Selector Guide
General Description
The MAX3440E–MAX3444E fault-protected RS-485 and
J1708 transceivers feature ±60V protection from signal
faults on communication bus lines. Each device contains
one differential line driver with three-state output and one
differential line receiver with three-state input. The 1/4-unitload receiver input impedance allows up to 128 transceivers on a single bus. The devices operate from a 5V
supply at data rates of up to 10Mbps. True fail-safe inputs
guarantee a logic-high receiver output when the receiver
inputs are open, shorted, or connected to an idle data line.
Hot-swap circuitry eliminates false transitions on the
data bus during circuit initialization or connection to a
live backplane. Short-circuit current-limiting and thermal shutdown circuitry protect the driver against excessive power dissipation, and on-chip ± 15kV ESD
protection eliminates costly external protection devices.
The MAX3440E–MAX3444E are available in 8-pin SO
and PDIP packages and are specified over industrial
and automotive temperature ranges.
Applications
RS-422/RS-485 Communications
Truck and Trailer Applications
Industrial Networks
Telecommunications Systems
Automotive Applications
HVAC Controls
Features
♦ ±15kV ESD Protection
♦ ±60V Fault Protection
♦ Guaranteed 10Mbps Data Rate
(MAX3441E/MAX3443E)
♦ Hot Swappable for Telecom Applications
♦ True Fail-Safe Receiver Inputs
♦ Enhanced Slew-Rate-Limiting Facilitates
Error-Free Data Transmission
(MAX3440E/MAX3442E/MAX3444E)
♦ Allow Up to 128 Transceivers on the Bus
♦ -7V to +12V Common-Mode Input Range
♦ Automotive Temperature Range (-40°C to +125°C)
♦ Industry-Standard Pinout
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
________________________________________________________________
Maxim Integrated Products
1
Pin Configurations and Typical Operating Circuits
Ordering Information
19-2666; Rev 2; 11/10
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
+
Denotes a lead(Pb)-free/RoHS-compliant package.
Ordering Information continued at end of data sheet.
Pin Configurations and Typical Operating Circuits continued at end of data sheet.
PART TEMP RANGE PIN-PACKAGE
MAX3440EESA+ -40°C to +85°C 8 SO
MAX3440EEPA+ -40°C to +85°C 8 PDIP
MAX3440EASA+ -40°C to +125°C 8 SO
MAX3440EAPA+ -40°C to +125°C 8 PDIP
PART TYPE
MAX3440E RS-485 0.25 No Yes 128 Yes
MAX3441E RS-485 2.5 to 10 No Yes 128 Yes
MAX3442E RS-485 0.25 Yes Yes 128 Yes
MAX3443E RS-485 2.5 to 10 Yes Yes 128 Yes
MAX3444E J1708 0.25 Yes Yes 128 Yes (only RE)
DATA RATE
(Mbps)
LOW-POWER
SHUTDOWN
RECEIVER/DRIVER
ENABLE
TRANSCEIVERS
ON BUS
HOT SWAP
TOP VIEW
FAULT
DE/RE
+
1
RO
DI
R
2
3
4
D
DIP/SO DIP/SO
FAULT
V
8
CC
B
7
A
DE/RE
6
GND
5
+
1
RO
DI
R
2
3
4
D
8
V
CC
B
7
Rt
6
A
5
GND
MAX3440E
MAX3441E
B
Rt
A
R
DE/RE
D
FAULT
DI
RO
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
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.
Voltages Referenced to GND
V
CC
........................................................................................+7V
FAULT, DE/RE, RE, DE, DE, DI, TXD..........-0.3V to (V
CC
+ 0.3V)
A, B (Note 1) ........................................................................±60V
RO ..............................................................-0.3V to (V
CC
+ 0.3V)
Short-Circuit Duration (RO, A, B) ...............................Continuous
Continuous Power Dissipation (T
A
= +70°C)
SO (derate 5.9mW/°C above +70°C)...........................471mW
PDIP (derate 9.09mW/°C above +70°C)......................727mW
Operating Temperature Ranges
MAX344_EE_ _ ...............................................-40°C to +85°C
MAX344_EA_ _ .............................................-40°C to +125°C
Storage Temperature Range .............................-65°C to +150°C
Junction Temperature......................................................+150°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow) .......................................+260°C
DC ELECTRICAL CHARACTERISTICS
(VCC= +4.75V to +5.25V, TA= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at VCC= +5V and TA= +25°C.)
Note 1: A, B must be terminated with 54Ω or 100Ω to guarantee ±60V fault protection.
