 24-pin DIP package.

________________________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

Next-Generation Device Features

♦♦

For Integrated ESD Protection

MAX1480E/MAX1490E: ±15kV ESD-Protected,

Isolated RS-485/RS-422 Data Interfaces

♦♦

For Space-Constrained Applications

MAX3157: High CMRR, RS-485 Transceiver with

±50V Isolation

MAX1480A/B/C/MAX1490A/B

Complete, Isolated RS-485/RS-422

Data Interface

________________________________________________________________

Maxim Integrated Products

AC1

AC2

ISO V

CC1

ISO RO DRVD2

GND1

ISO COM1

ISO DI DRV

ISO V

CC2

ISO RO LED

GND2

DIP

CC2

CC3

CC4

CC1

MAX1490A/B

MAX845

MAX488

MAX490

TOP VIEW

ISOLATION BARRIER

Pin Configurations

19-0259; Rev 5; 5/05

_______________Ordering Information

Ordering Information continued at end of data sheet.

†

Data rate for “A” parts is up to 2.5Mbps. Data rate for “B” and

“C” parts is up to 250kbps.

Pin Configurations continued at end of data sheet.

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

PART

†

TEMP RANGE PIN-PACKAGE

MAX1480ACPI 0°C to +70°C

28 Wide Plastic DIP

MAX1480AEPI -40°C to +85°C

28 Wide Plastic DIP

_____________________Selection Table

PART

HALF/

FULL

DUPLEX

DATA

RATE

(MBPS)

SLEW-

RATE

LIMITED

DRIVER

ENABLE

TIME

(µs)

MAX1480A Half 2.5 No 0.2

MAX1480B Half 0.25 Yes 35

MAX1480C Half 0.25 Yes 0.5

MAX1490A Full 2.5 No —

MAX1490B Full 0.25 Yes —

Summary of content (21 pages)

