Maxim MAX1490EBEPG 15kv esd-protected, isolated rs-485/rs-422 Datasheet

19-1940; Rev 0; 4/01
±15kV ESD-Protected, Isolated RS-485/RS-422
Data Interfaces
____________________________Features
The MAX1480EA/MAX1480EC/MAX1490EA/MAX1490EB
are complete, electrically isolated, RS-485/RS-422 data
communications interface solutions in a hybrid microcircuit. The RS-485/RS-422 I/O pins are protected against
±15kV electrostatic discharge (ESD) shocks, without
latchup. 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.
♦ Isolated Data Interface, Guaranteed to 1260VRMS
(1min)
♦ ±15kV ESD Protection on I/O Pins
♦ Slew-Rate Limited for Errorless Data
Transmission (MAX1480EC/MAX1490EB)
♦ High-Speed, Isolated, 2.5Mbps RS-485/RS-422
Interface (MAX1480EA/MAX1490EA)
♦ Full-Duplex Data Communication
(MAX1490EA/MAX1490EB)
♦ Single +5V Supply
♦ Current Limiting and Thermal Shutdown for
Driver Overload Protection
♦ Standard 0.6in DIP Packages
28-Pin DIP (MAX1480EA/MAX1480EC)
24-Pin DIP (MAX1490EA/MAX1490EB)
The MAX1480EC/MAX1490EB feature 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 160kbps. The
MAX1480EA/MAX1490EA driver slew rate is not limited,
allowing transmission rates up to 2.5Mbps. The
MAX1480EA/MAX1480EC are designed for half-duplex
communication, while the MAX1490EA/MAX1490EB feature full-duplex communication.
Drivers are short-circuit current limited and protected
against excessive power dissipation by thermal shutdown circuitry that places the driver outputs into a highimpedance state. The receiver input has a fail-safe
feature that guarantees a known output (RO low for the
MAX1480EA/MAX1480EC, RO high for the MAX1490EA/
MAX1490EB) if the input is open circuit.
The MAX1480EA/MAX1480EC/MAX1490EA/MAX1490EB
withstand 1260VRMS (1min) or 1520VRMS (1s). Their isolated outputs meet all RS-485/RS-422 specifications. The
MAX1480EA/MAX1480EC are available in a 28-pin DIP
package, and the MAX1490EA/MAX1490EB are available
in a 24-pin DIP package.
_______________Ordering Information
PART†
TEMP. RANGE
MAX1480EACPI
MAX1480EAEPI
PIN-PACKAGE
0°C to +70°C
28 Wide Plastic DIP*
-40°C to +85°C
28 Wide Plastic DIP*
Ordering Information continued at end of data sheet.
† Data rate for A parts is up to 2.5Mbps. Data rate for C parts is
up to 250kbps.
*See Reliability section at end of data sheet.
Pin Configurations
TOP VIEW
1
24 AC1
________________________Applications
VCC2
2
23 AC2
D1
3
22 ISO VCC1
D2
4
21 ISO RO DRV
GND1
5
20 A
Isolated RS-485/RS-422 Data Interface
Transceivers for EMI-Sensitive Applications
Industrial-Control Local Area Networks
Automatic Test Equipment
HVAC/Building Control Networks
Telecom
FS 6
MAX488E
MAX490E
VCC1
MAX845E
.
19 B
7
18 Z
VCC3 8
17 Y
SD
MAX1490EA/
MAX1490EB
9
16 ISO COM1
VCC4 10
15 ISO DI DRV
DI
14 ISO VCC2
RO 11
13 ISO RO LED
GND2 12
ISOLATION BARRIER
DIP
Selector Guide appears at end of data sheet.
Pin Configurations continued at end of data sheet.
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1
MAX1480E/MAX1490E
_________________General Description
MAX1480E/MAX1490E
±15kV ESD-Protected, Isolated RS-485/RS-422
Data Interfaces
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_ + 0.3V)
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
MAX1480E_CPI/MAX1490E_CPI ........................0°C to +70°C
MAX1480E_EPI/MAX1490E_EPI ......................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°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.
ELECTRICAL CHARACTERISTICS
(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
Switch Frequency
SYMBOL
CONDITIONS
TYP
VFS = 0
535
fSWH
FS = VCC_ or open
725
85
145
55
120
130
180
65
130
MAX1480EA,
DE´ = VCC_ or open
Operating Supply Current
MIN
fSWL
ICC
MAX1480EC,
DE´ = VCC_ or open
MAX1490EA
MAX1490EB
Shutdown Supply Current
(Note 3)
ISHDN
SD = VCC_
Shutdown Input Threshold
VSDH
VSDL
High
Low
RL = ∞
RL = 54Ω
RL = ∞
RL = 54Ω
RL = ∞
RL = 54Ω
RL = ∞
RL = 54Ω
FS Input Pullup Current
High
Low
FS low
FS Input Leakage Current
FS high
Input High Voltage
VIH
DE´, DI´, Figures 1 and 2
Input Low Voltage
VIL
DE´, DI´, Figures 1 and 2
180
µA
0.8
50
10
1260
TA = +25°C, VISO = 50VDC
100
Isolation Capacitance
CISO
TA = +25°C, f = 1MHz
Differential Driver Output
(No Load)
VOD1
Differential Driver Output
(with Load)
VOD2
V
VRMS
10,000
MΩ
10
pF
8
R = 50Ω (RS-422)
R = 27Ω (RS-485), Figure 4
µA
V
0.4
TA = +25°C, 1min (Note 4)
V
pA
VCC - 0.4
VISO
V
pA
2.4
RISO
mA
125
0.8
Isolation Resistance
mA
120
2.4
Isolation Voltage
2
120
10
VFSH
VFSL
UNITS
kHz
0.2
Shutdown Input Leakage
Current
FS Input Threshold
MAX
2
1.5
_______________________________________________________________________________________
5
V
V
±15kV ESD-Protected, Isolated RS-485/RS-422
Data Interfaces
(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
Change in Magnitude of
Driver Output Voltage for
Complementary Output States
∆VOD
Driver Common-Mode Output
VOC
CONDITIONS
ISO IIN
Receiver Differential Threshold
0.3
Common mode
0.3
DE´ = 0,
VCC_ = 0 or +5.5V
RIN
-7V ≤ VCM ≤ +12V
VTH
-7V ≤ VCM ≤ +12V
UNITS
V
4
MAX1490EA/
MAX1490EB
1.0
MAX1480EA/
MAX1480EC
0.25
MAX1490EA/
MAX1490EB
0.8
MAX1480EA/
MAX1480EC
0.2
48
(MAX1490E_)
12
kΩ
-0.2
∆VTH
VCM = 0
Receiver Output Low Voltage
VOL
Using resistor values listed in Tables 1 and 2
IOH
VOUT = 5.5V
V
mA
(MAX1480E_)
Receiver Input Hysteresis
Receiver Output High Current
MAX
Differential
R = 27Ω or 50Ω, Figure 4
VIN = -7V
Receiver Input Resistance
TYP
R = 27Ω or 50Ω, Figure 4
VIN = +12V
Input Current (A, B)
MIN
0.2
70
V
mV
0.4
250
V
µA
Driver Short-Circuit Current
ISO IOSD
-7V ≤ VO ≤ 12V (Note 5)
100
mA
ESD Protection
ISO IOSD
A, B, Y, and Z pins, tested using Human Body
Model, Figures 1 and 2
±15
kV
SWITCHING CHARACTERISTICS—MAX1480EA/MAX1490EA
(VCC_ = +5V ±10%, VFS = VCC_, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC_ = +5V and TA = +25°C.)
