MAXIM MAX3535E, MXL1535E User Manual

General Description

The MAX3535E/MXL1535E isolated RS-485/RS-422 full­duplex transceivers provide 2500V

RMS

of galvanic isola­tion 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 integrat­ed 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 inter­face 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-cir­cuit and overvoltage protected. Other features are hot­swap 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 sav­ings. The MXL1535E operates with a single +4.5V to
+5.5V power supply. The MXL1535E is a function-/pin­compatible improvement of the LTC1535. The
MAX3535E/MXL1535E are available over the commer­cial 0°C to +70°C and extended -40°C to +85°C temper­ature ranges.

Applications

Isolated RS-485 Systems

Systems with Large Common-Mode Voltages

Industrial-Control Local Area Networks

Telecommunications Systems

Features

♦ 2500V

RMS

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

MAX3535E/MXL1535E

+3V to +5V, 2500V

RMS

Isolated RS-485/RS-422

Transceivers with ±15kV ESD Protection

________________________________________________________________

Maxim Integrated Products

1

Pin Configuration

Ordering Information

19-3270; Rev 0; 4/04

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

Typical Application Circuit appears at end of data sheet.

EVALUATION KIT

AVAILABLE

PART TEMP RANGE

MAX3535ECWI 0°C to +70°C 28 Wi d e S O

MAX3535EEWI -40°C to +85°C 28 Wi d e S O

MXL1535ECWI 0°C to +70°C 28 Wi d e S O

MXL1535EEWI -40°C to +85°C 28 Wi d e S O+ 4.5 to + 5.5

TOP VIEW

PIN-

PACKAGE

1

V

CC1

2

ST1

3

ST2

4

GND1

MAX3535E
MXL1535E

11

GND2

12

Z

13

Y

V

14

CC2

PINS 5–10 and 19–24 ARE REMOVED FROM THE PACKAGE

WIDE SO

RO1

28

RE

27

DE

26

DI

25

SLO

18

RO2

17

A

16

B

15

POWER­SUPPLY

RANGE

(V)

+ 3.0 to + 5.5

+ 3.0 to + 5.5

+ 4.5 to + 5.5

MAX3535E/MXL1535E

+3V to +5V, 2500V

RMS

Isolated RS-485/RS-422

Transceivers with ±15kV ESD Protection

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

DC ELECTRICAL CHARACTERISTICS TABLE (MAX3535E)

(V

CC1

= +3.0V to +5.5V, V

CC2

= +3.13V to +7.5V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at V

CC1

= +3.3V,

V

CC2

= +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.
V

CC1

.........................................................................-0.3V to +6V

RE, DE, DI.................................................................-0.3V to +6V

RO1, ST1, ST2 ..........................................-0.3V to (V

CC1

+ 0.3V)
Isolated Side—All Voltages Referenced to GND2.
V

CC2

.........................................................................-0.3V to +8V

SLO...........................................................-0.3V to (V

CC2

+ 0.3V)

A, B ......................................................................................±14V

RO2 .....................-0.3V to the lower of (V

CC2

+ 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 (T

A

= +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

LOGIC-SIDE SUPPLY (V

Logic-Side Supply Voltage V

Logic-Side Supply Current I

V

CC1

Falling Trip

V

CC1

Rising Trip

LOGIC INPUTS (DI, DE, RE)

Input High Voltage, DE, DI, RE V
Input Low Voltage, DE, DI, RE V

Logic-Side Input Current, DE, DI I

LOGIC OUTPUTS (RO1, RE)

Receiver-Output High Voltage
(RO1)

Receiver-Output Low Voltage
(RO1)

Receiver-Output (RO1) Leakage
Current

RE Low Output Current for Fault
Detect

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Undervoltage-Lockout

Undervoltage-Lockout

, GND1)

