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19-2666; Rev 0; 10/02
15kV ESD-Protected, 60V Fault-Protected, 10Mbps, Fail-Safe RS-485/J1708 Transceivers
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. o 15kV ESD Protection o 60V Fault Protection o Guaranteed 10Mbps Data Rate (MAX3441E/MAX3443E) o Hot Swappable for Telecom Applications o True Fail-Safe Receiver Inputs o Enhanced Slew-Rate-Limiting Facilitates Error-Free Data Transmission (MAX3440E/MAX3442E/MAX3444E) o Allow Up to 128 Transceivers on the Bus o -7V to +12V Common-Mode Input Range o Automotive Temperature Range (-40C to +125C) o Industry-Standard Pinout
Features
MAX3440E-MAX3444E
Ordering Information
PART MAX3440EESA MAX3440EEPA MAX3440EASA MAX3440EAPA TEMP RANGE -40C to +85C -40C to +85C -40C to +125C -40C to +125C PIN-PACKAGE 8 SO 8 PDIP 8 SO 8 PDIP
Applications
RS-422/RS-485 Communications Truck and Trailer Applications Industrial Networks Telecommunications Systems Automotive Applications HVAC Controls
DATA RATE (Mbps) 0.25 2.5 to 10 0.25 2.5 to 10 0.25 LOW-POWER SHUTDOWN No No Yes Yes Yes
Ordering Information continued at end of data sheet.
Selector Guide
RECEIVER/DRIVER ENABLE Yes Yes Yes Yes Yes TRANSCEIVERS ON BUS 128 128 128 128 128 HOT SWAP Yes Yes Yes Yes Yes (only RE)
PART MAX3440E MAX3441E MAX3442E MAX3443E MAX3444E
TYPE RS-485 RS-485 RS-485 RS-485 J1708
Pin Configurations and Typical Operating Circuits
TOP VIEW
FAULT 1 RO 2 DE/RE 3 DI 4 D R 8 7 6 5 VCC B A GND FAULT 1 RO 2 DE/RE 3 D R 8 VCC 7B Rt 6 A 5 GND DE/RE
MAX3440E MAX3441E
B Rt A R
D
DI
DI 4
RO FAULT
DIP/SO DIP/SO Pin Configurations and Typical Operating Circuits continued at end of data sheet.
________________________________________________________________ Maxim Integrated Products
1
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15kV ESD-Protected, 60V Fault-Protected, 10Mbps, Fail-Safe RS-485/J1708 Transceivers MAX3440E-MAX3444E
ABSOLUTE MAXIMUM RATINGS
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 = +70C) 8-Pin SO (derate 5.9mW/C above +70C)..................471mW 8-Pin PDIP (derate 9.09mW/C above +70C).............727mW Operating Temperature Ranges MAX344_EE_ _ ...............................................-40C to +85C MAX344_EA_ _ .............................................-40C to +125C Storage Temperature Range .............................-65C to +150C Junction Temperature ......................................................+150C Lead Temperature (soldering, 10s) .................................+300C
Note 1: A, B must be terminated with 54 or 100 to guarantee 60V fault protection.
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.
DC ELECTRICAL CHARACTERISTICS
(VCC = +4.75V to +5.25V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25C.)
PARAMETER DRIVER Differential Driver Output 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 Driver Input Low Voltage Driver Input Current Driver Short-Circuit Output Current (Note 3) Driver Short-Circuit Foldback Output Current RECEIVER VCC = GND, VA, B = 12V Input Current Receiver Differential Threshold Voltage Receiver Input Hysteresis IA,B A, B VA, B = -7V VA, B = 60V VTH VTH -7V VCM +12V -200 25 250 -150 6 -50 A mA mV mV VDIH VDIL IDIN IOSD IOSDF 0 VOUT +12V -7V VOUT VCC (VCC - 1V) VOUT +12V (Note 3) -7V VOUT +1V (Note 3) -350 +25 -25 2 0.8 2 +350 V V A mA mA VOD VOD VOC VOC Figure 1, RL = 100 Figure 1, RL = 54 Figure 1, RL = 100 or 54 (Note 2) Figure 1, RL = 100 or 54 Figure 1, RL = 100 or 54 (Note 2) VCC / 2 2 1.5 VCC VCC 0.2 3 0.2 V V V V SYMBOL CONDITIONS MIN TYP MAX UNITS
2
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15kV ESD-Protected, 60V Fault-Protected, 10Mbps, Fail-Safe RS-485/J1708 Transceivers
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 = +25C.)