PARAMETER
Driver Input to Output
Propagation Delay
SYMBOL
tPLH
tPHL
TYP
MAX
Figures 5 and 7, RDIFF = 54Ω,
CL1 = CL2 = 100pF
CONDITIONS
MIN
90
275
60
275
UNITS
ns
Driver Output Skew
tSKEW
Figures 5 and 7, RDIFF = 54Ω, CL1 = CL2 = 100pF
30
100
ns
Driver Rise or Fall Time
tR, tF
Figures 5 and 7, RDIFF = 54Ω, CL1 = CL2 = 100pF
15
50
ns
Driver Enable to Output High
(MAX1480EA Only)
tZH
Figures 6 and 8, CL = 100pF, S2 closed
1.0
1.8
µs
Driver Enable to Output Low
(MAX1480EA Only)
tZL
Figures 6 and 8, CL = 100pF, S1 closed
1.0
1.8
µs
Driver Disable Time from Low
(MAX1480EA Only)
tLZ
Figures 6 and 8, CL = 15pF, S1 closed
0.5
1.8
µs
Driver Disable Time from High
(MAX1480EA Only)
tHZ
Figures 6 and 8, CL = 15pF, S2 closed
0.5
1.8
µs
Receiver Input to Output
Propagation Delay
tPLH
tPHL
Figures 5 and 10, RDIFF = 54Ω, CL1 = CL2 = 100pF
120
225
90
225
ns
_______________________________________________________________________________________
3
MAX1480E/MAX1490E
ELECTRICAL CHARACTERISTICS (continued)
MAX1480E/MAX1490E
±15kV ESD-Protected, Isolated RS-485/RS-422
Data Interfaces
SWITCHING CHARACTERISTICS—MAX1480EA/MAX1490EA (continued)
(VCC_ = +5V ±10%, VFS = 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
Shutdown to Driver Output High
Shutdown to Driver Output Low
SYMBOL
CONDITIONS
tSKD
Figures 5 and 10, RDIFF = 54Ω, CL1 = CL2 = 100pF
fMAX
tSHDN
tSKEW, tSKD, tPHL ≤ 25% of data period
tZH(SHDN)
tZH(SHDN)
Figures 6 and 9, CL = 100pF, S2 closed
Figures 6 and 9, CL = 100pF, S1 closed
MIN
TYP
MAX
UNITS
30
150
ns
15
15
Mbps
µs
µs
µs
2.5
100
3
3
SWITCHING CHARACTERISTICS—MAX1480EC/MAX1490EB
(VCC_ = +5V ±10%, VFS = VCC_, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC_ = +5V and TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
TYP
MAX
tPLH
tPHL
MIN
1.4
1.1
300
3.0
3.0
1200
UNITS
Driver Output Skew
tSKEW
Figures 5 and 7, RDIFF = 54Ω, CL1 = CL2 = 100pF
Figures 5 and 7, RDIFF = 54Ω, CL1 = CL2 = 100pF
Figures 5 and 7, RDIFF = 54Ω, CL1 = CL2 = 100pF
Driver Rise or Fall Time
tR, tF
Figures 5 and 7, RDIFF = 54Ω, CL1 = CL2 = 100pF
1.0
2.0
µs
Driver Input to Output
Propagation Delay
µs
ns
Driver Enable to Output High
(MAX1480EC Only)
tZH
Figures 6 and 8, CL = 100pF, S2 closed
1.4
4.5
µs
Driver Enable to Output Low
(MAX1480EC Only)
tZL
Figures 6 and 8, CL = 100pF, S1 closed
1.4
4.5
µs
Driver Disable Time from Low
(MAX1480EC Only)
tLZ
Figures 6 and 8, CL = 15pF, S1 closed
2.0
4.5
µs
Driver Disable Time from High
(MAX1480EC Only)
tHZ
Figures 6 and 8, CL = 15pF, S2 closed
1.7
4.5
µs
Receiver Input to Output
Propagation Delay
tPLH
tPHL
Figures 5 and 10, RDIFF = 54Ω, CL1 = CL2 = 100pF
0.9
1.1
3.0
3.0
µs
|tPLH - tPHL| Differential
Receiver Skew
tSKD
Figures 5 and 10, RDIFF = 54Ω, CL1 = CL2 = 100pF
200
Maximum Data Rate
fMAX
tSKEW, tSKD ≤ 25% of data period
Time to Shutdown
tSHDN
ns
160
kbps
100
µs
Shutdown to Driver Output High
tZH(SHDN)
Figures 6 and 9, CL = 100pF, S2 closed
3
15
µs
Shutdown to Driver Output Low
tZL(SHDN)
Figures 6 and 9, CL = 100pF, S1 closed
3
15
µs
Note 1: All currents into device pins are positive; all currents out of device pins are negative. All voltages are referenced to logicside ground (GND_), unless otherwise specified.
Note 2: For DE´ and DI´ pin descriptions, see Detailed Block Diagram and Typical Application Circuit (Figure 1 for MAX1480EA/
MAX1480EC, Figure 2 for MAX1490EA/MAX1490EB).
Note 3: Shutdown supply current is the current at VCC1 and VCC2 when shutdown is enabled.
Note 4: Limit guaranteed by applying 1520VRMS for 1s. Test voltage is applied between all pins on one side of the package to all
pins on the other side of the package, e.g., between pins 1–14 and pins 15–28 on the 28-pin package.
