MAX1490AEPG+ ,Complete, Isolated RS-485/RS-422 Data InterfaceELECTRICAL CHARACTERISTICS(V = 5V ±10%, V = V , T = T to T , unless otherwise noted. Typical values ..
MAX1490BCPG ,Complete / Isolated RS-485/RS-422 Data InterfaceELECTRICAL CHARACTERISTICS(V = 5V ±10%, V = V , T = T to T , unless otherwise noted. Typical values ..
MAX1490BCPG+ ,Complete, Isolated RS-485/RS-422 Data InterfaceELECTRICAL CHARACTERISTICS(V = 5V ±10%, V = V , T = T to T , unless otherwise noted. Typical values ..
MAX1490BEPG ,Complete / Isolated RS-485/RS-422 Data InterfaceGeneral Description ________
MAX1490BEPG+ ,Complete, Isolated RS-485/RS-422 Data InterfaceFeatures♦♦The MAX1480A/MAX1480B/MAX1480C/MAX1490A/ For Integrated ESD ProtectionMAX1480E/MAX1490E: ..
MAX1490EAEPG ,15kV ESD-Protected, Isolated RS-485/RS-422MAX1480E/MAX1490E19-1940; Rev 0; 4/01±15kV ESD-Protected, Isolated RS-485/RS-422Data Interfaces____ ..
MAX4117ESA ,Single/Dual/Quad / 400MHz / Low-Power / Current Feedback AmplifiersMAX4112/MAX4113/MAX4117–MAX412019-0440; Rev 2; 4/97Single/Dual/Quad, 400MHz, Low-Power,Current Feed ..
MAX4118ESA ,Single/Dual/Quad / 400MHz / Low-Power / Current Feedback AmplifiersMAX4112/MAX4113/MAX4117–MAX412019-0440; Rev 2; 4/97Single/Dual/Quad, 400MHz, Low-Power,Current Feed ..
MAX4119ESD ,Single/Dual/Quad / 400MHz / Low-Power / Current Feedback AmplifiersFeaturesThe single MAX4112/MAX4113, dual MAX4117/' 400MHz -3dB Bandwidth (MAX4112/MAX4117)MAX4118, ..
MAX412 ,Single/Dual/Quad, 28MHz, Low-Noise, Low-Voltage, Precision Op AmpsApplicationsMAX410EPA -40°C to +85°C 8 Plastic DIPLow-Noise Frequency Synthesizers MAX410BEPA -40°C ..
MAX4120ESD ,Single/Dual/Quad / 400MHz / Low-Power / Current Feedback AmplifiersGeneral Description ________
MAX4121CSA ,330MHz Buffered Video Switches/ Crosspoint Building Blocksfeaturesinclude -92dB crosstalk and -78dB isolation (MAX4121).' Ultra-Low Switching GlitchThe MAX41 ..
MAX1480ACPI+-MAX1480AEPI+-MAX1480BCPI+-MAX1480BEPI+-MAX1480CEPI+-MAX1490ACPG+-MAX1490AEPG+-MAX1490BCPG+-MAX1490BEPG+
Complete, Isolated RS-485/RS-422 Data Interface
_________________General DescriptionThe 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 (ROlow 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 1600VRMS(1 minute) or
2000VRMS(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.
________________________ApplicationsIsolated 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 Interface24
AC1
AC2
ISO VCC1
ISO RO DRVD2
GND1
ISO COM1
ISO DI DRV
ISO VCC2
ISO RO LEDGND2
DIPVCC2
VCC3
VCC4
VCC1MAX1490A/B
MAX845
MAX488MAX490
TOP VIEW
ISOLATION BARRIER
Pin Configurations19-0259; 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.
