MAX1490AEPG+ [MAXIM]
Line Transceiver, 1 Func, 1 Driver, 1 Rcvr, CMOS, PDIP24, PLASTIC, DIP-24;
| 型号： | MAX1490AEPG+ |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Line Transceiver, 1 Func, 1 Driver, 1 Rcvr, CMOS, PDIP24, PLASTIC, DIP-24 |
| 文件： | 总21页 (文件大小：1997K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-0259; Rev 3; 8/02
Complete, Isolated RS-485/RS-422
Data Interface
_________________General Description
____________________________Features
ꢀ Isolated Data Interface, Typically to 1600V
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.
RMS
(1 minute)
ꢀ Slew-Rate Limited for Errorless Data
Transmission (MAX1480B/MAX1480C/MAX1490B)
ꢀ High-Speed, Isolated, 2.5Mbps RS-485/RS-422
Interface (MAX1480A/MAX1490A)
ꢀ Full-Duplex Data Communication (MAX1490A/B)
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.
ꢀ -7V to +12V Common-Mode Input Voltage Range
with Respect to Isolated Ground
ꢀ Single +5V Supply
ꢀ Current Limiting and Thermal Shutdown for
Driver Overload Protection
ꢀ Standard 0.6" DIP Package:
28-Pin DIP (MAX1480A/B/C)
24-Pin DIP (MAX1490A/B)
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.
_______________Ordering Information
†
PART
TEMP RANGE
0°C to +70°C
-40°C to +85°C
PIN-PACKAGE
MAX1480ACPI
MAX1480AEPI
28 Wide Plastic DIP
28 Wide Plastic DIP
Ordering Information continued at end of data sheet.
The MAX1480A/MAX1480B/MAX1480C/MAX1490A/
†
Data rate for “A” parts is up to 2.5Mbps. Data rate for “B” and
MAX1490B typically withstand 1600V
(1 minute) or
RMS
“C” parts is up to 250kbps.
2000V
(1 second). Their isolated outputs meet all
RMS
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.
Pin Configurations
TOP VIEW
V
V
CC1
CC2
1
2
3
4
5
AC1
_____________________Selection Table
24
MAX1490A/B
23 AC2
DRIVER
ENABLE
TIME
HALF/
FULL
DUPLEX
DATA
RATE
(Mbps)
SLEW-
RATE
LIMITED
22
21
20
19
18
17
D1
D2
ISO V
CC1
PART
ISO RO DRV
(µs)
GND1
FS
A
B
Z
Y
MAX1480A
MAX1480B
MAX1480C
MAX1490A
MAX1490B
Half
Half
Half
Full
Full
2.5
0.25
0.25
2.5
No
Yes
Yes
No
0.2
35
0.5
—
6
SD
7
8
V
V
CC3
DI
9
16 ISO COM1
0.25
Yes
—
ISO DI DRV
10
11
12
15
14
CC4
RO
________________________Applications
Isolated RS-485/RS-422 Data Interface
Transceivers for EMI-Sensitive Applications
Industrial-Control Local Area Networks
Automatic Test Equipment
ISO V
CC2
GND2
13 ISO RO LED
ISOLATION BARRIER
DIP
Pin Configurations continued at end of data sheet.
HVAC/Building Control Networks
________________________________________________________________ Maxim Integrated Products
1
For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
Complete, Isolated RS-485/RS-422
Data Interface
ABSOLUTE MAXIMUM RATINGS
With Respect to GND_
Supply Voltage (V
LED Forward Current (DI, DE, ISO RO LED) ......................50mA
)...........................................-0.3V to +6V
Continuous Power Dissipation (T = +70°C)
CC_
A
Control Input Voltage (SD, FS)...............-0.3V to (V
Receiver Output Voltage (RO, RO)........-0.3V to (V
Output Switch Voltage (D1, D2)........................................+12V
With Respect to ISO COM_
+ 0.3V)
+ 0.3V)
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
CC_
CC_
Control Input Voltage (ISO DE_ )....-0.3V to (ISO V
Driver Input Voltage (ISO DI_ ) .......-0.3V to (ISO V
+ 0.3V)
+ 0.3V)
+ 0.3V)
CC_
CC_
Receiver Output Voltage (ISO RO_) ...-0.3V to (ISO V
CC_
Driver Output Voltage (A, B, Y, Z ) ......................-8V to +12.5V
Receiver Input Voltage (A, B)..............................-8V to +12.5V
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
= 5V 10ꢀ, V = V
FS
, T = T
to T
, unless otherwise noted. Typical values are at V = 5V and T = +25°C.) (Notes 1, 2)
CC_ A
CC_
CC_
A
MIN
MAX
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
535
725
60
MAX
UNITS
f
V
= 0V
FS
SWL
Switch Frequency
kHz
f
FS = V
or open
CC_
SWH
R = ∞, +25°C only
90
45
L
MAX1480A,
DE´ = V
or open
or open
or open
CC_
R = 54Ω
120
35
L
R = ∞, +25°C only
L
MAX1480B,
DE´ = V
CC_
R = 54Ω
L
95
R = ∞, +25°C only