CC1

CC1

Transformer not driven, ST1 and ST2

CC1

V

UVL1

V

UVH1

V

RO1H

V

RO1L

I

OZR

I

INC

OL

unconnected, RE = low, DE = high,

= 0, RO1 = no load

f

DATA

VIH is measured with respect to GND1 2.0 V

IH

VIL is measured with respect to GND1 0.8 V

IL

I

I

I

I

RE = high, V
0 ≤ V

RE = +0.4V, fault not asserted 40 60 80 µA

SOURCE

SOURCE

= 4mA, V

SINK

= 4mA, V

SINK

RO1

= 4mA, V

= 4mA, V

≤ V

= +4.5V 3.7

CC1

= +3V 2.4

CC1

= +4.5V 0.4

CC1

= +3V 0.4

CC1

= +5.5V,

CC1

CC1

3.0 5.5 V

5.9 13 mA

2.53 2.69 2.85 V

2.63 2.80 2.97 V

±2µA

±1 µA

V

V

+3V to +5V, 2500V

RMS

Isolated RS-485/RS-422

Transceivers with ±15kV ESD Protection

_______________________________________________________________________________________ 3

MAX3535E/MXL1535E

DC ELECTRICAL CHARACTERISTICS TABLE (MAX3535E) (continued)

(V

CC1

= +3.0V to +5.5V, V

CC2

= +3.13V to +7.5V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at V

CC1

= +3.3V,

V

CC2

= +5V, TA= +25°C.)

RE High Output Current for Fault
Detect

TRANSFORMER DRIVER (ST1, ST2)

DC-Converter Switching
Frequency (ST1, ST2)

DC-Converter Total Impedance
R

OH

ST1, ST2 Duty Cycle ST1, ST2, not loaded 44 50 56 %

ISOLATED-SIDE SUPPLY (V

Isolated-Side Supply Voltage V

Isolated-Side Supply Current I

V

CC2

Falling Trip

V

CC2

Rising Trip

DRIVER OUTPUTS (Y, Z)

Driver-Output High Voltage V

Differential Driver Output V

Driver Common-Mode Output
Voltage

Change in Magnitude of Driver
Differential Output Voltage for
Complementary Output States

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

+ ROL (ST1, ST2)

Undervoltage-Lockout

Undervoltage-Lockout

CC2

R

, GND2)

V

V

V

ΔV

I

OH

f

SW

OHL

CC2

CC2

UVL2

UVH2

DOH

OD

OC

RE = V

ST1, ST2, not loaded 290 460 590 kHz

V

CC1

V

CC1

f

DATA

RO2 = no load,
A, B floating, Figure 1

No load, V
GND2

RL = 50Ω (RS-422), V
Figure 1

RL = 27Ω (RS-485), V
Figure 1

RL = 27Ω or 50Ω, VOC is measured with
respect to GND2, Figure 1

RL = 27Ω or 50Ω, Figure 1 ±0.2 V

OD

- 0.5V, fault asserted -140 -100 -60 µA

CC1

= +4.5V, Figure 13 1.6 2.6

= +3V, Figure 13 1.8 2.9

3.13 7.50 V

= 0, SLO floating,

is measured with respect to

DOH

RL = 27Ω 56 70

R

= ∞ 10 16

L

2.68 2.85 3.02 V

2.77 2.95 3.13 V

= +3.13V,

CC2

= +3.13V,

CC2

2.0 2.35

1.5 1.95

1.0 3.0 V

4V

Ω

mA

V

Change in Magnitude of Driver
Common-Mode Output Voltage
for Complementary Output States

Driver Short-Circuit Output
Current

ΔV

I

OC

OSD

RL = 27Ω or 50Ω, Figure 1 ±0.2 V

Driver enabled (DE =1 )
DI = high, V
DI = low, V

Driver enabled (DE =1 )
DI = high, V
DI = low, V

> -7V

Y

> -7V

Z

< +12V

Z

< +12V

Y

-250

mA

+250

MAX3535E/MXL1535E

+3V to +5V, 2500V

RMS

Isolated RS-485/RS-422

Transceivers with ±15kV ESD Protection

4 _______________________________________________________________________________________

DC ELECTRICAL CHARACTERISTICS TABLE (MAX3535E) (continued)

(V

CC1

= +3.0V to +5.5V, V

CC2

= +3.13V to +7.5V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C,

V

CC1

= +3.3V, V

CC2

= +5V).