PART†TEMP RANGEPIN-PACKAGE
MAX1480ACPI0°C to +70°C28 Wide Plastic DIP
MAX1480AEPI-40°C to +85°C28 Wide Plastic DIP
_____________________Selection Table
PART
HALF/
FULL
DUPLEX
DATA
RATE
(MBPS)
SLEW-
RATE
LIMITED
DRIVER
ENABLE
TIME
(µs) MAX1480A Half 2.5 No0.2
MAX1480B Half 0.25 Yes 35
MAX1480C Half 0.25 Yes 0.5
MAX1490A Full 2.5 No —
MAX1490B Full 0.25 Yes —
Complete, Isolated RS-485/RS-422
Data Interface
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(VCC_= 5V ±10%, VFS= VCC_, TA= TMINto TMAX, unless otherwise noted. Typical values are at VCC_= 5V and TA= +25°C.) (Notes 1, 2)
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.
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_+ 0.3V)
Driver Input Voltage (ISO DI_ ).......-0.3V to (ISO VCC_+ 0.3V)
Receiver Output Voltage (ISO RO_)...-0.3V to (ISO VCC_+ 0.3V)
Driver Output Voltage (A, B, Y, Z )......................-8V to +12.5V
Receiver Input Voltage (A, B)..............................-8V to +12.5V
LED Forward Current (DI, DE, ISO RO LED)......................50mA
Continuous Power Dissipation (TA= +70°C)
24-Pin Plastic DIP (derate 8.7mW°C above +70°C).....696mW
28-Pin Plastic DIP (derate 9.09mW/°C above +70°C)..727mW
Operating Temperature Ranges
MAX1480_CPI/MAX1490_CPG............................0°C to +70°C
MAX1480_EPI/MAX1490_EPG.........................-40°C to +85°C
Storage Temperature Range.............................-65°C to +160°C
Lead Temperature (soldering, 10s).................................+300°C
MAX1480A/B/C/MAX1490A/B
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSfSWLVFS = 0V535Switch FrequencyfSWHFS = VCC_ or open725kHz
RL = ∞, +25°C only6090MAX1480A,
DE´ = VCC_ or openRL = 54Ω120
RL = ∞, +25°C only3545MAX1480B,
DE´ = VCC_ or openRL = 54Ω95
RL = ∞, +25°C only3575MAX1480C,
DE´ = VCC_ or openRL = 54Ω95
RL = ∞, +25°C only100150MAX1490ARL = 54Ω170
RL = ∞, +25°C only65125
Operating Supply CurrentICC
MAX1490BRL = 54Ω130
Shutdown Supply Current
(Note 3)ISHDNSD = VCC_0.2µA
VSDHHigh2.4Shutdown Input ThresholdVSDLLow0.8V
Shutdown Input Leakage Current10pA
VFSHHigh2.4FS Input ThresholdVFSLLow0.8V
FS Input Pullup CurrentFS low50µA
FS Input Leakage CurrentFS high10pA
Input High VoltageVIHDE´, DI´VCC_ - 0.4V
Input Low VoltageVILDE´, DI´0.4V
Isolation ResistanceRISOTA = +25°C, VISO = 50VDC10010,000MΩ
Isolation CapacitanceCISOTA = +25°C, VISO = 50VDC10pF
Differential Driver Output
(No Load)VOD18V
MAX1480A/B/C/MAX1490A/B
Complete, Isolated RS-485/RS-422
Data Interface
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSR = 50Ω (RS-422)2Differential Driver Output
(With Load)VOD2R = 27Ω (RS-485), Figure 41.55.0V
Differential0.3Change in Magnitude of
Differential Output Voltage for
Complementary Output States
ΔVODR = 27Ω or 50Ω,
Figure 4Common mode0.3
Driver Common-Mode Output
VoltageVOCR = 27Ω or 50Ω, Figure 44V
MAX1480A/B/C1VIN = 12VMAX1490A/B0.25
MAX1480A/B/C0.8Input Current (A, B)ISO IIN
DE´ = 0V,
VCC_ = 0V
or 5.5VVIN = -7VMAX1490A/B0.2
MAX1480A/B/C48Receiver Input ResistanceRIN-7V ≤ VCM ≤ 12VMAX1490A/B12kΩ
Receiver Differential Threshold
VoltageVTH-7V ≤ VCM ≤ 12V-0.2+0.2V
Receiver Input HysteresisΔVTHVCM = 0V70mV
Receiver Output/Receiver Output
Low VoltageVOLUsing resistor values listed in