L
35
75
MAX1480C,
DE´ = V
Operating Supply Current
I
mA
CC
CC_
R = 54Ω
L
95
R = ∞, +25°C only
100
170
65
150
125
L
MAX1490A
MAX1490B
R = 54Ω
L
R = ∞, +25°C only
L
R = 54Ω
L
130
Shutdown Supply Current
(Note 3)
I
SD = V
0.2
µA
SHDN
CC_
V
High
Low
2.4
2.4
SDH
Shutdown Input Threshold
V
pA
V
V
0.8
SDL
Shutdown Input Leakage Current
FS Input Threshold
10
V
High
Low
FSH
V
0.8
50
FSL
FS Input Pullup Current
FS Input Leakage Current
Input High Voltage
FS low
µA
pA
V
FS high
DE´, DI´
DE´, DI´
10
V
V
- 0.4
CC_
IH
Input Low Voltage
V
0.4
8
V
IL
Isolation Resistance
Isolation Capacitance
R
C
T
T
= +25°C, V
= 50VDC
100
10,000
10
MΩ
pF
ISO
ISO
A
A
ISO
ISO
= +25°C, V
= 50VDC
Differential Driver Output
(No Load)
V
V
OD1
2
_______________________________________________________________________________________
Complete, Isolated RS-485/RS-422
Data Interface
ELECTRICAL CHARACTERISTICS (continued)
(V
= 5V 10ꢀ, V = V
FS
, T = T
to T
, unless otherwise noted. Typical values are at V
= 5V and T = +25°C.) (Notes 1, 2)
CC_ A
CC_
CC_
A
MIN
MAX
PARAMETER
SYMBOL
CONDITIONS
R = 50Ω (RS-422)
MIN
2
TYP
MAX
UNITS
Differential Driver Output
(With Load)
V
V
OD2
R = 27Ω (RS-485), Figure 4
1.5
5.0
0.3
Change in Magnitude of
Differential Output Voltage for
Complementary Output States
Differential
R = 27Ω or 50Ω,
∆V
V
V
OD
Figure 4
Common mode
0.3
4
Driver Common-Mode Output
Voltage
V
R = 27Ω or 50Ω, Figure 4
OC
MAX1490A/B
0.25
1
V
V
= 12V
= -7V
IN
IN
DE´ = 0V,
= 0V
or 5.5V
MAX1480A/B/C
MAX1490A/B
V
Input Current (A, B)
ISO I
mA
CC_
IN
0.2
0.8
MAX1480A/B/C
Receiver Input Resistance
R
-7V ≤ V
-7V ≤ V
≤ 12V
≤ 12V
12
kΩ
V
IN
CM
CM
Receiver Differential Threshold
Voltage
V
-0.2
+0.2
TH
Receiver Input Hysteresis
∆V
V
= 0V
CM
70
mV
V
TH
Receiver Output/Receiver Output
Low Voltage
Using resistor values listed in
Tables 1 and 2
V
0.4
OL
Receiver Output/Receiver Output
High Current
I
V
= 5.5V
OUT
250
µA
OH
Driver Short-Circuit Current
ISO I
-7V ≤ V ≤ 12V (Note 4)
100
mA
OSD
O
SWITCHING CHARACTERISTICS—MAX1480A/MAX1490A
(V
= 5V 10ꢀ, FS = V
, T = T
to T
, unless otherwise noted. Typical values are at V
= 5V and TA = +25°C.)
CC_
CC_
A
MIN
MAX
CC_
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
100
100
MAX
275
UNITS
t
t
PLH
PHL
Driver Input to Output
Propagation Delay
Figures 5 and 7, R
= 100pF
= 54Ω, C = C
L1
DIFF
DIFF
DIFF
L2
L2
L2
ns
275
Figures 5 and 7, R
= 100pF
= 54Ω, C = C
L1
Driver Output Skew
t
25
15
90
40
ns
ns
µs
µs
µs
µs
ns
SKEW
Figures 5 and 7, R
= 100pF
= 54Ω, C = C
L1
Driver Rise or Fall Time
t
t
R, F
Driver Enable to Output High
(MAX1480A Only)
t
Figures 6 and 8, C = 100pF, S2 closed
0.2
0.2
0.2
0.2
1.5
1.5
1.5
1.5
ZH
L
Driver Enable to Output Low
(MAX1480A Only)
t
Figures 6 and 8, C = 100pF, S1 closed
L
ZL
LZ
HZ
Driver Disable Time from Low
(MAX1480A Only)
t
Figures 6 and 8, C = 15pF, S1 closed
L
Driver Disable Time from High
(MAX1480A Only)
t
Figures 6 and 8, C = 15pF, S2 closed
L
t
100
100
225
225
PLH
PHL
Receiver Input to Output
Propagation Delay
Figures 5 and 10, R = 54Ω, C = C
DIFF L1 L2
= 100pF
t
_______________________________________________________________________________________
3
Complete, Isolated RS-485/RS-422
Data Interface
SWITCHING CHARACTERISTICS—MAX1480A/MAX1490A (continued)
(V
CC_
= 5V 10ꢀ, FS = V
, T = T
to T
, unless otherwise noted. Typical values are at V
= 5V and TA = +25°C.)
CC_
A
MIN
MAX
CC_
PARAMETER
| Differential Receiver
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
|t
- t
Figures 5 and 10, R = 54Ω, C = C
DIFF L1 L2
PLH PHL
t
20
ns
SKD
Skew
= 100pF
Maximum Data Rate
f
t
, t
< 50ꢀ of data period
2.5
Mbps
µs
MAX
PLH PHL
Time to Shutdown
t
100
3
SHDN
Shutdown to Driver Output High
Shutdown to Driver Output Low
t
Figures 6 and 9, C = 100pF, S2 closed
10
10
µs
ZH(SHDN)
L
t
Figures 6 and 9, C = 100pF, S1 closed
3
µs
ZL(SHDN)
L
SWITCHING CHARACTERISTICS—MAX1480B/MAX1480C/MAX1490B
(V
CC_
= 5V 10ꢀ, FS = V
, T = T
to T
, unless otherwise noted. Typical values are at V
= 5V and TA = +25°C.)