Driver Short-Circuit Foldback
Output Current

SLEW-RATE SELECT (SLO)

Input High Voltage SLO V
Input Low Voltage SLO V
SLO Pullup Resistor R

RECEIVER INPUTS (A, B)

Receiver Input Current I

Receiver Differential Threshold
Voltage

Receiver-Input Hysteresis ΔV

Receiver-Input Resistance R

Receiver-Input Open Circuit
Voltage

RECEIVER OUTPUT (RO2)

Receiver-Output (RO2) High
Voltage

Receiver-Output (RO2) Low
Voltage

ISOLATION

Isolation Voltage (Notes 2, 3) V

Isolation Resistance R

Isolation Capacitance C

ESD Protection Human Body Model (A, B, Y, Z) ±15 kV

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

DI = high

Driver

I

OSFD

IHS

ILS

SLO

AB

V

V

OAB

V

RO2HISOURCE

V

RO2LISINK

ISO

ISO

ISO

enabled
(DE =1)

V

IHS

V

ILS

V

SLO

VA or VB = +12V +125

VA or VB = -7V -100

-7V ≤ VCM ≤ +12V -200 -90 -10 mV

TH

-7V ≤ V

TH

-7v ≤ V

-7V ≤ VCM ≤ +12V (Note 1) 96 200 kΩ

IN

60s 2500

1s 3000

TA = +25°C, V

TA = +25°C2pF

-7V < V

DI = low

-7V < V

DI = high
+1V < V

DI = low
+1V < V

is measured with respect to GND2 3.0 V

is measured with respect to GND2 1.0 V

= +3V 100 kΩ

≤ +12V, TA = 0°C to +70°C103070

CM

≤ +12V, TA = -40°C to +85°C 5 30 70

CM

= 4mA, V

= 4mA, V

< min[(V

Y

< min[(V

Z

< +12V

Z

< +12V

Y

= +3.13V 2.4 V

CC2

= +3.13V 0.4 V

CC2

= 50V (Note 3) 100 10,000 MΩ

ISO

- 1V) +2V]

CC2

- 1V) +2V]

CC2

+25

2.6 V

-25

V

µA

µA

mV

RMS

+3V to +5V, 2500V

RMS

Isolated RS-485/RS-422

Transceivers with ±15kV ESD Protection

_______________________________________________________________________________________ 5

MAX3535E/MXL1535E

SWITCHING ELECTRICAL CHARACTERISTICS (MAX3535E)

(V

CC1

= +3.0V to +5.5V, V

CC2

= +3.13V to +7.5V, RL= 27Ω, CL= 50pF, TA= -40°C to +85°C, unless otherwise noted. Typical values

are at V

CC1

= +3.3V, V

CC2

= +5V, TA= +25°C.)

Data Sample Jitter t

Maximum Data Rate f

Self-Oscillating Frequency f

Driver-Differential Output Delay
Time

Driver-Differential Output
Transition Time

Driver-Output Enable Time t

Driver-Output Disable Time t

Receiver-Propagation Delay Time
to RO1

Receiver-Propagation Delay Time
to RO2

RO1, RO2 Rise or Fall Time tR, t

Receiver-Output Enable Time
RO1

Receiver-Output Disable Time
RO1

Initial Startup Time (from Internal
Communication Fault)

Internal Communication Timeout
Fault Time

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Figure 6 220 285 ns

J

DATA

SOS

t

t

PZL

PHZ

t

PLH1

t

PHL1

t

PLH2

t

PHL2

t

ZL,tZH

t

LZ,tHZ

DD

TD

, t

tJ = 25% of data cell, receiver and driver,

SLO = high (Note 4)
SLO = high, Figure 5 250 450

SLO = low, Figure 5 200 375
SLO = high, Figures 2, 6 490 855
SLO = low, Figures 2, 6 850 1560
SLO = high, Figures 2, 6 30 100
SLO = low, Figures 2, 6 120 220 1000

SLO = high, DI = high or low,

PZH

Figures 3, 7

SLO = high, DI = high or low,

, t

PLZ

Figures 3, 7

,

Figures 4, 8 440 855 ns

,

Figures 4, 8 40 ns

Figures 4, 8 40 ns

F

Figures 4, 9 30 ns

Figures 4, 9 30 ns

(Note 5) 1200 ns

(Note 5) 1200 ns

877 1136 kbps

kHz

ns

ns

730 1400 ns

720 1300 ns

MAX3535E/MXL1535E

+3V to +5V, 2500V

RMS

Isolated RS-485/RS-422

Transceivers with ±15kV ESD Protection

6 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (MXL1535E)

(V

CC1

= +4.5V to +5.5V, V

CC2

= +4.5V to +7.5V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at V

CC1

= +5V,

V

CC2

= +5V, TA= +25°C.)