PARAMETER RECEIVER LOGIC Output High Voltage Output Low Voltage Three-State Output Current at Receiver Receiver Input Resistance Receiver Output Short-Circuit Current CONTROL Control Input High Voltage Input Current Latch During First Rising Edge SUPPLY CURRENT MAX3440E (DE/RE = VCC), MAX3442E (DE = VCC, RE = GND), MAX3444E (DE = RE = GND) MAX3441E (DE/RE = VCC), MAX3443E (DE = VCC, RE = GND) VCIH IIN DE, DE, RE, DE/RE DE, DE/RE, RE 2 90 V A VOH VOL IOZR RIN IOSR Figure 2, IOH = -1.6mA Figure 2, IOL = 1mA 0 VA, B VCC -7V VCM +12V 0 VRO VCC 48 95 VCC - 0.6 0.4 1 V V A k mA SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX3440E-MAX3444E
30 mA 10
Normal Operation
IQ
No load, DI = VCC or GND
DE = GND, RE = VCC (MAX3442E/ MAX3443E) Supply Current in Shutdown Mode ISHDN DE = GND, RE = VCC, TA = +25C (MAX3442E/MAX3443E) DE = RE = VCC (MAX3444E) DE = RE = VCC, TA = +25C (MAX3444E) Supply Current with Output Shorted to 60V ISHRT DE = GND, RE = GND, no load output in three-state (MAX3443E)
20 A
10 100 10 15
mA
PROTECTION SPECIFICATIONS
(VCC = +4.75V to +5.25V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25C.)
PARAMETER Overvoltage Protection ESD Protection FAULT DETECTION Receiver Differential Threshold Receiver Differential Threshold Fault-Detection Common-Mode Input Voltage Positive Fault-Detection Common-Mode Input Voltage Negative FDIPH FDIPL VCM = 0, high limit VCM = 0, low limit 270 -450 12 -7 450 -270 mV mV V V SYMBOL A, B CONDITIONS A, B; RSOURCE = 0, RL = 54 Human Body Model MIN 60 15 TYP MAX UNITS V kV
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15kV ESD-Protected, 60V Fault-Protected, 10Mbps, Fail-Safe RS-485/J1708 Transceivers MAX3440E-MAX3444E
SWITCHING CHARACTERISTICS (MAX3440E/MAX3442E/MAX3444E)
(VCC = +4.75V to +5.25V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25C.)
PARAMETER Driver Propagation Delay SYMBOL tPLHA, tPLHB tDPLH, tDPHL tLH,tHL tSKEWAB, tSKEWBA tDSKEW fMAX tPDZH tPDHZ tPDHS tPDZL tPDLZ tPDLS tSHDN tRPLH, tRPHL tRSKEW tRPZH tRPHZ tRPWAKE tRPZL tRPLZ tSHDN Figure 5, RL = 500, CL = 50pF Figure 5, RL = 500, CL = 50pF Figure 5, RL = 500, CL = 50pF (MAX3442E/MAX3444E) Figure 6, RL = 500, CL = 50pF Figure 6, RL = 500, CL = 50pF Figure 6, RL = 500, CL = 50pF (MAX3442E/MAX3444E) RL = 500, CL = 50pF (MAX3442E/MAX3444E) Figure 7, CL = 20pF, VID = 2V, VCM = 0 CL = 20pF, tRSKEW = |tRPLH - tRPHL| Figure 8, RL = 1k, CL = 20pF Figure 8, RL = 1k, CL = 20pF Figure 8, RL = 1k, CL = 20pF (MAX3442E/MAX3444E) Figure 8, RL = 1k, CL = 20pF Figure 8, RL = 1k, CL = 20pF RL = 500, CL= 50pF (MAX3442E/MAX3444E) CONDITIONS MAX3440E/MAX3442E, Figure 3, RL = 54, CL = 50pF MAX3444E, RDIFF = 60, CDIFF = 100pF Figure 4, RL = 54, CL = 50pF Figure 4, RL = 54, CL = 50pF RL = 54, CL = 50pF, tSKEWAB = |tPLHA - tPHLB|, tSKEWBA = |tPLHB - tPHLA| RL = 54, CL = 50pF, tDSKEW = |tDPLH - tDPHL| 250 2000 2000 4.2 2000 2000 4.2 800 2000 200 2000 2000 4.2 2000 2000 800 200 2000 2000 ns ns MIN TYP MAX 2000 UNITS ns