Note 5: Applies to peak current (see Typical Operating Characteristics). Although the MAX1480EA/MAX1480EC and
MAX1490EA/MAX1490EB provide electrical isolation between logic ground and signal paths, they do not provide isolation
between external shields and the signal paths (see Isolated Common Connection section).
4
_______________________________________________________________________________________
±15kV ESD-Protected, Isolated RS-485/RS-422
Data Interfaces
50
40
30
-20
-15
-10
20
10
0
-40
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
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
0.1
20
-10
0
0
-20
0
20
40
60
0
0
80
1
2
3 4
5
6
7 8
9 10 11 12
TEMPERATURE (°C)
OUTPUT LOW VOLTAGE (V)
DRIVER OUTPUT CURRENT
vs. DIFFERENTIAL OUTPUT VOLTAGE
DRIVER DIFFERENTIAL OUTPUT VOLTAGE
vs. TEMPERATURE
70
60
50
40
30
20
10
3.0
DI´ = HIGH OR OPEN
RL = 54Ω
2.9
2.8
2.7
2.6
2.5
2.4
2.3
2.2
DIFFERENTIAL OUTPUT VOLTAGE (V)
0.40
SD = VCC_, DI´ = VCC_
DE´= VCC_(MAX1480EC ONLY)
MEASURED AT VCC1 AND VCC2
0.35
0.30
0.25
0.20
0.15
0.10
0
2.0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
SHUTDOWN CURRENT
vs. TEMPERATURE
0.05
2.1
0
-7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
OUTPUT HIGH VOLTAGE (V)
MAX1480E/90E TOC08
DI´ = HIGH OR OPEN
DIFFERENTIAL OUTPUT VOLTAGE (V)
80
MAX1480E/90E TOC06
MAX1480E/90E TOC05
140
-90
MAX1480E/90E TOC09
0.3
160
-100
OUTPUT CURRENT (mA)
0.4
180
OUTPUT CURRENT (mA)
0.5
0
-20
RECEIVER OUTPUT LOW VOLTAGE
vs. TEMPERATURE
MAX1480E/90E TOC07
OUTPUT LOW VOLTAGE (V)
3.50
TEMPERATURE (°C)
0.6
-40
OUTPUT CURRENT (mA)
3.75
OUTPUT HIGH VOLTAGE (V)
MEASURED AT ISO RO DRV
IRO = 8mA
0.7
4.00
OUTPUT LOW VOLTAGE (V)
MAX1480E/90E TOC04
0.8
4.25
3.00
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
4.50
3.25
0
0
MEASURED AT ISO RO DRV
IRO = 8mA
4.75
-5
MAX1480E/90E TOC03
-25
5.00
OUTPUT HIGH VOLTAGE (V)
60
MEASURED AT ISO RO DRV
SHUTDOWN CURRENT (µA)
OUTPUT CURRENT (mA)
70
-30
MAX1480E/90E TOC02
MEASURED AT ISO RO DRV
OUTPUT CURRENT (mA)
80
RECEIVER OUTPUT HIGH VOLTAGE
vs. TEMPERATURE
OUTPUT CURRENT vs.
RECEIVER OUTPUT HIGH VOLTAGE
MAX1480E/90E TOC01
OUTPUT CURRENT vs.
RECEIVER OUTPUT LOW VOLTAGE
-40
-20
0
20
40
TEMPERATURE (°C)
60
80
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
_______________________________________________________________________________________
5
MAX1480E/MAX1490E
__________________________________________Typical Operating Characteristics
(VCC_ = +5V, VFS = VCC_, Figures 1 and 2, TA = +25°C, unless otherwise noted.)
____________________________Typical Operating Characteristics (continued)
(VCC_ = +5V, VFS = VCC_, Figures 1 and 2, TA = +25°C, unless otherwise noted.)
100
DE´ = VCC
RL = ∞
80
60
40
VCC = +5.5V
VCC = +4.5V
20
100
VCC = +5V
90
VCC = +4.5V
80
DE´ = VCC
70
60
VCC = +5.5V
50
VCC = +5V
VCC = +5V
40
0
VCC = +4.5V
20
-20
0
20
40
60
80
RL = 54Ω
VCC = +5.5V
180
VCC = +5V
160
VCC = +4.5V
140
VCC = +5.5V
120
VCC = +5V
RL = ∞
100
30
-40
RL = ∞
200
SUPPLY CURRENT (mA)
VCC = +4.5V
RL = 54Ω
VCC = +5.5V
110
MAX1490EA
SUPPLY CURRENT vs. TEMPERATURE
MAX1480E/90E T0C11
VCC = +5V
120
120
SUPPLY CURRENT (mA)
RL = 54Ω
VCC = +5.5V
140
MAX1480E/90E TOC10
160
MAX1480EC
SUPPLY CURRENT vs. TEMPERATURE
-40
-20
TEMPERATURE (°C)
0
20
40
60
VCC = +4.5V
80
80
-40
-20
TEMPERATURE (°C)
0
20
40
60
80
TEMPERATURE (°C)
150
VCC = +5.5V
140
VCC = +5V
130
SUPPLY CURRENT (mA)
MAX1480E/90E TOC13
MAX1490EB
SUPPLY CURRENT vs. TEMPERATURE
VCC = +4.5V
120
RL = 54Ω
110
100
90
80
VCC = +5V
VCC = +5.5V
RL = ∞
70
60
VCC = +4.5V
50
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
MAX1480EA/MAX1490EA
RECEIVER tPLH
MAX1480EA/MAX1490EA
RECEIVER tPHL
MAX1480E/90E toc15
MAX1480E/90E toc14
RECEIVER
INPUT A
1V/div
RECEIVER
INPUT B
1V/div
RECEIVER
INPUT B
1V/div
RECEIVER
INPUT A
1V/div
RO
2V/div
RO
2V/div
20ns/div
20ns/div
VCC_ = 5.0V, DE´= VCC_
DI´ = 0V TO 5V AT 1 25MHz
6
VCC_ = 5.0V, DE´= VCC_
_______________________________________________________________________________________
MAX1480E/90E TOC12
MAX1480EA
SUPPLY CURRENT vs. TEMPERATURE
SUPPLY CURRENT (mA)
MAX1480E/MAX1490E
±15kV ESD-Protected, Isolated RS-485/RS-422
Data Interfaces
±15kV ESD-Protected, Isolated RS-485/RS-422
Data Interfaces
(VCC_ = +5V, VFS = VCC_, VDI´ = 0, DE´ toggled 0 to 5V at 5kHz, Figures 1 and 2, TA = +25°C, unless otherwise noted.)