DRIVER
Differential Driver Output V
Change in Magnitude of
Differential Output Voltage
Driver Common-Mode
Output Voltage
Change in Magnitude of
Common-Mode Voltage
DRIVER LOGIC
Driver Input High Voltage V
Driver Input Low Voltage V
Driver Input Current I
Driver Short-Circuit Output Current
(Note 3)
Driver Short-Circuit Foldback
Output Current
RECEIVER
Input Current I
Receiver Differential Threshold
Voltage
Receiver Input Hysteresis VTH 25 mV
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Figure 1, RL = 100 2 V
OD
Figure 1, RL = 54 1.5 V
V
Figure 1, RL = 100 or 54 (Note 2) 0.2 V
OD
V
V
DIN
I
OSD
I
OSDF
A,B
V
Figure 1, RL = 100 or 54 V
OC
Figure 1, RL = 100 or 54 (Note 2) 0.2 V
OC
2 V
DIH
0.8 V
DIL
±2 μA
0V V
OUT
-7V V
OUT
(VCC - 1V) V
-7V V
OUT
VCC = GND, V
A, B
-7V VCM +12V -200 -50 mV
TH
V
V
A, B
A, B
CC
CC
/ 2 3 V
CC
+12V +350
VCC -350
+12V (Note 3) +25
OUT
+1V (Note 3) -25
= 12V 250
A, B
= -7V -150
= ±60V ±6 mA
V
mA
mA
μA
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
_______________________________________________________________________________________ 3
DC ELECTRICAL CHARACTERISTICS (continued)
(VCC= +4.75V to +5.25V, TA= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at VCC= +5V and TA= +25°C.)
PROTECTION SPECIFICATIONS
(VCC= +4.75V to +5.25V, TA= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at VCC= +5V and TA= +25°C.)
RECEIVER LOGIC
Output High Voltage VOH Figure 2, IOH = -1.6mA VCC - 0.6 V
Output Low Voltage VOL Figure 2, IOL = 1mA 0.4 V
Three-State Output Current at
Receiver
Receiver Input Resistance RIN -7V VCM +12V 48 k
Receiver Output Short-Circuit
Current
CONTROL
Control Input High Voltage V
Input Current Latch Dur ing First
Rising Edge
SUPPLY CURRENT
Normal Operation I
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
I
0V V
OZR
I
0V VRO V
OSR
DE, DE, RE, DE/RE 2 V
CIH
I
DE, DE/RE, RE 90 μA
IN
No load,
DI = V
Q
or GND
V
A, B
CC
±1 μA
CC
CC
MAX3440E (DE/RE = VCC),
MAX3442E (DE = V
RE = GND),
MAX3444E (DE = RE = GND)
MAX3441E (DE/RE = V
MAX3443E (DE = V
RE = GND)
CC
CC
,
),
CC
,
30
10
±95 mA
mA
Supply Current in Shutdown Mode I
Supply Current with Output Shorted
to ±60V
SHDN
I
SHRT
DE = GND, RE = VCC (MAX3442E/
MAX3443E)
DE = GND, RE = VCC, TA = +25°C
(MAX3442E/MAX3443E)
DE = RE = VCC (MAX3444E) 100
DE = RE = VCC, TA = +25°C (MAX3444E) 10
DE = GND, RE = GND, no load
output in three-state (MAX3443E)
20
10
±15 mA
μA
Overvoltage Protection A, B; R
ESD Protection A, B Human Body Model ±15 kV
FAULT DETECTION
Receiver Differential Threshold F
Receiver Differential Threshold F
Fault-Detect ion Common-Mode
Input Voltage Positive
Fault-Detect ion Common-Mode
Input Voltage Negative
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
SOURCE
VCM = 0V, high limit 270 450 mV
DIPH
VCM = 0V, low limit -450 -270 mV
DIPL
12 V
-7 V
= 0, RL = 54 ±60 V
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
4 _______________________________________________________________________________________
SWITCHING CHARACTERISTICS (MAX3440E/MAX3442E/MAX3444E)
(VCC= +4.75V to +5.25V, TA= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at VCC= +5V and TA= +25°C.)
PARAMETER SY MBOL CONDITIONS MIN TYP MAX UNITS
Driver Propagation Dela y
Driver Differential Propagation Delay
Driver Differential Output
Transit ion T ime
Driver Output S kew
Differential Driver Output Skew t
Maximum Data Rate f
Driver Enable Time to Output High t
Driver Disable Time from Output High t
Driver Enable Time from Shutdown to
Output High
Driver Enable Time to Output Low t
Driver Disable Time from Output Low t
Driver Enable Time from Shutdown to
Output Low
Driver Time to Shutdown t
Receiver Propagation Delay
Receiver Output Skew t
Receiver Enable Time to Output High t
Receiver Disable Time from Output
High
Receiver Wake Time from Shutdown t
Receiver Enable Time to Output Low t
Receiver Disable Time from Output Low t
Receiver Time to Shutdown t
t
PLHA,
t
PLHB
t
DPLH,
t
DPHL
t
LH,tHL
t
SKEWAB
t
SKEWBA
DSKEW
MAX
PDZH
PDHZ
t
PDHS
PDZL
PDLZ
t
PDLS
SHDN
t
RPLH
t
RPHL
RSKEW
RPZH
t
RPHZ
RPWAKE
RPZL
RPLZ
SHDN
MAX3440E/MAX3442E,
Figure 3, R
MAX3444E, R
= 54, CL = 50pF
L
= 60, C
DIFF
DIFF
= 100pF
Figure 4, RL= 54, CL= 50pF 2000 ns
Figure 4, RL = 54, CL= 50pF 200 2000 ns
RL = 54, CL= 50pF,
,
t
SKEWAB
t
SKEWBA
= |t
= |t
PLHA
PLHB
- t
- t
PHLB
PHLA
|,
|
RL = 54, CL= 50pF,
t
DSKEW
= |t
DPLH
- t
DPHL
|
250 kbp s
Figure 5, RL = 500, CL= 50pF 2000 ns
Figure 5, RL = 500, CL= 50pF 2000 ns
Figure 5, RL = 500, CL= 50pF
(MAX3442E/MAX3444E)
Figure 6, RL = 500, CL= 50pF 2000 ns
Figure 6, RL = 500, CL= 50pF 2000 ns
Figure 6, RL = 500, CL= 50pF
(MAX3442E/MAX3444E)
RL = 500, CL = 50pF (MAX3442E/MAX3444E) 800 ns
,
Figure 7, CL= 20pF, VID= 2V, VCM = 0V 2000 ns
CL = 20pF, t
RSKEW
= |t
RPLH
- t
| 200 ns
RPHL
Figure 8, RL = 1k, CL= 20pF 2000 ns
Figure 8, RL= 1k, CL= 20pF 2000 ns
Figure 8, RL = 1k, CL = 20pF
(MAX3442E/MAX3444E)
Figure 8, RL = 1k, CL= 20pF 2000 ns
Figure 8, RL = 1k, CL = 20pF 2000 ns
RL = 500, CL= 50pF
(MAX3442E/MAX3444E)
2000 ns
350 ns
200 ns
4.2 μs
4.2 μs
4.2 μs
800 ns
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
_______________________________________________________________________________________ 5
SWITCHING CHARACTERISTICS (MAX3441E/MAX3443E)
(VCC= +4.75V to +5.25V, TA= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at VCC= +5V and TA= +25°C.)
