19-0259; Rev 5; 5/05
Complete, Isolated RS-485/RS-422
Data Interface
_________________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/C) 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.
Next-Generation Device Features
o
For Integrated ESD Protection
MAX1480E/MAX1490E: ±15kV ESD-Protected,
Isolated RS-485/RS-422 Data Interfaces
o
For Space-Constrained Applications
MAX3157: High CMRR, RS-485 Transceiver with
±50V Isolation
MAX1480A/B/C/MAX1490A/B
_______________Ordering Information
PART
†
MAX1480ACPI
MAX1480AEPI
TEMP RANGE
0°C to +70°C
-40°C to +85°C
PIN-PACKAGE
28 Wide Plastic DIP
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 “B” and
“C” parts is up to 250kbps.
_____________________Selection Table
PART
HALF/
FULL
DUPLEX
Half
Half
Half
Full
Full
DATA
RATE
(MBPS)
2.5
0.25
0.25
2.5
0.25
SLEW-
RATE
LIMITED
No
Yes
Yes
No
Yes
DRIVER
ENABLE
TIME
(µS)
0.2
35
0.5
—
—
MAX1480A
MAX1480B
MAX1480C
MAX1490A
MAX1490B
Pin Configurations
TOP VIEW
V
CC1
V
CC2
D1
D2
GND1
1
2
3
4
5
MAX845
MAX488
MAX490
________________________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
24 AC1
23 AC2
MAX1490A/B
22 ISO V
CC1
21 ISO RO DRV
20 A
19 B
18 Z
17 Y
16 ISO COM1
15 ISO DI DRV
14 ISO V
CC2
13 ISO RO LED
ISOLATION BARRIER
FS 6
SD
7
V
CC3
8
DI
9
V
CC4
10
RO 11
GND2 12
DIP
Pin Configurations continued at end of data sheet.
________________________________________________________________
Maxim Integrated Products
1
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.
Complete, Isolated RS-485/RS-422
Data Interface
MAX1480A/B/C/MAX1490A/B
ABSOLUTE MAXIMUM RATINGS
With Respect to GND_
Supply Voltage (V
CC_
)...........................................-0.3V to +6V
Control Input Voltage (SD, FS)...............-0.3V to (V
CC_
+ 0.3V)
Receiver Output Voltage (RO, RO)........-0.3V to (V
CC_
+ 0.3V)
Output Switch Voltage (D1, D2)........................................+12V
With Respect to ISO COM_
Control Input Voltage (ISO DE_ ) ....-0.3V to (ISO V
CC_
+ 0.3V)
Driver Input Voltage (ISO DI_ ) .......-0.3V to (ISO V
CC_
+ 0.3V)
Receiver Output Voltage (ISO RO_) ...-0.3V to (ISO V
CC_
+ 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 (T
A
= +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
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
(V
CC_
= 5V ±10%, V
FS
= V
CC_
, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at V
CC_
= 5V and T
A
= +25°C.) (Notes 1, 2)
PARAMETER
Switch Frequency
SYMBOL
f
SWL
f
SWH
V
FS
= 0V
FS = V
CC_
or open
MAX1480A,
DE´ = V
CC_
or open
MAX1480B,
DE´ = V
CC_
or open
Operating Supply Current
I
CC
MAX1480C,
DE´ = V
CC_
or open
MAX1490A
MAX1490B
Shutdown Supply Current
(Note 3)
Shutdown Input Threshold
Shutdown Input Leakage Current
FS Input Threshold
FS Input Pullup Current
FS Input Leakage Current
Input High Voltage
Input Low Voltage
Isolation Resistance
Isolation Capacitance
Differential Driver Output
(No Load)
V
IH
V
IL
R
ISO
C
ISO
V
OD1
V
FSH
V
FSL
High
Low
FS low
FS high
DE´, DI´
DE´, DI´
T
A
= +25°C, V
ISO
= 50VDC
T
A
= +25°C, V
ISO
= 50VDC
100
10,000
10
8
V
CC_
- 0.4
0.4
10
2.4
0.8