MAX1480EC/MAX1490EB
RECEIVER tPHL
MAX1480EC/MAX1490EB
RECEIVER tPLH
MAX1480E/90E toc16
MAX1480E/90E toc17
RECEIVER
INPUT A
1V/div
RECEIVER
INPUT A
1V/div
RECEIVER
INPUT B
1V/div
RECEIVER
INPUT B
1V/div
RO
2V/div
RO
2V/div
200ns/div
500ns/div
VCC = 5 0V DE´= VCC
VCC = 5 0V DE´= VCC
MAX1480EC
DRIVER DISABLE TIME
MAX1480E/90E TOC18
MAX1480E/90E TOC19
MAX1480EC
DRIVER ENABLE TIME
DRIVER
OUTPUT B
2V/div
DRIVER
OUTPUT B
2V/div
DE´
2V/div
DE´
2V/div
500ns/div
500ns/div
VCC = 5.0V, DI´ = 0V
VCC = 5.0V, DI´= 0V
MAX1480E/90E TOC20
MAX1480EA/MAX1490EA
POWER-UP DELAY TO DRIVER OUTPUTS VALID
DRIVER
OUTPUT B
(Z FOR MAX1490)
2V/div
SD
2V/div
1µs/div
VDI´ = 0
VSD = 5V TO 0 AT 1kHz
_______________________________________________________________________________________
7
MAX1480E/MAX1490E
_____________________________Typical Operating Characteristics (continued)
MAX1480E/MAX1490E
±15kV ESD-Protected, Isolated RS-485/RS-422
Data Interfaces
________________________________________________________________Pin Description
PIN
8
MAX1480EA/
MAX1480EC
MAX1490EA/
MAX1490EB
NAME
FUNCTION
1, 2, 8, 10
3, 4
5
1, 2, 8, 10
3, 4
5
VCC1–VCC4
D1, D2
GND1
6
6
FS
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.
7
7
SD
Shutdown Input. Ground for normal operation. When high, the power oscillator is
disabled.
9
9
DI
Driver Input. With DE´ high (MAX1480EA/MAX1480EC 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 (see Table 1 for
MAX1480EA/MAX1480EC, Table 2 for MAX1490EA/MAX1490EB).
Logic-Side (Nonisolated Side) +5V Supply Voltages
Internal Connections. Leave these pins unconnected.
Logic-Side Ground. Connect to GND2 (pin 12).
11
—
DE
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 outputs 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).
—
11
RO
Receiver Output. If A > B by 200mV, RO is high; if A < B by 200mV, RO is low.
Open collector; must have pullup to VCC (Table 2).
12
12
GND2
13
—
RO
14
—
VCC5
15
13
ISO RO LED
16
—
ISO COM2
17
—
ISO DE DRV
18
14
ISO VCC2
Logic-Side Ground. Connect to GND1 (pin 5).
Receiver Output. If A > B by 200mV, RO is low; if A < B by 200mV, RO is high.
Open collector; must have pullup to VCC (Table 1).
Logic-Side (Nonisolated Side) +5V Supply Voltage
Isolated Receiver Output LED. Internal LED anode in MAX1480EA/MAX1480EC and
LED cathode in MAX1490EA/MAX1490EB. Connect to ISO RO DRV through a resistor (Table 1 for MAX1480EA/MAX1480EC; Table 2 for MAX1490EA/MAX1490EB).
Isolated Common. Connect to ISO COM1 (pin 20).
Isolated Driver-Enable Drive. 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
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).
Isolated Supply Voltage. Connect to ISO VCC1 (pin 26 for MAX1480EA/
MAX1480EC, or pin 22 for MAX1490EA/MAX1490EB).
19
15
ISO DI DRV
Isolated Driver-Input Drive. With DE´ high (MAX1480EA/MAX1480EC 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 MAX1480EA/MAX1480EC only)
for normal operation. Open-collector output; connect a pullup resistor to ISO VCC_
(Table 1 for MAX1480EA/MAX1480EC, Table 2 for MAX1490EA/MAX1490EB).
20
16
ISO COM1
Isolated Common. For MAX1480EA/MAX1480EC, connect to ISO COM2 (pin
16) (Figures 1 and 2).
_______________________________________________________________________________________
±15kV ESD-Protected, Isolated RS-485/RS-422
Data Interfaces
PIN
MAX1480EA/
MAX1480EC
MAX1490EA/
MAX1490EB
NAME
—
—
—
—
21
22
23
17
18
19
20
—
—
—
Y
Z
B
A
ISO DE IN
ISO DI IN
A
24
21
ISO RO DRV
25
26
27, 28
—
22
23, 24
B
ISO VCC1
AC2, AC1
FUNCTION
Noninverting Driver Output
Inverting Driver Output
Inverting Receiver Input
Noninverting Receiver Input
Isolated Driver-Enable Input. Connect to ISO DE DRV for normal operation.
Isolated Driver Input. Connect to ISO DI DRV for normal operation.
Noninverting Driver Output and Noninverting Receiver Input
Isolated Receiver-Output Drive. Connect to ISO RO LED through a resistor (see
Table 1 for MAX1480EA/MAX1480EC, Table 2 for MAX1490EA/MAX1490EB).
Inverting Driver Output and Inverting Receiver Input
Isolated Supply Voltage Source
Internal Connections. Leave these pins unconnected.
Note: For DE´ and DI´ pin descriptions, see Detailed Block Diagram and Typical Application Circuit (Figure 1 for MAX1480EA/
MAX1480EC, Figure 2 for MAX1490EA/MAX1490EB).
Detailed Description
The MAX1480EA/MAX1480EC/MAX1490EA/MAX1490EB
are complete, electrically isolated, RS-485/RS-422 datacommunications interface solutions. Transceivers, optocouplers, a power driver, and a transformer in one
standard 28-pin DIP package (24-pin package for the
MAX1490EA/MAX1490EB) 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 highspeed optocouplers. A single +5V supply on the logic
side powers both sides of the interface. The
MAX1480EA/MAX1480EC offer half-duplex communications while the MAX1490EA/MAX1490EB feature fullduplex communication. The functional input/output
relationships are shown in Tables 3 through 6.
The MAX1480EC/MAX1490EB feature reduced-slew-rate
drivers that minimize EMI and reduce reflections caused
by improperly terminated cables, allowing error-free
transmission at data rates up to 160kbps. The
MAX1480EA/MAX1490EA driver slew rate is not limited,
allowing transmission rates up to 2.5Mbps.