Note 2: ΔV
OD
and ΔVOCare the changes in VODand VOC, respectively, when the DI input changes state.
Note 3: The short-circuit output current applies to peak current just before foldback current limiting; the short-circuit foldback output
current applies during current limiting to allow a recovery from bus contention.
PARAMETER SY MBOL CONDITIONS MIN TYP MAX UNITS
Driver Propagation Dela y
Driver Differential Propagation Delay
Driver Differential Output
Transit ion T ime
Driver Output S kew
Differential Driver Output Skew t
Maximum Data Rate f
Driver Enable Time to Output High t
Driver Disable Time from Output High t
Driver Enable Time from Shutdown to
Output High
Driver Enable Time to Output Low t
Driver Disable Time from Output Low t
Driver Enable Time from Shutdown to
Output Low
Driver Time to Shutdown t
Receiver Propagation Delay
Receiver Output Skew t
Receiver Enable Time to Output High t
Receiver Disable Time from Output
High
Receiver Wake Time from Shutdown t
Receiver Enable Wake Time from
Shutdown
Receiver Disable Time from Output Low t
Receiver Time to Shutdown t
t
PLHA,
t
PLHB
t
DPLH,
t
DPHL
t
LH,tHL
t
SKEWAB
t
SKEWBA
DSKEW
MAX
PDZH
PDHZ
t
PDHS
PDZL
PDLZ
t
PDLS
SHDN
t
RPLH
t
RPHL
RSKEW
RPZH
t
RPHZ
RPWAKE
t
RPSH
RPLZ
SHDN
Figure 3, RL = 27, CL = 50pF 60 ns
Figure 4, RL= 54, CL= 50pF 60 ns
Figure 4, RL = 54, CL= 50pF 25 ns
RL = 54, CL= 50pF,
,
t
SKEWAB
t
SKEWBA
= |t
= |t
PLHA
PLHB
- t
- t
PHLB
PHLA
|,
|
RL = 54, CL= 50pF,
t
DSKEW
= |t
DPLH
- t
DPHL
|
10 Mbps
Figure 5, RL = 500, CL= 50pF 1200 ns
Figure 5, RL = 500, CL= 50pF 1200 ns
Figure 5, RL = 500, CL= 50pF (MAX3443E) 4.2 μs
Figure 6, RL = 500, CL= 50pF 1200 ns
Figure 6, RL = 500, CL= 50pF 1200 ns
Figure 6, RL = 500, CL= 50pF (MAX3443E) 4.2 μs
Figure 6, RL = 500, CL= 50pF (MAX3443E) 800 ns
,
Figure 7, CL= 20pF, VID= 2V, VCM = 0V 85 ns
CL = 20pF, t
RSKEW
= |t
RPLH
- t
Figure 8, RL = 1k, CL= 20pF 400 ns
Figure 8, RL= 1k, CL= 20pF 400 ns
Figure 8, RL = 1k, CL= 20pF (MAX3443E) 4.2 μs
Figure 8, RL = 1k, CL= 20pF 400 ns
Figure 8, RL = 1k, CL= 20pF 400 ns
RL = 500, CL= 50pF (MAX3443E) 800 ns
10 ns
10 ns
| 15 ns
RPHL
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
6 _______________________________________________________________________________________
Typical Operating Characteristics
(VCC= +5V, TA = +25°C, unless otherwise noted.)
