AVAILABLE
Functional Diagrams
Pin Configurations appear at end of data sheet.
Functional Diagrams continued at end of data sheet.
UCSP is a trademark of Maxim Integrated Products, Inc.
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
EVALUATION KIT AVAILABLE
General Description
The MAX3535E/MXL1535E isolated RS-485/RS-422 full-
duplex transceivers provide 2500VRMS of galvanic isola-
tion between the RS-485/RS-422 side and the processor
or control logic side. These devices allow fast,
1000kbps communication across an isolation barrier
when the common-mode voltages (i.e., the ground
potentials) on either side of the barrier are subject to
large differences. Isolation is achieved through integrat-
ed high-voltage capacitors. The MAX3535E/MXL1535E
also feature a 420kHz transformer driver that allows
power transfer to the RS-485 side using an external
transformer.
The MAX3535E/MXL1535E include one differential driver,
one receiver, and internal circuitry to send the RS-485
signals and control signals across the isolation barrier
(including the isolation capacitors). The MAX3535E/
MXL1535E RS-485 receivers are 1/8 unit load, allowing
up to 256 devices on the same bus.
The MAX3535E/MXL1535E feature true fail-safe circuitry.
The driver outputs and the receiver inputs are protected
from ±15kV electrostatic discharge (ESD) on the inter-
face side, as specified in the Human Body Model (HBM).
The MAX3535E/MXL1535E feature driver slew-rate
select that minimizes electromagnetic interference (EMI)
and reduces reflections. The driver outputs are short-cir-
cuit and overvoltage protected. Other features are hot-
swap capability and isolation-barrier fault detection.
The MAX3535E operates with a single +3V to +5.5V
power supply. The improved secondary supply range of
the MAX3535E allows the use of step-down transformers
for +5V operation, resulting in considerable power sav-
ings. The MXL1535E operates with a single +4.5V to
+5.5V power supply. The MXL1535E is a function-/pin-
compatible improvement of the LTC1535. The
MAX3535E/MXL1535E are available over the commer-
cial 0°C to +70°C and extended -40°C to +85°C temper-
ature ranges.
Applications
Isolated RS-485 Systems
Systems with Large Common-Mode Voltages
Industrial-Control Local Area Networks
Telecommunications Systems
Features
♦2500VRMS RS-485 Bus Isolation Using On-Chip
High-Voltage Capacitors
♦1000kbps Full-Duplex RS-485/RS-422
Communication
♦+3V to +5.5V Power-Supply Voltage Range
(MAX3535E)
♦+4.5V to +5.5V Power-Supply Voltage Range
(MXL1535E)
♦1/8 Unit Receiver Load, Allowing 256 Devices on
Bus
♦±15kV ESD Protection Using HBM
♦Pin-Selectable Slew-Rate Limiting Controls EMI
♦Hot-Swap-Protected Driver-Enable Input
♦Undervoltage Lockout
♦Isolation-Barrier Fault Detection
♦Short-Circuit Protected
♦Thermal Shutdown
♦Open-Line and Shorted-Line Fail-Safe Receiver
Inputs
+3V to +5V, 2500VRMS Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
28
27
26
25
18
17
16
15
1
2
3
4
11
12
13
14
RO1
RE
DE
DI
B
SLO
RO2
A
VCC2
PINS 5–10 and 19–24 ARE REMOVED FROM THE PACKAGE
Y
Z
GND2
GND1
ST2
ST1
VCC1
WIDE SO
TOP VIEW
MAX3535E
MXL1535E
PART TEMP RANGE PIN-
PACKAGE
POWER-
SUPPLY
RANGE
(V)
MAX3535ECWI 0°C to +70°C 28 Wi d e S O+ 3.0 to + 5.5
MAX3535EEWI -40°C to +85°C 28 Wi d e S O+ 3.0 to + 5.5
MXL1535ECWI 0°C to +70°C 28 Wi d e S O+ 4.5 to + 5.5
MXL1535EEWI -40°C to +85°C 28 Wi d e S O+ 4.5 to + 5.5
Pin Configuration
Ordering Information
19-3270; Rev 0; 4/04
Typical Application Circuit appears at end of data sheet.
MAX3535E/MXL1535E
Ordering Information
+3V to +5V, 2500VRMS Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
ABSOLUTE MAXIMUM RATINGS
DC ELECTRICAL CHARACTERISTICS TABLE (MAX3535E)
(VCC1 = +3.0V to +5.5V, VCC2 = +3.13V to +7.5V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at VCC1 = +3.3V,
VCC2 = +5V, TA= +25°C.)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
Logic Side—All Voltages Referenced to GND1.
VCC1 .........................................................................-0.3V to +6V
RE, DE, DI.................................................................-0.3V to +6V
RO1, ST1, ST2 ..........................................-0.3V to (VCC1 + 0.3V)
Isolated Side—All Voltages Referenced to GND2.
VCC2 .........................................................................-0.3V to +8V
SLO...........................................................-0.3V to (VCC2 + 0.3V)
A, B ......................................................................................±14V
RO2 .....................-0.3V to the lower of (VCC2 + 0.3V) and +3.4V
Y, Z ............................................................................-8V to +13V
Digital Outputs Maximum Current
RO1, RO2 .....................................................................±20mA
Y, Z Maximum Current .............................Short-Circuit Protected
ST1, ST2 Maximum Current............................................±300mA
Continuous Power Dissipation (TA= +70°C)
28-Pin Wide SO
(derate 9.5mW/°C above +70°C).................................750mW
Operating Temperature Range
MXL1535ECWI, MAX3535ECWI .........................0°C to +70°C
MXL1535EEWI, MAX3535EEWI.......................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
LOGIC-SIDE SUPPLY (VCC1, GND1)
Logic-Side Supply Voltage VCC1 3.0 5.5 V
Logic-Side Supply Current ICC1
Transformer not driven, ST1 and ST2
unconnected, RE = low, DE = high,
fDATA = 0, RO1 = no load
5.9 13 mA
VCC1 Undervoltage-Lockout
Falling Trip VUVL1 2.53 2.69 2.85 V
VCC1 Undervoltage-Lockout
Rising Trip VUVH1 2.63 2.80 2.97 V
LOGIC INPUTS (DI, DE, RE)
Input High Voltage, DE, DI, RE VIH VIH is measured with respect to GND1 2.0 V