CC_
A
MIN
MAX
CC_
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
2
MAX
3.0
UNITS
t
t
PLH
PHL
Driver Input to Output
Propagation Delay
Figures 5 and 7, R
= 54Ω,
= 54Ω,
= 54Ω,
DIFF
µs
C
= C = 100pF
L2
L1
2
3.0
Figures 5 and 7, R
DIFF
Driver Output Skew
t
900
1.0
35
1600
2.0
100
100
50
ns
µs
µs
µs
µs
µs
µs
µs
SKEW
C
= C = 100pF
L2
L1
Figures 5 and 7, R
DIFF
Driver Rise or Fall Time
t
t
R, F
C
= C = 100pF
L2
L1
Driver Enable to Output High
(MAX1480B Only)
t
Figures 6 and 8, C = 100pF, S2 closed
L
ZH
Driver Enable to Output Low
(MAX1480B Only)
t
t
Figures 6 and 8, C = 100pF, S1 closed
35
ZL
LZ
HZ
ZH
L
Driver Disable Time from Low
(MAX1480B Only)
Figures 6 and 8, C = 15pF, S1 closed
13
L
Driver Disable Time from High
(MAX1480B Only)
t
t
Figures 6 and 8, C = 15pF, S2 closed
13
50
L
Driver Enable to Output High
(MAX1480C Only)
Figures 6 and 8, C = 100pF, S2 closed
0.5
0.5
4.5
4.5
L
Driver Enable to Output Low
(MAX1480C Only)
t
ZL
Figures 6 and 8, C = 100pF, S1 closed
L
4
_______________________________________________________________________________________
Complete, Isolated RS-485/RS-422
Data Interface
SWITCHING CHARACTERISTICS—MAX1480B/MAX1480C/MAX1490B (continued)
(V
CC_
= 5V 10ꢀ, FS = V
, T = T
to T
, unless otherwise noted. Typical values are at V
= 5V and TA = +25°C.)
CC_
A
MIN
MAX
CC_
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Driver Disable Time from Low
(MAX1480C Only)
t
LZ
Figures 6 and 8, C = 15pF, S1 closed
2.0
4.5
µs
L
Driver Disable Time from High
(MAX1480C Only)
t
Figures 6 and 8, C = 15pF, S2 closed
2.0
4.5
µs
µs
ns
HZ
L
t
t
2
2
3.0
3.0
PLH
PHL
Receiver Input to Output
Propagation Delay
Figures 5 and 10, R
= 54Ω,
= 54Ω,
DIFF
C
= C = 100pF
L2
L1
|t
- t
| Differential Receiver
Figures 5 and 10, R
C = C = 100pF
L1
PLH PHL
DIFF
t
1200
SKD
Skew
L2
Maximum Data Rate
f
t
, t
< 50ꢀ of data period
0.25
Mbps
µs
MAX
PLH PHL
Time to Shutdown
t
100
35
SHDN
Shutdown to Driver Output High
Shutdown to Driver Output Low
t
Figures 6 and 9, C = 100pF, S2 closed
100
100
µs
ZH(SHDN)
L
t
Figures 6 and 9, C = 100pF, S1 closed
35
µs
ZL(SHDN)
L
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
and V
when shutdown is enabled.
CC1
CC2
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).
_______________________________________________________________________________________
5
Complete, Isolated RS-485/RS-422
Data Interface
__________________________________________Typical Operating Characteristics
(TV = +=25V°C, ,FuSn=leVss oth, eTrw=ise+2n5o°teCd,.u)nless otherwise noted.)
CC_
A
CC_
A
OUTPUT CURRENT vs.
RECEIVER OUTPUT LOW VOLTAGE
OUTPUT CURRENT vs.
RECEIVER OUTPUT HIGH VOLTAGE
RECEIVER OUTPUT HIGH VOLTAGE
vs. TEMPERATURE
80
-30
-25
5.00
4.75
4.50
4.25
4.00
3.75
3.50
MEASURED AT ISO RO DRV
MEASURED AT ISO RO DRV
MEASURED AT ISO RO DRV
I
= 8mA
RO
70
60
50
40
30
20
-20
-15
-10
-5
0
10
0
3.25
3.00
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
OUTPUT LOW VOLTAGE (V)
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
OUTPUT HIGH VOLTAGE (V)
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
RECEIVER OUTPUT LOW VOLTAGE
vs. TEMPERATURE
OUTPUT CURRENT vs.
DRIVER OUTPUT HIGH VOLTAGE
OUTPUT CURRENT vs.
DRIVER OUTPUT LOW VOLTAGE
0.8
0.7
0.6
0.5
0.4
0.3
0.2
180
160
140
120
100
80
-100
-90
MEASURED AT ISO RO DRV
I
RO
= 8mA
-80
-70
-60
-50
-40
-30
-20
60
40
20
0
0.1
0
-10
0
-40
-20
0
20
40
60
80
-7 -6 -5 -4 -3 -2 -1
0
1
2
3
4
5
6
0
1
2
3
4
5
6
7
8
9 10 11 12
TEMPERATURE (°C)
OUTPUT HIGH VOLTAGE (V)
OUTPUT LOW VOLTAGE (V)
DRIVER OUTPUT CURRENT
vs. DIFFERENTIAL OUTPUT VOLTAGE
DRIVER DIFFERENTIAL OUTPUT VOLTAGE
vs. TEMPERATURE
MAX1480B/MAX1480C/MAX1490B
SHUTDOWN CURRENT vs. TEMPERATURE
80
70
60
50
40
30
20
3.0
2.9
0.40
DI´ = HIGH OR OPEN
DI´ = HIGH OR OPEN
SD = V , DI´ = V
CC_
CC_
R = 54Ω
L
0.35
0.30
0.25
0.20
0.15
0.10
DE´ (MAX1480B/C ONLY) = V
CC_
CC2
2.8
2.7
2.6
MEASURED AT V AND V
CC1
2.5
2.4
2.3
2.2
10
0
0.05
0
2.1
2.0
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
DIFFERENTIAL OUTPUT VOLTAGE (V)
-40
-20
0
20
40
60
80
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
TEMPERATURE (°C)
6
_______________________________________________________________________________________
Complete, Isolated RS-485/RS-422
Data Interface
_____________________________Typical Operating Characteristics (continued)
(V
= 5V, FS = V
, T = +25°C, unless otherwise noted.)