NO-LOAD SUPPLY CURRENT
vs. TEMPERATURE
MAX3440E toc01
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
1109580655035205-10-25
1
2
3
4
5
6
0
-40 125
DRIVER AND RECEIVER
ENABLED
MAX3441E/MAX3443E
DRIVER DISABLED,
RECEIVER ENABLED
NO-LOAD SUPPLY CURRENT
vs. TEMPERATURE
MAX3440E toc02
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
1109580655035205-10-25
4
8
12
16
20
24
0
-40 125
MAX3440E/MAX3442E/MAX3444E
DRIVER AND RECEIVER
ENABLED
DRIVER DISABLED,
RECEIVER ENABLED
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX3443E toc03
TEMPERATURE (°C)
SUPPLY CURRENT (μA)
1109580655035205-10-25
0.1
1
10
0.01
-40 125
MAX3442E/MAX3443E/MAX3444E
A, B CURRENT
vs. A, B VOLTAGE (TO GROUND)
MAX3443E toc09
A, B VOLTAGE (V)
A, B CURRENT (μA)
4030 6050-50
-40
-30 -10 0 10-20 20
-800
-400
-1600
-2000
RL = 54Ω
-1200
0
400
800
1200
1600
2000
-60
DRIVER DISABLED,
RECEIVER ENABLED
RECEIVER OUTPUT CURRENT
40
35
30
25
20
15
10
RECEIVER OUTPUT CURRENT (mA)
vs. OUTPUT LOW VOLTAGE
5
0
0
1.5 2.5 3.0 3.52.0 4.0
1.0
OUTPUT LOW VOLTAGE (V)
MAX3443E toc04
5.04.50.5
DRIVER OUTPUT CURRENT
vs. DIFFERENTIAL OUTPUT VOLTAGE
80
70
60
50
40
30
20
DRIVER OUTPUT CURRENT (mA)
10
0
0.5
0
1.0
DIFFERENTIAL OUTPUT VOLTAGE (VA - VB) (V)
1.5 2.5 3.0 3.52.0
MAX3443E toc07
RECEIVER OUTPUT CURRENT
vs. OUTPUT HIGH VOLTAGE
40
35
30
25
20
15
10
RECEIVER OUTPUT CURRENT (mA)
5
0
0
1.5 2.5 3.0 3.52.0 4.0
1.0
OUTPUT HIGH VOLTAGE (V)
DIFFERENTIAL OUTPUT VOLTAGE
vs. TEMPERATURE
3.5
3.0
RL = 100Ω
2.5
2.0
RL = 54Ω
1.5
1.0
DIFFERENTIAL OUTPUT VOLTAGE (V)
0.5
MAX3441E/MAX3443E
0
-40 125
TEMPERATURE (°C)
RECEIVER OUTPUT VOLTAGE
vs. TEMPERATURE
5.0
4.5
MAX3443E toc05
4.0
3.5
3.0
2.5
2.0
1.5
RECEIVER OUTPUT VOLTAGE (V)
1.0
0.5
5.04.50.5
MAX3443E toc08
1109565 80-10 5 20 35 50-25
VOH, I
= +10mA
OUT
VOL, I
= -10mA
OUT
0
-40 125
TEMPERATURE (°C)
MAX3443E toc06
1109565 80-10 5 20 35 50-25
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
_______________________________________________________________________________________ 7
Figure 1. Driver VODand V
OC
Figure 2. Receiver VOHand V
OL
V
CC
V
OM
3V
0
V
OH
V
OM
V
OM
V
OM
V
OM
V
OL
V
OH
V
OL
50Ω
R
L
C
L
= 50pF
(NOTE 5)
GENERATOR
(NOTE 4)
D
DI
t
PLHA
1.5V
A
B
OUT
S1
DI
1.5V
t
PHLA
t
PHLB
t
PLHB
≈ 1.5V
V
OH
+ V
OL
2
V
OM
=
A
B
2
Test Circuits and Waveforms
Figure 4. Driver Differential Output Delay and Transition Times
Figure 3. Driver Propagation Times
R
L
A
V
D
DI
B
V
CC
A
V
ID
B
0
RO
R
OD
V
OL
2
R
L
V
OC
2
V
OH
I
OL
(+)
I
OH
(-)
C
A
DI
D
GENERATOR
(NOTE 4)
50Ω
B
V
CC
L
C
L
R
L
CL = 50pF (NOTE 5)
OUT
3V
DI
(A–B)
1.5V
t
DPLH
90%
50%
10%
t
LH
1.5V
t
DPHL
90%
50%
10%
0
≈ 2.0V
≈ -2.0V
t
HL
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
8 _______________________________________________________________________________________
Figure 6. Driver Enable and Disable Times
Figure 7. Receiver Propagation Delay
Test Circuits and Waveforms (continued)
Figure 5. Driver Enable and Disable Times
A
B
S1
CL = 50pF
(NOTE 5)
A, B
= 500Ω
R
L
+ V
V
OH
OL
=
V
OM
≈ 1.5V
2
GENERATOR
(NOTE 4)
DI
D0 OR 3V
DE
50Ω
V
CC
A
B
S1
= 50pF
C
L
(NOTE 5)
GENERATOR
(NOTE 4)
DI
D0 OR 3V
DE
50Ω
= 500Ω
R
L
A, B
A, B
DE
A, B
DE
t
PDZH
t
t
PDZL
t
PDLS
1.5V
PDHS
1.5V
3V
1.5V
0.25V
0.25V
0
V
OH
0
3V
0
V
CC
V
OL
t
PDHZ
V
OM
1.5V
t
PDLZ
V
OM
GENERATOR
(NOTE 4)
1.0V
A
V
ID
50Ω
0
B
R
R
O
= 20pF
C
L
(NOTE 5)
(A–B)
1.0V
t
RPLH
V
RO
OM
1.0V
2.0V
0
t
RPHL
V
CC
V
OM
0
MAX3440E–MAX3444E
Figure 8. Receiver Enable and Disable Times
Test Circuits and Waveforms (continued)
Note 4: The input pulse is supplied by a generator with the following characteristics: f = 5MHz, 50% duty cycle; tr ≤ 6ns; Z0= 50Ω.