The MAX1480EC/MAX1490EB shutdown feature reduces
supply current to as low as 0.2µA by using the SD pin (see
Low-Power Shutdown Mode section).
Drivers are short-circuit current limited and are protected 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 MAX1480EA/MAX1480EC, the driver outputs are
enabled by bringing DE´ high. Driver-enable time is typically 1.0µs. Allow time for the devices to be
enabled before sending data (see Typical Operating
Characteristics). When enabled, driver outputs function
as line drivers. Driver outputs are high impedance when
DE´ is low. When outputs are high impedance, they function as line receivers.
The MAX1480EA/MAX1480EC/MAX1490EA/MAX1490EB
withstand 1260VRMS (1min) or 1520VRMS (1s). The logic
inputs can be driven from TTL/CMOS logic with a series
resistor, and the received data output can directly drive
TTL or CMOS-logic families with only a resistive pullup.
Low-Power Shutdown Mode
The SD pin shuts down the oscillator on the internal power
driver. With the primary side in shutdown, no power is
transferred across the isolation barrier. The DI and DE
optocouplers, however, still consume current if the drive
signals on the nonsolated side are low. Therefore, leave
DI´ and DE´ high or floating when in shutdown mode.
Under these conditions, the MAX1480EC/MAX1490EB
supply current is reduced to as low as 0.2µA.
_______________________________________________________________________________________
9
MAX1480E/MAX1490E
___________________________________________________Pin Description (continued)
MAX1480E/MAX1490E
±15kV ESD-Protected, Isolated RS-485/RS-422
Data Interfaces
VCC3
ISO VCC1
D1
MAX845E
Q
OSC
1.07MHz/
1.45MHz
FS
MAX1480EA: MAX1487E
MAX1480EC: MAX487E
N
T F/F
B
ISO DI IN
D
D2
Q
N
A
ISO DE IN
ISO RO DRV
R
RE
GND1
SD
ISO COM1
EXTERNAL RS-485/RS-422 WIRING
VIN
+5V
C1
22µF
C2
0.1µF
VCC1
1
28 AC1 (MAKE NO CONNECTION)
VCC2
2
27 AC2 (MAKE NO CONNECTION)
D2 4
GND1
5
FS 6
SD
DI
VCC3
R1*
DRIVER INPUT
DI´
DE
R2*
DRIVER ENABLE
DE´
R3*
RECEIVER OUTPUT
DI
VCC4
DE
GND2
VCC5
*SEE TABLE 1.
24
MAX845E
MAX1487E
MAX487E
LOGIC GROUND
SHIELD (OPTIONAL)
A
TWISTED PAIR
TO OTHER TRANSCEIVERS
23 A
7
8
21
9
20 ISO COM1
19 ISO DI DRV
11
18 ISO VCC2
12
17 ISO DE DRV
16
15
SH
R6*
RL
ISO DE IN
10
14
RL
B
ISO RO DRV
22 ISO DI IN
RO 13
RO
TWISTED PAIR
TO OTHER TRANSCEIVERS
26 ISO VCC1
B
25
D1 3
74HC86
OR EQUIVALENT
TERMINATING RESISTOR
(ONE RESISTOR ON EACH END)
MAX1480EA
MAX1480EC
R4*
SHIELD (OPTIONAL)
R5*
R7
100Ω
ISO COM2
NOTE: RESISTOR R7 PROTECTS
THE MAX1480EA FROM TRANSIENT
CURRENTS BETWEEN SHIELD AND
TRANSMISSION LINES.
ISO RO LED
ISOLATION BARRIER
ISOLATED COMMON
270pF
4kV
Figure 1. MAX1480EA/MAX1480EC Detailed Block Diagram and Application Circuit
Table 1. Pullup and LED Drive Resistors for Figure 1
R1 (Ω)
R2 (Ω)
R3 (Ω)
R4 (Ω)
R5 (Ω)
R6 (Ω)
MAX1480EA
PART
200
200
1000
4300
1000
200
MAX1480EC
200
200
3000
3000
3000
200
The high-speed optocouplers on the MAX1480EA/
MAX1480EC/MAX1490EA consume an additional 10mA
through VCC5 (VCC4 for the MAX1490EA). Therefore, to
completely shut down these devices, use an external Pchannel MOSFET as shown in Figure 3. In normal operation, SD is low, turning the MOSFET on and thereby
providing power to all the VCC pins. When SD is pulled
high, the power oscillator is disabled and the switch is
turned off, disconnecting power from the DI and DE opto10
couplers. In normal operating mode, the switch carries
only the optocoupler currents, so an on-resistance of several ohms does not significantly degrade efficiency.
______________________________________________________________________________________
±15kV ESD-Protected, Isolated RS-485/RS-422
Data Interfaces
MAX1480E/MAX1490E
VCC3
D1
MAX845
Q
OSC
1.07MHz/
1.45MHz
FS
N
T F/F
A
R
D2
Q
ISO RO DRV
B
ISO DI DRV
N
MAX1490EA: MAX490E
MAX1490EB: MAX488E
Z
D
SD
MAX1490EA/
MAX1490EB
VIN
+5V
VCC1
C1
22µF
C2
0.1µF
VCC2
D1
24 AC1 (MAKE NO CONNECTION)
2
23 AC2 (MAKE NO CONNECTION)
3
22 ISO VCC1
R1*
DI´
RECEIVER OUTPUT
RO
R2*
MAX488E
MAX490E
MAX845
SD 7
DRIVER INPUT
TERMINATING RESISTOR
(ONE RESISTOR ON EACH END)
TWISTED PAIR
TO OTHER TRANSCEIVERS
21 ISO RO DRV
5
FS 6
74HC86
OR EQUIVALENT
EXTERNAL RS-485/RS-422 WIRING
1
D2 4
GND1
DI
Y
GND1
VCC3 8
RL
20 A
A
19 B
B
18 Z
Z
17 Y
16 ISO COM1
VCC4 10
15 ISO DI DRV
R4*
14 ISO VCC2
TWISTED PAIR
TO OTHER TRANSCEIVERS
RL
SH1
SHIELD (OPTIONAL)
SH2
R3*
ISOLATION BARRIER
ISOLATED COMMON
*SEE TABLE 2.
LOGIC GROUND
RL
R6, 100Ω
13 ISO RO LED
GND2 12
SHIELD (OPTIONAL)
Y
R5, 100Ω
DI 9
R0 11
RL
NOTE: RESISTORS R5 AND R6 PROTECT
THE MAX1490EA/MAX1490EB FROM
TRANSIENT CURRENTS BETWEEN SHIELD AND
TRANSMISSION LINES.