Driver Differential Propagation Delay Driver Differential Output Transition Time Driver Output Skew
350
ns
Differential Driver Output Skew Maximum Data Rate Driver Enable Time to Output High Driver Disable Time from Output High Driver Enable Time from Shutdown to Output High Driver Enable Time to Output Low Driver Disable Time from Output Low Driver Enable Time from Shutdown to Output Low Driver Time to Shutdown Receiver Propagation Delay Receiver Output Skew Receiver Enable Time to Output High Receiver Disable Time from Output High Receiver Wake Time from Shutdown Receiver Enable Time to Output Low Receiver Disable Time from Output Low Receiver Time to Shutdown
200
ns kbps ns ns s ns ns s ns ns ns ns ns s ns ns ns
4
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15kV ESD-Protected, 60V Fault-Protected, 10Mbps, Fail-Safe RS-485/J1708 Transceivers
SWITCHING CHARACTERISTICS (MAX3441E/MAX3443E)
(VCC = +4.75V to +5.25V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at VCC = +5V and TA = +25C.)
PARAMETER Driver Propagation Delay Driver Differential Propagation Delay Driver Differential Output Transition Time Driver Output Skew SYMBOL tPLHA, tPLHB tDPLH, tDPHL tLH,tHL tSKEWAB, tSKEWBA tDSKEW fMAX tPDZH tPDHZ tPDHS tPDZL tPDLZ tPDLS tSHDN tRPLH, tRPHL tRSKEW tRPZH tRPHZ tRPWAKE tRPSH tRPLZ tSHDN Figure 5, RL = 500, CL = 50pF Figure 5, RL = 500, CL = 50pF Figure 5, RL = 500, CL = 50pF (MAX3443E) Figure 6, RL = 500, CL = 50pF Figure 6, RL = 500, CL = 50pF Figure 6, RL = 500, CL = 50pF (MAX3443E) Figure 6, RL = 500, CL = 50pF (MAX3443E) Figure 7, CL = 20pF, VID = 2V, VCM = 0 CL = 20pF, tRSKEW = |tRPLH - tRPHL| Figure 8, RL = 1k, CL = 20pF Figure 8, RL = 1k, CL = 20pF Figure 8, RL = 1k, CL= 20pF (MAX3443E) Figure 8, RL = 1k, CL = 20pF Figure 8, RL = 1k, CL= 20pF RL = 500, CL= 50pF (MAX3443E) CONDITIONS Figure 3, RL = 27, CL = 50pF Figure 4, RL = 54, CL = 50pF Figure 4, RL = 54, CL = 50pF RL = 54, CL = 50pF, tSKEWAB = |tPLHA - tPHLB|, tSKEWBA = |tPLHB - tPHLA| RL = 54, CL = 50pF, tDSKEW = |tDPLH - tDPHL| 10 1200 1200 4.2 1200 1200 4.2 800 85 15 400 400 4.2 400 400 800 MIN TYP MAX 60 60 25 UNITS ns ns ns
MAX3440E-MAX3444E
10
ns
Differential Driver Output Skew Maximum Data Rate Driver Enable Time to Output High Driver Disable Time from Output High Driver Enable Time from Shutdown to Output High Driver Enable Time to Output Low Driver Disable Time from Output Low Driver Enable Time from Shutdown to Output Low Driver Time to Shutdown Receiver Propagation Delay Receiver Output Skew Receiver Enable Time to Output High Receiver Disable Time from Output High Receiver Wake Time from Shutdown Receiver Enable Wake Time from Shutdown Receiver Disable Time from Output Low Receiver Time to Shutdown
10
ns Mbps ns ns s ns ns s ns ns ns ns ns s ns ns ns
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.