Logic-Side Supply Voltage V

Isolated-Side Supply Voltage V

Logic-Side Supply Current I

Isolated-Side Supply Current I

Differential Driver Output V

Driver Output High Voltage V

Driver Common-Mode Output
Voltage

Change in Magnitude of Driver
Differential Output Voltage for
Complementary Output States

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

4.5 5.5 V

4.5 7.5 V

1.0 3.0 V

ΔV

CC1

CC2

CC1

CC2

OD

DOH

V

OC

Transformer not driven, ST1 and ST2
unconnected, RE = low, DE = high,

= 0, RO1 = no load

f

DATA

f

= 0, SLO floating,

DATA

RO2 = no load, A, B
floating, Figure 1

RL = 50Ω (RS-422), V

RL = 27Ω (RS-485), V

No load, V
GND2

RL = 27Ω or 50Ω, VOC is measured with
respect to GND2, Figure 1

RL = 27Ω or 50Ω, Figure 1 ±0.2 V

OD

is measured with respect to

DOH

RL = 27Ω 56 70

R

= ∞ 10 16

L

= +4.5V, Figure 1 2.0 3.0

CC2

= +4.5V, Figure 1 1.5 2.5

CC2

5.9 13 mA

mA

V

5.0 V

Change in Magnitude of Driver
Common-Mode Output Voltage
for Complementary Output States

Driver Short-Circuit Output
Current

Driver Short-Circuit Foldback
Output Current

ΔV

I

OSD

I

OSFD

RL = 27Ω or 50Ω, Figure 1 ±0.2 V

OC

Driver enabled (DE =1)
DI = high, V
DI = low, V

Driver enabled (DE =1)
DI = high, V
DI = low, V

Driver enabled (DE =1)
DI = high

-7V < V
DI = low

-7V < V

Driver enabled (DE =1)
DI = high
+1V < V
DI = low
+1V < V

> -7V

Y

> -7V

Z

< +12V

Z

< + 12V

Y

< min[(V

Y

< min[(V

Z

< +12V

Z

< +12V

Y

- 1V) +2V]

CC2

- 1V) +2V]

CC2

-250

+25

mA

+250

-25

mA

+3V to +5V, 2500V

RMS

Isolated RS-485/RS-422

Transceivers with ±15kV ESD Protection

_______________________________________________________________________________________ 7

MAX3535E/MXL1535E

ELECTRICAL CHARACTERISTICS (MXL1535E) (continued)

(V

CC1

= +4.5V to +5.5V, V

CC2

= +4.5V to +7.5V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at V

CC1

= +5V,

V

CC2

= +5V, TA= +25°C.)

Input High Voltage, DE, DI, RE V

Input High Voltage, SLO V

Input Low Voltage, DE, DI, RE V

Input Low Voltage, SLO V

Logic-Side Input Current, DE, DI I

Receiver Input Current I

Receiver Differential Threshold
Voltage

Receiver-Input Hysteresis ΔV

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

VIH is measured with respect to GND1 2.0 1.45 V

IH

V

is measured with respect to GND2 4.0 2.1 V

IHS

VIL is measured with respect to GND1 1.45 0.8 V

V

is measured with respect to GND2 2.1 1.0 V

ILS

VA or VB = +12V +0.25

VA or VB = -7V -0.20

-7V ≤ VCM ≤ +12V -200 -90 -10 mV

-7V ≤ VCM ≤ +12V, TA = 0°C to +70°C 10 30 70

-7V ≤ VCM ≤ +12V, TA = -40°C to +85°C 5 30 70

V

IHS

IL

ILS

INC

AB

TH

TH

±2µA

mA

mV

Receiver-Input Resistance R

Receiver-Input Open-Circuit
Voltage

Receiver-Output High Voltage
(RO1)