Tables 1 and 20.4V
Receiver Output/Receiver Output
High CurrentIOHVOUT = 5.5V250µA
Driver Short-Circuit CurrentISO IOSD-7V ≤ VO ≤ 12V (Note 4)100mA
ELECTRICAL CHARACTERISTICS (continued)(VCC_= 5V ±10%, VFS= VCC_, TA= TMINto TMAX, unless otherwise noted. Typical values are at VCC_= 5V and TA= +25°C.) (Notes 1, 2)
SWITCHING CHARACTERISTICS—MAX1480A/MAX1490A(VCC_= 5V ±10%, FS = VCC_, TA= TMINto TMAX, unless otherwise noted. Typical values are at VCC_= 5V and TA= +25°C.)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITStPLH100275Driver Input to Output
Propagation DelaytPHL
Figures 5 and 7, RDIFF = 54Ω, CL1 = CL2
= 100pF100275ns
Driver Output SkewtSKEWFigures 5 and 7, RDIFF = 54Ω, CL1 = CL2
= 100pF2590ns
Driver Rise or Fall TimetR, tFFigures 5 and 7, RDIFF = 54Ω, CL1 = CL2
= 100pF1540ns
Driver Enable to Output High
(MAX1480A Only)tZHFigures 6 and 8, CL = 100pF, S2 closed0.21.5µs
Driver Enable to Output Low
(MAX1480A Only)tZLFigures 6 and 8, CL = 100pF, S1 closed0.21.5µs
Driver Disable Time from Low
(MAX1480A Only)tLZFigures 6 and 8, CL = 15pF, S1 closed0.21.5µs
Driver Disable Time from High
(MAX1480A Only)tHZFigures 6 and 8, CL = 15pF, S2 closed0.21.5µs
tPLH100225Receiver Input to Output
Propagation DelaytPHL
Figures 5 and 10, RDIFF = 54Ω, CL1 = CL2
= 100pF100225ns
MAX1480A/B/C/MAX1490A/B
Complete, Isolated RS-485/RS-422
Data Interface
SWITCHING CHARACTERISTICS—MAX1480A/MAX1490A (continued)(VCC_= 5V ±10%, FS = VCC_, TA= TMINto TMAX, unless otherwise noted. Typical values are at VCC_= 5V and TA= +25°C.)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS|tPLH - tPHL| Differential Receiver
SkewtSKDFigures 5 and 10, RDIFF = 54Ω, CL1 = CL2
= 100pF20ns
Maximum Data RatefMAXtPLH, tPHL < 50% of data period2.5Mbps
Time to ShutdowntSHDN100µs
Shutdown to Driver Output HightZH(SHDN)Figures 6 and 9, CL = 100pF, S2 closed310µs
Shutdown to Driver Output LowtZL(SHDN)Figures 6 and 9, CL = 100pF, S1 closed310µs
SWITCHING CHARACTERISTICS—MAX1480B/MAX1480C/MAX1490B(VCC_= 5V ±10%, FS = VCC_, TA= TMINto TMAX, unless otherwise noted. Typical values are at VCC_= 5V and TA= +25°C.)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITStPLH23.0Driver Input to Output
Propagation DelaytPHL
Figures 5 and 7, RDIFF = 54Ω,
CL1 = CL2 = 100pF23.0µs
Driver Output SkewtSKEWFigures 5 and 7, RDIFF = 54Ω,
CL1 = CL2 = 100pF9001600ns
Driver Rise or Fall TimetR, tFFigures 5 and 7, RDIFF = 54Ω,
CL1 = CL2 = 100pF1.02.0µs
Driver Enable to Output High
(MAX1480B Only)tZHFigures 6 and 8, CL = 100pF, S2 closed35100µs
Driver Enable to Output Low
(MAX1480B Only)tZLFigures 6 and 8, CL = 100pF, S1 closed35100µs
Driver Disable Time from Low
(MAX1480B Only)tLZFigures 6 and 8, CL = 15pF, S1 closed1350µs
Driver Disable Time from High
(MAX1480B Only)tHZFigures 6 and 8, CL = 15pF, S2 closed1350µs
Driver Enable to Output High
(MAX1480C Only)tZHFigures 6 and 8, CL = 100pF, S2 closed0.54.5µs
Driver Enable to Output Low
(MAX1480C Only)tZLFigures 6 and 8, CL = 100pF, S1 closed0.54.5µs
MAX1480A/B/C, MAX1490A/B
Complete, Isolated RS-485/RS-422
Data Interface
Note 1:All currents into device pins are positive; all currents out of device pins are negative. All voltages are referenced to logic-
side ground (GND_), unless otherwise specified.
