19-0453; Rev 0; 1/96
Complete, Isolated, 3.3V
RS-485/RS-422 Data Interface
_______________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.
____________________________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
__________________Pin Configuration
TOP VIEW
________________________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
V
CC1
1
V
CC2
D1
D2
GND1
FS
2
3
4
5
6
7
8
9
MAX3480A/B
28 AC1
27 AC2
26 ISO V
CC1
25 B
24 ISO RO DRV
MAX845
MAX485
MAX487
23 A
22 ISO DI IN
21 ISO DE IN
20 ISO COM1
19 ISO DI DRV
18 ISO V
CC2
17 ISO DE DRV
16 ISO COM2
15 ISO RO LED
______________Ordering Information
PART
MAX3480ACPI
MAX3480AEPI
MAX3480BCPI
MAX3480BEPI
TEMP. RANGE PIN-PACKAGE
0°C to +70°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
28 Plastic DIP
28 Plastic DIP
28 Plastic DIP
28 Plastic DIP
DATA
RATE
(kbps)
2500
2500
250
250
SD
V
CC3
DI
V
CC4
10
DE 11
GND2 12
RO 13
V
CC5
14
ISOLATION BARRIER
DIP
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
Complete, Isolated, 3.3V
RS-485/RS-422 Data Interface
MAX3480A/MAX3480B
ABSOLUTE MAXIMUM RATINGS
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
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
= 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)
PARAMETER
Supply Voltage
Switch Frequency
SYMBOL
V
S
f
SWL
f
SWH
FS = 0V
FS = V
CC
or open
MAX3480A,
Operating Supply Current
I
CC
DE
´
= V
CC
or open
MAX3480B,
DE
´
=
V
CC
or open
Shutdown Supply Current (Note 3)
FS Input Threshold
FS Input Pull-Up Current
FS Input Leakage Current
Input High Voltage
Input Low Voltage
Isolation Resistance
Isolation Capacitance
Differential Driver Output (no load)
Differential Driver Output (with load)
Change in Magnitude of Driver
Output Voltage for Complementary
Output States
Driver Common-Mode Output
I
SHDN
V
FSH
V
FSL
I
FSL
I
FSM
V
IH
V
IL
R
ISO
C
ISO
V
OD1
R = 50Ω (RS-422)
V
OD2
R = 27Ω (RS-485), Figure 3
R = 27Ω or 50Ω,
Figure 3
Differential
Common Mode
2
1.5
5
0.3
V
0.3
4
V
V
SD = V
CC3
High
Low
FS low
FS high
DE
´
, DI
´
(Figure 1)
DE
´
, DI
´
(Figure 1)
T
A
= +25°C, V
ISO
= 50V
DC
T
A
= +25°C, V
ISO
= 50V
DC
V
CC
- 0.4
0.4
100
10,000
10
8
10
2.4
0.8
50
R
L
=
∞
R
L
= 54Ω
R
L
=
∞
R
L
= 54Ω
CONDITIONS
MIN
3.0
TYP
3.3
600
900
180
280
120
240
0.2
µA
V
µA
pA
V
V
MΩ
pF
V
200
260
mA
MAX
3.6
UNITS
V
kHz
∆V
OD
V
OC
R = 27Ω or 50Ω, Figure 4
2
_______________________________________________________________________________________
Complete, Isolated, 3.3V
RS-485/RS-422 Data Interface
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)
PARAMETER
SYMBOL
CONDITIONS
DE
´
= 0V,
V
CC
= 0V or 3.6V
V
IN
= 12V V
IN
= 12V
MAX3480A
V
IN
= -7V
MAX3480B
MAX3480A
MAX3480B
-0.2
70
0.4
250
100
V
IN
= 12V
V
IN
= -7V
12
48
0.2
MIN
TYP
MAX
1.0
0.8
-0.8
0.25
-0.2
kΩ
V
mV
V
µA
mA
mA
UNITS
MAX3480A/MAX3480B
Input Current (A, B)
ISO I
IN
Receiver Input Resistance
Receiver Differential Threshold
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
DI
´
= V
CC
V
OUT
= 3.6V, DI
´
= 0V
-7V
≤
V
O
≤
12V (Note 4)
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.)
PARAMETER
Driver Input to Output
Propagation Delay
Driver Output Skew (Note 5)
Driver Rise or Fall Time
Driver Enable to Output High
Driver Enable to Output Low
Driver Disable Time from High
Driver Disable Time from Low
Receiver Input to Output
Propagation Delay
SYMBOL
t
PLH
t
PHL
t
SKEW
t
R
, t
F
t
ZH
t
ZL
t
HZ
t
LZ
t
PLH
t
PHL
t
SKD
f
MAX
CONDITIONS
Figures 4, 6; R
DIFF
= 54Ω,
C
L1
= C
L2
= 100pF
Figures 4, 6; R
DIFF
= 54Ω,
C
L1
= C
L2
= 100pF
Figures 4, 6; R
DIFF
= 54Ω,
C
L1
= C
L2
= 100pF
Figures 5, 7; C
L
= 100pF, S2 closed
Figures 5, 7; C
L
= 100pF, S1 closed
Figures 5, 7; C
L
= 15pF, S2 closed
Figures 5, 7; C
L
= 15pF, S1 closed
Figures 4, 8; R
DIFF
= 54Ω,
C
L1
= C
L2
= 100pF
Figures 4, 8; R
DIFF
= 54Ω,
C
L1
= C
L2
= 100pF
t
PLH
, t
PHL
< 50% of data period
2.5
MIN
TYP
100
100
25
15
0.2
0.2
0.3
0.3
100
100
20
MAX
275
275
90
40
1.5
1.5
1.5
1.5
225
225
UNITS
ns
ns
ns
µs
µs
µs
µs
ns
ns
Mbps
tPLH - tPHL
Differential
Receiver Skew
Maximum Data Rate
_______________________________________________________________________________________
3
Complete, Isolated, 3.3V
RS-485/RS-422 Data Interface
MAX3480A/MAX3480B
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.)