50
I
SHDN
V
SDH
V
SDL
SD = V
CC_
High
Low
10
2.4
0.8
R
L
=
∞,
+25°C only
R
L
= 54Ω
R
L
=
∞,
+25°C only
R
L
= 54Ω
R
L
=
∞,
+25°C only
R
L
= 54Ω
R
L
=
∞,
+25°C only
R
L
= 54Ω
R
L
=
∞,
+25°C only
R
L
= 54Ω
CONDITIONS
MIN
TYP
535
725
60
120
35
95
35
95
100
170
65
130
0.2
µA
V
pA
V
µA
pA
V
V
MΩ
pF
V
125
150
75
mA
45
90
MAX
UNITS
kHz
2
_______________________________________________________________________________________
Complete, Isolated RS-485/RS-422
Data Interface
ELECTRICAL CHARACTERISTICS (continued)
(V
CC_
= 5V ±10%, V
FS
= V
CC_
, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at V
CC_
= 5V and T
A
= +25°C.) (Notes 1, 2)
PARAMETER
Differential Driver Output
(With Load)
Change in Magnitude of
Differential Output Voltage for
Complementary Output States
Driver Common-Mode Output
Voltage
SYMBOL
V
OD2
∆V
OD
V
OC
CONDITIONS
R = 50Ω (RS-422)
R = 27Ω (RS-485), Figure 4
R = 27Ω or 50Ω,
Figure 4
Differential
Common mode
MIN
2
1.5
5.0
0.3
V
0.3
4
MAX1480A/B/C
MAX1490A/B
MAX1480A/B/C
MAX1490A/B
MAX1480A/B/C
MAX1490A/B
48
12
-0.2
70
0.4
250
100
+0.2
1
0.25
0.8
0.2
kΩ
V
mV
V
µA
mA
mA
V
TYP
MAX
UNITS
V
MAX1480A/B/C/MAX1490A/B
R = 27Ω or 50Ω, Figure 4
DE´ = 0V,
V
CC_
= 0V
or 5.5V
V
IN
= 12V
V
IN
= -7V
Input Current (A, B)
ISO I
IN
Receiver Input Resistance
Receiver Differential Threshold
Voltage
Receiver Input Hysteresis
Receiver Output/Receiver
Output
Low Voltage
Receiver Output/Receiver
Output
High Current
Driver Short-Circuit Current
R
IN
V
TH
∆V
TH
V
OL
I
OH
ISO I
OSD
-7V
≤
V
CM
≤
12V
-7V
≤
V
CM
≤
12V
V
CM
= 0V
Using resistor values listed in
Tables 1 and 2
V
OUT
= 5.5V
-7V
≤
V
O
≤
12V (Note 4)
SWITCHING CHARACTERISTICS—MAX1480A/MAX1490A
(V
CC_
= 5V ±10%, FS = V
CC_
, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at V
CC_
= 5V and TA = +25°C.)
PARAMETER
Driver Input to Output
Propagation Delay
Driver Output Skew
Driver Rise or Fall Time
Driver Enable to Output High
(MAX1480A Only)
Driver Enable to Output Low
(MAX1480A Only)
Driver Disable Time from Low
(MAX1480A Only)
Driver Disable Time from High
(MAX1480A Only)
Receiver Input to Output
Propagation Delay
SYMBOL
t
PLH
t
PHL
t
SKEW
t
R,
t
F
t
ZH
t
ZL
t
LZ
t
HZ
t
PLH
t
PHL
CONDITIONS
Figures 5 and 7, R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF
Figures 5 and 7, R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF
Figures 5 and 7, R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF
Figures 6 and 8, C
L
= 100pF, S2 closed
Figures 6 and 8, C
L
= 100pF, S1 closed
Figures 6 and 8, C
L
= 15pF, S1 closed
Figures 6 and 8, C
L
= 15pF, S2 closed
Figures 5 and 10, R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF
MIN
TYP
100
100
25
15
0.2
0.2
0.2
0.2
100
100
MAX
275
275
90
40
1.5
1.5
1.5
1.5
225
225
UNITS
ns
ns
ns
µs
µs
µs
µs
ns
_______________________________________________________________________________________
3
Complete, Isolated RS-485/RS-422
Data Interface
MAX1480A/B/C/MAX1490A/B
SWITCHING CHARACTERISTICS—MAX1480A/MAX1490A (continued)
(V
CC_
= 5V ±10%, FS = V
CC_
, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at V
CC_
= 5V and TA = +25°C.)