Note 2:For DE´ and DI´pin descriptions, see Detailed Block Diagram and Typical Application Circuit (Figure 1 for MAX1480A/
MAX1480B/MAX1480C, Figure 2 for MAX1490A/MAX1490B).
Note 3:Shutdown supply current is the current at VCC1and VCC2when shutdown is enabled.
Note 4:Applies to peak current (see Typical Operating Characteristics). Although the MAX1480A/B/C and MAX1490A/B provide
electrical isolation between logic ground and signal paths, they do not provide isolation between external shields and the
signal paths (see Isolated Common Connectionsection).
SWITCHING CHARACTERISTICS—MAX1480B/MAX1480C/MAX1490B (continued)(VCC_= 5V ±10%, FS = VCC_, TA= TMINto TMAX, unless otherwise noted. Typical values are at VCC_= 5V and TA= +25°C.)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSDriver Disable Time from Low
(MAX1480C Only)tLZFigures 6 and 8, CL = 15pF, S1 closed2.04.5µs
Driver Disable Time from High
(MAX1480C Only)tHZFigures 6 and 8, CL = 15pF, S2 closed2.04.5µs
tPLH23.0Receiver Input to Output
Propagation DelaytPHL
Figures 5 and 10, RDIFF = 54Ω,
CL1 = CL2 = 100pF23.0µs
|tPLH - tPHL| Differential Receiver
SkewtSKDFigures 5 and 10, RDIFF = 54Ω,
CL1 = CL2 = 100pF1200ns
Maximum Data RatefMAXtPLH, tPHL < 50% of data period0.25Mbps
Time to ShutdowntSHDN100µs
Shutdown to Driver Output HightZH(SHDN)Figures 6 and 9, CL = 100pF, S2 closed35100µs
Shutdown to Driver Output LowtZL(SHDN)Figures 6 and 9, CL = 100pF, S1 closed35100µs
MAX1480A/B/C, MAX1490A/B
Complete, Isolated RS-485/RS-422
Data Interface
OUTPUT CURRENT vs.
RECEIVER OUTPUT LOW VOLTAGEMAX1480/90A/B-01
OUTPUT LOW VOLTAGE (V)
OUTPUT CURRENT (mA)
1.5MEASURED AT ISO RO DRV
OUTPUT CURRENT vs.
RECEIVER OUTPUT HIGH VOLTAGE
MAX1480/90A/B-02
OUTPUT HIGH VOLTAGE (V)
OUTPUT CURRENT (mA)
MEASURED AT ISO RO DRV
RECEIVER OUTPUT HIGH VOLTAGE
vs. TEMPERATURE
MAX1480/90A/B-03
TEMPERATURE (°C)
OUTPUT HIGH VOLTAGE (V)-20604080
5.00MEASURED AT ISO RO DRV
IRO = 8mA
RECEIVER OUTPUT LOW VOLTAGE
vs. TEMPERATURE
MAX1480/90A/B-04
TEMPERATURE (°C)
OUTPUT LOW VOLTAGE (V)-20604080
0.8MEASURED AT ISO RO DRV
IRO = 8mA
DRIVER OUTPUT CURRENT
vs. DIFFERENTIAL OUTPUT VOLTAGEMAX1480/90A/B-07
DIFFERENTIAL OUTPUT VOLTAGE (V)
OUTPUT CURRENT (mA)
DI´ = HIGH OR OPEN
OUTPUT CURRENT vs.