270 pF
4kV
Figure 2. MAX1490EA/MAX1490EB Detailed Block Diagram and Typical Application Circuit
Table 2. Pullup and LED Drive Resistors for Figure 2
R1 (Ω)
R2 (Ω)
R3 (Ω)
R4 (Ω)
MAX1490EA
PART
200
1000
330
1000
MAX1490EB
200
3000
330
3000
MAX1480EC/MAX1490EB:
Reduced EMI and Reflections
The MAX1480EC/MAX1490EB are slew-rate-limited,
minimizing EMI and reducing reflections caused by
improperly terminated cables. Figure 11 shows both
the driver output waveform of a MAX1480EA/
MAX1490EA transmitting a 150kHz signal and the
Fourier analysis of that waveform. High-frequency harmonics with large amplitudes are evident. Figure 12
shows the same information for the slew-rate-limited
MAX1480EC/MAX1490EB transmitting the same signal.
The high-frequency harmonics have much lower amplitudes, and therefore the potential for EMI is significantly
reduced.
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 cir-
______________________________________________________________________________________
11
MAX1480E/MAX1490E
±15kV ESD-Protected, Isolated RS-485/RS-422
Data Interfaces
MAX1480EA
VIN
+5V
Si9433DY
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
MAX1487E
22 ISO DI IN
VCC3 8
21 ISO DE IN
DI 9
20 ISO COM1
VCC4 10
19 ISO DI DRV
DE 11
DE´
R3
18 ISO VCC2
GND2 12
17 ISO DE DRV
RO 13
RO
23 A
SD 7
VCC5
16 ISO COM2
15 ISO RO LED
14
ISOLATION BARRIER
GND
Figure 3. MAX1480EA Low-Power Shutdown Mode
Test Circuits
ISOLATION BARRIER
ISOLATION BARRIER
ISOLATION BARRIER
(DE´)
D
DI´
VOD
R
Figure 4. Driver DC Test Load
12
( ) ARE FOR
THE MAX1480EA/MAX1480EC.
CL1
R
VOC
D
RDIFF
VID
CL2
R
RO (RO)*
* OPTOCOUPLER
OUTPUTS. SEE FIGURES 1
AND 2 FOR DETAILED BLOCK
DIAGRAM AND TYPICAL
APPLICATION CIRCUIT.
Figure 5. Driver/Receiver Timing Test Circuit
______________________________________________________________________________________
±15kV ESD-Protected, Isolated RS-485/RS-422
Data Interfaces
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
0
tPLH
DE´
tPHL
0
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 0
-VO
VCC_ -0.4V
10%
VDIFF = V (A) - V (B)
90%
tR
OUTPUT NORMALLY HIGH
A, B
90%
VOL + 0.5V
VOH - 0.5V
2.3V
10%
0
tF
tZH
tHZ
tSKEW = tPLH - tPHL 
Figure 7. Driver Propagation Delays and Transition Times
Figure 8. Driver Enable and Disable Times
INPUT
VID
2.4V
SD
0.8V
1.6V
1.6V
tZL(SHDN)
-VID
VA - V B
MAX1490EA/MAX1490EB
OUTPUT
tSHDN
A, B
VOL
0
0
2.3V OUTPUT NORMALLY LOW
VOL + 0.5V
RO VOH
VOL
1.5V
tPLH
1.5V
tPHL
OUTPUT NORMALLY HIGH
A, B
VOH - 0.5V
2.3V
0
tZH(SHDN)
Figure 9. Times to/from Shutdown
tSHDN
RO
VOH
VOL
1.5V
MAX1480EA/MAX1480EC
1.5V
OUTPUT
tPHL
tSKEW = tPLH - tPHL
tPLH
Figure 10. Receiver Propagation Delays
______________________________________________________________________________________
13
MAX1480E/MAX1490E
____________________________________________________Test Circuits (continued)
MAX1480E/MAX1490E
±15kV ESD-Protected, Isolated RS-485/RS-422
Data Interfaces
cuits over the entire common-mode range (see Typical
Operating Characteristics). In addition, a thermal shutdown circuit forces the driver outputs into a high-im
pedance state if the die temperature rises excessively.
_____________________Function Tables
Half-Duplex Devices
(MAX1480EA/MAX1480EC)
Propagation Delay Skew
Propagation delay skew is the difference between the
low-to-high and high-to-low propagation delay. Small
driver/receiver skew times help reduce EMI and reflections by maintaining balanced differential signals.
Table 3. Transmitting
INPUTS*
OUTPUTS
DE´
DI´
B
1
1
0
1
0
1
0
0
X
High-Z
High-Z
A
1
X = Don’t care; High-Z = High impedance
Table 4. Receiving
INPUTS*
10dB/div
0
DE´
VA - VB
OUTPUT
(RO)
0
≥ +0.2V
0
0
≤ -0.2V
1
0
Open
0
5MHz
Full-Duplex Devices
(MAX1490EA/MAX1490EB)
500kHz/div
Figure 11. Driver Output Waveform and FFT Plot of
MAX1480EA/MAX1490EA Transmitting a 150kHz Signal
Table 5. Transmitting
INPUT*
OUTPUTS
(DI´)
Z
Y
1
0
1
0
1
0
* For DE´ and DI´ pin descriptions, see Detailed Block Diagram
and Typical Application Circuit (Figure 1 for MAX1480EA/
MAX1480EC, Figure 2 for MAX1490EA/MAX1490EB).
10dB/div
Table 6. Receiving
0
5MHz
500kHz/div
Figure 12. Driver Output Waveform and FFT Plot of
MAX1480EC/ MAX1490EB Transmitting a 150kHz Signal
14
INPUT
(VA - VB)
OUTPUT
(RO)
≥ +0.2V
1
≤ -0.2V
0
Open
1
______________________________________________________________________________________
±15kV ESD-Protected, Isolated RS-485/RS-422
Data Interfaces
These E versions of the MAX1480EA/MAX1480EC/
1490EA/MAX1490EB provide extra protection against
ESD. The rugged MAX1480EA/MAX1480EC/MAX1490EA/
MAX1490EB are intended for harsh environments where
high-speed communication is important. These devices
eliminate the need for transient suppressor diodes or the
use of discrete protection components. The standard
(non-E) MAX1480A/MAX1480C/MAX1490A/MAX1490B
are recommended for applications where cost is critical.
±15kV ESD Protection
As with all Maxim devices, ESD-protection structures are
incorporated on all pins to protect against electrostatic
discharges encountered during handling and assembly.