Note 5: C
L
includes probe and stray capacitance.
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
_______________________________________________________________________________________ 9
S1
S2
1.5V
t
RPLZ
0.5V
t
RPZL
t
RPSL
1.5V
V
CC
3V
0
V
CC
V
OL
3V
0
V
CC
S1 CLOSED
S2 OPEN
= -1.5V
V
S3
S1 CLOSED
S2 OPEN
= -1.5V
V
S3
1.5V
t
RPHZ
t
RPZH
t
RPSH
t
RPWAKE
S3
GENERATOR
(NOTE 4)
1.5V
1.5V
A
V
ID
B
R
50Ω
3V
0
V
0
3V
0
V
OH
OH
R
O
S1 OPEN
S2 CLOSED
= 1.5V
V
S3
S1 OPEN
S2 CLOSED
V
= 1.5V
S3
= 20pF
C
L
(NOTE 5)
1kΩ
RE
RO
RE
RO
1.5V
-1.5V
RE
RO
RE
RO
0.5V
1.5V
0
V
OL
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
10 ______________________________________________________________________________________
Pin Description
PIN
MAX3440E
MAX3441E
1 — — FAULT
2 1 1 RO
— 2 2 RE Receiver Output Enable. Pull RE low to enable RO.
— — 3 DE
MAX3442E
MAX3443E
MAX3444E
3 — — DE/RE
— 3 — DE
4 4 — DI
— — 4 TXD
5 5 5 GND Ground
6 6 6 A Noninverting Receiver Input/Driver Output
7 7 7 B Inverting Receiver Input/Driver Output
8 8 8 VCC Positive Supply, VCC = +4.75V to +5.25V
NAME FUNCTION
Fault output. 1 = fault; 0 = normal operation
A or B under the fol lowing conditions:
• A-B differential <200mV
• A shorted to B
• A shorted to a voltage within the common-mode range
(detected onl y when the driver is enabled)
• B shorted to a voltage within the common-mode range
(detected onl y when the driver is enabled)
• A or B outs ide the common-mode range
Receiver Output. If receiver enabled and (A-B) -50mV,
RO = high; if (A-B) -200mV, RO = low.
Driver Output Enable. Pull DE low to enable the outputs.
Force DE high to three-state the outputs. Drive RE and DE
high to enter low-power shutdown mode.
Driver/Receiver Output Enable. Pull DE/RE low to threestate the driver output and enable RO. Force DE/RE high
to enable driver output and three-state RO.
Driver Output Enable. Force DE high to enable driver. Pull
DE low to three-state the driver output. Dri ve RE h igh and
pull DE low to enter low-power shutdown mode.
Driver Input. A logic-low on DI forces the noninverting
output low and the in verting output high. A logic-high on
DI forces the nonin verting output h igh and the in verting
output low.
J1708 Input. A logic-low on TXD forces outputs A and B
to the dominant state. A logic-high on TXD forces outputs
A and B to the recessi ve state.
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
______________________________________________________________________________________ 11
Function Tables
Table 1. MAX3440E/MAX3441E Fault Table
X = Don’t care.
Note 1: Receiver output may oscillate with this differential input condition.
Table 2. MAX3440E/MAX3441E
(RS-485/RS-422)
X = Don’t care.
Table 3. MAX3442E/MAX3443E
(RS-485/RS-422)
X = Don’t care.
Table 4. MAX3444E (J1708) Application
Table 5. MAX3440E/MAX3441E
(RS-485/RS-422)
X = Don’t care.
