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-unit-
load receiver input impedance allows up to 128 transceiv-
ers on a single bus. The devices operate from a 5V supply
at data rates of up to 10Mbps. True fail-safe inputs guar-
antee 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 shut-
down 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
●Industrial Networks
●Telecommunications Systems
●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
19-2666; Rev 3; 4/14
+Denotes a lead(Pb)-free/RoHS-compliant package.
Ordering Information 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
Ordering Information
Pin Configurations and Typical Operating Circuits continued at end of data sheet.
PART TYPE DATA RATE
(Mbps)
LOW-POWER
SHUTDOWN
RECEIVER/DRIVER
ENABLE
TRANSCEIVERS
ON BUS HOT SWAP
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)
TOP VIEW
1
2
3
4
8
5
VCC
GND
DI
DE/RE
RO
FAULT
R
D
Rt
Rt
7
6
D
R
DE/RE
FAULT
DI
RO
A
B
1
2
3
4
8
7
6
5
VCC
B
A
GND
DI
DE/RE
RO
FAULT
++
DIP/SO DIP/SO
B
A
MAX3440E
MAX3441E
R
D
MAX3440E–MAX3444E ±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
Selector Guide
Pin Congurations and Typical Operating Circuits
Voltages Referenced to GND
VCC ........................................................................................+7V
FAULT, DE/RE, RE, DE, DE, DI, TXD ...... -0.3V to (VCC + 0.3V)
A, B (Note 1) .......................................................................±60V
RO ............................................................ -0.3V to (VCC + 0.3V)
Short-Circuit Duration (RO, A, B) ..............................Continuous
Continuous Power Dissipation (TA = +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
(VCC = +4.75V to +5.25V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
DRIVER
Differential Driver Output VOD
Figure 1, RL = 100Ω 2 VCC V
Figure 1, RL = 54Ω 1.5 VCC
Change in Magnitude of
Differential Output Voltage ∆VOD Figure 1, RL = 100Ω or 54Ω (Note 2) 0.2 V
Driver Common-Mode
Output Voltage VOC Figure 1, RL = 100Ω or 54Ω VCC / 2 3 V
Change in Magnitude of
Common-Mode Voltage ∆VOC Figure 1, RL = 100Ω or 54Ω (Note 2) 0.2 V
DRIVER LOGIC
Driver Input High Voltage VDIH 2 V
Driver Input Low Voltage VDIL 0.8 V
Driver Input Current IDIN ±2 µA
Driver Short-Circuit Output Current
(Note 3) IOSD
0V ≤ VOUT ≤ +12V +350 mA
-7V ≤ VOUT ≤ VCC -350
Driver Short-Circuit Foldback
Output Current IOSDF
(VCC - 1V) ≤ VOUT ≤ +12V (Note 3) +25 mA
-7V ≤ VOUT ≤ +1V (Note 3) -25
RECEIVER
Input Current IA,B A, B
VCC = GND, VA, B = 12V 250 µA
VA, B = -7V -150
VA, B = ±60V ±6 mA
Receiver Differential Threshold
Voltage VTH -7V ≤ VCM ≤ +12V -200 -50 mV
Receiver Input Hysteresis ∆VTH 25 mV
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MAX3440E–MAX3444E ±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
DC Electrical Characteristics
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.
Note 1: A, B must be terminated with 54Ω or 100Ω to guarantee ±60V fault protection.
Absolute Maximum Ratings
(VCC = +4.75V to +5.25V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.)