The driver outputs and receiver inputs have extra protection against static electricity. Maxim’s engineers developed state-of-the-art structures to protect these pins
against ESD of ±15kV without damage. The ESD structures withstand high ESD in all states: normal operation,
shutdown, and powered down. After an ESD event,
Maxim’s MAX1480EA/MAX1480EC/MAX1490EA/
MAX1490EB keep working without latchup. An isolation
capacitor of 270pF 4kV should be placed between ISO
COM and logic ground for optional performance against
an ESD pulse with respect to logic ground.
ESD protection can be tested in various ways; the transmitter outputs and receiver inputs of this product family
are characterized for protection to ±15kV using the
Human Body Model.
ESD Test Conditions
The ±15kV ESD test specifications apply only to the A, B,
Y, and Z I/O pins. The test surge may be referenced to
either the ISO COM or to the nonisolated GND (Figures 1
and 2).
R C 1MΩ
CHARGE-CURRENT
LIMIT RESISTOR
R D 1500Ω
Human Body Model
Figure 13 shows the Human Body Model, and Figure 14
shows the current waveform it generates when discharged into low impedance. This model consists of a
100pF capacitor charged to the ESD voltage of interest,
which is then discharged into the test device through a
1.5kΩ resistor.
Machine Model
The Machine Model for ESD tests all pins using a 200pF
storage capacitor and zero discharge resistance. Its
objective is to simulate the stress caused by contact that
occurs with handling and assembly during manufacturing. All pins require this protection during manufacturing—not just inputs and outputs. Therefore, after PC
board assembly, the Machine Model is less relevant to
I/O ports.
The MAX1480EA/MAX1480EC are designed for bidirectional data communications on multipoint bus-transmission lines. The MAX1490EA/MAX1490EB are designed
for full-duplex bidirectional communications that are primarily point-to-point. Figures 15 and 16 show half-duplex
and full-duplex typical network application circuits,
respectively. 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. The
slew-rate-limited MAX1480EC/MAX1490EB are more tolerant of imperfect termination and stubs off the main line.
Layout Considerations
The MAX1480EA/MAX1480EC/MAX1490EA/MAX1490EB
pinouts enable optimal PC board layout by minimizing
interconnect lengths and crossovers:
• For maximum isolation, the “isolation barrier” should
not be breached except by the MAX1480EA/
IP 100%
90%
DISCHARGE
RESISTANCE
Ir
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
AMPERES
HIGHVOLTAGE
DC
SOURCE
Cs
100pF
STORAGE
CAPACITOR
DEVICE
UNDER
TEST
36.8%
10%
0
0
Figure 13. Human Body ESD Test Model
tRL
TIME
tDL
CURRENT WAVEFORM
Figure 14. Human Body Current Waveform
______________________________________________________________________________________
15
MAX1480E/MAX1490E
___________Applications Information
MAX1480E/MAX1490E
±15kV ESD-Protected, Isolated RS-485/RS-422
Data Interfaces
TERMINATING RESISTOR
(ONE RESISTOR ON EACH END)
B
DI
D
120Ω
DE
A
A
A
B
B
RO
R
100Ω
RE
R
RE
R
RE
D
D
RO DE
DI
RO DE
DI
MAX1480EA/
MAX1480EC
VIN
+5V
C1
22µF
C2
0.1µF
VCC1
1
28 AC1 (MAKE NO CONNECTION)
VCC2
2
27 AC2 (MAKE NO CONNECTION)
26 ISO VCC1
D1 3
FS 6
SD
7
DI
DE
VCC3
DRIVER INPUT
DRIVER ENABLE
R1
R2
R3
RECEIVER OUTPUT
RO
DI
VCC4
DE
GND2
24
MAX845E
MAX487E
MAX1487E
ISO RO DRV
23 A
22 ISO DI IN
ISO DE IN
8
21
9
20 ISO COM1
10
19 ISO DI DRV
11
18 ISO VCC2
12
17 ISO DE DRV
RO 13
VCC5
14
LOGIC GROUND
B
25 B
D2 4
GND1
5
74HC86
OR EQUIVALENT
TERMINATING RESISTOR
(ONE RESISTOR ON EACH END)
16
15
ISOLATION BARRIER
A
R6
120Ω
SH
R4
SHIELD
(OPTIONAL)
R5
R7
100Ω
NOTE: RESISTOR R7 PROTECTS
THE MAX1480EA/MAX1480EC
FROM TRANSIENT CURRENTS
BETWEEN SHIELD AND
TRANSMISSION LINES.
ISO COM2
ISO RO LED
ISOLATED COMMON
270pF
4kV
Figure 15. Typical Half-Duplex RS-485/RS-422 Network
16
______________________________________________________________________________________
±15kV ESD-Protected, Isolated RS-485/RS-422
Data Interfaces
C1
22µF
C2
0.1µF
VCC1
1
24 AC1 (MAKE NO CONNECTION)
VCC2
2
23 AC2 (MAKE NO CONNECTION)
D1 3
22 ISO VCC1
D2 4
21 ISO RO DRV
FS 6
SD 7
74HC86
OR EQUIVALENT
VCC3
R1
DI
DRIVER INPUT
DI´
R2
MAX488E
MAX490E
MAX845E
GND1 5
8
RECEIVER OUTPUT
A
19 B
B
18 Z
Z
17 Y
Y
16 ISO COM1
VCC4 10
15 ISO DI DRV
R4
13 ISO RO LED
GND2 12
DI
R
RO
SHIELD (OPTIONAL)
120Ω
B
120Ω
A
SHIELD (OPTIONAL)
R6, 100Ω
R3
ISOLATED COMMON
ISOLATION BARRIER
LOGIC GROUND
SH2
D
Z
R5, 100Ω
SH1
14 ISO VCC2
RO 11
RO
120Ω
20 A
DI 9
Y
120Ω
NOTE: RESISTORS R5 AND R6 PROTECT
THE MAX1490EA/MAX1490EB FROM TRANSIENT
CURRENTS BETWEEN SHIELD AND
TRANSMISSION LINES.
270pF
4kV
Figure 16. Typical Full-Duplex RS-485/RS-422 Network
MAX1480EC/MAX1490EA/MAX1490EB. Connections
and components from one side should not be located near those of the other side.
• 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.
Pullup and LED Drive Resistors
The MAX1480EA/MAX1480EC/MAX1490EA/MAX1490EB
are specified and characterized using the resistor values shown in Tables 1 and 2. Altering the recommended values can degrade performance.
DI and DE are intended to be driven through a series
current-limiting resistor. Directly grounding these
pins destroys the device.