CC_
A
CC_
MAX1480C
SUPPLY CURRENT vs. TEMPERATURE
MAX1480B
SUPPLY CURRENT vs. TEMPERATURE
MAX1480A
SUPPLY CURRENT vs. TEMPERATURE
120
110
100
90
140
120
160
140
R = 54Ω
L
V
V
= 5.5V
= 5.0V
= 4.5V
CC
R = 54Ω
L
V
= 5.5V
= 5.0V
= 4.5V
CC
V
= 5.5V
= 5.0V
R = 54Ω
L
CC
CC
V
CC
120
100
80
V
CC
100
80
V
CC
V
CC
V
= 4.5V
80
CC
DE´ = V
CC
DE´ = V
CC
R = ∞
L
70
DE´ = V
CC
60
60
60
V
= 5.5V
CC
R = ∞
L
50
V
= 5.5V
CC
V
= 5.0V
CC
R = ∞
L
V
= 5.0V
40
CC
V
= 5.0V
V
= 5.5V
CC
CC
40
30
20
V
= 4.5V
40
20
CC
20
0
V
= 4.5V
CC
V
= 4.5V
60
CC
-40
-20
0
20
40
60
80
-40
-20
0
20
40
80
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
MAX1490B
SUPPLY CURRENT vs. TEMPERATURE
MAX1490A
SUPPLY CURRENT vs. TEMPERATURE
150
140
130
120
110
100
90
200
180
160
V
CC
V
CC
V
CC
= 5.5V
= 5.0V
= 4.5V
R = 54Ω
L
V
= 5.5V
CC
V
V
= 5.0V
= 4.5V
CC
R = 54Ω
L
CC
140
120
100
80
V
= 5.5V
CC
R = ∞
L
V
= 5.5V
V
= 5.0V
CC
CC
80
V
= 5.0V
CC
R = ∞
L
70
60
50
V
= 4.5V
V
= 4.5V
CC
CC
-40
-20
0
20
40
60
80
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
TEMPERATURE (°C)
DRIVER ENABLE TIME
vs. TEMPERATURE
DRIVER DISABLE TIME
vs. TEMPERATURE
100
100
MAX1480B
MAX1480B
MAX1480C
10
1
10
1
R
V
= 54Ω
DI´
L
= 0V MEASURED FROM
DE´ TO VALID OUTPUT
R
V
= 54Ω
DI´
L
MAX1480C
= 0V MEASURED FROM
DE´ TO VALID OUTPUT
MAX1480A
MAX1480A
20 40
TEMPERATURE (°C)
0.1
0.1
-40
-20
0
20
40
60
80
-40
-20
0
60
80
TEMPERATURE (°C)
_______________________________________________________________________________________
7
Complete, Isolated RS-485/RS-422
Data Interface
_____________________________Typical Operating Characteristics (continued)
(V
= 5V, FS = V , V = 0V, DE´ toggled 0V to 5V at 5kHz, T = +25°C, unless otherwise noted.)
CC_ DI´
A
CC_
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
200ns/div
V
= 5.0V, DI´ = 0V
V
= 5.0V, DI´= 0V
CC_
CC_
DE´ TOGGLED 0V TO 5V AT 5kHz
DE´ TOGGLED 0V TO 5V AT 5kHz
MAX1480B
DRIVER ENABLE TIME
MAX1480B
DRIVER DISABLE TIME
DRIVER
OUTPUT B
2V/div
DRIVER
OUTPUT B
2V/div
DE´
2V/div
DE´
2V/div
10µs/div
5µs/div
V
= 5.0V, DI´= 0V
V
= 5.0V, DI´= 0V
CC_
CC_
DE´ TOGGLED 0V TO 5V AT 5kHz
DE´ TOGGLED 0V TO 5V AT 5kHz
MAX1480C
DRIVER DISABLE TIME
MAX1480C
DRIVER ENABLE TIME
DRIVER
OUTPUT B
2V/div
DRIVER
OUTPUT B
2V/div
DE´
2V/div
DE´
2V/div
500ns/div
500ns/div
V
= 5.0V, DI´ = 0V
CC_
V
= 5.0V, DI´= 0V
CC_
DE´ TOGGLED 0V TO 5V AT 5kHz
8
_______________________________________________________________________________________
Complete, Isolated RS-485/RS-422
Data Interface
_____________________________Typical Operating Characteristics (continued)
(V
= 5V, FS = V
, DE´ = V
, V = 0V to 5V at 1.25MHz, T = +25°C, unless otherwise noted.)
CC_ DI´
A
CC_
CC_
MAX1480A/MAX1490A
MAX1480A/MAX1490A
RECEIVER t
PHL
RECEIVER t
PLH
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
2V/div
RO
2V/div
20ns/div
20ns/div
V
= 5.0V, DE´= V
CC_
CC_
V
= 5.0V, DE´= V
CC_ CC_
DI´ = 0V TO 5V AT 1.25MHz
DI´ = 0V TO 5V AT 1.25MHz
MAX1480B/MAX1480C/MAX1490B
MAX1480B/MAX1480C/MAX1490B
RECEIVER t
RECEIVER t
PHL
PLH
MAX1480/90-23
MAX1480/90-24
RECEIVER
INPUT A
1V/div
RECEIVER
INPUT A
1V/div
RECEIVER
INPUT B
1V/div
RECEIVER
INPUT B
1V/div
RO
RO
2V/div
2V/div
200ns/div
500ns/div
V
= 5.0V, DE´= V
CC_
CC_
V
= 5.0V, DE´= V
CC_ CC_
DI´= 0V TO 5V AT 125kHz
DI´= 0V TO 5V AT 125kHz
POWER-UP DELAY TO DRIVER OUTPUTS VALID
DRIVER
OUTPUT B
(Z FOR MAX1490)
2V/div
SD
2V/div
1µs/div
V
V
= 0V
DI´
= 5V TO 0V AT 1kHz
SD
_______________________________________________________________________________________
9
Complete, Isolated RS-485/RS-422
Data Interface
________________________________________________________________Pin Description
PIN
NAME
FUNCTION
MAX1480A/B/C MAX1490A/B
PINSONTHENON-ISOLATEDSIDE
1, 2, 8, 10
1, 2, 8, 10
V
–V
Logic-Side (nonisolated side) +5V Supply Voltages
Internal Connections. Leave these pins unconnected.
Logic-Side Ground. Connect to GND2 (pin 12).
CC1 CC4
3, 4
5
3, 4
5
D1, D2
GND1
Frequency Select Input. If FS = V
or is open, switch frequency is high; if FS
CC_
6
7
6
7
FS
= GND, switch frequency is low. For optimal performance and minimal supply
current, connect FS to V or leave unconnected.
CC_
Shutdown Input. Ground for normal operation. When high, the power oscillator is
disabled.