(VCC = +4.75V to +5.25V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Overvoltage Protection A, B; RSOURCE = 0, RL = 54Ω ±60 V
ESD Protection A, B Human Body Model ±15 kV
FAULT DETECTION
Receiver Differential Threshold FDIPH VCM = 0V, high limit 270 450 mV
Receiver Differential Threshold FDIPL VCM = 0V, low limit -450 -270 mV
Fault-Detection Common-Mode
Input Voltage Positive 12 V
Fault-Detection Common-Mode
Input Voltage Negative -7 V
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
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 IOZR 0V ≤ VA, B ≤ VCC ±1 µA
Receiver Input Resistance RIN -7V ≤ VCM ≤ +12V 48 kΩ
Receiver Output Short-Circuit
Current IOSR 0V ≤ VRO ≤ VCC ±95 mA
CONTROL
Control Input High Voltage VCIH DE, DE, RE, DE/RE 2 V
Input Current Latch During First
Rising Edge IIN DE, DE/RE, RE 90 µA
SUPPLY CURRENT
Normal Operation IQ
No load,
DI = VCC
or GND
MAX3440E (DE/RE = VCC),
MAX3442E (DE = VCC,
RE = GND),
MAX3444E (DE = RE = GND)
30
mA
MAX3441E (DE/RE = VCC),
MAX3443E (DE = VCC,
RE = GND)
10
Supply Current in Shutdown Mode ISHDN
DE = GND, RE = VCC (MAX3442E/
MAX3443E) 20
µA
DE = GND, RE = VCC, TA = +25°C
(MAX3442E/MAX3443E) 10
DE = RE = VCC (MAX3444E) 100
DE = RE = VCC, TA = +25°C (MAX3444E) 10
Supply Current with Output Shorted
to ±60V ISHRT
DE = GND, RE = GND, no load
output in three-state (MAX3443E) ±15 mA
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MAX3440E–MAX3444E ±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
Protection Specications
DC Electrical Characteristics (continued)
(VCC = +4.75V to +5.25V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Driver Propagation Delay tPLHA,
tPLHB
MAX3440E/MAX3442E,
Figure 3, RL = 54Ω, CL = 50pF 2000 ns
MAX3444E, RDIFF = 60Ω, CDIFF = 100pF
Driver Differential Propagation Delay tDPLH,
tDPHL Figure 4, RL = 54Ω, CL = 50pF 2000 ns
Driver Differential Output
Transition Time tLH,tHLFigure 4, RL = 54Ω, CL = 50pF 200 2000 ns
Driver Output Skew tSKEWAB,
tSKEWBA
RL = 54Ω, CL = 50pF,
tSKEWAB = |tPLHA - tPHLB|,
tSKEWBA = |tPLHB - tPHLA|
350 ns
Differential Driver Output Skew tDSKEW
RL = 54Ω, CL = 50pF,
tDSKEW = |tDPLH - tDPHL|200 ns
Maximum Data Rate fMAX 250 kbps
Driver Enable Time to Output High tPDZH Figure 5, RL = 500Ω, CL = 50pF 2000 ns
Driver Disable Time from Output High tPDHZ Figure 5, RL = 500Ω, CL = 50pF 2000 ns
Driver Enable Time from Shutdown to
Output High tPDHS
Figure 5, RL = 500Ω, CL = 50pF
(MAX3442E/MAX3444E) 4.2 µs
Driver Enable Time to Output Low tPDZL Figure 6, RL = 500Ω, CL = 50pF 2000 ns
Driver Disable Time from Output Low tPDLZ Figure 6, RL = 500Ω, CL = 50pF 2000 ns
Driver Enable Time from Shutdown to
Output Low tPDLS
Figure 6, RL = 500Ω, CL = 50pF
(MAX3442E/MAX3444E) 4.2 µs
Driver Time to Shutdown tSHDN
RL = 500Ω, CL = 50pF
(MAX3442E/MAX3444E) 800 ns
Receiver Propagation Delay tRPLH,
tRPHL Figure 7, CL = 20pF, VID = 2V, VCM = 0V 2000 ns
Receiver Output Skew tRSKEW CL = 20pF, tRSKEW = |tRPLH - tRPHL| 200 ns
Receiver Enable Time to Output High tRPZH Figure 8, RL = 1kΩ, CL = 20pF 2000 ns
Receiver Disable Time from Output
High tRPHZ Figure 8, RL = 1kΩ, CL = 20pF 2000 ns
Receiver Wake Time from Shutdown tRPWAKE
Figure 8, RL = 1Ω, CL = 20pF
(MAX3442E/MAX3444E) 4.2 µs
Receiver Enable Time to Output Low tRPZL Figure 8, RL = 1kΩ, CL = 20pF 2000 ns
Receiver Disable Time from Output Low tRPLZ Figure 8, RL = 1Ω, CL = 20pF 2000 ns
Receiver Time to Shutdown tSHDN
RL = 50Ω, CL= 50pF
(MAX3442E/MAX3444E) 800 ns
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MAX3440E–MAX3444E ±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
Switching Characteristics (MAX3440E/MAX3442E/MAX3444E)
Note 2: ∆VOD and ∆VOC are the changes in VOD and 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.