Input Low Voltage, DE, DI, RE VIL VIL is measured with respect to GND1 0.8 V
Logic-Side Input Current, DE, DI IINC ±2µA
LOGIC OUTPUTS (RO1, RE)
ISOURCE = 4mA, VCC1 = +4.5V 3.7
Receiver-Output High Voltage
(RO1) VRO1H ISOURCE = 4mA, VCC1 = +3V 2.4 V
ISINK = 4mA, VCC1 = +4.5V 0.4
Receiver-Output Low Voltage
(RO1) VRO1L ISINK = 4mA, VCC1 = +3V 0.4 V
Receiver-Output (RO1) Leakage
Current IOZR
RE = high, VCC1 = +5.5V,
0 ≤ VRO1 ≤ VCC1 ±1 µA
RE Low Output Current for Fault
Detect IOL RE = +0.4V, fault not asserted 40 60 80 µA
MAX3535E/MXL1535E
2
Maxim Integrated
MAX3535E/MXL1535E
+3V to +5V, 2500VRMS Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
DC ELECTRICAL CHARACTERISTICS TABLE (MAX3535E) (continued)
(VCC1 = +3.0V to +5.5V, VCC2 = +3.13V to +7.5V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at VCC1 = +3.3V,
VCC2 = +5V, TA= +25°C.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
RE High Output Current for Fault
Detect IOH RE = VCC1 - 0.5V, fault asserted -140 -100 -60 µA
TRANSFORMER DRIVER (ST1, ST2)
DC-Converter Switching
Frequency (ST1, ST2) fSW ST1, ST2, not loaded 290 460 590 kHz
VCC1 = +4.5V, Figure 13 1.6 2.6
DC-Converter Total Impedance
ROH + ROL (ST1, ST2) ROHL VCC1 = +3V, Figure 13 1.8 2.9
Ω
ST1, ST2 Duty Cycle ST1, ST2, not loaded 44 50 56 %
ISOLATED-SIDE SUPPLY (VCC2, GND2)
Isolated-Side Supply Voltage VCC2 3.13 7.50 V
RL = 27Ω56 70
Isolated-Side Supply Current ICC2
fDATA = 0, SLO floating,
RO2 = no load,
A, B floating, Figure 1 RL = ∞10 16
mA
VCC2 Undervoltage-Lockout
Falling Trip VUVL2 2.68 2.85 3.02 V
VCC2 Undervoltage-Lockout
Rising Trip VUVH2 2.77 2.95 3.13 V
DRIVER OUTPUTS (Y, Z)
Driver-Output High Voltage VDOH No load, VDOH is measured with respect to
GND2 4V
RL = 50Ω (RS-422), VCC2 = +3.13V,
Figure 1 2.0 2.35
Differential Driver Output VOD RL = 27Ω (RS-485), VCC2 = +3.13V,
Figure 1 1.5 1.95
V
Driver Common-Mode Output
Voltage VOC RL = 27Ω or 50Ω, VOC is measured with
respect to GND2, Figure 1 1.0 3.0 V
Change in Magnitude of Driver
Differential Output Voltage for
Complementary Output States
ΔVOD RL = 27Ω or 50Ω, Figure 1 ±0.2 V
Change in Magnitude of Driver
Common-Mode Output Voltage
for Complementary Output States
ΔVOC RL = 27Ω or 50Ω, Figure 1 ±0.2 V
Driver enabled (DE =1 )
DI = high, VY > -7V
DI = low, VZ > -7V
-250
Driver Short-Circuit Output
Current IOSD
Driver enabled (DE =1 )
DI = high, VZ < +12V
DI = low, VY < +12V
+250
mA
MAX3535E/MXL1535E
Maxim Integrated
3
+3V to +5V, 2500VRMS Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
DC ELECTRICAL CHARACTERISTICS TABLE (MAX3535E) (continued)
(VCC1 = +3.0V to +5.5V, VCC2 = +3.13V to +7.5V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C,
VCC1 = +3.3V, VCC2 = +5V).
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
DI = high
-7V < VY < min[(VCC2 - 1V) +2V]
DI = low
-7V < VZ < min[(VCC2 - 1V) +2V]
-25
DI = high
+1V < VZ < +12V
Driver Short-Circuit Foldback
Output Current IOSFD
Driver
enabled
(DE =1)
DI = low
+1V < VY < +12V
+25
µA
SLEW-RATE SELECT (SLO)
Input High Voltage SLO VIHS VIHS is measured with respect to GND2 3.0 V
Input Low Voltage SLO VILS VILS is measured with respect to GND2 1.0 V
SLO Pullup Resistor RSLO VSLO = +3V 100 kΩ
RECEIVER INPUTS (A, B)
VA or VB = +12V +125
Receiver Input Current IAB VA or VB = -7V -100 µA
Receiver Differential Threshold
Voltage VTH -7V ≤ VCM ≤ +12V -200 -90 -10 mV
-7V ≤ VCM
≤ +12V, TA = 0°C to +70°C103070
Receiver-Input Hysteresis ΔVTH -7v ≤ VCM
≤ +12V, TA = -40°C to +85°C 5 30 70 mV
Receiver-Input Resistance RIN -7V ≤ VCM ≤ +12V (Note 1) 96 200 kΩ
Receiver-Input Open Circuit
Voltage VOAB 2.6 V
RECEIVER OUTPUT (RO2)
Receiver-Output (RO2) High
Voltage VRO2H ISOURCE = 4mA, VCC2 = +3.13V 2.4 V
Receiver-Output (RO2) Low
Voltage VRO2L ISINK = 4mA, VCC2 = +3.13V 0.4 V
ISOLATION
60s 2500
Isolation Voltage (Notes 2, 3) VISO 1s 3000 VRMS
Isolation Resistance RISO TA = +25°C, VISO = 50V (Note 3) 100 10,000 MΩ
Isolation Capacitance CISO TA = +25°C2pF
ESD Protection Human Body Model (A, B, Y, Z) ±15 kV
MAX3535E/MXL1535E
4
Maxim Integrated
MAX3535E/MXL1535E
+3V to +5V, 2500VRMS Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
SWITCHING ELECTRICAL CHARACTERISTICS (MAX3535E)
(VCC1 = +3.0V to +5.5V, VCC2 = +3.13V to +7.5V, RL= 27Ω, CL= 50pF, TA= -40°C to +85°C, unless otherwise noted. Typical values
are at VCC1 = +3.3V, VCC2 = +5V, TA= +25°C.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Data Sample Jitter tJFigure 6 220 285 ns
Maximum Data Rate fDATA tJ = 25% of data cell, receiver and driver,
SLO = high (Note 4) 877 1136 kbps
SLO = high, Figure 5 250 450
Self-Oscillating Frequency fSOS SLO = low, Figure 5 200 375 kHz
SLO = high, Figures 2, 6 490 855
Driver-Differential Output Delay
Time tDD SLO = low, Figures 2, 6 850 1560 ns
SLO = high, Figures 2, 6 30 100
Driver-Differential Output
Transition Time tTD SLO = low, Figures 2, 6 120 220 1000 ns
Driver-Output Enable Time tPZL, tPZH
SLO = high, DI = high or low,
Figures 3, 7 730 1400 ns
Driver-Output Disable Time tPHZ, tPLZ
SLO = high, DI = high or low,
Figures 3, 7 720 1300 ns
Receiver-Propagation Delay Time
to RO1
tPLH1,
tPHL1 Figures 4, 8 440 855 ns
Receiver-Propagation Delay Time
to RO2
tPLH2,
tPHL2 Figures 4, 8 40 ns
RO1, RO2 Rise or Fall Time tR, tFFigures 4, 8 40 ns
Receiver-Output Enable Time
RO1 tZL,tZH Figures 4, 9 30 ns
Receiver-Output Disable Time
RO1 tLZ,tHZ Figures 4, 9 30 ns
Initial Startup Time (from Internal
Communication Fault) (Note 5) 1200 ns
Internal Communication Timeout
Fault Time (Note 5) 1200 ns
MAX3535E/MXL1535E
Maxim Integrated
5
+3V to +5V, 2500VRMS Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
ELECTRICAL CHARACTERISTICS (MXL1535E)
(VCC1 = +4.5V to +5.5V, VCC2 = +4.5V to +7.5V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at VCC1 = +5V,