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15kV ESD-Protected, 60V Fault-Protected, 10Mbps, Fail-Safe RS-485/J1708 Transceivers MAX3440E-MAX3444E
Typical Operating Characteristics
(VCC = +5V, TA = +25C, unless otherwise noted.)
NO-LOAD SUPPLY CURRENT vs. TEMPERATURE
MAX3440E toc01
NO-LOAD SUPPLY CURRENT vs. TEMPERATURE
MAX3440E toc02
SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE
MAX3443E toc03
6 5 SUPPLY CURRENT (mA) 4 3 2 1 MAX3441E/MAX3443E 0 DRIVER DISABLED, RECEIVER ENABLED DRIVER AND RECEIVER ENABLED
24 20 SUPPLY CURRENT (mA) 16 12 8 4 MAX3440E/MAX3442E/MAX3444E 0 DRIVER AND RECEIVER ENABLED
10
SUPPLY CURRENT (nA)
1
DRIVER DISABLED, RECEIVER ENABLED
0.1
MAX3442E/MAX3443E/MAX3444E 0.01 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
RECEIVER OUTPUT CURRENT vs. OUTPUT LOW VOLTAGE
MAX3443E toc04
RECEIVER OUTPUT CURRENT vs. OUTPUT HIGH VOLTAGE
MAX3443E toc05
RECEIVER OUTPUT VOLTAGE vs. TEMPERATURE
4.5 RECEIVER OUTPUT VOLTAGE (V) 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 VOL, IOUT = -10mA VOH, IOUT = +10mA
MAX3443E toc06
40 RECEIVER OUTPUT CURRENT (mA) 35 30 25 20 15 10 5 0
40 RECEIVER OUTPUT CURRENT (mA) 35 30 25 20 15 10 5 0
5.0
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 OUTPUT LOW VOLTAGE (V)
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 OUTPUT HIGH VOLTAGE (V)
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
DRIVER OUTPUT CURRENT vs. DIFFERENTIAL OUTPUT VOLTAGE
MAX3443E toc07
DIFFERENTIAL OUTPUT VOLTAGE vs. TEMPERATURE
MAX3443E toc08
A, B CURRENT vs. A, B VOLTAGE (TO GROUND)
1600 1200 A, B CURRENT (A) 800 400 0 -400 -800 -1200 DRIVER DISABLED, RECEIVER ENABLED -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 A, B VOLTAGE (V) RL = 54
MAX3443E toc09
80 70 DRIVER OUTPUT CURRENT (mA) 60 50 40 30 20 10 0 0 0.5
3.5 DIFFERENTIAL OUTPUT VOLTAGE (V) 3.0 2.5 2.0 RL = 54 1.5 1.0 0.5 MAX3441E/MAX3443E 0 RL = 100
2000
-1600 -2000
1.0
1.5
2.0
2.5
3.0
3.5
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
DIFFERENTIAL OUTPUT VOLTAGE (VA - VB) (V)
6
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15kV ESD-Protected, 60V Fault-Protected, 10Mbps, Fail-Safe RS-485/J1708 Transceivers
Test Circuits and Waveforms
RL A DI D B VCC VOD RL 2 2
MAX3440E-MAX3444E
VOC
Figure 1. Driver VOD and VOC
A VID B 0 VOL IOL (+) VOH IOH (-) R RO
Figure 2. Receiver VOH and VOL
3V VOM
DI
A DI D GENERATOR (NOTE 4) B 50 VCC VOH + VOL 1.5V 2 B CL = 50pF (NOTE 5) A RL 2
1.5V
1.5V 0
S1
OUT
tPLHA
tPHLA VOH VOM VOM VOL
tPHLB
tPLHB
VOH VOM VOM VOL
VOM =
Figure 3. Driver Propagation Times
3V DI RL OUT 1.5V 1.5V 0 tDPLH tDPHL 2.0V 50% 10% tHL
DI D GENERATOR (NOTE 4)
A
CL
B 50 VCC CL
90% (A-B) CL = 50pF (NOTE 5) tLH 50% 10%
90%
-2.0V
Figure 4. Driver Differential Output Delay and Transition Times _______________________________________________________________________________________ 7
15kV ESD-Protected, 60V Fault-Protected, 10Mbps, Fail-Safe RS-485/J1708 Transceivers MAX3440E-MAX3444E
Test Circuits and Waveforms (continued)