(VCC = +4.75V to +5.25V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25°C.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Driver Propagation Delay tPLHA,
tPLHB
Figure 3, RL = 27Ω, CL = 50pF 60 ns
Driver Differential Propagation Delay tDPLH,
tDPHL
Figure 4, RL = 54Ω, CL = 50pF 60 ns
Driver Differential Output
Transition Time tLH,tHL Figure 4, RL = 54Ω, CL = 50pF 25 ns
Driver Output Skew tSKEWAB,
tSKEWBA
RL = 54Ω, CL = 50pF,
tSKEWAB = |tPLHA - tPHLB|,
tSKEWBA = |tPLHB - tPHLA|
10 ns
Differential Driver Output Skew tDSKEW
RL = 54Ω, CL = 50pF,
tDSKEW = |tDPLH - tDPHL|10 ns
Maximum Data Rate fMAX 10 Mbps
Driver Enable Time to Output High tPDZH Figure 5, RL = 500Ω, CL = 50pF 1200 ns
Driver Disable Time from Output High tPDHZ Figure 5, RL = 500Ω, CL = 50pF 1200 ns
Driver Enable Time from Shutdown to
Output High tPDHS Figure 5, RL = 500Ω, CL = 50pF (MAX3443E) 4.2 µs
Driver Enable Time to Output Low tPDZL Figure 6, RL = 500Ω, CL = 50pF 1200 ns
Driver Disable Time from Output Low tPDLZ Figure 6, RL = 500Ω, CL = 50pF 1200 ns
Driver Enable Time from Shutdown to
Output Low tPDLS Figure 6, RL = 500Ω, CL = 50pF (MAX3443E) 4.2 µs
Driver Time to Shutdown tSHDN Figure 6, RL = 500Ω, CL = 50pF (MAX3443E) 800 ns
Receiver Propagation Delay tRPLH,
tRPHL
Figure 7, CL = 20pF, VID = 2V, VCM = 0V 85 ns
Receiver Output Skew tRSKEW CL = 20pF, tRSKEW = |tRPLH - tRPHL| 15 ns
Receiver Enable Time to Output High tRPZH Figure 8, RL = 1kΩ, CL = 20pF 400 ns
Receiver Disable Time from Output
High tRPHZ Figure 8, RL = 1kΩ, CL = 20pF 400 ns
Receiver Wake Time from Shutdown tRPWAKE Figure 8, RL = 1kΩ, CL= 20pF (MAX3443E) 4.2 µs
Receiver Enable Wake Time from
Shutdown tRPSH Figure 8, RL = 1kΩ, CL = 20pF 400 ns
Receiver Disable Time from Output Low tRPLZ Figure 8, RL = 1kΩ, CL= 20pF 400 ns
Receiver Time to Shutdown tSHDN RL = 500Ω, CL= 50pF (MAX3443E) 800 ns
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MAX3440E–MAX3444E ±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
Switching Characteristics (MAX3441E/MAX3443E)
(VCC = +5V, TA = +25°C, unless otherwise noted.)