VCC2 = +5V, TA= +25°C.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Logic-Side Supply Voltage VCC1 4.5 5.5 V
Isolated-Side Supply Voltage VCC2 4.5 7.5 V
Logic-Side Supply Current ICC1
Transformer not driven, ST1 and ST2
unconnected, RE = low, DE = high,
fDATA = 0, RO1 = no load
5.9 13 mA
RL = 27Ω56 70
Isolated-Side Supply Current ICC2
fDATA = 0, SLO floating,
RO2 = no load, A, B
floating, Figure 1 RL = ∞10 16
mA
RL = 50Ω (RS-422), VCC2 = +4.5V, Figure 1 2.0 3.0
Differential Driver Output VOD RL = 27Ω (RS-485), VCC2 = +4.5V, Figure 1 1.5 2.5 V
Driver Output High Voltage VDOH No load, VDOH is measured with respect to
GND2 5.0 V
Driver Common-Mode Output
Voltage VOC RL = 27Ω or 50Ω, VOC is measured with
respect to GND2, Figure 1 1.0 3.0 V
Change in Magnitude of Driver
Differential Output Voltage for
Complementary Output States
ΔVOD RL = 27Ω or 50Ω, Figure 1 ±0.2 V
Change in Magnitude of Driver
Common-Mode Output Voltage
for Complementary Output States
ΔVOC RL = 27Ω or 50Ω, Figure 1 ±0.2 V
Driver enabled (DE =1)
DI = high, VY > -7V
DI = low, VZ > -7V
-250
Driver Short-Circuit Output
Current IOSD
Driver enabled (DE =1)
DI = high, VZ < +12V
DI = low, VY < + 12V
+250
mA
Driver enabled (DE =1)
DI = high
-7V < VY < min[(VCC2 - 1V) +2V]
DI = low
-7V < VZ < min[(VCC2 - 1V) +2V]
-25
Driver Short-Circuit Foldback
Output Current IOSFD
Driver enabled (DE =1)
DI = high
+1V < VZ < +12V
DI = low
+1V < VY < +12V
+25
mA
MAX3535E/MXL1535E
6
Maxim Integrated
MAX3535E/MXL1535E
+3V to +5V, 2500VRMS Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
ELECTRICAL CHARACTERISTICS (MXL1535E) (continued)
(VCC1 = +4.5V to +5.5V, VCC2 = +4.5V to +7.5V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at VCC1 = +5V,
VCC2 = +5V, TA= +25°C.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Input High Voltage, DE, DI, RE VIH VIH is measured with respect to GND1 2.0 1.45 V
Input High Voltage, SLO VIHS VIHS is measured with respect to GND2 4.0 2.1 V
Input Low Voltage, DE, DI, RE VIL VIL is measured with respect to GND1 1.45 0.8 V
Input Low Voltage, SLO VILS VILS is measured with respect to GND2 2.1 1.0 V
Logic-Side Input Current, DE, DI IINC ±2µA
VA or VB = +12V +0.25
Receiver Input Current IAB VA or VB = -7V -0.20 mA
Receiver Differential Threshold
Voltage VTH -7V ≤ VCM ≤ +12V -200 -90 -10 mV
-7V ≤ VCM ≤ +12V, TA = 0°C to +70°C 10 30 70
Receiver-Input Hysteresis ΔVTH
-7V ≤ VCM ≤ +12V, TA = -40°C to +85°C 5 30 70
mV
Receiver-Input Resistance RIN -7V ≤ VCM ≤ +12V (Note 1) 96 140 200 kΩ
Receiver-Input Open-Circuit
Voltage VOAB 2.6 V
Receiver-Output High Voltage
(RO1) VRO1H ISOURCE = 4mA, VCC1 = +4.5V 3.7 4.3 V
Receiver-Output Low Voltage
(RO1) VRO1L ISINK = 4mA, VCC1 = +4.5V 0.4 0.8 V
Driver-Output Leakage Current IOZ DE = low
-7V < VY < +12V, -7V < VZ < +12V ±30 µA
Driver-Output Leakage Current IOZ DE = low
-7V < VY < +12V, -7V < VZ < +12V ±30 ±100 µA
Receiver-Output (RO2) High
Voltage VRO2H ISOURCE = 4mA, VCC2 = +4.5V 2.8 3.4 V
Receiver-Output (RO2) Low
Voltage VRO2L ISINK = 4mA, VCC2 = +4.5V 0.4 0.8 V
DC-Converter Switching
Frequency (ST1, ST2) fSW ST1, ST2 not loaded 290 460 590 kHz
MAX3535E/MXL1535E
Maxim Integrated
7
+3V to +5V, 2500VRMS Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
ELECTRICAL CHARACTERISTICS (MXL1535E) (continued)
(VCC1 = +4.5V to +5.5V, VCC2 = +4.5V to +7.5V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at VCC1 = +5V,
VCC2 = +5V, TA= +25°C.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
DC-Converter Impedance High
ST1, ST2 ROH Figure 13 4 6 Ω
DC-Converter Impedance Low
ST1, ST2 ROL Figure 13 2.5 5 Ω
RE Low Output Current for Fault
Detect IOL
RE = sink current,
RE = +0.4V, fault not asserted -40 -50 -80 µA
RE High Output Current for Fault
Detect IOH
RE = source current,
RE = +VCC1 - 0.5V, fault asserted 60 100 140 µA
VCC2 Undervoltage-Lockout
Falling Trip VUVL2 2.68 2.85 3.02 V
VCC2 Undervoltage-Lockout
Rising Trip VUVH2 2.77 2.95 3.13 V
VCC1 Undervoltage-Lockout
Falling Trip VUVL1 2.53 2.69 2.85 V
VCC1 Undervoltage-Lockout
Rising Trip VUVH1 2.63 2.80 2.97 V
60s 2500
Isolation Voltage (Note 2) VISO 1s 3000 VRMS
SLO Pullup Resistor RSLO VSLO = +3V 100 kΩ
MAX3535E/MXL1535E
8
Maxim Integrated
MAX3535E/MXL1535E
+3V to +5V, 2500VRMS Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
SWITCHING ELECTRICAL CHARACTERISTICS (MXL1535E)
(VCC1 = +4.5V to +5.5V, VCC2 = +4.5V to +7.5V, RL= 27Ω, CL= 50pF, TA= -40°C to +85°C, unless otherwise noted. Typical values
are at VCC1 = +5V, VCC2 = +5V, TA= +25°C.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Data Sample Jitter tJFigure 6 220 285 ns
Max Baud Rate fMAX SLO = high, Figure 5, (Note 6) 250 450 kBd
SLO = high, Figures 2, 6 430 855
Driver-Differential Output Delay
Time tDD SLO = low, Figures 2, 6 850 1560 ns
SLO = high, VCC2 = +4.5V 45 100
Driver-Differential Output
Transition Time tTD SLO = low, VCC2 = +4.5V 150 260 1000 ns
Driver-Output Enable Time tPZL, tPZH
SLO = high, DI = high or low,
Figure 3, 7 730 1400 ns
Driver-Output Disable Time tPHZ, tPLZ
SLO = high, DI = high or low,
Figures 3, 7 720 1300 ns
Receiver-Propagation Delay Time
to RO1
tPLH1,
tPHL1 Figures 4, 8 440 855 ns
Receiver-Propagation Delay Time
to RO2
tPLH2,
tPHL2 Figures 4, 8 40 ns
RO1, RO2 Rise or Fall Time tR, tFFigures 4, 8 40 ns
Receiver-Output Enable Time
RO1 tZL, tZH Figures 4, 9 30 ns
Receiver-Output Disable Time
RO1 tLZ, tHZ Figures 4, 9 30 ns
Initial Startup Time (from Internal
Communication Fault) (Note 5) 1200 ns
Internal Communication Timeout
Fault Time (Note 5) 1200 ns
0°C to +70°C 56
ST1, ST2 Duty Cycle -40°C to +85°C 57 %
ESD Protection Human Body Model (A, B, Y, Z) ±15 kV
Note 1: Receiver inputs are 96kΩminimum resistance, which is 1/8 unit load.