SD
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
9
DI
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
—
DE
Receiver Output. If A > B by 200mV, RO will be high; if A < B by 200mV, RO
—
12
13
14
11
12
—
—
RO
GND2
RO
will be low. Open collector; must have pullup to V
(Table 2 of Figure 2).
CC
Logic-Side Ground. Connect to GND1 (pin 5).
Receiver Output. If A > B by 200mV, RO will be low; if A < B by 200mV, RO will
be high. Open collector; must have pullup to V (Table 1 of Figure 1).
CC_
V
CC5
Logic-Side (non-isolated side) +5V Supply Voltage
PINSONTHEISOLATEDRS-485/RS-422SIDE
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
16
13
ISO RO LED
ISO COM2
—
Isolated Common. Connect to ISO COM1 (pin 20).
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-
17
—
ISO DE DRV
collector output; must have pullup to ISO V
for normal operation (Table 1 of Figure 1).
and be connected to ISO DE IN
CC_
Isolated Supply Voltage. Connect to ISO V
pin 22 for MAX1490A/B).
(pin 26 for MAX1480A/B/C, or
CC1
18
19
20
14
15
16
ISO V
CC2
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 V
(Table 1 of Figure 1 for MAX1480A/B/C; Table 2 of Figure 2 for MAX1490A/B).
ISO DI DRV
ISO COM1
CC_
Isolated Common. For MAX1480A/B/C, connect to ISO COM2 (pin 16)
(Figures 1 and 2).
10 ______________________________________________________________________________________
Complete, Isolated RS-485/RS-422
Data Interface
___________________________________________________Pin Description (continued)
PIN
NAME
FUNCTION
MAX1480A/B/C MAX1490A/B
PINS ON THE ISOLATED RS-485/RS-422 SIDE (continued)
—
—
—
—
21
22
23
17
18
19
20
—
—
—
Y
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
Z
B
A
ISO DE IN
ISO DI IN
A
Isolated 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).
24
21
ISO RO DRV
25
26
—
22
B
ISO V
Inverting Driver Output and Inverting Receiver Input
Isolated Supply Voltage Source
CC1
27, 28
23, 24
AC2, AC1
Internal Connections. Leave these pins unconnected.
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).
Use the FS pin to select between high and low switching
Detailed Description
frequencies for the isolated power driver. The driver
The MAX1480A/MAX1480B/MAX1480C/MAX1490A/
switches at the lower frequency 535kHz when FS is low,
MAX1490B are complete, electrically isolated, RS-485/
and at the higher frequency 725kHz when FS is high. The
RS-422 data-communications interface solutions.
FS pin has a weak internal pull-up that switches the
Transceivers, optocouplers, a power driver, and a
device to the high-frequency mode when FS is left
transformer in one standard 28-pin DIP package (24-
unconnected. With FS high or open, no-load supply
pin for the MAX1490A/B) provide a complete interface.
current is reduced by approximately 4mA, and by up to
Signals and power are internally transported across the
8mA when fully loaded. For optimal performance and
isolation barrier (Figures 1, 2). Power is transferred from
minimal supply current, connect FS to V
unconnected.
or leave
CC_
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.
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.
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 Low-Power Shutdown Mode section).
______________________________________________________________________________________ 11
Complete, Isolated RS-485/RS-422
Data Interface
V
CC3
ISO V
CC1
D1
D2
MAX845
Q
MAX1480A: MAX1487
MAX1480B: MAX487
MAX1480C: MAX487
N
OSC
1.07MHz/
1.45MHz
T
F/F
FS
B
A
ISO DI IN
D
Q
N
ISO DE IN
ISO RO DRV
R
GND1
RE
SD
ISO COM1
EXTERNAL RS-485/RS-422 WIRING
TERMINATING RESISTOR
(ONE RESISTOR ON EACH END)
MAX1480A/B/C
V
V
V
CC1
IN
5V
AC1 (MAKE NO CONNECTION)
AC2 (MAKE NO CONNECTION)
1
2
28
27
26
25
24
23
22
21
20
19
18
17
16
15
TWISTED PAIR
CC2
TO OTHER TRANSCEIVERS
C1
22µF
C2
ISO V
CC1
R
R
L
L
3
D1
D2
B
0.1µF
B
4
SHIELD (OPTIONAL)
GND1
ISO RO DRV
A
5
A
TWISTED PAIR
TO OTHER TRANSCEIVERS
MAX1487
MAX487
MAX845
FS
6
SD
ISO DI IN
R6
SH
7
74HC86
OR EQUIVALENT
V
V
CC3
DI
ISO DE IN
8
R1
R4
SHIELD (OPTIONAL)
DI
DRIVER INPUT
ISO COM1
ISO DI DRV
9
DI´
CC4
DE
10
11
12
13
14
R2
R3
R5
NOTE: RESISTOR R7 PROTECTS
DE
DRIVER ENABLE
ISO V
CC2
THE MAX1480A/B/C FROM TRANSIENT
CURRENTS BETWEEN SHIELD AND
TRANSMISSION LINES.
DE´
R7
100Ω
GND2
ISO DE DRV
ISO COM2
ISO RO LED
RECEIVER OUTPUT
RO
RO
V
CC5
LOGIC GROUND
ISOLATION BARRIER
ISOLATED COMMON
Table 1. Pull-Up and LED Drive Resistors
PART
R1 (Ω)
200
R2 (Ω)
200
R3 (Ω)
1000
3000
3000
R4 (Ω)
4300
2200
3000
R5 (Ω)
1000
3000
3000
R6 (Ω)
MAX1480A
MAX1480B
MAX1480C
200
200
200
200
510
200
200
Figure 1. MAX1480A/MAX1480B/MAX1480C Detailed Block Diagram and Typical Application Circuit
The MAX1480A/MAX1480B/MAX1480C/MAX1490A/
MAX1490B typically withstand 1600V (1 minute) or
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 nonisolated side are low. Therefore, leave
DI´ and DE´ high or floating when in shutdown mode.