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
DIFFERENTIAL OUTPUT VOLTAGE
vs. TEMPERATURE
MAX3443E toc08
TEMPERATURE (°C)
DIFFERENTIAL OUTPUT VOLTAGE (V)
1109565 80-10 5 20 35 50-25
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0
-40 125
RL = 100Ω
RL = 54Ω
MAX3441E/MAX3443E
DRIVER OUTPUT CURRENT
vs. DIFFERENTIAL OUTPUT VOLTAGE
MAX3443E toc07
DIFFERENTIAL OUTPUT VOLTAGE (VA - VB) (V)
DRIVER OUTPUT CURRENT (mA)
0.5
1.0
1.5 2.5 3.0 3.52.0
10
20
30
40
50
60
70
80
0
0
RECEIVER OUTPUT VOLTAGE
vs. TEMPERATURE
MAX3443E toc06
TEMPERATURE (°C)
RECEIVER OUTPUT VOLTAGE (V)
1109565 80-10 5 20 35 50-25
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0
-40 125
VOL, IOUT = -10mA
VOH, IOUT = +10mA
RECEIVER OUTPUT CURRENT
vs. OUTPUT HIGH VOLTAGE
MAX3443E toc05
OUTPUT HIGH VOLTAGE (V)
RECEIVER OUTPUT CURRENT (mA)
5.04.50.5
1.0
1.5 2.5 3.0 3.52.0 4.0
5
10
15
20
25
30
35
40
0
0
RECEIVER OUTPUT CURRENT
vs. OUTPUT LOW VOLTAGE
MAX3443E toc04
OUTPUT LOW VOLTAGE (V)
RECEIVER OUTPUT CURRENT (mA)
5.04.50.5
1.0
1.5 2.5 3.0 3.52.0 4.0
5
10
15
20
25
30
35
40
0
0
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX3443E toc03
TEMPERATURE (°C)
SUPPLY CURRENT (A)
1109580655035205-10-25
0.1
1
10
0.01
-40 125
MAX3442E/MAX3443E/MAX3444E
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
NO-LOAD SUPPLY CURRENT
vs. TEMPERATURE
MAX3440E toc01
WTEMPERATURE (°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
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MAX3440E–MAX3444E ±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
Typical Operating Characteristics
Figure 4. Driver Differential Output Delay and Transition Times
Figure 3. Driver Propagation Times
Figure 2. Receiver VOH and VOL
Figure 1. Driver VOD and VOC
VCC
50Ω
RL
CL = 50pF (NOTE 5)
GENERATOR
(NOTE 4)
D
DI OUT
CL
CL
tDPLH tDPHL
tLH
50%
1.5V
10%
(A–B)
DI
90%
50%
1.5V
10%
90%
3V
0
ª 2.0V
tHL
ª -2.0V
A
B
VCC
VOM
3V
0
VOH
VOM
VOM
VOM
VOM
VOL
VOH
VOL
50Ω
RL
CL = 50pF
(NOTE 5)
GENERATOR
(NOTE 4)
D
DI tPLHA
1.5V
A
B
OUT
S1
DI 1.5V
tPHLA
tPHLB tPLHB
ª 1.5V
VOH + VOL
2
VOM =
A
B
2
RRO
0
VOH IOH
(-)
IOL
(+)
VOL
VID
A
B
VCC
DVOD
VOC
2
RL
2
RL
DI
A
B
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MAX3440E–MAX3444E ±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
Test Circuits and Waveforms
Figure 7. Receiver Propagation Delay
Figure 6. Driver Enable and Disable Times
Figure 5. Driver Enable and Disable Times
50Ω
GENERATOR
(NOTE 4) CL = 20pF
(NOTE 5)
VID RRO
tRPLH
1.0V
RO
1.0V
0
(A–B) 1.0V
2.0V
0
tRPHL
VCC
VOM VOM
0
A
B
A, B
DE
VCC
3V
0
VCC
VOL
VOM
tPDLS
1.5V
0.25V
1.5V
tPDLZ
50Ω
GENERATOR
(NOTE 4)
D0 OR 3V A, B
S1
CL = 50pF
(NOTE 5)
RL = 500Ω
DI
DE
A
B
tPDZL
50W
GENERATOR
(NOTE 4)
ª 1.5V
VOH + VOL
2
VOM =
3V
0
VOH
VOM
0
D0 OR 3V
tPDHS tPDHZ
1.5V
0.25V
A, B
A, B
S1
DE 1.5V
CL = 50pF
(NOTE 5)
RL = 500W
DI
A
B
DE
tPDZH
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MAX3440E–MAX3444E ±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
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: CL includes probe and stray capacitance.