Note 2: 60s test result is guaranteed by correlation from 1s result.
Note 3: VISO is the voltage difference between GND1 and GND2.
Note 4: The maximum data rate is specified using the maximum jitter value according to the formula: data rate = 1 / (4tJ). See the
Skew
section for more information.
Note 5: Initial startup time is the time for communication to recover after a fault condition. Internal communication timeout fault time
is the time before a fault is indicated on RE, after internal communication has stopped.
Note 6: Bd = 2 bits.
MAX3535E/MXL1535E
Maxim Integrated
9
+3V to +5V, 2500VRMS Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
Typical Operating Characteristics
(VCC1 = +5V, CL= 50pF (Figure 1), unless otherwise noted.)
ICC1 SUPPLY CURRENT
vs. TEMPERATURE
MAX3535E toc01
TEMPERATURE (°C)
ICC1 (mA)
603510-15
20
40
60
80
100
0
-40 85
FIGURE 1
RL = 27Ω
RL = 60Ω
RL = OPEN
HALO
TGM-250NS
1:1:1 TRANSFORMER
ICC1 SUPPLY CURRENT
vs. TEMPERATURE
MAX3535E toc02
TEMPERATURE (°C)
ICC1 (mA)
603510-15
20
40
60
80
100
0
-40 85
FIGURE 1
VCC1 = +3.3V
RL = 60Ω
RL = OPEN
HALO
TGM-240NS
1:1.3:1.3 TRANSFORMER
RL = 27Ω
ICC2 SUPPLY CURRENT
vs. TEMPERATURE
MAX3535E toc03
TEMPERATURE (°C)
ICC2 (mA)
603510-15
40
50
60
70
80
30
-40 85
FIGURE 1
VCC2 = +6V
fDATA = 700kbps
SLO = LOW
RL = 27Ω
VCC2 = +3.9V
(MAX3535E)
VCC2 = +3.13V
(MAX3535E)
VCC2 SUPPLY VOLTAGE
vs. TEMPERATURE
MAX3535E toc04
TEMPERATURE (°C)
VCC2 (V)
6035-15 10
3.5
4.0
4.5
5.0
6.0
5.5
6.5
7.0
3.0
-40 85
HALO
TGM-240NS
1:1.3:1.3 TRANSFORMER
FIGURE 1
RL = OPEN, VCC1 = +5V
RL = 27Ω, VCC1 = +5V
RL = 27Ω, VCC1 = +3V
(MAX3535E)
SELF-OSCILLATION FREQUENCY
vs. TEMPERATURE
MAX3535E toc05
TEMPERATURE (°C)
fSOS (kHz)
603510-15
300
350
400
450
500
250
-40 85
FIGURE 5
SLO = HIGH VCC1 = VCC2
RL = 27Ω
SLO = LOW
DRIVER DIFFERENTIAL OUTPUT
TRANSITION TIME vs. TEMPERATURE
MAX3535E toc06
TEMPERATURE (°C)
tTD (ns)
603510-15
10
20
30
40
50
60
70
80
90
100
0
-40 85
RL = 27Ω
SLO = VCC2
FIGURES 2, 6
VCC2 = +5V
VCC2 = +3.13V (MAX3535E)
DRIVER DIFFERENTIAL OUTPUT
TRANSITION TIME vs. TEMPERATURE
MAX3535E toc07
TEMPERATURE (°C)
tTD (ns)
603510-15
300
400
500
600
700
800
200
-40 85
RL = 27Ω
SLO = GND2
FIGURES 2, 6
VCC2 = +5V
VCC2 = +3.13V (MAX3535E)
SWITCHER FREQUENCY
vs. TEMPERATURE
MAX3535E toc08
TEMPERATURE (°C)
fSW (kHz)
603510-15
350
400
450
500
550
600
300
-40 85
SWITCHER FREQUENCY
vs. SUPPLY VOLTAGE
MAX3535E toc09
VCC1 (V)
fSW (kHz)
5.04.54.03.5
350
400
450
500
550
600
300
3.0 5.5
MAX3535E/MXL1535E
10
Maxim Integrated
MAX3535E/MXL1535E
+3V to +5V, 2500VRMS Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
RECEIVER-OUTPUT (RO1) LOW VOLTAGE
vs. TEMPERATURE
MAX3535E toc10
TEMPERATURE (°C)
VRO1L (V)
603510-15
0.2
0.4
0.6
0.8
1.0
0
-40 85
ISINK = 4mA
VCC1 = +4.5V
VCC1 = +3V
(MAX3535E)
VCC1 = +5V
RECEIVER-OUTPUT (RO1) HIGH VOLTAGE
vs. TEMPERATURE
MAX3535E toc11
TEMPERATURE (°C)
VRO1H (V)
603510-15
2.5
3.0
3.5
4.0
4.5
5.0
2.0
-40 85
ISOURCE = 4mA
VCC1 = +3V
(MAX3535E)
VCC1 = +4.5V
VCC1 = +5V
DRIVER DIFFERENTIAL OUTPUT VOLTAGE
vs. DIFFERENTIAL OUTPUT CURRENT
MAX3535E toc12
DRIVER DIFFERENTIAL OUTPUT CURRENT (mA)
VOD (V)
1008020 40 60
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0
0 120
DE = HIGH
VCC2 = +3.9V
(MAX3535E)
VCC2 = +3.13V
(MAX3535E)
VCC2 = +7.5V
DRIVER-OUTPUT HIGH VOLTAGE
vs. DRIVER SOURCE CURRENT
MAX3535E toc13
DRIVER SOURCE CURRENT (mA)
VDOH (V)
10080604020
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
-7
0 120
DE = HIGH
VCC2 = +3.13V
(MAX3535E)
VCC2 = +3.9V
(MAX3535E)
VCC2 = +7.5V
DRIVER-OUTPUT LOW VOLTAGE
vs. DRIVER SINK CURRENT
MAX3535E toc14
DRIVER SINK CURRENT (mA)
VDOL (V)
10080604020
1
2
3
4
5
6
7
8
9
10
11
12
0
0 120
DE = HIGH
VCC2 = +3.13V
(MAX3535E)
VCC2 = +3.9V
(MAX3535E)
VCC2 = +7.5V
DRIVER DIFFERENTIAL OUTPUT VOLTAGE
vs. VCC2 SUPPLY VOLTAGE
MAX3535E toc15
VCC2 (V)
VOD (V)
7.06.56.05.55.04.54.03.5
1.8
2.0
2.2
2.4
2.6
2.8
1.6
3.0 7.5
RL = 27Ω
FIGURE 1
RECEIVER OUTPUT (RO1) VOLTAGE
vs. LOAD CURRENT
MAX3535E toc16
LOAD CURRENT (mA)
OUTPUT VOLTAGE (V)
105
1
2
3
4
5
0
015
OUTPUT HIGH, SOURCING
OUTPUT LOW, SINKING
DRIVER DIFFERENTIAL OUTPUT VOLTAGE
vs. TEMPERATURE
MAX3535E toc17
TEMPERATURE (°C)
VOD (V)
603510-15
1
2
3
4
5
0
-40 85
FIGURE 1
VCC2 = +6V
RL = 27Ω
SLO = GND2
VCC2 = +3.13V
(MAX3535E)
VCC2 = +7.5V
ICC1 SUPPLY CURRENT
vs. VCC1 SUPPLY VOLTAGE
MAX3535E toc18
VCC1 SUPPLY VOLTAGE (V)
ICC1 (mA)
5.04.54.03.5
1
2
3
4
5
6
7
8
9
10
0
3.0 5.5
RL = OPEN
TRANSFORMER IS NOT DRIVEN
Typical Operating Characteristics (continued)
(VCC1 = +5V, CL= 50pF (Figure 1), unless otherwise noted.)
