19-1778; Rev 3; 11/01
High CMRR RS-485 Transceiver
with ±50V Isolation
General Description
The MAX3157 is a high CMRR RS-485/RS-422 data-com-
munications interface providing ±50V isolation in a
hybrid microcircuit. A single +5V supply on the logic side
powers both sides of the interface, with external ±50V
capacitors transferring power from the logic side to the
isolated side. Each MAX3157 contains one transmitter
and one receiver and is guaranteed to operate at data
rates up to 250kbps. Drivers are short-circuit current lim-
ited and protected against excessive power dissipation
by thermal shutdown circuitry that places the driver out-
puts into a high-impedance state. The receiver input has
a fail-safe feature that guarantees a logic high receiver
output if the inputs are open, shorted, or connected to a
terminated transmission line with all drivers disabled.
The MAX3157 typically draws 25mA of supply current
when unloaded or when fully loaded with the driver dis-
abled. Supply current drops to 25µA when the device is
placed in shutdown mode. The device is pin selectable
between half- and full-duplex mode and also features
independently programmable receiver and transmitter
output phase through separate pins. The MAX3157 is a
low-cost replacement for opto-isolated transceivers. For
fully isolated RS-485/RS-422 transceivers, refer to the
MAX1480 family data sheet.
o
±50V Isolated Data Interface
o
+5V Single Supply
o
Low-Cost Replacement for Opto-Isolated
Transceivers
o
True Fail-Safe Receiver While Maintaining
EIA/TIA-485 Compliance
o
Pin-Selectable Full/Half-Duplex Operation
o
Phase Controls to Correct for Twisted-Pair
Reversal
o
25µA Low-Power Shutdown Mode
o
Thermal Shutdown for Driver Overload Protection
o
28-Pin SSOP Package
o
Slew Rate Limited Reduced EMI
Features
MAX3157
Ordering Information
PART
MAX3157CAI
MAX3157EAI
MAX3157CPI
MAX3157EPI
TEMP. RANGE
0°C to +70°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
PIN-PACKAGE
28 SSOP
28 SSOP
28 PDIP
28 PDIP
________________________Applications
Industrial Controls
Level Translators
Telecommunications
Local Area Networks
V
CC
0.1µF
V
CC
H/F
TXP
RXP
MICRO
DE
DI
RE
RO
GND
ISOV
CC
A
B
Y
Z
YR
ZR
AR
BR
Pin Configurations appear at end of data sheet.
Typical Operating Circuit
MAX3157
RT = 100Ω
RS-485
NODE
RG
C1LO C1HI C2LO C2HI ISOCOM
±50V
C1
0.047µF
C2
0.047µF
C4
10nF
GND OFFSET
REMOTE GND
________________________________________________________________
Maxim Integrated Products
REMOTE MICRO
C3
1µF
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.
High CMRR RS-485 Transceiver
with ±50V Isolation
MAX3157
ABSOLUTE MAXIMUM RATINGS
All voltages referenced to GND unless otherwise noted.
Supply Voltage (V
CC
).............................................................+7V
Cable Ground (ISOCOM) ....................................................±75V
Isolated Supply ISOVCC Relative to Cable Ground
(ISOCOM) ............................................................................+7V
Digital Input, Output Voltage
(DI, DE,
RE,
TXP, RXP, RO)......................-0.3V to (V
CC
+ 0.3V)
Digital Inputs (H/F) Relative to Cable Ground
(ISOCOM) ..........................................-0.3V to (ISOVCC + 0.3V)
Driver Output Voltage (Y, Z), Relative to Cable Ground
(ISOCOM).............................................................-8V to +12.5V
Receiver Input Voltage (A, B), Relative to Cable Ground
(ISOCOM).............................................................-8V to +12.5V
Termination Connections (YR, ZR, AR, BR) Relative to Cable
Ground (ISOCOM)................................................-8V to +12.5V
Charge-Pump Capacitance Low
(C1LO, C2LO) .......................................-0.3V to (V
CC
+ 0.3V)
Charge-Pump Capacitance High (C1HI, C2HI) Relative
to Cable Ground (ISOCOM) ...........-0.3V to (ISOVCC + 0.3V)
Continuous Power Dissipation
28-Pin SSOP (derate 10.8mW/°C above +70°C) ........860mW
28-Pin PDIP (derate 14.3mW/°C above +70°C)........1143mW
Operating Temperature Ranges
MAX3157C_I .....................................................0°C to +70°C
MAX3157E_I ..................................................-40°C to +85°C
Junction Temperature ......................................................+150°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 ±5%, YR = ZR = AR = BR = ISOCOM, C1 = C2 = 0.047µF, C3 = C4 = 1µF, T
A
= T
MIN
to T
MAX
, unless otherwise noted.