Receiver-Output Low Voltage
(RO1)

Driver-Output Leakage Current I

Driver-Output Leakage Current I

Receiver-Output (RO2) High
Voltage

Receiver-Output (RO2) Low
Voltage

DC-Converter Switching
Frequency (ST1, ST2)

V

V

V

V

V

-7V ≤ VCM ≤ +12V (Note 1) 96 140 200 kΩ

IN

OAB

RO1HISOURCE

RO1LISINK

OZ

OZ

RO2H

RO2LISINK

f

SW

= 4mA, V

DE = low

-7V < V

DE = low

-7V < V

I

SOURCE

= 4mA, V

ST1, ST2 not loaded 290 460 590 kHz

= 4mA, V

< +12V, -7V < VZ < +12V

Y

< +12V, -7V < VZ < +12V

Y

= 4mA, V

= +4.5V 3.7 4.3 V

CC1

= +4.5V 0.4 0.8 V

CC1

= +4.5V 2.8 3.4 V

CC2

= +4.5V 0.4 0.8 V

CC2

2.6 V

±30 µA

±30 ±100 µA

MAX3535E/MXL1535E

+3V to +5V, 2500V

RMS

Isolated RS-485/RS-422

Transceivers with ±15kV ESD Protection

8 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (MXL1535E) (continued)

(V

CC1

= +4.5V to +5.5V, V

CC2

= +4.5V to +7.5V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at V

CC1

= +5V,

V

CC2

= +5V, TA= +25°C.)

DC-Converter Impedance High
ST1, ST2

DC-Converter Impedance Low
ST1, ST2

RE Low Output Current for Fault
Detect

RE High Output Current for Fault
Detect

V

CC2

Falling Trip

V

CC2

Rising Trip

V

CC1

Falling Trip

V

CC1

Rising Trip

Isolation Voltage (Note 2) V

SLO Pullup Resistor R

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Undervoltage-Lockout

Undervoltage-Lockout

Undervoltage-Lockout

Undervoltage-Lockout

R

R

I

I

V

UVL2

V

UVH2

V

UVL1

V

UVH1

OH

OL

OH

ISO

SLO

Figure 13 4 6 Ω

Figure 13 2.5 5 Ω

OL

RE = sink current,
RE = +0.4V, fault not asserted

RE = source current,
RE = +V

60s 2500

1s 3000

V

SLO

- 0.5V, fault asserted

CC1

= +3V 100 kΩ

-40 -50 -80 µA

60 100 140 µA

2.68 2.85 3.02 V

2.77 2.95 3.13 V

2.53 2.69 2.85 V

2.63 2.80 2.97 V

V

RMS

MAX3535E/MXL1535E

+3V to +5V, 2500V

RMS

Isolated RS-485/RS-422

Transceivers with ±15kV ESD Protection

_______________________________________________________________________________________ 9

MAX3535E/MXL1535E

SWITCHING ELECTRICAL CHARACTERISTICS (MXL1535E)

(V

CC1

= +4.5V to +5.5V, V

CC2

= +4.5V to +7.5V, RL= 27Ω, CL= 50pF, TA= -40°C to +85°C, unless otherwise noted. Typical values

are at V

CC1

= +5V, V

CC2

= +5V, TA= +25°C.)

Note 1: Receiver inputs are 96kΩ minimum resistance, which is 1/8 unit load.
Note 2: 60s test result is guaranteed by correlation from 1s result.
Note 3: V

ISO

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.

Data Sample Jitter t

Max Baud Rate f

Driver-Differential Output Delay
Time

Driver-Differential Output
Transition Time

Driver-Output Enable Time t

Driver-Output Disable Time t

Receiver-Propagation Delay Time
to RO1

Receiver-Propagation Delay Time
to RO2

RO1, RO2 Rise or Fall Time tR, t

Receiver-Output Enable Time
RO1

Receiver-Output Disable Time
RO1

Initial Startup Time (from Internal
Communication Fault)