MAX3535E/MXL1535E
Maxim Integrated
11
+3V to +5V, 2500VRMS Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
Typical Operating Characteristics (continued)
(VCC1 = +5V, CL= 50pF (Figure 1), unless otherwise noted.)
RECEIVER (RO1) PROPAGATION DELAY
(tPLH1)
MAX3535E toc19
RO
1V/div
A-B
1V/div
100ns/div
DRIVER PROPAGATION DELAY
(SLO = LOW)
MAX3535E toc20
Y
2V/div
DI
2V/div
400ns/div
Z
2V/div
DRIVER PROPAGATION DELAY
(SLO = HIGH)
MAX3535E toc21
Y
2V/div
DI
2V/div
400ns/div
Z
2V/div
JITTER vs. TEMPERATURE
MAX3535E toc22
TEMPERATURE (°C)
tJ (ns)
603510-15
220
240
260
280
300
200
-40 85
VCC1 = 5.5V
VCC1 = 3.13V
DRIVER ENABLE
TIME PLUS JITTER
MAX3535E toc23
Y
2V/div
DE
2V/div
200ns/div
DRIVER DISABLE
TIME PLUS JITTER
MAX3535E toc24
Y
2V/div
DE
2V/div
200ns/div
RECEIVER (RO1) PROPAGATION DELAY
(tPHL1)
MAX3535E toc25
RO
1V/div
A-B
1V/div
100ns/div
MAX3535E/MXL1535E
12
Maxim Integrated
MAX3535E/MXL1535E
+3V to +5V, 2500VRMS Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
Pin Description
PIN NAME ISOLATION SIDE FUNCTION
1V
CC1 Logic Logic-Side/Transformer-Driver Power Input. Bypass VCC1 to GND1 with 10µF and 0.1µF
capacitors.
2 ST1 Logic Transformer-Driver Phase 1 Power Output. Connect ST1 to isolation-transformer
primary to send power to isolation side of barrier.
3 ST2 Logic Transformer-Driver Phase 2 Power Output. Connect ST2 to isolation-transformer
primary to send power to isolation side of barrier.
4 GND1 Logic Logic-Side Ground. For isolated operation do not connect to GND2.
5–10,
19–24 — — Removed from Package
11 GND2 Isolated Isolation-Side Ground. For isolated operation do not connect to GND1.
12 Z Isolated RS-485/RS-422 Inverting Driver Output. Output floats when DE is low or in a barrier fault
event. (See the Detailed Description section for more information.)
13 Y Isolated RS-485/RS-422 Noninverting Driver Output. Output floats when DE is low or in a barrier
fault event. (See the Detailed Description section for more information.)
14 VCC2 Isolated Isolated-Side Power Input. Connect VCC2 to the rectified output of transformer
secondary. Bypass VCC2 to GND2 with 10µF and 0.1µF capacitors.
15 B Isolated RS-485/RS-422 Differential-Receiver Inverting Input
16 A Isolated RS-485/RS-422 Differential-Receiver Noninverting Input
17 RO2 Isolated
Isol ated - S i d e Recei ver O utp ut. RO2 i s al w ays enab l ed . RO 2 g oes hi g h i f A - B > - 10m V .
RO2 g oes l ow i f A - B < - 200m V . Fai l - safe ci r cui tr y causes RO 2 to g o hi g h w hen A and B
fl oat or ar e shor ted .
18 SLO Isolated Driver Slew-Rate Control Logic Input. Connect SLO to GND2 for data rates up to
400kbps. Connect SLO to VCC2 or leave floating for high data rates.
25 DI Logic Driver Input. Pull DI low (high) to force driver output Y low (high) and driver output Z
high (low).
26 DE Logic
Driver-Enable Input. The driver outputs are enabled and follow the driver input (DI)
when DE is high. When DE is floated, the driver is disabled. DE does not affect whether
the receiver is on or off.
27 RE Logic
Receiver-Output Enable and Fault Current Output. The receiver output (RO1) is
enabled and follows the differential-receiver inputs, A and B, when RE is low, otherwise
RO1 floats. RE does not affect RO2 and does not disable the driver. The asserted fault
output is a pullup current, otherwise RE shows a pulldown current.
28 RO1 Logic
Receiver Output. RO1 is enabled when RE is low. RO1 goes high if A - B > -10mV. RO1
goes low if A - B < -200mV. Fail-safe circuitry causes RO1 to go high when A and B
float or are shorted.
MAX3535E/MXL1535E
Maxim Integrated
13
+3V to +5V, 2500VRMS Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
Test Circuits
RL
RL
VOD VOC
Y
Z
Figure 1. Driver DC Test Load
DI
DE
HIGH
CL
CL
Y
Z
GND
GND2
RL
RL
Figure 2. Driver Timing Test Circuit
TGM-240 1/2
BAT54C
TRANSFORMER
DRIVER
BARRIER
TRANSCEIVER
ISOLATION BARRIER
BARRIER
TRANSCEIVER
1/2
BAT54C
VOLTAGE
REGULATOR
GND2
+3.0V TO +5.5V
DRIVER
RECEIVER
A
B
Y
Z
CL
SLO
RO2
ST1
RO1
RE
DE
DI
GND1
ST2 VCC2
VCC1
VCC2
0.1μF
0.1μF
CONTROL GROUND
RS-485 GROUND
10μF
10μF
MAX3535E
CL
2RL
Figure 5. Self-Oscillating Configuration
500Ω
VCC2
CL
Y/Z
GND2
500Ω
Figure 3. Driver Timing Test Load
1kΩ
VCC1/VCC2
CL
RO1/RO2
GND1/GND2
1kΩ
Figure 4. Receiver Timing Test Load
MAX3535E/MXL1535E
14
Maxim Integrated
MAX3535E/MXL1535E
+3V to +5V, 2500VRMS Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
Switching Waveforms
DI
Z
Y
V
DOH
V
DOH
t
DD
t
DD
t
TD
t
TD
t
J
V
OD
= V
Y
- V
Z
t
R
< 10ns, t
F
< 10ns
1/2 V
DOH
0V
-V
DOH
20%
80%
1.5V 1.5V
80%
20%
Figure 6. Driver Propagation Delay
t
PLZ
V
DOL
+ 0.5V
V
DOH
- 0.5V
V
DOH
/2
V
DOH
/2
t
R
< 10ns, t
F
< 10ns
1.5V
1.5V
DE
V
DOH
Y, Z
V
DOL
V
DOH
0V
Y, Z
t
PZL
2 x t
J
t
PZH
t
J
t
PHZ
OUTPUT NORMALLY HIGH
OUTPUT NORMALLY LOW
Figure 7. Driver Enable and Disable Times
t
R
< 10ns, t
F
< 10ns
t
PLH1
V
RO1H
/2
80%
80%
20%
20%
V
RO1H
/2
OUTPUT
INPUT
0V 0V
V
A
- V
B
V
RO1H
V
RO1L
RO1
RO2
t
PLH1
t
PHL1
t
PLH2
t
PLH2
t
J
t
R
t
F
t
J
Figure 8. Receiver Propagation Delays
t
R
< 10ns, t
F
< 10ns
1.5V
1.5V
RE
V
RO1H
RO1
V
RO1L
V
RO1L
+ 0.5V
V
RO1H
- 0.5V
V
RO1H
RO1
0V
OUTPUT NORMALLY LOW
OUTPUT NORMALLY HIGH
t
HZ
t
LZ
t
ZL
t
ZH
Figure 9. Receiver Enable and Disable Times
MAX3535E/MXL1535E
Maxim Integrated
15
+3V to +5V, 2500VRMS Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
Detailed Description
The MAX3535E/MXL1535E isolated RS-485/RS-422 full-
duplex transceivers provide 2500VRMS of galvanic isola-
tion between the RS-485/RS-422 isolation side and the
processor or logic side. These devices allow fast,
1000kbps communication across an isolation barrier even
when the common-mode voltages (i.e., the ground poten-
tials) on either side of the barrier are subject to large dif-
ferences. The isolation barrier consists of two parts. The
first part is a capacitive isolation barrier (integrated high-
voltage capacitors) that allows data transmission
between the logic side and the RS-485/RS-422 isolation
side. Data is sampled and encoded before it is transmit-
ted across the isolation barrier introducing sampling jitter
and further delay into the communication system.