Typical values are at V
CC
= +5V and T
A
= +25°C.) (Note 1)
PARAMETER
DRIVER
Differential Driver Output,
No Load
Differential Driver Output,
Loaded
Change in Magnitude of
Differential Output Voltage
(Note 2)
Driver Common-Mode Voltage
Change in Magnitude of
Common-Mode Voltage
(Note 2)
Input High Voltage
Input Low Voltage
DI Input Hysteresis
Input Current
V
OD1
V
OD2
Figure 1, R = 10MΩ
Figure 1, R = 50Ω (RS-422)
Figure 1, R = 27Ω (RS-485)
Figure 1, R = 50Ω or R = 27Ω
Figure 1, R = 50Ω or R = 27Ω,
V
OC
relative to ISOCOM
Figure 1, R = 50Ω or R = 27Ω
DE, DI,
RE,
TXP, RXP, relative to GND,
H/F relative to ISOCOM
DE, DI,
RE,
TXP, RXP, relative to GND,
H/F relative to ISOCOM
100
DE, DI,
RE
H/F, TXP, RXP internal pulldown
DE = GND, V
CC
= GND or 5.25V, -7V
≤
(V
IN
-
V
ISOCOM
)
≤
12V, AR = BR = ISOCOM
DE = GND, V
CC
= GND or 5.25V, -7V
≤
(V
IN
-
V
ISOCOM
)
≤
12V, AR open, BR open
10
-5.0
-0.58
±2
40
8.0
mA
1.0
2.0
1.5
0.2
6
V
V
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
∆V
OD
V
V
OC
3.5
V
∆V
OC
0.2
V
V
IH
V
IL
V
HYS
I
IN1
I
IN2
2.0
0.8
V
V
mV
µA
Input Current (A and B)
I
IN3
2
_______________________________________________________________________________________
High CMRR RS-485 Transceiver
with ±50V Isolation
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +5V ±5%, YR = ZR = AR = BR = ISOCOM, C1 = C2 = 0.047µF, C3 = C4 = 1µF, T
A
= T
MIN
to T
MAX
, unless otherwise noted.
Typical values are at V
CC
= +5V and T
A
= +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
DE = GND, V
CC
= GND or 5.25V, -7V
≤
(V
IN
-
V
ISOCOM
)
≤
12V, YR = ZR = ISOCOM
DE = GND, V
CC
= GND or 5.25V, -7V
≤
(V
IN
-
V
ISOCOM
)
≤
12V, YR open, ZR open
V
ISOCOM
- 7V
≤
V
OUT
≤
V
ISOVCC
V
ISOCOM
- 7V
≤
V
OUT
≤
V
ISOCOM
+12V
MIN
-5.0
-0.58
-250
250
TYP
MAX
8.0
mA
1.0
mA
UNITS
MAX3157
Output Leakage (Y and Z)
Full Duplex
I
O
Driver Short-Circuit Output
Current (Note 3)
RECEIVER
Receiver Differential Threshold
Voltage
Receiver Input Hysteresis
Receiver Output High Voltage
Receiver Output Low Voltage
Three-State Output Current at
Receiver
I
OSD1
I
OSD2
V
TH
∆V
TH
V
OH
V
OL
I
OZR
-7V
≤
V
CM
- V
ISOCOM
≤
12V
-200
-125
25
-50
mV
mV
V
I
O
= -4mA, V
ID
= -50mV
I
O
= 4mA, V
ID
= -200mV
0.4V
≤
V
O
≤
2.4V
-7V
≤
V
CM
- V
ISOCOM
≤
12V, AR = BR =
ISOCOM
V
CC
- 1.5
0.4
±1
1.5
V
µA
Receiver Input Resistance
R
IN
-7V
≤
V
CM
- V
ISOCOM
≤
12V, AR open,
BR open
0V
≤
V
RO
≤
V
CC
kΩ
12
±7
±100
mA
Receiver Output Short-Circuit
Current
SUPPLY CURRENT
Supply Current
Supply Current in Shutdown
Mode
Maximum Ground Differential
I
OSR
I
CC
I
SHDN
∆V
GND
No load,
RE
= DE = DI = GND or V
CC
DE = GND,
RE
= V
CC
, V
ISOCOM
= GND
DE = GND,
RE
= V
CC
, V
ISOCOM
=
±50V
DE = GND,
RE
= V
CC
,
| ISOCOM leakage |
≤
600µA
±50
25
25
85
60
±600
mA
µA
V
SWITCHING CHARACTERISTICS
(V
CC
= +5V ±5%, YR = ZR = AR = BR = ISOCOM, C1 = C2 = 0.047µF, C3 = C4 = 1µF. Typical values are at V
CC
= +5V and T
A
= +25°C.)