A DI 0 OR 3V D B DE GENERATOR (NOTE 4)
S1 A, B RL = 500W DE 1.5V tPDZH tPDHS 1.5V
3V
0 tPDHZ VOH
CL = 50pF (NOTE 5)
50W A, B VOM = VOH + VOL 2 VOM
0.25V
1.5V
0
Figure 5. Driver Enable and Disable Times
VCC 3V A DI 0 OR 3V D B DE GENERATOR (NOTE 4) CL = 50pF (NOTE 5) A, B 50 VOM 0.25V VOL VCC S1 RL = 500 A, B DE 1.5V tPDZL tPDLS 1.5V 0 tPDLZ
Figure 6. Driver Enable and Disable Times
A GENERATOR (NOTE 4) VID 50 B R RO CL = 20pF (NOTE 5) tRPLH tRPHL (A-B) 1.0V 1.0V
2.0V
0
VCC 1.0V 0 RO VOM VOM 0
Figure 7. Receiver Propagation Delay
8
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15kV ESD-Protected, 60V Fault-Protected, 10Mbps, Fail-Safe RS-485/J1708 Transceivers
Test Circuits and Waveforms (continued)
1.5V -1.5V S3 VID B CL = 20pF (NOTE 5) GENERATOR (NOTE 4) 50 S1 A R RO 1k S2 VCC
MAX3440E-MAX3444E
3V RE tRPZH tRPSH tRPWAKE RO 1.5V 0 3V RE 1.5V 0 tRPHZ RO 0.5V VOH RO 0 S1 OPEN S2 CLOSED S3 = 1.5V RE 1.5V 1.5V 0 S1 OPEN S2 CLOSED S3 = 1.5V RE tRPZL tRPSL VOH RO 1.5V 1.5V
3V S1 CLOSED S2 OPEN S3 = -1.5V
0
VCC
VOL 3V S1 CLOSED S2 OPEN S3 = -1.5V
0
tRPLZ
0.5V
VCC
VOL
Figure 8. Receiver Enable and Disable Times Note 4: The input pulse is supplied by a generator with the following characteristics: f = 5MHz, 50% duty cycle; tr 6ns; Z0 = 50. Note 5: CL includes probe and stray capacitance.
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15kV ESD-Protected, 60V Fault-Protected, 10Mbps, Fail-Safe RS-485/J1708 Transceivers MAX3440E-MAX3444E
Pin Description
PIN MAX3440E MAX3441E MAX3442E MAX3443E MAX3444E NAME FUNCTION
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 Receiver Output. If receiver enabled and (A-B) -50mV, RO = high; if (A-B) -200mV, RO = low. Receiver Output Enable. Pull RE low to enable RO. 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. Drive RE high and pull DE low to enter low-power shutdown mode. 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. 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. Ground Noninverting Receiver Input/Driver Output Inverting Receiver Input/Driver Output Positive Supply, VCC = +4.75V to +5.25V
2 -- --
1 2 --
1 2 3
RO RE DE
3
--
--
DE/RE
--
3
--
DE
4
4
--
DI
-- 5 6 7 8
-- 5 6 7 8
4 5 6 7 8
TXD GND A B VCC
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15kV ESD-Protected, 60V Fault-Protected, 10Mbps, Fail-Safe RS-485/J1708 Transceivers
Function Tables
Table 1. MAX3440E/MAX3441E Fault Table
INPUTS A-B VID DIFFERENTIAL INPUT VOLTAGE 0.45V <0.45V and 0.27V <0.27V and -0.05V -0.05V and -0.2V -0.2V and >-0.27V -0.27V and >-0.45V -0.45V X <-7V or >+12V 12V and -7V COMMON-MODE VOLTAGE RO 1 1 1 Indeterminate (Note 1) 0 0 0 Indeterminate OUTPUTS FAULT CONDITIONED BY DELAY 0 Indeterminate 1 1 1 Indeterminate 0 1 FAULT CONDITION
MAX3440E-MAX3444E
Normal operation Indeterminate Low-input differential voltage Low-input differential voltage Low-input differential voltage Indeterminate Outside common-mode voltage range
X = Don't care. Note 1: Receiver output may oscillate with this differential input condition.