DRIVER OUTPUT LOW VOLTAGE
MAX1480/90A/B-05
OUTPUT LOW VOLTAGE (V)
OUTPUT CURRENT (mA)
OUTPUT CURRENT vs.
DRIVER OUTPUT HIGH VOLTAGE
MAX1480/90A/B-06
OUTPUT HIGH VOLTAGE (V)
OUTPUT CURRENT (mA)
DRIVER DIFFERENTIAL OUTPUT VOLTAGE
vs. TEMPERATURE
MAX1480/90A/B-08
TEMPERATURE (°C)
DIFFERENTIAL OUTPUT VOLTAGE (V)-20604080
DI´ = HIGH OR OPEN
RL = 54Ω
MAX1480B/MAX1480C/MAX1490B
SHUTDOWN CURRENT vs. TEMPERATURE
MAX1480/90A/B-09
TEMPERATURE (°C)
SHUTDOWN CURRENT (-20604080
SD = VCC_, DI´ = VCC_
DE´ (MAX1480B/C ONLY) = VCC_
MEASURED AT VCC1 AND VCC2
__________________________________________Typical Operating Characteristics (VCC_= 5V, FS = VCC_, TA = +25°C, unless otherwise noted.)
MAX1480A/B/C, MAX1490A/B
Complete, Isolated RS-485/RS-422
Data Interface
_____________________________Typical Operating Characteristics (continued)(VCC_= 5V, FS = VCC_, TA = +25°C, unless otherwise noted.)
MAX1480A
SUPPLY CURRENT vs. TEMPERATURE
MAX1480/90A/B-10
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
VCC = 5.5V
VCC = 5.0V
VCC = 5.5VVCC = 5.0VVCC = 4.5V
RL = 54Ω
RL = ∞
VCC = 4.5V
DE´ = VCC
MAX1480B
SUPPLY CURRENT vs. TEMPERATURE
MAX1480/90A/B-11
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
VCC = 5.5V
VCC = 5.0V
VCC = 5.5VVCC = 5.0V
RL = 54Ω
RL = ∞
DE´ = VCC
VCC = 4.5V
VCC = 4.5V
MAX1480C
SUPPLY CURRENT vs. TEMPERATURE
MAX1480/90A/B-12
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
VCC = 5.5V
VCC = 5.0V
VCC = 5.5V
VCC = 5.0V
VCC = 4.5V
RL = 54Ω
RL = ∞
VCC = 4.5V
DE´ = VCC
MAX1490A
SUPPLY CURRENT vs. TEMPERATURE
MAX1480/90A/B-13
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
VCC = 5.5V
VCC = 5.0V
VCC = 5.5V
VCC = 5.0V
VCC = 4.5V
RL = 54Ω
RL = ∞
VCC = 4.5V
MAX1490B
SUPPLY CURRENT vs. TEMPERATURE
MAX1480/90A/B-14
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
VCC = 5.5V
VCC = 5.0V
VCC = 5.5VVCC = 5.0V
VCC = 4.5V
RL = 54Ω
RL = ∞
VCC = 4.5V
DRIVER DISABLE TIME
vs. TEMPERATURE
MAX1480/90A/B-15a
TEMPERATURE (°C)
DRIVER DISABLE TIME (
MAX1480A
MAX1480B
MAX1480C
RL = 54Ω
VDI´ = 0V MEASURED FROM
DE´ TO VALID OUTPUT
DRIVER ENABLE TIME
vs. TEMPERATURE
MAX1480/90A/B-15b
TEMPERATURE (°C)
DRIVER ENABLE TIME (
MAX1480A
MAX1480C
MAX1480B
RL = 54Ω
VDI´ = 0V MEASURED FROM
DE´ TO VALID OUTPUT
MAX1480A/B/C, MAX1490A/B
Complete, Isolated RS-485/RS-422
Data InterfaceVCC_ = 5.0V, DI´= 0V
DE´ TOGGLED 0V TO 5V AT 5kHz
MAX1480B
DRIVER ENABLE TIMEDRIVER
OUTPUT B
2V/div
DE´
2V/div
10μs/div
MAX1480/90-17
VCC_ = 5.0V, DI´= 0V
DE´ TOGGLED 0V TO 5V AT 5kHz
MAX1480B
DRIVER DISABLE TIMEDE´
2V/div
5μs/div
DRIVER
OUTPUT B
2V/div
MAX1480/90-18
VCC_ = 5.0V, DI´= 0V