A-B
V
DIFFERENTIAL
ID
INPUT VOLTAGE
≥0.45V 1 0 Normal operation
<0.45V and ≥0.27V 1 Indeterminate Indeterminate
<0.27V and ≥-0.05V 1 1 Low-input differential voltage
≤-0.05V and ≥-0.2V
≤-0.2V and >-0.27V 0 1 Low-input differential voltage
≤-0.27V and >-0.45V 0 Indeterminate
≤-0.45V
INPUTS OUTPUTS
DE/RE DI A B
0 X High-Z High-Z
1001
1110
INPUTS OUTPUTS
COMMON-MODE
VOLTAGE
≤12V and ≥-7V
X <-7V or >+12V Indeterminate 1 Outside common-mode voltage range
RO
Indeterminate
(Note 1)
00
FAULT
CONDITIONED
BY DELAY
1 Low-input differential voltage
FAULT CONDITION
Indeterminate
TRANSMITTING
INPUTS OUTPUTS
TRANSMITTING
RE DE DI A B
0 0 X High-Z High-Z
01001
01110
1 0 X Shutdown Shutdown
11001
11110
TRANSMITTING
INPUTS OUTPUTS CONDITIONS
TXD DE AB —
0 1 High-Z High-Z —
1 1 High-Z High-Z —
0 0 0 1 Dominant state
1 0 High-Z High-Z Recessive state
RECEIVING
INPUTS OUTPUTS
DE/RE (A - B) RO
0 ≥-0.05V 1
0 ≤-0.2V 0
0 Open/shorted 1
1 X High-Z
Detailed Description
The MAX3440E–MAX3444E fault-protected transceivers
for RS-485/RS-422 and J1708 communication contain
one driver and one receiver. These devices feature failsafe circuitry, which guarantees a logic-high receiver
output when the receiver inputs are open or shorted, or
when they are connected to a terminated transmission
line with all drivers disabled (see the
True Fail-Safe
section). All devices have a hot-swap input structure
that prevents disturbances on the differential signal
lines when a circuit board is plugged into a hot backplane (see the
Hot-Swap Capability
section). The
MAX3440E/MAX3442E/MAX3444E feature a reduced
slew-rate driver that minimizes EMI and reduces reflections caused by improperly terminated cables, allowing
error-free data transmission up to 250kbps (see the
Reduced EMI and Reflections
section). The MAX3441E/
MAX3443E drivers are not slew-rate limited, allowing
transmit speeds up to 10Mbps.
Driver
The driver accepts a single-ended, logic-level input
(DI) and transfers it to a differential, RS-485/RS-422
level output (A and B). Deasserting the driver enable
places the driver outputs (A and B) into a high-impedance state.
Receiver
The receiver accepts a differential, RS-485/RS-422
level input (A and B), and transfers it to a single-ended,
logic-level output (RO). Deasserting the receiver enable
places the receiver inputs (A and B) into a high-impedance state (see Tables 1–7).
Low-Power Shutdown
(MAX3442E/MAX3443E/MAX3444E)
The MAX3442E/MAX3443E/MAX3444E offer a low-power
shutdown mode. Force DE low and RE high to shut down
the MAX3442E/MAX3443E. Force DE and RE high to
shut down the MAX3444E. A time delay of 50ns prevents
the device from accidentally entering shutdown due to
logic skews when switching between transmit and
receive modes. Holding DE low and RE high for at least
800ns guarantees that the MAX3442E/MAX3443E enter
shutdown. In shutdown, the devices consume a maximum 20µA supply current.
±
60V Fault Protection
The driver outputs/receiver inputs of RS-485 devices in
industrial network applications often experience voltage
faults resulting from shorts to the power grid that
exceed the -7V to +12V range specified in the EIA/TIA485 standard. In these applications, ordinary RS-485
devices (typical absolute maximum -8V to +12.5V)
require costly external protection devices. To reduce
system complexity and eliminate this need for external
protection, the driver outputs/receiver inputs of the
MAX3440E–MAX3444E withstand voltage faults up to
± 60V with respect to ground without damage.
Protection is guaranteed regardless whether the device
is active, shut down, or without power.
True Fail-Safe
The MAX3440E–MAX3444E use a -50mV to -200mV
differential input threshold to ensure true fail-safe
receiver inputs. This threshold guarantees the receiver
outputs a logic-high for shorted, open, or idle data
lines. The -50mV to -200mV threshold complies with
the ±200mV threshold EIA/TIA-485 standard.
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
12 ______________________________________________________________________________________
Table 6. MAX3442E/MAX3443E
(RS-485/RS-422)
X = Don’t care.
Table 7. MAX3444E (RS-485/RS-422)
Function Tables (continued)
X = Don’t care.
RECEIVING
INPUTS OUTPUTS
RE DE (A - B) RO
0X≥-0.05V 1
0X≤-0.2V 0
0 X Open/shorted 1
1 1 X High-Z
1 0 X Shutdown
RECEIVING
INPUTS OUTPUTS
RE DE (A - B) RO
0X≥-0.05V 1
0X≤-0.2V 0
0 X Open/shorted 1
1 0 X High-Z
1 1 X Shutdown
±15kV ESD Protection
As with all Maxim devices, ESD-protection structures
are incorporated on all pins to protect against ESD
encountered during handling and assembly. The
MAX3440E–MAX3444E receiver inputs/driver outputs
(A, B) have extra protection against static electricity
found in normal operation. Maxim’s engineers have
developed state-of-the-art structures to protect these
pins against ±15kV ESD without damage. After an ESD
event, the MAX3440E–MAX3444E continue working
without latchup.
ESD protection can be tested in several ways. The
receiver inputs are characterized for protection to
±15kV using the Human Body Model.
ESD Test Conditions
ESD performance depends on a number of conditions.
Contact Maxim for a reliability report that documents
test setup, methodology, and results.
Human Body Model
Figure 9a shows the Human Body Model, and Figure
9b shows the current waveform it generates when discharged into a low impedance. This model consists of
a 100pF capacitor charged to the ESD voltage of interest, which is then discharged into the device through a
1.5kΩ resistor.
Driver Output Protection
Two mechanisms prevent excessive output current and
power dissipation caused by faults or bus contention.
The first, a foldback current limit on the driver output
stage, provides immediate protection against short circuits over the whole common-mode voltage range. The
second, a thermal shutdown circuit, forces the driver outputs into a high-impedance state if the die temperature
exceeds +160°C. Normal operation resumes when the
die temperature cools to +140°C, resulting in a pulsed
output during continuous short-circuit conditions.