The second part of the isolation barrier consists of an
external transformer with the required primary-to-sec-
ondary isolation, allowing the transmission of operating
power from the logic side across the isolation barrier to
the isolation side. Connect the primary of the external
transformer to the MAX3535E/MXL1535E’s 420kHz
transformer driver outputs ST1 and ST2. Since the
MXL1535E and the MAX3535E operate with different
supply-voltage requirements at their respective isolated
and logic sides, different isolation transformers must be
used with each device (see the
Transformer Selection
section). The only external components needed to
complete the system are the isolation transformer, two
diodes, and two low-voltage, 10µF decoupling capaci-
tors (see the
Typical Application Circuit
).
The MAX3535E/MXL1535E include one differential dri-
ver, one receiver, and internal circuitry to send the RS-
485 signals and logic signals across the isolation barrier
(including the isolation capacitors). The MAX3535E/
MXL1535E receivers are 1/8 unit load, allowing up to 256
devices on a single bus.
The MAX3535E/MXL1535E feature fail-safe circuitry
ensuring the receiver output maintains a logic-high
state when the receiver inputs are open or shorted, or
when connected to a terminated transmission line with
all drivers disabled (see the
Fail Safe
section).
The MAX3535E/MXL1535E feature driver slew-rate
select that minimizes electromagnetic interference
(EMI) and reduces reflections caused by improperly
terminated cables at data rates below 400kbps. The
driver outputs are short-circuit protected for sourcing or
sinking current and have overvoltage protection. Other
features include hot-swap capability, which holds the
driver off if the driver logic signals are floated after
power is applied. The MAX3535E/MXL1535E have
error-detection circuitry that alerts the processor when
there is a fault and disables the driver until the fault is
removed.
Fail Safe
The MAX3535E/MXL1535E guarantee a logic-high
receiver output when the receiver inputs are shorted or
open, or when connected to a terminated transmission
line with all drivers disabled. The receiver threshold is
fixed between -10mV and -200mV. If the differential
receiver input voltage (A - B) is greater than or equal to
-10mV, RO1 is logic-high (Table 2). In the case of a ter-
minated bus with all transmitters disabled, the receiv-
er’s differential input voltage is pulled to zero by the
termination. Due to the receiver thresholds of the
MAX3535E/MXL1535E, this results in a logic-high at
RO1 with a 10mV minimum noise margin.
Driver Output Protection
Two mechanisms prevent excessive output current and
power dissipation caused by faults or by bus con-
tention. The first, a foldback current limit on the output
stage, provides immediate protection against short cir-
cuits over the entire common-mode voltage range. The
second, a thermal-shutdown circuit, forces the driver
outputs into a high-impedance state if the die tempera-
ture exceeds +150°C.
Monitoring Faults on
RE
RE functions as both an input and an output. As an
input, RE controls the receiver output enable (RO1). As
an output, RE is used to indicate when there are faults
associated with the operation of the part. This dual
functionality is made possible by using an output driver
stage that can easily be overdriven by most logic
gates. When an external gate is not actively driving RE,
it is driven either high using a 100µA internal pullup
current (fault present), or low using a 60µA internal pull-
down current (no fault). When using RE to control the
receiver-enable output function, be sure to drive it
using a gate that has enough sink and source capabili-
ty to overcome the internal drive.
MAX3535E/MXL1535E
16
Maxim Integrated
MAX3535E/MXL1535E
+3V to +5V, 2500VRMS Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
When not actively driving RE, it functions as the fault
indicator (Table 3). A low on RE indicates the part is
functioning properly, while a high indicates a fault is
present. The four causes of a fault indication are:
1) The voltage on VCC1 is below its undervoltage-lock-
out threshold (2.69V nominal)
2) The voltage on VCC2 is below its undervoltage-lock-
out threshold (2.80V nominal)
3) There is a problem that prevents the MAX3535E/
MXL1535E from communicating across its isolation
barrier
4) The die temperature exceeds +150°C nominally,
causing the part to go into thermal shutdown
When a fault occurs, RO1 is switched to a logic-high
state if RE is low (Table 3). Open-circuit or short-circuit
conditions on the receiver inputs do not generate fault
conditions; however, any such condition also puts RO1
in a logic-high state (see the
Fail Safe
section).
Read RE for fault conditions by using a bidirectional
microcontroller I/O line or a tri-stated buffer as shown in
Figure 10. When using a tri-stated buffer, enable the
driver whenever the voltage on RE needs to be forced
to a logic-high or logic-low. To read RE for a fault con-
dition, disable the driver.
Slew-Rate Control Logic
The SLO input selects between a fast and a slow slew
rate for the driver outputs. Connecting SLO to GND2
selects the slow slew-rate option that minimizes EMI
and reduces reflections caused by improperly terminat-
ed cables at data rates up to 400kbps. This occurs
because lowering the slew rate decreases the rise and
fall times for the signal at the driver outputs, drastically
reducing the high-frequency components and harmon-
ics at the output. Floating SLO or connecting it to VCC2
selects the fast slew rate, which allows high-speed
operation.