MAX1480C
DRIVER ENABLE TIMEDE´
2V/div
500ns/div
DRIVER
OUTPUT B
2V/div
MAX1480/90-25
VCC_ = 5.0V, DI´ = 0V
MAX1480C
DRIVER DISABLE TIMEDE´
2V/div
500ns/div
DRIVER
OUTPUT B
2V/div
MAX1480/90-26
VCC_ = 5.0V, DI´= 0V
DE´ TOGGLED 0V TO 5V AT 5kHz
MAX1480A
DRIVER ENABLE TIMEDE´
2V/div
200ns/div
DRIVER
OUTPUT B
2V/div
MAX1480/90-19
_____________________________Typical Operating Characteristics (continued)(VCC_= 5V, FS = VCC_, VDI´= 0V, DE´toggled 0V to 5V at 5kHz, TA = +25°C, unless otherwise noted.)
VCC_ = 5.0V, DI´ = 0V
DE´ TOGGLED 0V TO 5V AT 5kHz
MAX1480A
DRIVER DISABLE TIMEDE´
2V/div
200ns/div
DRIVER
OUTPUT B
2V/div
MAX1480/90-20
MAX1480A/B/C, MAX1490A/B
Complete, Isolated RS-485/RS-422
Data Interface
_____________________________Typical Operating Characteristics (continued)(VCC_= 5V, FS = VCC_, DE´= VCC_, VDI´= 0V to 5V at 1.25MHz, TA = +25°C, unless otherwise noted.)
VCC_ = 5.0V, DE´= VCC_
DI´ = 0V TO 5V AT 1.25MHz
MAX1480A/MAX1490A
RECEIVER tPHLRO/RO
2V/div
20ns/div
RECEIVER
INPUT A
1V/div
RECEIVER
INPUT B
1V/div
MAX1480/90-21
VCC_ = 5.0V, DE´= VCC_
DI´ = 0V TO 5V AT 1.25MHz
MAX1480A/MAX1490A
RECEIVER tPLHRO/RO
2V/div
20ns/div
RECEIVER
INPUT B
1V/div
RECEIVER
INPUT A
1V/div
MAX1480/90-22
VCC_ = 5.0V, DE´= VCC_
DI´= 0V TO 5V AT 125kHz
MAX1480B/MAX1480C/MAX1490B
RECEIVER tPHLRECEIVER
INPUT A
1V/div
RECEIVER
INPUT B
1V/div
RO/RO
2V/div
200ns/div
MAX1480/90-23
VCC_ = 5.0V, DE´= VCC_
DI´= 0V TO 5V AT 125kHz
MAX1480B/MAX1480C/MAX1490B
RECEIVER tPLHRECEIVER
INPUT A
1V/div
RECEIVER
INPUT B
1V/div
RO/RO
2V/div
500ns/div
MAX1480/90-24
VDI´ = 0V
VSD = 5V TO 0V AT 1kHz
POWER-UP DELAY TO DRIVER OUTPUTS VALIDDRIVER
OUTPUT B
(Z FOR MAX1490)
2V/div
1μs/div
2V/div
MAX1480/90-16
MAX1480A/B/C, MAX1490A/B
Complete, Isolated RS-485/RS-422
Data Interface
________________________________________________________________Pin DescriptionInternal Connections. Leave these pins unconnected.3, 43, 4
Logic-Side (nonisolated side) +5V Supply Voltages1, 2, 8, 101, 2, 8, 10
FUNCTION
PIND1, D2
VCC1–VCC4
NAMEShutdown Input. Ground for normal operation. When high, the power oscillator is
disabled.77
Frequency Select Input. If FS = VCC_or is open, switch frequency is high; if FS
= GND, switch frequency is low. For optimal performance and minimal supply
current, connect FS to VCC_or leave unconnected.6
Logic-Side Ground. Connect to GND2 (pin 12).55
GND1
Logic-Side (non-isolated side) +5V Supply Voltage—14
Receiver Output. If A > B by 200mV, ROwill be low; if A < B by 200mV, ROwill
be high. Open collector; must have pullup to VCC_(Table 1 of Figure 1).—13