PAGE 1
9-0259; Rev 5; 5/05 Complete, Isolated RS-485/RS-422 Data Interface Next-Generation Device Features The MAX1480A/MAX1480B/MAX1480C/MAX1490A/ MAX1490B are complete, electrically isolated, RS-485/ RS-422 data-communications interface solutions in a hybrid microcircuit. Transceivers, optocouplers, and a transformer provide a complete interface in a standard DIP package. A single +5V supply on the logic side powers both sides of the interface.
PAGE 2
MAX1480A/B/C/MAX1490A/B Complete, Isolated RS-485/RS-422 Data Interface ABSOLUTE MAXIMUM RATINGS With Respect to GND_ Supply Voltage (VCC_)...........................................-0.3V to +6V Control Input Voltage (SD, FS)...............-0.3V to (VCC_ + 0.3V) Receiver Output Voltage (RO, RO)........-0.3V to (VCC_ + 0.3V) Output Switch Voltage (D1, D2)........................................+12V With Respect to ISO COM_ Control Input Voltage (ISO DE_ ) ....-0.3V to (ISO VCC_ + 0.
PAGE 3
Complete, Isolated RS-485/RS-422 Data Interface (VCC_ = 5V ±10%, VFS = VCC_, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC_ = 5V and TA = +25°C.) (Notes 1, 2) PARAMETER SYMBOL Differential Driver Output (With Load) VOD2 Change in Magnitude of Differential Output Voltage for Complementary Output States ΔVOD Driver Common-Mode Output Voltage VOC Input Current (A, B) ISO IIN CONDITIONS R = 50Ω (RS-422) DE´ = 0V, VCC_ = 0V or 5.
PAGE 4
MAX1480A/B/C/MAX1490A/B Complete, Isolated RS-485/RS-422 Data Interface SWITCHING CHARACTERISTICS—MAX1480A/MAX1490A (continued) (VCC_ = 5V ±10%, FS = VCC_, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC_ = 5V and TA = +25°C.) PARAMETER |tPLH - tPHL| Differential Receiver Skew Maximum Data Rate Time to Shutdown SYMBOL CONDITIONS tSKD Figures 5 and 10, RDIFF = 54Ω, CL1 = CL2 = 100pF fMAX tPLH, tPHL < 50% of data period MIN TYP MAX 20 ns 2.
PAGE 5
Complete, Isolated RS-485/RS-422 Data Interface MAX1480A/B/C, MAX1490A/B SWITCHING CHARACTERISTICS—MAX1480B/MAX1480C/MAX1490B (continued) (VCC_ = 5V ±10%, FS = VCC_, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC_ = 5V and TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Driver Disable Time from Low (MAX1480C Only) tLZ Figures 6 and 8, CL = 15pF, S1 closed 2.0 4.5 µs Driver Disable Time from High (MAX1480C Only) tHZ Figures 6 and 8, CL = 15pF, S2 closed 2.
PAGE 6
__________________________________________Typical Operating Characteristics (VCC_ = 5V, FS = VCC_, TA = +25°C, unless otherwise noted.) 50 40 30 -20 -15 -10 20 10 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 3.50 3.00 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 -40 0 20 40 60 80 OUTPUT CURRENT vs. DRIVER OUTPUT LOW VOLTAGE OUTPUT CURRENT vs. DRIVER OUTPUT HIGH VOLTAGE 0.2 120 100 80 60 -80 -70 -60 -50 -40 -30 40 -20 0.
PAGE 7
Complete, Isolated RS-485/RS-422 Data Interface (VCC_ = 5V, FS = VCC_, TA = +25°C, unless otherwise noted.) VCC = 4.5V 100 DE´ = VCC RL = ∞ 80 60 40 VCC = 5.5V VCC = 4.5V 20 RL = 54Ω VCC = 5.5V VCC = 5.0V 100 120 100 VCC = 4.5V 80 DE´ = VCC 60 VCC = 5.5V VCC = 5.0V RL = ∞ VCC = 5.0V RL = 54Ω VCC = 5.5V 110 VCC = 5.0V 90 VCC = 4.5V 80 DE´ = VCC 70 60 VCC = 5.5V 50 30 VCC = 4.5V 20 20 40 60 80 -40 TEMPERATURE (°C) -20 0 20 40 60 -20 0 180 VCC = 5.0V VCC = 4.
PAGE 8
_____________________________Typical Operating Characteristics (continued) (VCC_ = 5V, FS = VCC_, VDI´ = 0V, DE´ toggled 0V to 5V at 5kHz, TA = +25°C, unless otherwise noted.) MAX1480/90-19 MAX1480/90-20 MAX1480A DRIVER DISABLE TIME MAX1480A DRIVER ENABLE TIME DRIVER OUTPUT B 2V/div DRIVER OUTPUT B 2V/div DE´ 2V/div DE´ 2V/div 200ns/div VCC_ = 5.0V, DI´ = 0V DE´ TOGGLED 0V TO 5V AT 5kHz 200ns/div VCC_ = 5.
PAGE 9
Complete, Isolated RS-485/RS-422 Data Interface (VCC_ = 5V, FS = VCC_, DE´ = VCC_, VDI´ = 0V to 5V at 1.25MHz, TA = +25°C, unless otherwise noted.) MAX1480A/MAX1490A RECEIVER tPHL MAX1480A/MAX1490A RECEIVER tPLH MAX1480/90-21 MAX1480/90-22 RECEIVER INPUT A 1V/div RECEIVER INPUT B 1V/div RECEIVER INPUT B 1V/div RECEIVER INPUT A 1V/div RO/RO 2V/div RO/RO 2V/div 20ns/div 20ns/div VCC_ = 5.0V, DE´= VCC_ DI´ = 0V TO 5V AT 1.25MHz VCC_ = 5.0V, DE´= VCC_ DI´ = 0V TO 5V AT 1.
PAGE 10
MAX1480A/B/C, MAX1490A/B Complete, Isolated RS-485/RS-422 Data Interface ________________________________________________________________Pin Description PIN MAX1480A/B/C MAX1490A/B NAME PINS PINSON ONTHE THENON-ISOLATED NON-ISOLATEDSIDE SIDE 1, 2, 8, 10 1, 2, 8, 10 VCC1–VCC4 3, 4 3, 4 D1, D2 5 5 GND1 FUNCTION Logic-Side (nonisolated side) +5V Supply Voltages Internal Connections. Leave these pins unconnected. Logic-Side Ground. Connect to GND2 (pin 12). 6 6 FS Frequency Select Input.