PARAMETER
Driver Input to Output
Propagation Delay
Driver Output Skew
Driver Rise or Fall Time
Driver Enable to Output High
Driver Enable to Output Low
Driver Disable Time from Low
Driver Disable Time from High
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
t
SKD
f
MAX
CONDITIONS
Figures 4, 6; R
DIFF
= 54Ω,
C
L1
= C
L2
= 100pF
Figures 4, 6; R
DIFF
= 54Ω,
C
L1
= C
L2
= 100pF
Figures 4, 6; R
DIFF
= 54Ω,
C
L1
= C
L2
= 100pF
Figures 5, 7; C
L
= 100pF, S2 closed
Figures 5, 7; C
L
= 100pF, S1 closed
Figures 5, 7; C
L
= 15pF, S1 closed
Figures 5, 7; C
L
= 15pF, S2 closed
Figures 4, 8; R
DIFF
= 54Ω,
C
L1
= C
L2
= 100pF
Figures 4, 8; R
DIFF
= 54Ω,
C
L1
= C
L2
= 100pF
t
PLH
, t
PHL
< 50% of data period
0.25
MIN
TYP
1.0
1.0
100
1.0
50
50
13
13
0.8
0.8
50
MAX
2.0
2.0
800
2.0
100
100
50
50
2.0
2.0
UNITS
µs
ns
µs
µs
µs
µs
µs
µs
ns
Mbps
t
PLH
- t
PHL
Differential
Receiver Skew
Maximum Data Rate
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.
4
_______________________________________________________________________________________
Complete, Isolated, 3.3V
RS-485/RS-422 Data Interface
__________________________________________Typical Operating Characteristics
(V
CC_
= 3.3V, T
A
= +25°C, unless otherwise noted.)
MAX3480A/MAX3480B
DRIVER DIFFERENTIAL OUTPUT VOLTAGE
vs. TEMPERATURE
DIFFERENTIAL OUTPUT VOLTAGE (V)
2.9
2.8
2.7
2.6
2.5
2.4
2.3
2.2
2.1
2.0
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
DI
´
= HIGH OR OPEN
R
L
= 54Ω
MAX3480A/B-08
OUTPUT CURRENT
vs. DRIVER OUTPUT HIGH VOLTAGE
-90
OUTPUT CURRENT (mA)
-80
-70
-60
-50
-40
-30
-20
-10
0
-6
-4
-2
0
2
4
6
OUTPUT HIGH VOLTAGE (V)
MAX3480 A/B-06
OUTPUT CURRENT
vs. DRIVER OUTPUT LOW VOLTAGE
160
OUTPUT CURRENT (mA)
140
120
100
80
60
40
20
0
0
2
4
6
8
10
12
OUTPUT LOW VOLTAGE (V)
MAX3480 A/B-05
3.0
-100
180
RECEIVER OUTPUT LOW VOLTAGE
vs. TEMPERATURE
MAX3480 A/B-04
RECEIVER OUTPUT HIGH VOLTAGE
vs. TEMPERATURE
4.75
OUTPUT HIGH VOLTAGE (V)
4.50
4.25
4.00
3.75
3.50
3.25
3.00
MEASURED AT ISO RO DRV
I
RO
= 8mA
MAX3480 A/B-03
0.8
0.7
OUTPUT LOW VOLTAGE (V)
0.6
0.5
0.4
0.3
0.2
0.1
0
-40
MEASURED AT ISO RO DRV
I
RO
= 8mA
5.00
-20
0
20
40
60
80
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
TEMPERATURE (°C)
OUTPUT CURRENT
vs. RECEIVER OUTPUT LOW VOLTAGE
MAX3480 A/B-01
OUTPUT CURRENT
vs. RECEIVER OUTPUT HIGH VOLTAGE
MEASURED AT ISO RO DRV
MAX3480 A/B-02
80
70
OUTPUT CURRENT (mA)
60
50
40
30
20
10
0
0
-30
-25
OUTPUT CURRENT (mA)
-20
-15
-10
-5
0
MEASURED AT ISO RO DRV
1.0
2.0
3.0
4.0
5.0
0
1.0
2.0
3.0
4.0
5.0
OUTPUT LOW VOLTAGE (V)
OUTPUT HIGH VOLTAGE (V)
_______________________________________________________________________________________
5
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