Figure 8. Receiver Enable and Disable Times
50Ω
GENERATOR
(NOTE 4)
CL = 20pF
(NOTE 5)
VCC
3V
0
VCC
VOL
R
1.5V
-1.5V VID
1.5V
RO
S1
S2
1kΩ
RE 1.5V
S1 CLOSED
S2 OPEN
VS3 = -1.5V
tRPZL
tRPSL
3V
0
VOH
0
1.5V
RE 1.5V
S1 OPEN
S2 CLOSED
VS3 = 1.5V
tRPZH
tRPSH
tRPWAKE
3V
0
VCC
VOL
0.5V
RO
RE 1.5V
S1 CLOSED
S2 OPEN
VS3 = -1.5V
tRPLZ
3V
0
VOH
0
0.5V
1.5V
RO
RE
S1 OPEN
S2 CLOSED
VS3 = 1.5V
tRPHZ
S3
RO
A
B
RO
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MAX3440E–MAX3444E ±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
Test Circuits and Waveforms (continued)
PIN
NAME FUNCTION
MAX3440E
MAX3441E
MAX3442E
MAX3443E MAX3444E
1 — — FAULT
Fault output. 1 = fault; 0 = normal operation
A or B under the following conditions:
• A-B differential <200mV
• A shorted to B
• A shorted to a voltage within the common-mode range
(detected only when the driver is enabled)
• B shorted to a voltage within the common-mode range
(detected only when the driver is enabled)
• A or B outside the common-mode range
2 1 1 RO Receiver Output. If receiver enabled and (A-B) ≥ -50mV,
RO = high; if (A-B) ≤ -200mV, RO = low.
— 2 2 RE Receiver Output Enable. Pull RE low to enable RO.
— — 3 DE
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.
3 — — DE/RE
Driver/Receiver Output Enable. Pull DE/RE low to three-
state the driver output and enable RO. Force DE/RE high to
enable driver output and three-state RO
— 3 — DE
Driver Output Enable. Force DE high to enable driver. Pull
DE low to three-state the driver output. Drive RE high and
pull DE low to enter low-power shutdown mode.
4 4 — DI
Driver Input. A logic-low on DI forces the noninverting
output low and the inverting output high. A logic-high on
DI forces the noninverting output high and the inverting
output low.
— — 4 TXD
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 recessive state.
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
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MAX3440E–MAX3444E ±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
Pin Description
X = Don’t care.
X = Don’t care.
X = Don’t care.
X = Don’t care.
X = Don’t care.
Note 1: Receiver output may oscillate with this differential input condition.