Logic-Side Ground. Connect to GND1 (pin 5).1212
VCC5
GND2
Receiver Output. If A > B by 200mV, RO will be high; if A < B by 200mV, RO
will be low. Open collector; must have pullup to VCC(Table 2 of Figure 2).11—
Driver-Enable Input. The driver outputs, A and B, are enabled by bringing DE´
high. The driver outputs are high impedance when DE´is low. If the driver out-
puts are enabled, the device functions as a line driver. While the driver outputs
are high impedance, the device functions as a line receiver. Drives internal
LED cathode through a resistor (Table 1 of Figure 1).11
Driver Input. With DE´high (MAX1480A/B/C only), a low on DI´forces output A
low and output B high. Similarly, a high on DI´forces output A high and output
B low. Drives internal LED cathode through a resistor (Table 1 of Figure 1 for
MAX1480A/B/C, Table 2 of Figure 2 for MAX1490A/B).9
Isolated Driver-Input Drive. With DE´high (MAX1480A/B/C only), a low on DI´
forces output A low and output B high. Similarly, a high on DI´forces output A
high and output B low. Connect to ISO DI IN (on the MAX1480A/B/C only) for
normal operation. Open-collector output; connect a pullup resistor to ISO VCC_
(Table 1 of Figure 1 for MAX1480A/B/C; Table 2 of Figure 2 for MAX1490A/B).19
Isolated Supply Voltage. Connect to ISO VCC1(pin 26 for MAX1480A/B/C, or
pin 22 for MAX1490A/B).1418
Isolated Driver-Enable Drive. The driver outputs, A and B, are enabled by bring-
ing DE´high. The driver outputs are high impedance when DE´ is low. If the driv-
er outputs are enabled, the device functions as a line driver. While the driver
outputs are high impedance, the device functions as a line receiver. Open-
collector output; must have pullup to ISO VCC_and be connected to ISO DE IN
for normal operation (Table 1 of Figure 1).17
ISO DI DRV
ISO VCC2
ISO DE DRV
Isolated Common. Connect to ISO COM1 (pin 20).—16
Isolated Receiver Output LED. Internal LED anode in MAX1480A/B/C and LED
cathode in MAX1490A/B. Connect to ISO RO DRV through a resistor (Table 1 of
Figure 1 for MAX1480A/B/C; Table 2 of Figure 2 for MAX1490A/B).15
Isolated Common. For MAX1480A/B/C, connect to ISO COM2 (pin 16)
(Figures 1 and 2).1620ISO COM1
ISO COM2
ISO RO LED
MAX1480A/B/CMAX1490A/B
PINS ON THE NON-ISOLATED SIDE
PINS ON THE ISOLATED RS-485/RS-422 SIDE
PINS ON THE NON-ISOLATED SIDE
PINS ON THE ISOLATED RS-485/RS-422 SIDE
MAX1480A/B/C, MAX1490A/B
Complete, Isolated RS-485/RS-422
Data Interface
Detailed DescriptionThe MAX1480A/MAX1480B/MAX1480C/MAX1490A/
MAX1490B are complete, electrically isolated, RS-485/
RS-422 data-communications interface solutions.