PARAMETER
SYMBOL
t
DPLH
Driver Input to Output
t
DPHL
Driver Output Skew
|
t
DPLH
- t
DPHL
|
Driver Rise or Fall Time
Maximum Data Rate
t
DSKEW
t
DR
, t
DF
f
MAX
CONDITIONS
Figures 3 and 5, R
DIFF
= 54Ω,
C
L1
= C
L2
= 100pF
Figures 3 and 5, R
DIFF
= 54Ω,
C
L1
= C
L2
= 100pF
Figures 3 and 5, R
DIFF
= 54Ω,
C
L1
= C
L2
= 100pF
Figures 3 and 5, R
DIFF
= 54Ω,
C
L1
= C
L2
=100pF
200
250
1200
MIN
400
400
TYP
1400
1400
MAX
2000
ns
2000
250
2200
ns
ns
kbps
UNITS
_______________________________________________________________________________________
3
High CMRR RS-485 Transceiver
with ±50V Isolation
MAX3157
SWITCHING CHARACTERISTICS (continued)
(V
CC
= +5V ±5%, YR = ZR = AR = BR = ISOCOM, C1 = C2 = 0.047µF, C3 = C4 = 1µF. Typical values are at V
CC
= +5V and T
A
= +25°C.)
PARAMETER
Driver Enable to Output High
Driver Enable to Output Low
Driver Disable Time from Low
Driver Disable Time from High
Receiver Input to Output
Differential Receiver Skew
|t
RPLH
- t
RPHL
|
Receiver Enable to Output Low
Receiver Enable to Output High
Receiver Disable Time from Low
Receiver Disable Time from High
Time to Shutdown
Driver Enable from Shutdown to
Output High
Driver Enable from Shutdown to
Output Low
Receiver Enable from Shutdown
to Output High
Receiver Enable from Shutdown
to Output Low
Charge-Pump Oscillating
Frequency
SYMBOL
t
DZH
t
DZL
t
DLZ
t
DHZ
t
RPLH
,
t
RPHL
t
RSKEW
t
RZL
t
RZH
t
RLZ
t
RHZ
t
SHDN
t
DZH
(SHDN)
t
DZL
(SHDN)
t
RZH
(SHDN)
t
RZL
(SHDN)
f
OSC
CONDITIONS
Figures 4 and 6, C
L
= 100pF, S2 closed
Figures 4 and 6, C
L
= 100pF, S1 closed
Figures 4 and 6, C
L
= 15pF, S1 closed
Figures 4 and 6, C
L
= 15pF, S2 closed
Figures 7 and 9;
|
V
ID
| ≥
2.0V
Figures 7 and 9;
|
V
ID
| ≥
2.0V
Figures 2 and 8, C
L
= 100pF, S1 closed
Figures 2 and 8, C
L
= 100pF, S2 closed
Figures 2 and 8, C
L
= 100pF, S1 closed
Figures 2 and 8, C
L
= 100pF, S2 closed
(Note 4)
Figures 4 and 6, C
L
= 15pF, S2 closed
Figures 4 and 6, C
L
= 15pF, S1 closed
Figures 2 and 8, C
L
= 100pF, S2 closed
Figures 2 and 8, C
L
= 100pF, S1 closed
50
440
20
20
20
200
200
200
0.2
0.2
0.2
0.2
1.3
50
50
500
500
700
1
1
1
1
MIN
TYP
MAX
3500
3500
300
300
600
UNITS
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ms
ms
ms
ms
MHz
Note 1:
All currents into the device are positive; all currents out of the device are negative. All voltages are referred to device
ground unless otherwise noted.