Table 5. MAX3440E/MAX3441E
(RS-485/RS-422)
Table 4. MAX3444E (J1708) Application
Table 3. MAX3442E/MAX3443E
(RS-485/RS-422)
Table 2. MAX3440E/MAX3441E
(RS-485/RS-422)
Table 1. MAX3440E/MAX3441E Fault Table
RECEIVING
INPUTS OUTPUTS
DE/RE (A - B) RO
0≥-0.05V 1
0≤-0.2V 0
0 Open/shorted 1
1 X High-Z
TRANSMITTING
INPUTS OUTPUTS CONDITIONS
TXD DE A B —
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
TRANSMITTING
INPUTS OUTPUTS
RE DE DI A B
0 0 X High-Z High-Z
0 1 0 0 1
0 1 1 1 0
1 0 X Shutdown Shutdown
1 1 0 0 1
1 1 1 1 0
TRANSMITTING
INPUTS OUTPUTS
DE/RE DI A B
0 X High-Z High-Z
1001
1110
INPUTS OUTPUTS
FAULT CONDITION
A-B
VID DIFFERENTIAL
INPUT VOLTAGE
COMMON-MODE
VOLTAGE RO
FAULT
CONDITIONED
BY DELAY
≥0.45V
≤12V and ≥-7V
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 Indeterminate
(Note 1) 1 Low-input differential voltage
≤-0.2V and >-0.27V 0 1 Low-input differential voltage
≤-0.27V and >-0.45V 0 Indeterminate Indeterminate
≤-0.45V 0 0
X<-7V or >+12V Indeterminate 1 Outside common-mode voltage range
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MAX3440E–MAX3444E ±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
Function Tables
X = Don’t care.
X = Don’t care.
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 fail-
safe circuitry, which guarantees a logic-high receiver out-
put 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 cir-
cuit board is plugged into a hot backplane (see the Hot-
Swap Capability section). The MAX3440E/MAX3442E/
MAX3444E feature a reduced slew-rate driver that mini-
mizes 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, log-
ic-level output (RO). Deasserting the receiver enable
places the receiver inputs (A and B) into a high-imped-
ance 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/TIA-485 stan-
dard. 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.
Table 7. MAX3444E (RS-485/RS-422)
Table 6. MAX3442E/MAX3443E
(RS-485/RS-422)
RECEIVING
INPUTS OUTPUTS
RE DE (A - B) RO
0 X ≥-0.05V 1
0 X £-0.2V 0
0 X Open/shorted 1
1 0 X High-Z
1 1 X Shutdown
RECEIVING
INPUTS OUTPUTS
RE DE (A - B) RO
0 X ≥-0.05V 1
0 X ≤-0.2V 0
0 X Open/shorted 1
1 1 X High-Z
1 0 X Shutdown
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12
MAX3440E–MAX3444E ±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
Function Tables (continued)
±15kV ESD Protection
As with all Maxim devices, ESD-protection structures
are incorporated on all pins to protect against ESD encoun-
tered 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 dis-
charged into a low impedance. This model consists of
a 100pF capacitor charged to the ESD voltage of inter-
est, 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 tem-
perature cools to +140°C, resulting in a pulsed output
during continuous short-circuit conditions.
Figure 9b. Human Body Model Current WaveformFigure 9a. Human Body ESD Test Model
IP 100%
90%
36.8%
tRL TIME
tDL
CURRENT WAVEFORM
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
Ir
10%
0
0
AMPERES
CHARGE-CURRENT-
LIMIT RESISTOR
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
Cs
100pF
RC
1MΩ
RD
1.5kΩ
HIGH-
VOLTAGE
DC
SOURCE
DEVICE
UNDER
TEST
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MAX3440E–MAX3444E ±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
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 VCC or GND, could cause an input to
drift to an incorrect logic state. To prevent such a condi-
tion 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 situ-
ations. The MAX3444E has hot-swap input circuitry only
on RE. When VCC 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 VCC ramps from
zero, an internal 15µs timer turns on M2 and sets the SR
latch, which also turns on M1. Transistors M2, a 2mA cur-
rent sink, and M1, a 100µA current sink, pull DE to GND
through a 5.6kW 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 deac-
tivates 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 stan-
dard, high-impedance CMOS input. Whenever VCC drops
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 (48kW) allows up to 128 trans-
ceivers 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 Reections
The MAX3440E/MAX3442E/MAX3444E are slew-rate lim-
ited, 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 har-
monic 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)
VCC
TIMER
TIMER
DE
(HOT SWAP)
15µs
100µA
M1 M2
5.6kΩ
2mA
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14
MAX3440E–MAX3444E ±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
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 = tRISE/(10 x 1.5ns/ft)
where tRISE 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 unterminat-
ed 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 dominant-mode
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 reces-
sive 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 untermi-
nated, at high frequencies, R3 and R4 perform a pseudo-
termination. This makes the implementation more flexible,
as no specific termination nodes are required at the ends
of the bus.