Internal Communication Timeout
Fault Time

ST1, ST2 Duty Cycle

ESD Protection Human Body Model (A, B, Y, Z) ±15 kV

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Figure 6 220 285 ns

J

SLO = high, Figure 5, (Note 6) 250 450 kBd
SLO = high, Figures 2, 6 430 855
SLO = low, Figures 2, 6 850 1560
SLO = high, V
SLO = low, V

SLO = high, DI = high or low,

PZH

Figure 3, 7

SLO = high, DI = high or low,

, t

PLZ

Figures 3, 7

,

Figures 4, 8 440 855 ns

,

Figures 4, 8 40 ns

Figures 4, 8 40 ns

F

Figures 4, 9 30 ns

ZH

Figures 4, 9 30 ns

HZ

(Note 5) 1200 ns

(Note 5) 1200 ns

0°C to +70°C 56

-40°C to +85°C 57

= +4.5V 45 100

CC2

= +4.5V 150 260 1000

CC2

730 1400 ns

720 1300 ns

PZL

PHZ

t

t

t

t

t

ZL

t

LZ

MAX

t

DD

t

TD

, t

PLH1

PHL1

PLH2

PHL2

, t

, t

ns

ns

%

MAX3535E/MXL1535E

+3V to +5V, 2500V

RMS

Isolated RS-485/RS-422

Transceivers with ±15kV ESD Protection

10 ______________________________________________________________________________________

Typical Operating Characteristics

(V

CC1

= +5V, CL= 50pF (Figure 1), unless otherwise noted.)

I

I

SUPPLY CURRENT

CC1

vs. TEMPERATURE

100

80

RL = 27Ω

60

(mA)

CC1

I

RL = 60Ω

40

RL = OPEN

20

FIGURE 1

0

-40 85
TEMPERATURE (°C)

HALO
TGM-250NS
1:1:1 TRANSFORMER

I

SUPPLY CURRENT

CC1

vs. TEMPERATURE

MAX3535E toc02

80

70

60

(mA)

CC2

I

50

40

FIGURE 1

30

-40 85

100

V

= +3.3V

CC1

MAX3535E toc01

80

60

(mA)

CC1

I

603510-15

RL = 60Ω

40

RL = OPEN

20

FIGURE 1

0

-40 85

HALO
TGM-240NS
1:1.3:1.3 TRANSFORMER

TEMPERATURE (°C)

RL = 27Ω

603510-15

SUPPLY CURRENT

CC2

vs. TEMPERATURE

TEMPERATURE (°C)

f

= 700kbps

DATA

SLO = LOW
R

= 27Ω

L

V

= +6V

CC2

V

= +3.9V

CC2

(MAX3535E)

V

= +3.13V

CC2

(MAX3535E)

603510-15

MAX3535E toc03

V

SUPPLY VOLTAGE

7.0

6.5

6.0

5.5

(V)

5.0

CC2

V

4.5

4.0

3.5

3.0

-40 85

CC2

vs. TEMPERATURE

HALO
TGM-240NS
1:1.3:1.3 TRANSFORMER

TEMPERATURE (°C)

RL = OPEN, V

RL = 27Ω, V

RL = 27Ω, V
(MAX3535E)

CC1

= +5V

CC1

= +3V

CC1

FIGURE 1

6035-15 10

= +5V

MAX3535E toc04

500

450

400

(kHz)

SOS

f

350

300

FIGURE 5

250

-40 85

DRIVER DIFFERENTIAL OUTPUT

TRANSITION TIME vs. TEMPERATURE

800

700

600

(ns)

500

TD

t

400

V

= +5V

CC2

300

V

= +3.13V (MAX3535E)

CC2

200

-40 85
TEMPERATURE (°C)

RL = 27Ω
SLO = GND2

FIGURES 2, 6

603510-15

MAX3535E toc07

600

550

500

(kHz)

450

SW

f

400

350

300

-40 85

SELF-OSCILLATION FREQUENCY

vs. TEMPERATURE

V

= V

SLO = HIGH

SLO = LOW

TEMPERATURE (°C)

CC1

RL = 27Ω

603510-15

SWITCHER FREQUENCY

vs. TEMPERATURE

603510-15

TEMPERATURE (°C)

