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_______________General Description
The MAX3480A/MAX3480B are electrically isolated
RS-485/RS-422 data-communications interfaces.
Transceivers, optocouplers, and a transformer are all
included in one low-cost, 28-pin DIP package. A single
+3.3V supply on the logic side powers both sides of the
interface.
The MAX3480B features 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 250kbps. The
MAX3480A's driver slew rate is not limited, allowing
transmission rates up to 2.5Mbps.
These devices typically draw 180mA of quiescent sup-
ply current. The MAX3480B provides a low-power shut-
down mode in which it consumes only 0.2µA.
Drivers are short-circuit current limited and are protect-
ed against excessive power dissipation by thermal
shutdown circuitry that places the driver outputs into a
high-impedance state. The receiver input has a fail-safe
feature that guarantees a logic-high output if the input
is open circuit.
The MAX3480A/MAX3480B typically withstand 1600V
RMS
(1 minute) or 2000V
RMS
(1 second). Their isolated inputs
and outputs meet RS-485/RS-422 specifications.
________________________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
____________________________Features
o
Isolated Data Interface to 1600V
RMS
(1 minute)
o
Slew-Rate-Limited Data Transmission (MAX3480B)
o
High-Speed, Isolated, 2.5Mbps RS-485 Interface
(MAX3480A)
o
-7V to +12V Common-Mode Input Voltage Range
with Respect to Isolated Ground
o
Single +3.3V Supply
o
Current Limiting and Thermal Shutdown for
Driver Overload Protection
o
Standard 28-Pin DIP Package
MAX3480A/MAX3480B
Complete, Isolated, 3.3V
RS-485/RS-422 Data Interface
________________________________________________________________
Maxim Integrated Products
1
28
27
26
25
24
23
22
21
1
2
3
4
5
6
7
8
AC1
AC2
ISO V
CC1
B
D2
D1
V
CC2
V
CC1
ISO RO DRV
A
ISO DI IN
ISO DE IN
V
CC3
SD
FS
GND1
20
19
18
17
9
10
11
12
ISO COM1
ISO DI DRV
ISO V
CC2
ISO DE DRV
GND2
DE
V
CC4
DI
16
15
13
14
ISO COM2
ISO RO LED
V
CC5
RO
MAX485
MAX487
MAX845
ISOLATION BARRIER
TOP VIEW
MAX3480A/B
DIP
__________________Pin Configuration
19-0453; Rev 0; 1/96
PART
MAX3480A
CPI
MAX3480AEPI
MAX3480B
CPI
0°C to +70°C
-40°C to +85°C
0°C to +70°C
TEMP. RANGE
PIN-PACKAGE
28 Plastic DIP
28 Plastic DIP
28 Plastic DIP
MAX3480BEPI
-40°C to +85°C
28 Plastic DIP
DATA
RATE
(kbps)
2500
2500
250
250
______________Ordering Information
MAX3480A/MAX3480B
Complete, Isolated, 3.3V
RS-485/RS-422 Data Interface
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(V
CC
= V
CC1
= V
CC2
= V
CC4
= V
CC5
= 3.0V to 3.6V, FS = 0V, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at
V
CC
= V
CC1
= V
CC2
= V
CC4
= V
CC5
= 3.3V and T
A
= +25°C.) (Notes 1, 2, 3)
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
With Respect to GND:
Supply Voltage (V
CC1,
V
CC2,
V
CC4,
V
CC5
) .........-0.3V to +3.8V
Supply Voltage (V
CC3
) ..........................................-0.3V to +7V
Control Input Voltage (SD, FS) ................-0.3V to (V
CC
+ 0.3V)
Receiver Output Voltage (RO).................-0.3V to (V
CC
+ 0.3V)
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)................................-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)
Plastic DIP (derate 9.09mW/°C above +70°C) ...............727mW
Operating Temperature Ranges
MAX3480_CPI ......................................................0°C to +70°C
MAX3480_EPI ...................................................-40°C to +85°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10sec) .............................+300°C
R = 50
(RS-422)
T
A
= +25°C, V
ISO
= 50V