RMS
2000V
(1 second). The logic inputs can be driven
RMS
from TTL/CMOS-logic with a series resistor, and the
received data output can directly drive TTL or CMOS-
logic families with only resistive pullup.
12 ______________________________________________________________________________________
Complete, Isolated RS-485/RS-422
Data Interface
V
CC3
D1
MAX845
Q
N
OSC
1.07MHz/
1.45MHz
A
R
T
F/F
FS
ISO RO DRV
ISO DI DRV
D2
B
Z
Q
MAX1490A: MAX490
MAX1490B: MAX488
N
D
Y
SD
GND1
MAX1490A/B
EXTERNAL RS-485/RS-422 WIRING
V
IN
5V
V
V
TERMINATING RESISTOR
(ONE RESISTOR ON EACH END)
CC1
CC2
AC1 (MAKE NO CONNECTION)
AC2 (MAKE NO CONNECTION)
1
2
C1
C2
24
23
22
21
20
19
18
17
16
15
14
13
22µF
0.1µF
TWISTED PAIR
TO OTHER TRANSCEIVERS
ISO V
CC1
D1
D2
3
ISO RO DRV
R
4
R
L
L
GND1
A
B
Z
Y
A
B
5
SHIELD (OPTIONAL)
FS
6
TWISTED PAIR
TO OTHER TRANSCEIVERS
Z
SD
7
R
L
74HC86
OR EQUIVALENT
V
Y
CC3
8
R
L
R1
R5, 100Ω
R6, 100Ω
SH1
DI
DRIVER INPUT
ISO COM1
ISO DI DRV
DI
9
R4
V
DI´
SHIELD (OPTIONAL)
CC4
SH2
10
11
12
R2
RECEIVER OUTPUT
ISO V
CC2
R0
RO
R3
ISO RO LED
GND2
NOTE: RESISTORS R5 AND R6 PROTECT
THE MAX1490A/B FROM TRANSIENT
CURRENTS BETWEEN SHIELD AND
TRANSMISSION LINES.
ISOLATION BARRIER
LOGIC GROUND
ISOLATED COMMON
Table 2. Pull-Up and LED Drive Resistors
PART
R1 (Ω)
200
R2 (Ω)
1000
R3 (Ω)
330
R4 (Ω)
1000
MAX1490A
MAX1490B
200
3000
330
3000
Figure 2. MAX1490A/MAX1490B Detailed Block Diagram and Typical Application Circuit
Under these conditions, the MAX1480B/MAX1480C/
MAX1490B supply current is reduced to as low as 0.2µA.
tion, SD is low, turning the MOSFET on and thereby pro-
viding power to all the V pins. When SD is pulled high,
the power oscillator is disabled and the switch is turned
off, disconnecting power from the DI and DE optocou-
plers. In normal operating mode, the switch carries only
the optocoupler currents, so an on-resistance of several
ohms will not significantly degrade efficiency.
CC_
The high-speed optocouplers on the MAX1480A/
MAX1480C/MAX1490A consume an additional 10mA
through V
(V
for the MAX1490A). Therefore, to
CC4
CC5
completely shut down these devices, use an external P-
channel MOSFET as shown in Figure 3. In normal opera-
______________________________________________________________________________________ 13
Complete, Isolated RS-485/RS-422
Data Interface
MAX1480A
V
V
CC1
CC2
D1
V
AC1
AC2
ISO V
B
IN
5V
1
2
28
27
26
25
24
23
22
21
3
CC1
D2
4
GND1
FS
ISO RO DRV
5
Si943304
P
A
6
MAX845
MAX1487
SD
ISO DI IN
ISO DE IN
7
SHUTDOWN
V
CC3
8
R1
R2
DI
CC4
DE
ISO COM1
ISO DI DRV
9
20
19
18
17
DI
V
10
11
12
13
14
ISO V
CC2
DE
GND2
RO
ISO DE DRV
ISO COM2
ISO RO LED
R3
16
15
RO
V
CC5
ISOLATION BARRIER
GND
Figure 3. MAX1480A Low-Power Shutdown Mode
Test Circuits
ISOLATION BARRIER
ISOLATION BARRIER
(DE´)
R
( ) ARE FOR
THE MAX1480A/B/C
C
L1
V
D
OD
R
DIFF
D
V
R
RO (RO)*
R
DI´
V
ID
OC
* OPTOCOUPLER
C
L2
OUTPUTS. SEE FIGURES 1
AND 2 FOR DETAILED BLOCK
DIAGRAM AND TYPICAL
APPLICATION CIRCUIT.
Figure 4. Driver DC Test Load
Figure 5. Driver/Receiver Timing Test Circuit
14 ______________________________________________________________________________________
Complete, Isolated RS-485/RS-422
Data Interface
____________________________________________________Test Circuits (continued)
ISO V
_
CC
S1
S2
500Ω
OUTPUT
UNDER TEST
C
L
Figure 6. Driver Timing Test Load
Switching Waveforms
V
- 0.4V
2
V
- 0.4V
CC_
2
CC_
V
-0.4V
0V
V
- 0.4V
0V
CC_
CC_
V
- 0.4V
V
CC_
- 0.4V
CC_
2
2
DE´
DI´
t
t
PHL
PLH
1/2 V
O
t
t
LZ
ZL
B
A
A, B
V
O
2.3V
V
V
+ 0.5V
- 0.5V
OUTPUT NORMALLY LOW
OUTPUT NORMALLY HIGH
OL
V
OL
1/2 V
O
V
= V (A) - V (B)
DIFF
V
O
A, B
0V
V
DIFF
90%
90%
0V
2.3V
OH
10%
10%
-V
O
t
t
F
R
t
t
HZ
ZH
t
t - t
SKEW = PLH PHL
Figure 7. Driver Propagation Delays and Transition Times
Figure 8. Driver Enable and Disable Times
INPUT
V
ID
ID
2.4V
0V
0V
-V
SD
0.8V
1.6V
1.6V
V - V
A
B
MAX1490A/B
t
t
SHDN
ZL(SHDN)
OUTPUT
A, B
RO V
OH
t
t
PHL
2.3V
V
V
+ 0.5V
- 0.5V
OUTPUT NORMALLY LOW
OUTPUT NORMALLY HIGH
OL
1.5V
t
1.5V
1.5V
V
OL
V
OL
PLH
A, B
0V
V
OH
2.3V
OH
MAX1480A/B/C
OUTPUT
RO
1.5V
V
OL
t
t
SHDN
ZH(SHDN)
t
PHL
PLH
t
= t
t
SKEW
PLH - PHL
Figure 10. Receiver Propagation Delays
Figure 9. Times to/from Shutdown
______________________________________________________________________________________ 15
Complete, Isolated RS-485/RS-422
Data Interface
MAX1480B/MAX1480C/MAX1490B:
_____________________Function Tables
Reduced EMI and Reflections
The MAX1480B/MAX1480C/MAX1490B are slew-rate-
limited, 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-fre-
quency harmonics with large amplitudes are evident.