PAGE 11
Complete, Isolated RS-485/RS-422 Data Interface PIN MAX1480A/B/C MAX1490A/B NAME FUNCTION PINS ON THE ISOLATED RS-485/RS-422 SIDE (continued) — 17 Y Noninverting Driver Output — 18 Z Inverting Driver Output — 19 B Inverting Receiver Input — 20 A Noninverting Receiver Input 21 — ISO DE IN Isolated Driver-Enable Input. Connect to ISO DE DRV for normal operation. 22 — ISO DI IN Isolated Driver Input. Connect to ISO DI DRV for normal operation.
PAGE 12
MAX1480A/B/C, MAX1490A/B Complete, Isolated RS-485/RS-422 Data Interface VCC3 ISO VCC1 D1 MAX845 Q FS OSC 1.07MHz/ 1.45MHz MAX1480A: MAX1487 MAX1480B: MAX487 MAX1480C: MAX487 N T F/F ISO DI IN Q N A ISO DE IN ISO RO DRV R RE GND1 SD B D D2 ISO COM1 EXTERNAL RS-485/RS-422 WIRING VIN 5V C1 C2 22μF 0.
PAGE 13
Complete, Isolated RS-485/RS-422 Data Interface D1 MAX845 Q OSC 1.07MHz/ 1.45MHz FS N A R T F/F ISO RO DRV D2 Q B ISO DI DRV N MAX1490A: MAX490 MAX1490B: MAX488 Z D SD Y GND1 MAX1490A/B EXTERNAL RS-485/RS-422 WIRING VIN 5V C1 VCC1 C2 VCC2 22μF 0.
PAGE 14
MAX1480A/B/C, MAX1490A/B Complete, Isolated RS-485/RS-422 Data Interface VIN 5V Si943304 VCC1 1 28 AC1 VCC2 2 27 AC2 D1 3 26 ISO VCC1 D2 4 25 B 24 ISO RO DRV GND1 5 P FS 6 SHUTDOWN R1 DI R2 MAX845 MAX1487 R3 22 ISO DI IN VCC3 8 21 ISO DE IN DI 9 20 ISO COM1 VCC4 10 19 ISO DI DRV 18 ISO VCC2 GND2 12 17 ISO DE DRV RO 13 RO 23 A SD 7 DE 11 DE MAX1480A VCC5 16 ISO COM2 15 ISO RO LED 14 ISOLATION BARRIER GND Figure 3.
PAGE 15
Complete, Isolated RS-485/RS-422 Data Interface ISO VCC_ S1 500Ω OUTPUT UNDER TEST CL S2 Figure 6. Driver Timing Test Load Switching Waveforms VCC_ - 0.4V DI´ VCC_ - 0.4V 2 VCC_ - 0.4V 2 0V tPLH DE´ tPHL 0V 1/2 VO VCC_ - 0.4V 2 VCC_ - 0.4V 2 tLZ tZL B A, B VO A 2.3V OUTPUT NORMALLY LOW VOL 1/2 VO VO VDIFF 0V -VO VCC_ -0.4V 10% VDIFF = V (A) - V (B) tR OUTPUT NORMALLY HIGH A, B 90% 90% VOH - 0.5V 2.3V 10% 0V tF tZH tSKEW = ⎢tPLH - tPHL ⎢ Figure 7.
PAGE 16
MAX1480A/B/C, MAX1490A/B Complete, Isolated RS-485/RS-422 Data Interface MAX1480B/MAX1480C/MAX1490B: Reduced EMI and Reflections _____________________Function Tables The MAX1480B/MAX1480C/MAX1490B are slew-ratelimited, minimizing EMI and reducing reflections caused by improperly terminated cables. Figure 11 shows both the driver output waveform of a MAX1480A/MAX1490A transmitting a 150kHz signal and the Fourier analysis of that waveform. High-frequency harmonics with large amplitudes are evident.
PAGE 17
Complete, Isolated RS-485/RS-422 Data Interface MAX1480A/B/C, MAX1490A/B TERMINATING RESISTOR (ONE RESISTOR ON EACH END) B DI D 120Ω DE A A B A B RO R 100Ω RE R RE R RE D RO DE D DI VIN 5V C1 C2 22μF 0.
PAGE 18
Driver Output Protection 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 entire common-mode range (see the Typical Operating Characteristics). In addition, a thermal shutdown circuit forces the driver outputs into a high-impedance state if the die temperature rises excessively.
PAGE 19
Complete, Isolated RS-485/RS-422 Data Interface • A shield trace connected to the ground on each side of the barrier can help intercept capacitive currents that might otherwise couple into the signal path. In a double-sided or multilayer board, these shield traces should be present on all conductor layers. • Try to maximize the width of the isolation barrier wherever possible; a clear space of at least 0.25 inches between ground and isolated common is suggested.
PAGE 20
MAX1480A/B/C, MAX1490A/B Complete, Isolated RS-485/RS-422 Data Interface Doubly Isolated RS-485 Repeater The RS-422/RS-485 standard is specified for cable lengths up to 4000 feet. When approaching or exceeding the specified maximum cable length, a groundpotential difference of several tens of volts can easily develop. This difference can be either DC, AC, at power-line frequency, or any imaginable noise or impulse waveform.
PAGE 21
Complete, Isolated RS-485/RS-422 Data Interface Ordering Information (continued) PART† TOP VIEW MAX1480A/B/C TEMP RANGE PIN-PACKAGE MAX1480BCPI 0°C to +70°C 28 Wide Plastic DIP MAX1480BEPI -40°C to +85°C 28 Wide Plastic DIP MAX1480CCPI 0°C to +70°C 28 Wide Plastic DIP MAX1480CEPI -40°C to +85°C 28 Wide Plastic DIP 24 Wide Plastic DIP VCC1 1 28 AC1 VCC2 2 27 AC2 MAX1490ACPG 0°C to +70°C D1 3 26 ISO VCC1 MAX1490AEPG -40°C to +85°C 24 Wide Plastic DIP D2 4 25 B MAX1490BCPG 0°C to