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
______________________________________________________________________________________ 13
Figure 9a. Human Body ESD Test Model
Figure 9b. Human Body Model Current Waveform
R
D
1.5kΩ
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
DEVICE
UNDER
TEST
HIGH-
VOLTAGE
DC
SOURCE
R
C
1MΩ
CHARGE-CURRENT-
LIMIT RESISTOR
C
100pF
s
PEAK-TO-PEAK RINGING
I
r
(NOT DRAWN TO SCALE)
AMPERES
IP 100%
90%
36.8%
10%
0
0
t
RL
TIME
t
DL
CURRENT WAVEFORM
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
14 ______________________________________________________________________________________
Hot-Swap Capability
Hot-Swap Inputs
Inserting circuit boards into a hot, or powered, backplane may cause voltage transients on DE, DE/RE, RE,
and receiver inputs A and B that can lead to data errors.
For example, upon initial circuit board insertion, the
processor undergoes a power-up sequence. During this
period, the high-impedance state of the output drivers
makes them unable to drive the MAX3440E–MAX3444E
enable inputs to a defined logic level. Meanwhile, leakage currents of up to 10µA from the high-impedance output, or capacitively coupled noise from VCCor GND,
could cause an input to drift to an incorrect logic state.
To prevent such a condition from occurring, the
MAX3440E–MAX3443E feature hot-swap input circuitry
on DE, DE/RE, and RE to guard against unwanted driver activation during hot-swap situations. The
MAX3444E has hot-swap input circuitry only on RE.
When V
CC
rises, an internal pulldown (or pullup for RE)
circuit holds DE low for at least 10µs, and until the current into DE exceeds 200µA. After the initial power-up
sequence, the pulldown circuit becomes transparent,
resetting the hot-swap tolerable input.
Hot-Swap Input Circuitry
At the driver-enable input (DE), there are two NMOS
devices, M1 and M2 (Figure 10). When VCCramps from
zero, an internal 15µs timer turns on M2 and sets the
SR latch, which also turns on M1. Transistors M2, a
2mA current sink, and M1, a 100µA current sink, pull
DE to GND through a 5.6kΩ resistor. M2 pulls DE to the
disabled state against an external parasitic capacitance up to 100pF that may drive DE high. After 15µs,
the timer deactivates M2 while M1 remains on, holding
DE low against three-state leakage currents that may
drive DE high. M1 remains on until an external current
source overcomes the required input current. At this
time, the SR latch resets M1 and turns off. When M1
turns off, DE reverts to a standard, high-impedance
CMOS input. Whenever VCCdrops below 1V, the input
is reset.
A complementary circuit for RE uses two PMOS
devices to pull RE to VCC.
__________Applications Information
128 Transceivers on the Bus
The MAX3440E–MAX3444E transceivers 1/4-unit-load
receiver input impedance (48kΩ) allows up to 128
transceivers connected in parallel on one communication line. Connect any combination of these devices,
and/or other RS-485 devices, for a maximum of 32-unit
loads to the line.
Reduced EMI and Reflections
The MAX3440E/MAX3442E/MAX3444E are slew-rate
limited, minimizing EMI and reducing reflections
caused by improperly terminated cables. Figure 11
shows the driver output waveform and its Fourier analysis of a 125kHz signal transmitted by a MAX3443E.
High-frequency harmonic components with large amplitudes are evident.
Figure 12 shows the same signal displayed for a
MAX3442E transmitting under the same conditions.
Figure 12’s high-frequency harmonic components are
much lower in amplitude, compared with Figure 11’s,
and the potential for EMI is significantly reduced.
Figure 10. Simplified Structure of the Driver Enable Pin (DE)
V
CC
15μs
TIMER
TIMER
DE
(HOT SWAP)
5.6kΩ
100μA
M1 M2
2mA
In general, a transmitter’s rise time relates directly to
the length of an unterminated stub, which can be driven with only minor waveform reflections. The following
equation expresses this relationship conservatively:
Length = t
RISE
/ (10 x 1.5ns/ft)
where t
RISE
is the transmitter’s rise time.
For example, the MAX3442E’s rise time is typically
800ns, which results in excellent waveforms with a stub
length up to 53ft. A system can work well with longer
unterminated stubs, even with severe reflections, if the
waveform settles out before the UART samples them.
RS-485 Applications
The MAX3440E–MAX3443E transceivers provide bidirectional data communications on multipoint bus transmission lines. Figures 13 and 14 show a typical network
applications circuit. The RS-485 standard covers line
lengths up to 4000ft. To minimize reflections and
reduce data errors, terminate the signal line at both
ends in its characteristic impedance, and keep stub
lengths off the main line as short as possible.
J1708 Applications
The MAX3444E is designed for J1708 applications. To
configure the MAX3444E, connect DE and RE to GND.
Connect the signal to be transmitted to TXD. Terminate
the bus with the load circuit as shown in Figure 15. The
drivers used by SAE J1708 are used in a dominantmode application. DE is active low; a high input on DE
places the outputs in high impedance. When the driver is
disabled (TXD high or DE high), the bus is pulled high by
external bias resistors R1 and R2. Therefore, a logic level
high is encoded as recessive. When all transceivers are
idle in this configuration, all receivers output logic high
because of the pullup resistor on A and pulldown resistor
on B. R1 and R2 provide the bias for the recessive state.