RO1
RE
DE
DI
GND1
RE
OE
FAULT
VCC1
VCC1
TRI-STATED BUFFER/
BIDIRECTIONAL MICROCONTROLLER I/O
FAULT
DRIVER OUTPUT BECOMES HIGH IMPEDANCE
FAULT DETECTED
OE
R
MAX3535E
MXL1535E
D
Figure 10. Reading a Fault Condition
MAX3535E/MXL1535E
Maxim Integrated
17
+3V to +5V, 2500VRMS Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
Functional Tables
Table 1. Transmitting Logic
TRANSMITTING LOGIC
INPUTS OUTPUTS
DE DI Y Z
1110
1001
0 X High impedance High impedance
Table 2. Receiving Logic
RECEIVING LOGIC
INPUTS OUTPUTS
RE VA - VBRO1 RO2
0 >-10mV 1 1
0 <-200mV 0 0
0 Inputs open/shorted 1 1
1 >-10mV High impedance 1
1 <-200mV High impedance 0
1 Inputs open/shorted High impedance 1
Table 3. Fault Mode
NORMAL
MODE FAULT MODES
FUNCTION
VCC1 > VUVH1
VCC2 > VUVH2
VCC1 < VUVL1
VCC2 > VUVH2
VCC1 > VUVH1
VCC2 < VUVL2
VCC1 < VUVL1
VCC2 < VUVL2
THERMAL
SHUTDOWN
INTERNAL
COMMUNICATION
FAULT
Transformer
driver
(ST1, ST2)
On On On On Off On
RE = 0 Active High High High High High
RE = VCC1 High
impedance
High
impedance
High
impedance
High
impedance
High
impedance High impedance
RO1
RE = floating Active High
impedance
High
impedance
High
impedance
High
impedance High impedance
RO2 Active Active Active Active Active Active
Driver outputs (Y, Z) Active High
impedance
High
impedance
High
impedance
High
impedance High impedance
Internal barrier
communication Active Disabled Disabled Disabled Disabled Communication
attempted
Fault indicator on RE
Low
(60µA pull-
down)
High
(100µA pullup)
High
(100µA pullup)
High
(100µA pullup)
High
(100µA pullup)
High
(100µA pullup)
MAX3535E/MXL1535E
18
Maxim Integrated
MAX3535E/MXL1535E
+3V to +5V, 2500VRMS Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
Applications Information
Typical Applications
The MAX3535E/MXL1535E transceivers facilitate bi-
directional data communications on multipoint bus
transmission lines. Figure 11 shows a typical RS-485
multidrop-network applications circuit. Figure 12 shows
the MAX3535E/MXL1535E functioning as line repeaters
with cable lengths longer than 4000ft. To minimize
reflections, terminate the line at both ends in its charac-
teristic impedance. Keep stub lengths off the main line
as short as possible.
DI
DE
RO
TGM-240
1/2
BAT54C
TRANSFORMER
DRIVER
BARRIER
TRANSCEIVER
ISOLATION BARRIER
BARRIER
TRANSCEIVER
1/2
BAT54C
VOLTAGE
REGULATOR
BA
R
D
RE
RO
DE
DI
R
120ΩD
A
B
RERE
DI
DE
RO
BA
R
D
GND2
+3.3V
DRIVER
RECEIVER
A
B
Y
Z
SLO
RO2
ST1
RO1
RE
DE
DI
GND1
ST2 VCC2
VCC1
VCC2
120Ω
0.1μF
0.1μF
CONTROL GROUND
RS-485 GROUND
10μF
10μF
MAX3535E
R
D
Figure 11. Typical Half-Duplex Multidrop RS-485 Network
MAX3535E/MXL1535E
Maxim Integrated
19
Transformer Selection
The MXL1535E is a pin-for-pin compatible upgrade of
the LTC1535, making any transformer designed for that
device suitable for the MXL1535E (see Table 4). These
transformers all have a turns ratio of about 1:1.3CT.
The MAX3535E can operate with any of the transformers
listed in Table 4, in addition to smaller, thinner transform-
ers designed for the MAX845 and MAX253. The 420kHz
transformer driver operates with single primary and cen-
ter-tapped secondary transformers. When selecting a
transformer, do not exceed its ET product, the product of
the maximum primary voltage and half the highest period
of oscillation (lowest oscillating frequency). This ensures
that the transformer does not enter saturation. Calculate
the minimum ET product for the transformer primary as:
ET = VMAX / (2 x fMIN)
where, VMAX is the worst-case maximum supply voltage,
and fMIN is the minimum frequency at that supply voltage.
Using +5.5V and 290kHz gives a required minimum ET
+3V to +5V, 2500VRMS Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
TGM-250
1/2
BAT54C
TRANSFORMER
DRIVER
BARRIER
TRANSCEIVER
ISOLATION BARRIER
BARRIER
TRANSCEIVER
1/2
BAT54C
VOLTAGE
REGULATOR
GND2 +5V
DRIVER
RECEIVER
A
B
Y
Z
Y
Z
SLO
RO2
ST1
RO1
RO
RE
DE
DI
DI
GND1
ST2
VCC2
VCC1
VCC2
0.1μF
0.1μF
CONTROL GROUND
RS-422 GROUND
10μF
10μF
MAX3535E
MXL1535E
MAX488
R
D
A
B
120Ω
120Ω
RD
DR
Figure 12. Using the MAX3535E/MXL1535E as an RS-422 Line Repeater
VCC1
ROH ROH
ROL ROL
TRANSFORMER DRIVER OUTPUT STAGE
TRANSFORMER
PRIMARY
GND1
ST1 ST2
Figure 13. Transformer Driver Output Stage
MAX3535E/MXL1535E
20
Maxim Integrated
MAX3535E/MXL1535E
+3V to +5V, 2500VRMS Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
product of 9.5V-µs. The commercially available trans-
formers for the MAX845 listed in Table 5 meet that
requirement. In most cases, use half of the center-tapped
primary winding with the MAX3535E and leave the other
end of the primary floating. Most of the transformers in
Table 5 are 1:1:1 or 1:1:1:1 turns ratio.
For +3.3V operation (+3.6V maximum) the required pri-
mary ET product is 6.2V-µs. All of the previously men-
tioned transformers meet this requirement. Table 6 lists
some other transformers with step-up turns ratios
specifically tailored for +3.3V operation. Most of the
transformers in Table 6 are 1:1:1.3:1.3.
By using a HALO TGM-010 or Midcom 95061 trans-
former, it becomes possible to build a complete isolated
RS-485/RS-422 transceiver with a maximum thickness
less than 0.1in. To minimize power consumption, select
the turns ratio of the transformer to produce the minimum
DC voltage required at VCC2 (+3.13V) under worst-case,
high-temperature, low-VCC1, and full-load conditions. For
light loads on the isolated side, ensure that the voltage at
VCC2 does not exceed +7.5V. For example, the CTX01-
14659 transformer results in 85mA (typ) VCC1 supply cur-
rent with full load on the RS-485 driver. Using a TGM250
1:1:1 transformer lowers the VCC1 supply current to 65mA
(typ), while maintaining good margin on the VCC2 supply.
A slight step-down transformer can result in extra power
savings in some situations. A custom wound sample
transformer with 23 primary turns and 20:20 secondary
turns on a Ferronics 11-050B core operates well with a
VCC1 supply current of 51mA (typ).
Table 4. Transformers for the MXL1535E/MAX3535E
MANUFACTURER PART NUMBER ISOLATION VOLTAGE (1s) PHONE NUMBER
Cooper Electronic Technologies, Inc. CTX01-14659 500V 561-241-7876
Cooper Electronic Technologies, Inc. CTX01-14608 3750VRMS 561-241-7876
EPCOS AG (Germany)
(USA) B78304-A1477-A3 500V 0 89-626-2-80-00
800-888-7724
Midcom, Inc. 31160R 1250V 605-886-4385
Pulse FEE (France) P1597 500V 33-3-85-35-04-04
Sumida Corporation (Japan) S-167-5779 100V 03-3667-3320
Transpower Technologies, Inc. TTI7780-SM 500V 775-852-0145
Table 5. Transformers for MAX3535E at +5V
MANUFACTURER PART
NUMBER
ISOLATION
VOLTAGE (1s)
PHONE
NUMBER WEBSITE
TGM-010 500VRMS
TGM-250 2000VRMS
TGM-350 3000VRMS
HALO Electronics, Inc.