Note 2:
∆V
OD
and
∆V
OC
are the changes in V
OD
and V
OC
, respectively, when the DI input changes state.
Note 3:
Current level applies to peak current just prior to foldback-current limiting.
Note 4:
The device is put into shutdown by bringing
RE
high and DE low. If the enable inputs are in this state for less than 50ns,
the device is guaranteed not to enter shutdown. If the enable inputs are in this state for at least 700ns, the device is guaran-
teed to have entered shutdown.
4
_______________________________________________________________________________________
High CMRR RS-485 Transceiver
with ±50V Isolation
Typical Operating Characteristics
(V
CC
= +5V, YR = ZR = AR = BR = ISOCOM, C1 = C2 = 0.047µF, C3 = 1µF, C4 = 10nF, T
A
= +25°C, unless otherwise noted.)
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX1357toc01
MAX1357toc02
MAX3157
SUPPLY CURRENT vs. TEMPERATURE
160
140
SUPPY CURRENT (mA)
120
100
80
60
40
20
0
-40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90
TEMPERATURE (°C)
NO LOAD
R
L
= 54Ω
300
200
SUPPY CURRENT (µA)
RECEIVER OUTPUT CURRENT
vs. RECEIVER OUTPUT LOW VOLTAGE
40
OUTPUT CURRENT (mA)
35
30
25
20
15
10
5
MAX3157toc03
45
V
ISOCOM
= -50V
100
0
V
ISOCOM
= 0
-100
V
ISOCOM
= +50V
-200
-300
-40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90
TEMPERATURE (°C)
0
0
1
2
3
4
5
6
OUTPUT LOW VOLTAGE (V)
RECEIVER OUTPUT CURRENT
vs. RECEIVER OUTPUT HIGH VOLTAGE
MAX3157toc04
RECEIVER OUTPUT LOW VOLTAGE
vs. TEMPERATURE
MAX3157toc05
RECEIVER OUTPUT HIGH VOLTAGE
vs. TEMPERATURE
4.35
4.30
OUTPUT VOLTAGE (V)
4.25
4.20
4.15
4.10
4.05
4.00
3.95
I
RO
= -8mA
MAX3157toc06
20
18
16
OUTPUT CURRENT (mA)
14
12
10
8
6
4
2
0
0.50
0.45
OUTPUT LOW VOLTAGE (V)
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
I
RO
= 8mA
4.40
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
OUTPUT HIGH VOLTAGE (V)
-40
-20
0
20
40
60
80
100
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
TEMPERATURE (°C)
DRIVER OUTPUT CURRENT
vs. DRIVER OUTPUT LOW VOLTAGE
MAX3157toc07
DRIVER OUTPUT CURRENT
vs. DRIVER OUTPUT HIGH VOLTAGE
MAX3157toc08
DRIVER OUTPUT CURRENT
vs. DIFFERENTIAL OUTPUT VOLTAGE
MAX3157toc09
160
140
OUTPUT CURRENT (mA)
120
100
80
60
40
20
0
0
2
4
6
8
10
12
0
-10
OUTPUT CURRENT (mA)
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
100
OUTPUT CURRENT (mA)
-8
-6
-4
-2
0
2
4
6
10
1
0.1
0.01
0
1
2
3
4
5
6
OUTPUT HIGH VOLTAGE (V)
DIFFERENTIAL OUTPUT VOLTAGE (V)
14
OUTPUT VOLTAGE (V)
_______________________________________________________________________________________
5
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