DC
T
A
= +25°C, V
ISO
= 50V
DC
FS = 0V
DE
´
, DI
´
(Figure 1)
DE
´
, DI
´
(Figure 1)
FS high
FS low
SD = V
CC3
Low
High
R
L
= 54
MAX3480A,
DE
´
= V
CC
or open
R
L
=
CONDITIONS
V
0.3
V
OD2
Differential Driver Output (no load)
V
2
V
OD1
8
pF
10
C
ISO
Isolation Capacitance
M
100
10,000
R
ISO
Isolation Resistance
V
0.4
V
IL
Input Low Voltage
V
V
CC
- 0.4
V
IH
Input High Voltage
pA
10
I
FSM
FS Input Leakage Current
µA
50
I
FSL
FS Input Pull-Up Current
V
0.8
V
FSL
FS Input Threshold
2.4
V
FSH
180
260
V
600
V
S
3.0
3.3
3.6
Supply Voltage
µA
Shutdown Supply Current (Note 3)
0.2
mA
240
I
CC
Operating Supply Current
280
120
200
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
I
SHDN
R = 27
(RS-485), Figure 3
1.5
5
Switch Frequency
f
SWL
kHz
R
L
= 54
R = 27
or 50
,
Figure 3
R = 27
or 50
, Figure 4
V
4
V
OD
Change in Magnitude of Driver
Output Voltage for Complementary
Output States
f
SWH
900
R
L
=
FS = V
CC
or open
MAX3480B,
DE
´
=
V
CC
or open
Differential Driver Output (with load)
Driver Common-Mode Output
V
OC
V
Differential
0.3
Common Mode
0.8
V
IN
= 12V
MAX3480A/MAX3480B
Complete, Isolated, 3.3V
RS-485/RS-422 Data Interface
_______________________________________________________________________________________
3
DI
´
= V
CC
CONDITIONS
1.0
ISO I
IN
V
CM
= 0V
V
0.4
V
OL
Receiver Output/Receiver Output
Low Voltage
mA
70
V
TH
Input Current (A, B)
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= V
CC1
= V
CC2
= V
CC4
= V
CC5
= 3.0V to 3.6V, FS = 0V, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at
V
CC
= V
CC1
= V
CC2
= V
CC4
= V
CC5
= 3.3V and T
A
= +25°C.) (Notes 1, 2, 3)
Receiver Input Hysteresis
V
OUT
= 3.6V, DI
´
= 0V
µA
250
I
OH
Receiver Output/Receiver Output
High Current
-7V
V
O
12V (Note 4)
mA
100
ISO I
OSD
Driver Short-Circuit Current
DE
´
= 0V,
V
CC
= 0V or 3.6V
mV
SWITCHING CHARACTERISTICS--MAX3480A
(V
CC
= V
CC1
= V
CC2
= V
CC4
= V
CC5
= 3.0V to 3.6V, FS = 0V, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at
V
CC
= V
CC1
= V
CC2
= V
CC4
= V
CC5
= 3.3V and T
A
= +25°C.)
ns
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS
tPLH - tPHL
Differential
Receiver Skew
Driver Input to Output
Propagation Delay
t
PLH
100
275
ns
Driver Output Skew (Note 5)
t
SKEW
25
90
ns
Driver Rise or Fall Time
t
R
, t
F
15
40
ns
Driver Enable to Output High
t
ZH
0.2
1.5
µs
Driver Enable to Output Low
t
ZL
0.2
1.5
µs
Driver Disable Time from High
t
HZ
0.3
1.5
µs
CONDITIONS
Figures 4, 6; R
DIFF
= 54
,
C
L1
= C
L2
= 100pF
Figures 5, 7; C
L
= 100pF, S2 closed
Figures 5, 7; C
L
= 100pF, S1 closed
Figures 4, 6; R
DIFF
= 54
,
C
L1
= C
L2
= 100pF
Figures 4, 6; R
DIFF
= 54
,
C
L1
= C
L2
= 100pF
Figures 5, 7; C
L
= 15pF, S2 closed
Driver Disable Time from Low
t
LZ
0.3
1.5
µs
Figures 5, 7; C
L
= 15pF, S1 closed
t
SKD
100
225
Receiver Input to Output
Propagation Delay
t
PLH
ns
Figures 4, 8; R
DIFF
= 54
,
C
L1
= C
L2
= 100pF
20
Figures 4, 8; R
DIFF
= 54
,
C
L1
= C
L2
= 100pF
Maximum Data Rate
f
MAX
2.5
Mbps
t
PLH
, t
PHL
< 50% of data period
t
PHL
t
PHL
100
275
100
225
-7V
V
CM
12V
0.25
R
IN
k
Receiver Input Resistance
-7V
V
CM
12V
-0.2
0.2
V
TH
V
Receiver Differential Threshold
MAX3480B
48
12
-0.2
-0.8
V
IN
= 12V
V
IN
= -7V
V
IN
= 12V
V
IN
= -7V
MAX3480B
MAX3480A
MAX3480A
MAX3480A/MAX3480B
Complete, Isolated, 3.3V
RS-485/RS-422 Data Interface
4
_______________________________________________________________________________________
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 (GND1, GND2), unless otherwise specified.
Note 2:
For DE
´
and DI
´
pin descriptions, see
Detailed Block Diagram and Typical Application Circuit (Figure 1 for
MAX3480A/MAX3480B).