Table 3. MAX3442E/MAX3443E (RS-485/RS-422) Table 2. MAX3440E/MAX3441E (RS-485/RS-422)
TRANSMITTING INPUTS DE/RE 0 1 1 DI X 0 1 A High-Z 0 1 OUTPUTS B High-Z 1 0 RE 0 0 0 1 1 1 TRANSMITTING INPUTS DE 0 1 1 0 1 1 DI X 0 1 X 0 1 A High-Z 0 1 Shutdown 0 1 OUTPUTS B High-Z 1 0 Shutdown 1 0
X = Don't care.
X = Don't care.
Table 4. MAX3444E (J1708) Application
TRANSMITTING INPUTS TXD 0 1 0 1 DE 1 1 0 0 A High-Z High-Z 1 High-Z OUTPUTS B High-Z High-Z 0 High-Z CONDITIONS -- -- -- Dominant state Recessive state
Table 5. MAX3440E/MAX3441E (RS-485/RS-422)
RECEIVING INPUTS DE/RE 0 0 0 1 (A - B) -0.05V -0.2V Open/shorted X OUTPUTS RO 1 0 1 High-Z
X = Don't care.
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15kV ESD-Protected, 60V Fault-Protected, 10Mbps, Fail-Safe RS-485/J1708 Transceivers MAX3440E-MAX3444E
Function Tables (continued)
Table 6. MAX3442E/MAX3443E (RS-485/RS-422)
RECEIVING INPUTS RE 0 0 0 1 1 DE X X X 1 0 (A - B) -0.05V -0.2V Open/shorted X X OUTPUTS RO 1 0 1 High-Z Shutdown RE 0 0 0 1 1 DE X X X 0 1
Table 7. MAX3444E (RS-485/RS-422)
RECEIVING INPUTS (A - B) -0.05V -0.2V Open/shorted X X OUTPUTS RO 1 0 1 High-Z Shutdown
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 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.
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 20A 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.
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).
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.
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15kV ESD-Protected, 60V Fault-Protected, 10Mbps, Fail-Safe RS-485/J1708 Transceivers
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 1.5k resistor.
MAX3440E-MAX3444E
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 +160C. Normal operation resumes when the die temperature cools to +140C, resulting in a pulsed output during continuous short-circuit conditions.
RC 1M9 CHARGE-CURRENTLIMIT RESISTOR HIGHVOLTAGE DC SOURCE
RD 1.5k9 DISCHARGE RESISTANCE DEVICE UNDER TEST
IP 100% 90% AMPERES
Ir
PEAK-TO-PEAK RINGING (NOT DRAWN TO SCALE)
Cs 100pF
STORAGE CAPACITOR
36.8% 10% 0 0 tRL TIME tDL CURRENT WAVEFORM
Figure 9a. Human Body ESD Test Model
Figure 9b. Human Body Model Current Waveform
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15kV ESD-Protected, 60V Fault-Protected, 10Mbps, Fail-Safe RS-485/J1708 Transceivers MAX3440E-MAX3444E
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 10A 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 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 VCC rises, an internal pulldown (or pullup for RE) circuit holds DE low for at least 10s, and until the current into DE exceeds 200A. 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 15s timer turns on M2 and sets the SR latch, which also turns on M1. Transistors M2, a 2mA current sink, and M1, a 100A current sink, pull DE to GND through a 5.6k resistor. M2 pulls DE to the disabled state against an external parasitic capacitance up to 100pF that may drive DE high. After 15s, 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 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 (48k) 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.
VCC 15s TIMER TIMER
DE (HOT SWAP)
5.6k
100A M1
2mA M2
Figure 10. Simplified Structure of the Driver Enable Pin (DE)
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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 unterminated stubs, even with severe reflections, if the waveform settles out before the UART samples them.
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
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.