C1 and C2 combine to form a 6MHz lowpass filter, effective for reducing FM interference. R2, C1, R4, and C2
combine to form a 1.6MHz lowpass filter, effective for
reducing AM interference. Because the bus is unterminated, at high frequencies, R3 and R4 perform a
pseudotermination. This makes the implementation more
flexible, as no specific termination nodes are required at
the ends of the bus.
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
______________________________________________________________________________________ 15
Figure 11. Driver Output Waveform and FFT Plot of MAX3443E
Transmitting a 125kHz Signal
Figure 12. Driver Output Waveform and FFT Plot of MAX3442E
Transmitting a 125kHz Signal
20dB/div
2V/div
5.00MHz500kHz/div0
20dB/div
2V/div
5.00MHz500kHz/div0
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
16 ______________________________________________________________________________________
Figure 13. MAX3440E/MAX3441E Typical RS-485 Network
Figure 14. MAX3442E/MAX3443E Typical RS-485 Network
120Ω 120Ω
B
D
A
R
DE/RE
FAULT
DI
D
RO
R
B
A
BB
AA
DE/RE
DI
RO
FAULT
MAX3440E
D
MAX3441E
DE/RE
DI RO DE/RE
DI
D
DE
RO
RE
R
MAX3442E
120Ω 120Ω
B
A
BB
D
MAX3443E
DI RO DE
DE
R
D
FAULT FAULT
R
DI
D
DI
R
RO
AA
RO
B
D
A
R
R
RERE
DE
DI
RO
RE
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
______________________________________________________________________________________ 17
Figure 15. J1708 Application Circuit
TOP VIEW
1
2
3
4
8
5
V
CC
GND
DI
DE
RE
RO
R
D
Rt
Rt
7
6
D
R
DE
RE
DI
RO
A
B
1
2
3
4
8
7
6
5
V
CC
B
A
GND
DI
DE
RE
RO
DIP/SO DIP/SO
R
D
B
A
MAX3442E
MAX3443E
+
+
Pin Configurations and Typical Operating Circuits (continued)
1
2
3
4
8
5
V
CC
GND
TXD
DE
RE
RO
R
D
Rt
Rt
7
6
D
R
DE
RE
TXD
RO
A
B
1
2
3
4
8
7
6
5
V
CC
B
A
GND
TXD
DE
RE
RO
DIP/SO DIP/SO
R
D
B
A
MAX3444E
+
+
Ordering Information (continued)
+
Denotes a lead(Pb)-free/RoHS-compliant package.
DE
Tx
TXD
D
MAX3444E
Rx
RO
R
RE
PART TEMP RANGE PIN-PACKAGE
MAX3441EESA+ -40°C to +85°C 8 SO
R1
4.7kΩ
R3
C1
2.2nF
C2
2.2nF
R2
4.7kΩ
47Ω
47Ω
J1708 BUS
R4
B
A
MAX3441EEPA+ -40°C to +85°C 8 PDIP
MAX3441EASA+ -40°C to +125°C 8 SO
MAX3441EAPA+ -40°C to +125°C 8 PDIP
MAX3442EESA+ -40°C to +85°C 8 SO
MAX3442EEPA+ -40°C to +85°C 8 PDIP
MAX3442EASA+ -40°C to +125°C 8 SO
MAX3442EAPA+ -40°C to +125°C 8 PDIP
MAX3443ECSA+ 0°C to +70°C 8 SO
MAX3443ECPA+ 0°C to +70°C 8 PDIP
MAX3443EESA+ -40°C to +85°C 8 SO
MAX3443EEPA+ -40°C to +85°C 8 PDIP
MAX3443EASA+ -40°C to +125°C 8 SO
V
CC
MAX3443EAPA+ -40°C to +125°C 8 PDIP
MAX3444EESA+ -40°C to +85°C 8 SO
MAX3444EEPA+ -40°C to +85°C 8 PDIP
MAX3444EASA+ -40°C to +125°C 8 SO
MAX3444EAPA+ -40°C to +125°C 8 PDIP
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
18 ______________________________________________________________________________________
Chip Information
PROCESS: BiCMOS
Package Information
For the latest package outline information and land patterns,
go to www.maxim-ic.com/packages
. Note that a “+”, “#”, or
“-” in the package code indicates RoHS status only. Package
drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
8 SO S8+4
21-0041 90-0096
MAX3440E–MAX3444E
±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
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 ____________________
19
© 2010 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.
Revision History
REVISIO N
NUMBER
0 10/02 Initial release —
1 12/05
2 11/10
REVISIO N
DATE
DESCRIPTION
Corrected the supply current units from μA to mA for the Shutdown Supply Current
vs. Temperature graph in the Typical Operating Characteristics section; updated the
outputs in Table 4; updated Figure 15
Added lead(Pb)-free parts to the Ordering Information table; added the soldering
temperature to the Absolute Maximum Ratings section; updated Table 4 output s
PAGES
CHANGED
6, 11, 17
1, 2, 11, 17
Loading...