Figure 12 shows the same information for the slew-rate-
limited MAX1480B/MAX1480C/MAX1490B transmitting
the same signal. The high-frequency harmonics have
much lower amplitudes, and therefore the potential for
EMI is significantly reduced.
Half-Duplex Devices
(MAX1480A/MAX1480B/MAX1480C)
Table 3. Transmitting
INPUTS*
OUTPUTS
B
0
1
A
DE´
1
DI´
1
1
0
1
0
0
X
High-Z
High-Z
X = Don’t care
High-Z = High impedance
Table 4. Receiving
INPUTS*
OUTPUT
(RO)
V
- V
B
DE´
0
A
≥ +0.2V
≤ -0.2V
Open
0
1
0
10dB/div
0
0
0Hz
5MHz
500kHz/div
Full-Duplex Devices
(MAX1490A/MAX1490B)
Figure 11. Driver Output Waveform and FFT Plot of
MAX1480A/MAX1490A Transmitting a 150kHz Signal
Table 5. Transmitting
OUTPUTS
INPUT*
Z
Y
1
0
(DI´)
1
0
1
0
* 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).
10dB/div
Table 6. Receiving
OUTPUT
(RO)
INPUT
(V - V )
0Hz
5MHz
500kHz/div
A
B
≥ +0.2V
≤ -0.2V
Open
1
0
1
Figure 12. Driver Output Waveform and FFT Plot of
MAX1480B/MAX1480C/MAX1490B Transmitting a 150kHz
Signal
16 ______________________________________________________________________________________
Complete, Isolated RS-485/RS-422
Data Interface
TERMINATING RESISTOR
(ONE RESISTOR ON EACH END)
B
DI
D
120Ω
DE
RO
A
A
B
A
B
R
100Ω
RE
R
R
RE
RE
D
D
RO DE
DI
RO DE
DI
TERMINATING RESISTOR
V
IN
5V
(ONE RESISTOR ON EACH END)
MAX1480A/B/C
V
V
CC1
AC1 (MAKE NO CONNECTION)
AC2 (MAKE NO CONNECTION)
1
2
28
27
26
25
24
23
22
21
20
19
18
17
16
15
CC2
C1
C2
ISO V
CC1
3
D1
D2
B
22µF
0.1µF
B
4
GND1
ISO RO DRV
A
120Ω
5
A
MAX487
MAX1487
MAX845
FS
6
R6
SD
ISO DI IN
ISO DE IN
ISO COM1
ISO DI DRV
SH
7
74HC86
OR EQUIVALENT
R4
R5
SHIELD
V
V
CC3
DI
(OPTIONAL)
8
R1
DI
DRIVER INPUT
NOTE: RESISTOR R7 PROTECTS
THE MAX1480A/B/C FROM
TRANSIENT CURRENTS
9
CC4
DE
10
11
12
13
14
R2
R3
BETWEEN SHIELD AND
TRANSMISSION LINES.
DE
DRIVER ENABLE
ISO V
CC2
R7
GND2
ISO DE DRV
ISO COM2
ISO RO LED
100Ω
RECEIVER OUTPUT
RO
RO
V
CC5
LOGIC GROUND ISOLATION BARRIER
ISOLATED COMMON
Figure 13. Typical Half-Duplex RS-485/RS-422 Network
______________________________________________________________________________________ 17
Complete, Isolated RS-485/RS-422
Data Interface
Driver Output Protection
___________Applications Information
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-
cuits over the entire common-mode range (see the
Typical Operating Characteristics). In addition, a ther-
mal shutdown circuit forces the driver outputs into a
high-impedance state if the die temperature rises
excessively.
DI and DE are intended to be driven through a
series current-limiting resistor. Directly grounding
these pins destroys the device.
The MAX1480A/MAX1480B/MAX1480C are designed
for bidirectional data communications on multipoint
bus-transmission lines. The MAX1490A/MAX1490B are
designed for full-duplex bidirectional communications
that are primarily point-to-point. Figures 13 and 14
show half-duplex and full-duplex typical network appli-
cation 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 MAX1480B/
MAX1480C/MAX1490B are more tolerant of imperfect
termination and stubs off the main line.
Propagation Delay Skew
Typical propagation delays are shown in the Typical
Operating Characteristics using the test circuit of
Figure 5. Propagation delay skew is simply the differ-
ence between the low-to-high and high-to-low propaga-
tion delay. Small driver/receiver skew times help
reduce EMI and reflections by maintaining balanced
differential signals.
Layout Considerations
The MAX1480A/MAX1480B/MAX1480C/MAX1490A/
MAX1490B pinouts enable optimal PC board layout by
minimizing interconnect lengths and crossovers.
The receiver skew time, t
100ns for the MAX1480A/MAX1490A and under 1µs for
the MAX1480B/MAX1480C/MAX1490B.
- t
, is typically under
PLH PHL
I
I
• For maximum isolation, the “isolation barrier” should
not be breached except by the MAX1480A/
MAX1480B/MAX1480C/MAX1490A/MAX1490B.
The driver skew time is typically 25ns for the
MAX1480A/MAX1490A and 100ns for the MAX1480B/
MAX1480C/MAX1490B.