PARAMETER
|t
PLH
- t
PHL
| Differential Receiver
Skew
Maximum Data Rate
Time to Shutdown
Shutdown to Driver Output High
Shutdown to Driver Output Low
SYMBOL
t
SKD
f
MAX
t
SHDN
t
ZH(SHDN)
t
ZL(SHDN)
Figures 6 and 9, C
L
= 100pF, S2 closed
Figures 6 and 9, C
L
= 100pF, S1 closed
CONDITIONS
Figures 5 and 10, R
DIFF
= 54Ω, C
L1
= C
L2
= 100pF
t
PLH
, t
PHL
< 50% of data period
2.5
100
3
3
10
10
MIN
TYP
20
MAX
UNITS
ns
Mbps
µs
µs
µs
SWITCHING CHARACTERISTICS—MAX1480B/MAX1480C/MAX1490B
(V
CC_
= 5V ±10%, FS = V
CC_
, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at V
CC_
= 5V and TA = +25°C.)
PARAMETER
Driver Input to Output
Propagation Delay
Driver Output Skew
Driver Rise or Fall Time
Driver Enable to Output High
(MAX1480B Only)
Driver Enable to Output Low
(MAX1480B Only)
Driver Disable Time from Low
(MAX1480B Only)
Driver Disable Time from High
(MAX1480B Only)
Driver Enable to Output High
(MAX1480C Only)
Driver Enable to Output Low
(MAX1480C Only)
SYMBOL
t
PLH
t
PHL
t
SKEW
t
R,
t
F
t
ZH
t
ZL
t
LZ
t
HZ
t
ZH
t
ZL
CONDITIONS
Figures 5 and 7, R
DIFF
= 54Ω,
C
L1
= C
L2
= 100pF
Figures 5 and 7, R
DIFF
= 54Ω,
C
L1
= C
L2
= 100pF
Figures 5 and 7, R
DIFF
= 54Ω,
C
L1
= C
L2
= 100pF
Figures 6 and 8, C
L
= 100pF, S2 closed
Figures 6 and 8, C
L
= 100pF, S1 closed
Figures 6 and 8, C
L
= 15pF, S1 closed
Figures 6 and 8, C
L
= 15pF, S2 closed
Figures 6 and 8, C
L
= 100pF, S2 closed
Figures 6 and 8, C
L
= 100pF, S1 closed
MIN
TYP
2
2
900
1.0
35
35
13
13
0.5
0.5
MAX
3.0
3.0
1600
2.0
100
100
50
50
4.5
4.5
UNITS
µs
ns
µs
µs
µs
µs
µs
µs
µs
4
_______________________________________________________________________________________
Complete, Isolated RS-485/RS-422
Data Interface
SWITCHING CHARACTERISTICS—MAX1480B/MAX1480C/MAX1490B (continued)
(V
CC_
= 5V ±10%, FS = V
CC_
, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at V
CC_
= 5V and TA = +25°C.)
PARAMETER
Driver Disable Time from Low
(MAX1480C Only)
Driver Disable Time from High
(MAX1480C Only)
Receiver Input to Output
Propagation Delay
|t
PLH
- t
PHL
| Differential Receiver
Skew
Maximum Data Rate
Time to Shutdown
Shutdown to Driver Output High
Shutdown to Driver Output Low
SYMBOL
t
LZ
t
HZ
t
PLH
t
PHL
t
SKD
f
MAX
t
SHDN
t
ZH(SHDN)
t
ZL(SHDN)
Figures 6 and 9, C
L
= 100pF, S2 closed
Figures 6 and 9, C
L
= 100pF, S1 closed
CONDITIONS
Figures 6 and 8, C
L
= 15pF, S1 closed
Figures 6 and 8, C
L
= 15pF, S2 closed
Figures 5 and 10, R
DIFF
= 54Ω,
C
L1
= C
L2
= 100pF
Figures 5 and 10, R
DIFF
= 54Ω,
C
L1
= C
L2
= 100pF
t
PLH
, t
PHL
< 50% of data period
0.25
100
35
35
100
100
MIN
TYP
2.0
2.0
2
2
1200
MAX
4.5
4.5
3.0
3.0
UNITS
µs
µs
µs
ns
Mbps
µs
µs
µs
MAX1480A/B/C, MAX1490A/B
5
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 V
CC1
and V
CC2
when 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 Connection
section).
_______________________________________________________________________________________
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