Transceivers, optocouplers, a power driver, and a
transformer in one standard 28-pin DIP package (24-
pin for the MAX1490A/B) provide a complete interface.
Signals and power are internally transported across the
isolation barrier (Figures 1, 2). Power is transferred from
the logic side (nonisolated side) to the isolated side of
the barrier through a center-tapped transformer.
Signals cross the barrier through high-speed optocou-
plers. A single +5V supply on the logic side powers
both sides of the interface. The MAX1480A/B/C offer
half-duplex communications while the MAX1490A/B
feature full-duplex communication. The functional
input/output relationships are shown in Tables 3–6.
The MAX1480B/MAX1480C/MAX1490B feature reduced-
slew-rate drivers that minimize EMI and reduce reflec-
tions caused by improperly terminated cables, allowing
error-free transmission at data rates up to 250kbps. The
MAX1480A/MAX1490A driver slew rate is not limited,
allowing transmission rates up to 2.5Mbps.
The MAX1480B/MAX1480C/MAX1490B shutdown feature
reduces supply current to as low as 0.2µA by using the
SD pin (see the Low-Power Shutdown Mode section).
Use the FS pin to select between high and low switching
frequencies for the isolated power driver. The driver
switches at the lower frequency 535kHz when FS is low,
and at the higher frequency 725kHz when FS is high. The
FS pin has a weak internal pull-up that switches the
device to the high-frequency mode when FS is left
unconnected. With FS high or open, no-load supply
current is reduced by approximately 4mA, and by up to
8mA when fully loaded. For optimal performance and
minimal supply current, connect FS to VCC_or leave
unconnected.
Drivers are short-circuit current limited and are protect-
ed against excessive power dissipation by thermal
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 RO (logic-low RO)
output if the input is open circuit.
On the MAX1480A/B/C, the driver outputs are enabled
by bringing DE´high. Driver-enable times are typically
0.2µs for the MAX1480A, 35µs for the MAX1480B, and
0.5µs for the MAX1480C. Allow time for the devices to be
enabled before sending data (see the Driver Enable
Time vs. Temperature graph in the Typical Operating
Characteristics). When enabled, driver outputs function
as line drivers. Driver outputs are high impedance when
DE´is low. While outputs are high impedance, they func-
tion as line receivers.
___________________________________________________Pin Description (continued)
Note:For DE´and DI´pin descriptions, see Detailed Block Diagram and Typical Application Circuit(Figure 1 for MAX1480A/B/C,
Figure 2 for MAX1490A/B).
PIN
MAX1490A/BMAX1480A/B/CISO RO DRV—Noninverting Driver Output and Noninverting Receiver Input21Isolated Receiver-Output Drive. Connect to ISO RO LED through a resistor
(Table 1 of Figure 1 for MAX1480A/B/C, Table 2 of Figure 2 for MAX1490A/B).—Inverting Driver Output and Inverting Receiver Input
ISO VCC1
AC2, AC122Isolated Supply Voltage Source
27, 2823, 24Internal Connections. Leave these pins unconnected.
ISO DI IN22—Isolated Driver Input. Connect to ISO DI DRV for normal operation.—18Inverting Driver Output
ISO DE IN19Inverting Receiver Input20Noninverting Receiver Input—Isolated Driver-Enable Input. Connect to ISO DE DRV for normal operation.
NAMEFUNCTION—17Noninverting Driver Output
PINS ON THE ISOLATED RS-485/RS-422 SIDE (continued)