TGM-450 4500VRMS
650-903-3800 www.haloelectronics.com/6pin.html
BH Electronics, Inc. 500-1749 3750VRMS 952-894-9590 www.bhelectronics.com/PDFs/DC-
DCConverterTransformers.pdf
Coilcraft, Inc. U6982-C 1500VRMS 800-322-2645
44-1236-730595 www.coilcraft.com/minitrans.cfm
7825355 1500V
Newport/C&D Technologies 7625335 4000V 520-295-4300 www.dc-dc.com/products/productline.asp?ED=9
Midcom, Inc. 95061 1250V 605-886-4385 www.midcom-inc.com
PCA Electronics, Inc. EPC3115S-5 700V DC 818-894-5791 www.pca.com/Datasheets/EPC3117S-X.pdf
Rhom b us Ind ustr i es, Inc. T-1110 1800VRMS 714-898-0960 www.rhombus-ind.com/pt-cat/maxim.pdf
Premier Magnetics, Inc. PM-SM15 1500VRMS 949-452-0511 www.premiermag.com/pdf/pmsm15.pdf
MAX3535E/MXL1535E
Maxim Integrated
21
±15kV ESD Protection
As with all Maxim devices, ESD-protection structures
are incorporated on all pins to protect against electro-
static discharges encountered during handling and
assembly. The driver outputs and receiver inputs have
extra protection against static electricity. Maxim’s engi-
neers have developed state-of-the-art structures to pro-
tect these pins against ESD of ±15kV without damage.
The ESD structures withstand high ESD in all states.
After an ESD event, the MAX3535E/MXL1535E keep
working without latchup. ESD protection can be tested
in various ways. The transmitter outputs and receiver
inputs of this product family are characterized for pro-
tection to ±15kV using the Human Body Model.
ESD Test Conditions
The ±15kV ESD test specifications apply only to the A,
B, Y, and Z I/O pins. The test surge is referenced to
GND2. All remaining pins are ±2kV ESD protected.
Human Body Model
Figure 14 shows the Human Body Model, and Figure
15 shows the current waveform it generates when dis-
charged into low impedance. This model consists of a
100pF capacitor charged to the ESD voltage of interest,
which is then discharged into the test device through a
1.5kΩresistor.
+3V to +5V, 2500VRMS Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
Table 6. Transformers for MAX3535E at +3.3V
MANUFACTURER PART
NUMBER
ISOLATION
VOLTAGE (1s)
PHONE
NUMBER WEBSITE
TGM-040 500VRMS
TGM-240 2000VRMS
TGM-340 3000VRMS
HALO Electronics, Inc.
TGM-340 4500VRMS
650-903-3800 www.haloelectronics.com/6pin.html
BH Electronics, Inc. 500-2582 2000VRMS 952-894-9590 www.bhelectronics.com/PDFs/DC-
DCConverterTransformers.pdf
Coilcraft, Inc. Q4470-C 1500VRMS 800-322-2645
44-1236-730595 www.coilcraft.com/minitrans.cfm
78253335 1500V
Newport/C&D Technologies 76253335 4000V 520-295-4300 www.dc-dc.com/products/productline.asp?ED=9
95062 1250V
Midcom, Inc. 95063 1250V 605-886-4385 www.midcom-inc.com
PCA Electronics, Inc. EPC3115S-2 700V DC 818-894-5791 www.pca.com/Datasheets/EPC3117S-X.pdf
Rhom b us Ind ustr i es, Inc. T-1107 1800VRMS 714-898-0960 www.rhombus-ind.com/pt-cat/maxim.pdf
Premier Magnetics Inc. PM-SM16 1500VRMS 949-452-0511 www.premiermag.com/pdf/pmsm15.pdf
CHARGE-CURRENT-
LIMIT RESISTOR
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
Cs
100pF
RC 1MΩRD 1500Ω
HIGH-
VOLTAGE
DC
SOURCE
DEVICE
UNDER
TEST
Figure 14. Human Body ESD Test Model
MAX3535E/MXL1535E
22
Maxim Integrated
MAX3535E/MXL1535E
+3V to +5V, 2500VRMS Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
Machine Model
The Machine Model for ESD tests all pins using a
200pF storage capacitor and zero discharge resis-
tance. Its objective is to simulate the stress caused by
contact that occurs with handling and assembly during
manufacturing. All pins require this protection during
manufacturing, not just inputs and outputs. Therefore,
after PC board assembly, the Machine Model is less
relevant to I/O ports.
Skew
The self-oscillation circuit shown in Figure 5 is an excel-
lent way to get an approximate measure of the speed
of the MAX3535E/MXL1535E. An oscillation frequency
of 250kHz in this configuration implies a data rate of at
least 500kbps for the receiver and transmitter com-
bined. In practice, data can usually be sent and
received at a considerably higher data rate, normally
limited by the allowable jitter and data skew. If the sys-
tem can tolerate a 25% data skew, (the difference
between tPLH1 and tPHL1), the 285ns maximum jitter
specification implies a data rate of 877kbps. Lower
data rates result in less distortion and jitter (Figure 16).
Higher rates are possible but with more distortion and
jitter. The data rate should always be limited below
1.75Mbps for both receiver and driver to avoid interfer-
ence with the internal barrier communication.
Layout Considerations
The MAX3535E/MXL1535E pin configurations enable
optimal PC board layout by minimizing interconnection
lengths and crossovers:
• For maximum isolation, the isolation barrier should not
be breached except by the MAX3535E/MXL1535E and
the transformer. Connections and components from
one side of the barrier should not be located near those
of the other side of barrier.
• A shield trace connected to the ground on each side of
the barrier can help intercept capacitive currents that
might otherwise couple into the DI and SLO inputs. In a
double-sided or multilayer board, these shield traces
should be present on all conductor layers.
• Try to maximize the width of the isolation barrier
wherever possible. A clear space of at least 0.25in
between GND1 and GND2 is recommended.
IP 100%
90%
36.8%
tRL TIME
tDL
CURRENT WAVEFORM
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
Ir
10%
0
0
AMPERES
Figure 15. Human Body Current Waveform
0
10
5
20
15
30
25
35
45
40
50
0 500 750250 1000 1250 1500 1750 2000
DATA SKEW vs. DATA RATE
DATA RATE (kbps)
DATA SKEW (%)
TYP SKEW
MAX SKEW
Figure 16. Data Skew vs. Data Rate Graph
MAX3535E/MXL1535E
Maxim Integrated
23
+3V to +5V, 2500VRMS Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
Chip Information
PROCESS: BiCMOS
TRANSISTOR COUNT: 7379
TGM-240 1/2
BAT54C
TRANSFORMER
DRIVER
BARRIER
TRANSCEIVER
ISOLATION BARRIER
BARRIER
TRANSCEIVER
1/2
BAT54C
VOLTAGE
REGULATOR
GND2
+3.3V
DRIVER
RECEIVER
A
B
Y
Z
SLO
RO2
ST1
RO1
μCRE
DE
DI
GND1
ST2 VCC2
VCC1
VCC2
0.1μF
0.1μF
CONTROL GROUND
RS-485 GROUND
10μF
10μF
MAX3535E
Typical Application Circuit
MAX3535E/MXL1535E
24
Maxim Integrated
MAX3535E/MXL1535E
+3V to +5V, 2500VRMS Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
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.)
28L 16L SOIC.EPS
MAX3535E/MXL1535E
Maxim Integrated
25
MAX3535E/MXL1535E
+3V to +5V, 2500VRMS Isolated RS-485/RS-422
Transceivers with ±15kV ESD Protection
26 Maxim Integrated 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000
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. 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.
© 2004 Maxim Integrated The Maxim logo and Maxim Integrated are trademarks of Maxim Integrated Products, Inc.