Figure 12. Driver Output Waveform and FFT Plot of
MAX3442E Transmitting a 125kHz Signal
Figure 11. Driver Output Waveform and FFT Plot of
MAX3443E Transmitting a 125kHz Signal
5.00MHz500kHz/div0
20dB/div
2V/div
5.00MHz500kHz/div0
20dB/div
2V/div
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15
MAX3440E–MAX3444E ±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
Figure 14. MAX3442E/MAX3443E Typical RS-485 Network
Figure 13. MAX3440E/MAX3441E Typical RS-485 Network
DI RO DE
A
B
RE
RO
RO
RO
DI
DI
DI
DE
DE
DE
DD
D
R
R
R
B B
B
AA
A
120Ω120Ω
D
R
MAX3442E
MAX3443E
RERE
RE
DI RO DE/RE
A
B
FAULT
RO
RO
RO
DI
DI
DI
DE/RE
DE/RE
DE/RE
DD
D
R
R
R
B B
B
AA
A
120Ω120Ω
D
R
MAX3440E
MAX3441E
FAULT FAULT
FAULT
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MAX3440E–MAX3444E ±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
+Denotes a lead(Pb)-free/RoHS-compliant package.
Figure 15. J1708 Application Circuit
PART TEMP RANGE PIN-PACKAGE
MAX3441EESA+ -40°C to +85°C 8 SO
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
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
TOP VIEW
1
2
3
4
8
5
VCC
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
VCC
B
A
GND
DI
DE
RE
RO
DIP/SO DIP/SO
R
D
B
A
MAX3442E
MAX3443E
++
R1
4.7kΩ
R3
47Ω
C1
2.2nF
C2
2.2nF
R2
4.7kΩ
RO
Rx
Tx
R4
47Ω
J1708 BUS
B
A
TXD D
R
DE
RE
MAX3444E
VCC
1
2
3
4
8
5
VCC
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
VCC
B
A
GND
TXD
DE
RE
RO
DIP/SO DIP/SO
R
D
B
A
MAX3444E
++
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17
MAX3440E–MAX3444E ±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
Pin Congurations and Typical Operating Circuits (continued)
Ordering Information (continued)
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
8 SO S8+4 21-0041 90-0096
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MAX3440E–MAX3444E ±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.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.
Chip Information
PROCESS: BiCMOS
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 10/02 Initial release —
1 12/05
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
6, 11, 17
2 11/10 Added lead(Pb)-free parts to the Ordering Information table; added the soldering
temperature to the Absolute Maximum Ratings section; updated Table 4 outputs 1, 2, 11, 17
3 4/14 Deleted “Truck and Trailer Applications” and “Automotive Applications” from
Applications section 1
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
MAX3440E–MAX3444E ±15kV ESD-Protected, ±60V Fault-Protected,
10Mbps, Fail-Safe RS-485/J1708 Transceivers
© 2014 Maxim Integrated Products, Inc.
│
19
Revision History
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MAX3440EEPA+ MAX3440EESA+ MAX3442EESA+ MAX3443ECSA+ MAX3443EESA+ MAX3444EESA+
MAX3440EAPA+ MAX3440EASA+ MAX3440EASA+T MAX3440EESA+T MAX3441EASA+ MAX3441EASA+T
MAX3441EEPA+ MAX3441EESA+ MAX3441EESA+T MAX3442EAPA+ MAX3442EASA+ MAX3442EASA+T
MAX3442EEPA+ MAX3442EESA+T MAX3443EAPA+ MAX3443EASA+ MAX3443EASA+T MAX3443ECPA+
MAX3443ECSA+T MAX3443EEPA+ MAX3443EESA+T MAX3444EASA+ MAX3444EASA+T MAX3444EESA+T