CC2

MAX3535E toc05

MAX3535E toc08

DRIVER DIFFERENTIAL OUTPUT

TRANSITION TIME vs. TEMPERATURE

100

90

80

70

60

(ns)

50

TD

t

V

= +5V

CC2

40

30

20

10

0

-40 85

V

= +3.13V (MAX3535E)

CC2

TEMPERATURE (°C)

SWITCHER FREQUENCY

vs. SUPPLY VOLTAGE

600

550

500

(kHz)

450

SW

f

400

350

300

3.0 5.5
V

(V)

CC1

RL = 27Ω
SLO = V

CC2

FIGURES 2, 6

603510-15

5.04.54.03.5

MAX3535E toc06

MAX3535E toc09

+3V to +5V, 2500V

RMS

Isolated RS-485/RS-422

Transceivers with ±15kV ESD Protection

______________________________________________________________________________________

11

Typical Operating Characteristics (continued)

(V

CC1

= +5V, CL= 50pF (Figure 1), unless otherwise noted.)

MAX3535E/MXL1535E

RECEIVER-OUTPUT (RO1) LOW VOLTAGE

vs. TEMPERATURE

1.0

0.8

0.6

(V)

RO1L

V

0.4

V

= +4.5V

0.2

0

-40 85

CC1

TEMPERATURE (°C)

V

CC1

(MAX3535E)

V

= +5V

CC1

I

SINK

= +3V

603510-15

= 4mA

MAX3535E toc10

DRIVER-OUTPUT HIGH VOLTAGE

vs. DRIVER SOURCE CURRENT

5
4
3
2
1

V

= +3.13V

CC2

(MAX3535E)

0

(V)

-1

DOH

V

-2

-3

-4

-5
V

= +3.9V

CC2

-6

(MAX3535E)

-7

0 120

DRIVER SOURCE CURRENT (mA)

DE = HIGH

V

CC2

10080604020

MAX3535E toc13

= +7.5V

RECEIVER-OUTPUT (RO1) HIGH VOLTAGE

vs. TEMPERATURE

5.0

V

= +5V

CC1

4.5

V

= +4.5V

CC1

4.0

(V)

3.5

RO1H

V

3.0

2.5

V

= +3V

CC1

(MAX3535E)

2.0

-40 85
TEMPERATURE (°C)

I

DRIVER-OUTPUT LOW VOLTAGE

vs. DRIVER SINK CURRENT

12
11
10

9
8
7

(V)

V

DOL

V

= +3.9V

CC2

6

(MAX3535E)

5
4

V

= +3.13V

CC2

3

(MAX3535E)

2
1
0

0 120

DRIVER SINK CURRENT (mA)

SOURCE

DE = HIGH

V

CC2

= 4mA

603510-15

= +7.5V

10080604020

MAX3535E toc11

MAX3535E toc14

DRIVER DIFFERENTIAL OUTPUT VOLTAGE

vs. DIFFERENTIAL OUTPUT CURRENT

4.0

3.5

V

3.0

2.5

(V)

2.0

OD

V

V

= +3.13V

CC2

1.5

(MAX3535E)

1.0
V

= +7.5V

CC2

0.5

0

0 120

DRIVER DIFFERENTIAL OUTPUT CURRENT (mA)

= +3.9V

CC2

(MAX3535E)

DRIVER DIFFERENTIAL OUTPUT VOLTAGE

SUPPLY VOLTAGE

vs. V

2.8

2.6

2.4

(V)

2.2

OD

V

2.0

1.8

1.6

3.0 7.5

CC2

V

(V)

CC2

DE = HIGH

1008020 40 60

RL = 27Ω

FIGURE 1

7.06.56.05.55.04.54.03.5

MAX3535E toc12

MAX3535E toc15

RECEIVER OUTPUT (RO1) VOLTAGE

DRIVER DIFFERENTIAL OUTPUT VOLTAGE

vs. LOAD CURRENT

5

OUTPUT HIGH, SOURCING

4

3

2

OUTPUT VOLTAGE (V)

1

OUTPUT LOW, SINKING

0

015

LOAD CURRENT (mA)

105

MAX3535E toc16

5

4

3

(V)

OD

V

2

FIGURE 1

V
(MAX3535E)