The DI and DE (MAX1480EA/MAX1480EC only) inputs
are the cathodes of LEDs whose anodes are connected
to the supply. These points are best driven by a CMOSlogic gate with a series resistor to limit the current. The
resistor values shown in Tables 1 and 2 are recommended when the 74HC86 gate or equivalent is used. These
values may need to be adjusted if a driving gate with dissimilar series resistance is used.
All pullup resistors are based on optocoupler specifications in order to optimize the devices’ data-transfer rates.
Isolated Common Connection
The isolated common may be completely floating with
respect to the logic ground and the effective network
ground. The receiver input resistors cause the isolated
common voltage to go to the mean voltage of the receiver
inputs. If using shielded cable, connect the isolated common to the shield through a 100Ω resistor. In the case of
the MAX1490EA/MAX1490EB, each shield should have its
own 100Ω resistor (Figures 1, 2, 15, and 16).
Double-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 ground-potential
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. It
is typically very low impedance so that if a connection
between the two grounds is attempted, very large cur-
______________________________________________________________________________________
17
MAX1480E/MAX1490E
MAX1490EA/
MAX1490EB
VIN
+5V
MAX1480E/MAX1490E
±15kV ESD-Protected, Isolated RS-485/RS-422
Data Interfaces
rents may flow. These currents are by their nature unstable and unpredictable. In addition, they may cause noise
to be injected into sensitive instrumentation and, in
severe cases, might actually cause physical damage to
such equipment.
Figure 17 shows a half-duplex (2-wire), bidirectional,
party-line repeater system that prevents interference
and/or damage from ground-potential differences. Two
MAX1480EA/MAX1480EC isolated RS-485 transceivers
are used to isolate each of the network segments from
the electrical environment of the repeater. The
MAX1480EA/MAX1480EC also regenerate bus signals
that may have been degraded by line attenuation or dispersion.
In the idle state, both transmitters are disabled, while all
receivers in the system are enabled. If any device on the
system has information for any other device, it starts
sending its data onto the bus. Each data transmission on
the bus retriggers the one-shot, keeping the sending
transmitter enabled until there are no more transmissions. All receivers receive all data; if this is undesirable,
the protocol must allow for an address field so receivers
can ignore data not directed to them.
Each node must refrain from transmitting when data
already exists on the bus, and must resend data that is
corrupted by the collisions that inevitably occur with a
party-line system. With the repeater of Figure 17, there
might be transmitters up to 8000 feet apart. That represents more than 8µs (assuming 1ns/foot of delay) in
which two nodes could be transmitting simultaneously.
The circuit in Figure 17 can be used either directly as
shown, with the slew-rate-limited MAX1480EC, for data
transfer rates up to 160kbps, or with the MAX1480EA for
data rates up to 2.5Mbps (see Table 1 for pullup and
LED resistor values when using the MAX1480EA). If dualport isolation is not needed, one of the MAX1480EC
devices can be replaced by a MAX487E for 250kbps
applications.
Reliability
These products contain transformers, optocouplers, and
capacitors, in addition to several monolithic ICs and
diodes. As such, the reliability expectations more closely
represent those of discrete optocouplers rather than the
more robust characteristics of monolithic silicon ICs. The
reliability testing programs for these multicomponent
devices may be viewed on the Maxim website
(www.maxim-ic.com) under Technical Support,
Technical Reference, Multichip Products.
+5V
+5V
NETWORK SEGMENT B
NETWORK SEGMENT A
2 8 10 14
A
23
B
25
2 8 10 14
3kΩ
13
1
26
3kΩ
3kΩ
200Ω
2
9
19
22
17
21
11
24
200Ω
200Ω
4
MAX1480EC
3
13
DRIVER
ENABLE
200Ω
A>B
DRIVER
ENABLE
B>A
23
A
25
B
26
3kΩ
74HC04
MAX1480EC
9
3kΩ
19
22
17
21
11
3kΩ
24
200Ω
200Ω
15
15
5 7 12
5 7 12
+5V
+5V
51kΩ 1000pF
16
15
2 B
7
14
Q 13
10 B
Q 4
9 A
CLR
3
6
Q 5
74HC123
74HC123
1 A
51kΩ 1000pF
Q 12
CLR
11
Figure 17. Double-Isolated RS-485 Repeater
18
______________________________________________________________________________________
±15kV ESD-Protected, Isolated RS-485/RS-422
Data Interfaces
Pin Configurations (continued)
PART†
TEMP. RANGE
MAX1480ECCPI
0°C to +70°C
28 Wide Plastic DIP
MAX1480ECEPI
-40°C to +85°C
28 Wide Plastic DIP
0°C to +70°C
24 Wide Plastic DIP
-40°C to +85°C
24 Wide Plastic DIP
0°C to +70°C
24 Wide Plastic DIP
VCC1 1
24 Wide Plastic DIP
VCC2 2
MAX1490EACPG
MAX1490EAEPG
MAX1490EBCPG
MAX1490EBEPG
-40°C to +85°C
PIN-PACKAGE
† Data rate for A parts is up to 2500kbps. Data rate for C parts is
up to 250kbps.
MAX1480EA/
MAX1480EC
TOP VIEW
28 AC1
27 AC2
26 ISO VCC1
D1 3
25 B
D2 4
GND1 5
FS 6
Selector Guide
MAX845
MAX487E
MAX1487E
23 A
SD 7
22 ISO DI IN
VCC3 8
21 ISO DE IN
DI 9
20 ISO COM1
VCC4 10
19 ISO DI DRV
PART
HALF/
FULL
DUPLEX
DATA
RATE
(Mbps)
SLEWRATE
LIMITED
MAX1480EA
Half
2.5
No
RO 13
MAX1480EC
MAX1490EA
MAX1490EB
Half
Full
Full
0.25
2.5
0.25
Yes
No
Yes
VCC5 14
This device is constructed using a unique set of packaging
techniques that impose a limit on the thermal profile the device
can be exposed to during board-level solder attach and
rework. Maxim recommends the use of the solder profiles recommended in the industry-standard specification, JEDEC
020A, paragraph 7.6, Table 3 for IR/VPR and Convection
Reflow processes. Preheating, per this standard, is required.
Hand or wave soldering is not recommended.
24 ISO RO DRV
18 ISO VCC2
DE 11
17 ISO DE DRV
GND2 12
16 ISO COM2
15 ISO RO LED
ISOLATION BARRIER
DIP
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600___________________ 19
© 2001 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
MAX1480E/MAX1490E
Ordering Information (continued)