20dB/div
20dB/div
2V/div
2V/div
0
500kHz/div
5.00MHz
0
500kHz/div
5.00MHz
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
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15kV ESD-Protected, 60V Fault-Protected, 10Mbps, Fail-Safe RS-485/J1708 Transceivers MAX3440E-MAX3444E
120 DI D DE/RE RO FAULT R B 120 B D DI A B A B A A R RO FAULT R R D DE/RE
MAX3440E MAX3441E
DI
D
DE/RE RO FAULT
DI
DE/RE
RO FAULT
Figure 13. MAX3440E/MAX3441E Typical RS-485 Network
120 DI D DE RO RE R R B
120 B D DI DE
A
B
A
B
A
A R RO RE R
MAX3442E MAX3443E
DI
D
D
DE
RO RE
DI
DE
RO RE
Figure 14. MAX3442E/MAX3443E Typical RS-485 Network
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15kV ESD-Protected, 60V Fault-Protected, 10Mbps, Fail-Safe RS-485/J1708 Transceivers
VCC DE
Chip Information
TRANSISTOR COUNT: 310 PROCESS: BiCMOS
R1 4.7k R3 47 C1 2.2nF J1708 BUS
MAX3440E-MAX3444E
Tx
TXD
D
B
MAX3444E
A Rx RO R
C2 2.2nF R4 47 R2 4.7k
RE
Figure 15. J1708 Application Circuit
Pin Configurations and Typical Operating Circuits (continued)
TOP VIEW
RO RE 1 2 R 8 7 6 D 5 VCC B A GND RO 1 R 8 VCC 7B Rt 6 A 5 GND DE
MAX3442E MAX3443E
B Rt A R
D
DI
RE 2 DE DI 3 4 D
DE 3 DI 4
RO RE
DIP/SO
DIP/SO
DE RO 1 R 8 7 6 D 5 VCC B A GND RO 1 R
MAX3444E
8 VCC 7B Rt 6 A 5 GND D B Rt A R RE RO TXD
RE 2 DE TXD 3 4
RE 2 DE 3 D
TXD 4
DIP/SO
DIP/SO
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15kV ESD-Protected, 60V Fault-Protected, 10Mbps, Fail-Safe RS-485/J1708 Transceivers MAX3440E-MAX3444E
Ordering Information (continued)
PART MAX3441EESA MAX3441EEPA MAX3441EASA MAX3441EAPA MAX3442EESA MAX3442EEPA MAX3442EASA MAX3442EAPA MAX3443ECSA MAX3443ECPA MAX3443EESA MAX3443EEPA MAX3443EASA MAX3443EAPA MAX3444EESA MAX3444EEPA MAX3444EASA MAX3444EAPA TEMP RANGE -40C to +85C -40C to +85C -40C to +125C -40C to +125C -40C to +85C -40C to +85C -40C to +125C -40C to +125C 0C to +70C 0C to +70C -40C to +85C -40C to +85C -40C to +125C -40C to +125C -40C to +85C -40C to +85C -40C to +125C -40C to +125C PIN-PACKAGE 8 SO 8 PDIP 8 SO 8 PDIP 8 SO 8 PDIP 8 SO 8 PDIP 8 SO 8 PDIP 8 SO 8 PDIP 8 SO 8 PDIP 8 SO 8 PDIP 8 SO 8 PDIP
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15kV ESD-Protected, 60V Fault-Protected, 10Mbps, Fail-Safe RS-485/J1708 Transceivers
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
SOICN .EPS
MAX3440E-MAX3444E
INCHES DIM A A1 B C e E H L MAX MIN 0.069 0.053 0.010 0.004 0.014 0.019 0.007 0.010 0.050 BSC 0.150 0.157 0.228 0.244 0.016 0.050
MILLIMETERS MAX MIN 1.35 1.75 0.10 0.25 0.35 0.49 0.19 0.25 1.27 BSC 3.80 4.00 5.80 6.20 0.40 1.27
N
E
H
VARIATIONS:
1
INCHES
MILLIMETERS MIN 4.80 8.55 9.80 MAX 5.00 8.75 10.00 N MS012 8 AA 14 AB 16 AC
TOP VIEW
DIM D D D
MIN 0.189 0.337 0.386
MAX 0.197 0.344 0.394
D C
A e B A1
0 -8 L
FRONT VIEW
SIDE VIEW
PROPRIETARY INFORMATION TITLE:
PACKAGE OUTLINE, .150" SOIC
APPROVAL DOCUMENT CONTROL NO. REV.
21-0041
B
1 1
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15kV ESD-Protected, 60V Fault-Protected, 10Mbps, Fail-Safe RS-485/J1708 Transceivers MAX3440E-MAX3444E
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
PDIPN.EPS
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.
20 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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