MAX1490A/B
V
IN
5V
V
V
CC1
AC1 (MAKE NO CONNECTION)
1
2
C1
C2
24
23
22
21
20
19
18
17
16
15
14
13
CC2
AC2 (MAKE NO CONNECTION)
22µF
0.1µF
ISO V
CC1
D1
D2
3
Y
120Ω
ISO RO DRV
4
D
R
DI
120Ω
Z
GND1
A
A
B
Z
Y
5
SHIELD (OPTIONAL)
B
FS
6
SD
Z
7
120Ω
74HC86
B
V
CC3
Y
8
OR EQUIVALENT
120Ω
RO
R1
R2
R5, 100Ω
DI
ISO COM1
DI
SH1
9
A
R4
SHIELD (OPTIONAL)
DI´
V
ISO DI DRV
SH2
CC4
10
11
12
DRIVER INPUT
ISO V
CC2
RO
R6, 100Ω
RO
NOTE: RESISTORS R5 AND R6 PROTECT
THE MAX1490A/B FROM TRANSIENT
CURRENTS BETWEEN SHIELD AND
TRANSMISSION LINES.
R3
RECEIVER OUTPUT
ISO RO LED
GND2
ISOLATED COMMON
ISOLATION BARRIER
LOGIC GROUND
Figure 14. Typical Full-Duplex RS-485/RS-422 Network
18 ______________________________________________________________________________________
Complete, Isolated RS-485/RS-422
Data Interface
Connections and components from one side should
The DI and DE (MAX1480A/B/C only) inputs are the
cathodes of LEDs whose anodes are connected to the
supply. These points are best driven by a CMOS-logic
gate with a series resistor to limit the current. The resis-
tor 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.
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.
All pull-up resistors are based on optocoupler specifica-
tions 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 will cause the iso-
lated 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 MAX1490, each shield should have
its own 100Ω resistor (Figures 1, 2, 13, and 14).
Pullup and LED Drive Resistors
The MAX1480A/MAX1480B/MAX1480C/MAX1490A/
MAX1490B are specified and characterized using the
resistor values shown in Table 1 of Figure 1 and Table
2 of Figure 2. Altering the recommended values can
degrade performance.
+5V
+5V
NETWORK SEGMENT B
2 8 10 14
NETWORK SEGMENT A
2 8 10 14
13
3kΩ
200Ω
A
B
23
25
23
25
A
1
2
9
B
26
26
3kΩ
74HC04
MAX1480C
MAX1480C
3kΩ
200Ω
3kΩ
4
3
13
11
9
19
22
17
21
19
22
17
21
3kΩ
3kΩ
DRIVER
ENABLE
B > A
DRIVER
ENABLE
A > B
200Ω
200Ω
11
24
24
200Ω
200Ω
15
15
5 7 12
5 7 12
+5V
+5V
51kΩ 1000pF
51kΩ 1000pF
16 15 14
7
6
5
2
B
Q
Q
10
B
Q
13
4
74HC123
74HC123
Q 12
1 A
9
A
CLR
3
CLR
11
Figure 15. Doubly Isolated RS-485 Repeater
______________________________________________________________________________________ 19
Complete, Isolated RS-485/RS-422
Data Interface
In the idle state, both transmitters are disabled, while all
Doubly Isolated RS-485 Repeater
The RS-422/RS-485 standard is specified for cable
lengths up to 4000 feet. When approaching or exceed-
ing 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 currents may flow. These cur-
rents are by their nature unstable and unpredictable. In
addition, they may cause noise to be injected into sen-
sitive instrumentation and, in severe cases, might actu-
ally cause physical damage to such equipment.
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 transmis-
sions. All receivers receive all data; if this is undesir-
able, 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 15, there
might be transmitters up to 8000 feet apart. That repre-
sents more than 8µs (assuming 1ns/foot of delay) in
which two nodes could be transmitting simultaneously.
Figure 15 shows a half-duplex (two-wire), bidirectional,
party-line repeater system that prevents interference
and/or damage from ground-potential differences. Two
MAX1480A/MAX1480B/MAX1480C isolated RS-485
transceivers are used to isolate each of the network
segments from the electrical environment of the
repeater. The MAX1480A/MAX1480B/MAX1480C also
regenerate bus signals that may have been degraded
by line attenuation or dispersion.
The circuit in Figure 15 can be used either directly as
shown, with the slew-rate-limited MAX1480B/
MAX1480C, for data transfer rates up to 250kbps, or
with the MAX1480A for data rates up to 2.5Mbps (see
Table 1 for pullup and LED resistor values when using
the MAX1480A or MAX1480B). If dual-port isolation is
not needed, one of the MAX1480C devices can be
replaced by a MAX487 for 250kbps applications.
20 ______________________________________________________________________________________
Ordering Information (continued)
Pin Configurations (continued)
†
PART
TEMP RANGE PIN-PACKAGE
TOP VIEW
MAX1480BCPI
MAX1480BEPI
MAX1480CCPI
MAX1480CEPI
MAX1490ACPG
MAX1490AEPG
MAX1490BCPG
MAX1490BEPG
0°C to +70°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
28 Wide Plastic DIP
28 Wide Plastic DIP
28 Wide Plastic DIP
28 Wide Plastic DIP
24 Wide Plastic DIP
24 Wide Plastic DIP
24 Wide Plastic DIP
24 Wide Plastic DIP
MAX1480A/B/C
V
V
CC1
CC2
D1
1
2
3
4
5
AC1
28
27 AC2
ISO V
26
25
CC1
B
D2
GND1
FS
24 ISO RO DRV
MAX845
MAX487
MAX1487
†
23
22
A
6
7
8
9
Data rate for “A” parts is up to 2500kbps. Data rate for “B” and
“C” parts is up to 250kbps.
ISO DI IN
SD
V
V
CC3
DI
21 ISO DE IN
ISO COM1
ISO DI DRV
20
19
CC4 10
DE 11
18 ISO V
CC2
ISO DE DRV
GND2 12
17
16 ISO COM2
ISO RO LED
RO
13
14
V
CC5
15
ISOLATION BARRIER
DIP
Package Information
For the latest package outline information, go to
www.maxim-ic.com/packages.
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 ____________________ 21
© 2002 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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