Note 3:
Shutdown supply current is the current at V
CC1
when shutdown is enabled.
Note 4:
Applies to peak current. See
Typical Operating Characteristics and Applications Information.
SWITCHING CHARACTERISTICS--MAX3480B
(V
CC
= V
CC1
= V
CC2
= V
CC4
= V
CC5
= 3.0V to 3.6V, FS = 0V, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at
V
CC
= V
CC1
= V
CC2
= V
CC4
= V
CC5
= 3.3V and T
A
= +25°C.)
ns
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS
t
PLH
- t
PHL
Differential
Receiver Skew
t
PLH
1.0
2.0
Driver Input to Output
Propagation Delay
µs
Driver Output Skew
t
SKEW
100
800
ns
Driver Rise or Fall Time
t
R
, t
F
1.0
2.0
µs
Driver Enable to Output High
t
ZH
50
100
µs
Driver Enable to Output Low
t
ZL
50
100
µs
Driver Disable Time from Low
t
LZ
13
50
µs
CONDITIONS
Figures 4, 6; R
DIFF
= 54
,
C
L1
= C
L2
= 100pF
Figures 5, 7; C
L
= 100pF, S2 closed
Figures 5, 7; C
L
= 100pF, S1 closed
Figures 4, 6; R
DIFF
= 54
,
C
L1
= C
L2
= 100pF
Figures 4, 6; R
DIFF
= 54
,
C
L1
= C
L2
= 100pF
Figures 5, 7; C
L
= 15pF, S1 closed
Driver Disable Time from High
t
HZ
13
50
µs
Figures 5, 7; C
L
= 15pF, S2 closed
t
SKD
t
PLH
0.8
2.0
Receiver Input to Output
Propagation Delay
t
PHL
0.8
2.0
µs
Figures 4, 8; R
DIFF
= 54
,
C
L1
= C
L2
= 100pF
50
Figures 4, 8; R
DIFF
= 54
,
C
L1
= C
L2
= 100pF
Maximum Data Rate
f
MAX
0.25
Mbps
t
PLH
, t
PHL
< 50% of data period
t
PHL
1.0
2.0
MAX3480A/MAX3480B
Complete, Isolated, 3.3V
RS-485/RS-422 Data Interface
_______________________________________________________________________________________
5
2.0
-40
20
DRIVER DIFFERENTIAL OUTPUT VOLTAGE
vs. TEMPERATURE
MAX3480A/B-08
TEMPERATURE (°C)
DIFFERENTIAL OUTPUT VOLTAGE (V)
0
-20
60
40
80
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
3.0
DI
´
= HIGH OR OPEN
R
L
= 54
0
OUTPUT CURRENT
vs. DRIVER OUTPUT HIGH VOLTAGE
MAX3480 A/B-06
OUTPUT HIGH VOLTAGE (V)
OUTPUT CURRENT (mA)
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-6
-4
-2
2
4
6
OUTPUT CURRENT
vs. DRIVER OUTPUT LOW VOLTAGE
MAX3480 A/B-05
OUTPUT LOW VOLTAGE (V)
OUTPUT CURRENT (mA)
0
160
180
140
100
120
80
40
60
0
20
2
4
6
8
10
12
0
-40
20
RECEIVER OUTPUT LOW VOLTAGE
vs. TEMPERATURE
MAX3480 A/B-04
TEMPERATURE (°C)
OUTPUT LOW VOLTAGE (V)
0
-20
60
40
80
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
MEASURED AT ISO RO DRV
I
RO
= 8mA
3.00
-40
20
RECEIVER OUTPUT HIGH VOLTAGE
vs. TEMPERATURE
MAX3480 A/B-03
TEMPERATURE (°C)
OUTPUT HIGH VOLTAGE (V)
0
-20
60
40
80
3.25
3.50
3.75
4.00
4.25
4.50
4.75
5.00
MEASURED AT ISO RO DRV
I
RO
= 8mA
__________________________________________Typical Operating Characteristics
(V
CC_
= 3.3V, T
A
= +25°C, unless otherwise noted.)
0
OUTPUT CURRENT
vs. RECEIVER OUTPUT HIGH VOLTAGE
MAX3480 A/B-02
OUTPUT HIGH VOLTAGE (V)
OUTPUT CURRENT (mA)
-5
MEASURED AT ISO RO DRV
1.0
0
3.0
2.0
5.0
4.0
-10
-15
-20
-25
-30
0
OUTPUT CURRENT
vs. RECEIVER OUTPUT LOW VOLTAGE
MAX3480 A/B-01
OUTPUT LOW VOLTAGE (V)
OUTPUT CURRENT (mA)
10
20
30
40
50
60
70
80
MEASURED AT ISO RO DRV
1.0
0
3.0
2.0
5.0
4.0
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