1

0

-40 85

vs. TEMPERATURE

V

= +7.5V

CC2

= +3.13V

CC2

TEMPERATURE (°C)

RL = 27Ω
SLO = GND2

V

= +6V

CC2

603510-15

MAX3535E toc17

I

SUPPLY CURRENT

CC1

SUPPLY VOLTAGE

vs. V

10

RL = OPEN

9

TRANSFORMER IS NOT DRIVEN

8

7

6

(mA)

5

CC1

I

4

3

2

1

0

3.0 5.5

CC1

V

SUPPLY VOLTAGE (V)

CC1

MAX3535E toc18

5.04.54.03.5

MAX3535E/MXL1535E

+3V to +5V, 2500V

RMS

Isolated RS-485/RS-422

Transceivers with ±15kV ESD Protection

12 ______________________________________________________________________________________

Typical Operating Characteristics (continued)

(V

CC1

= +5V, CL= 50pF (Figure 1), unless otherwise noted.)

RECEIVER (RO1) PROPAGATION DELAY

)

(t

PLH1

100ns/div

300

280

260

(ns)

J

t

240

220

200

-40 85

MAX3535E toc19

A-B
1V/div

RO
1V/div

JITTER vs. TEMPERATURE

V

= 3.13V

CC1

V

= 5.5V

CC1

603510-15

TEMPERATURE (°C)

DRIVER PROPAGATION DELAY

MAX3535E toc22

(SLO = LOW)

400ns/div

MAX3535E toc20

DI
2V/div

Y
2V/div

Z
2V/div

TIME PLUS JITTER

DRIVER PROPAGATION DELAY

(SLO = HIGH)

400ns/div

DRIVER ENABLE

MAX3535E toc23

200ns/div

DE
2V/div

Y
2V/div

MAX3535E toc21

DI
2V/div

Y
2V/div

Z
2V/div

DRIVER DISABLE

TIME PLUS JITTER

200ns/div

MAX3535E toc24

DE
2V/div

Y
2V/div

RECEIVER (RO1) PROPAGATION DELAY

)

(t

PHL1

100ns/div

MAX3535E toc25

A-B
1V/div

RO
1V/div

+3V to +5V, 2500V

RMS

Isolated RS-485/RS-422

Transceivers with ±15kV ESD Protection

______________________________________________________________________________________ 13

MAX3535E/MXL1535E

Pin Description

PIN NAME ISOLATION SIDE FUNCTION

1V

2 ST1 Logic

3 ST2 Logic

4 GND1 Logic Logic-Side Ground. For isolated operation do not connect to GND2.

5–10,

19–24

11 GND2 Isolated Isolation-Side Ground. For isolated operation do not connect to GND1.

12 Z Isolated

13 Y Isolated

14 V

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

CC1

— — Removed from Package

CC2

Logic

Isolated

Logic-Side/Transformer-Driver Power Input. Bypass V
capacitors.

Transformer-Driver Phase 1 Power Output. Connect ST1 to isolation-transformer
primary to send power to isolation side of barrier.

Transformer-Driver Phase 2 Power Output. Connect ST2 to isolation-transformer
primary to send power to isolation side of barrier.

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.)

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.)

Isolated-Side Power Input. Connect V
secondary. Bypass V

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 .

to GND2 with 10µF and 0.1µF capacitors.

CC2

to the rectified output of transformer

CC2

to GND1 with 10µF and 0.1µF

CC1

18 SLO Isolated

25 DI Logic

26 DE Logic

27 RE Logic

28 RO1 Logic

Driver Slew-Rate Control Logic Input. Connect SLO to GND2 for data rates up to
400kbps. Connect SLO to V

Driver Input. Pull DI low (high) to force driver output Y low (high) and driver output Z
high (low).

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.

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.

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.

or leave floating for high data rates.

CC2

MAX3535E/MXL1535E

+3V to +5V, 2500V

RMS

Isolated RS-485/RS-422

Transceivers with ±15kV ESD Protection

14 ______________________________________________________________________________________

Test Circuits

Figure 1. Driver DC Test Load

Figure 2. Driver Timing Test Circuit

Figure 5. Self-Oscillating Configuration

Figure 3. Driver Timing Test Load

Figure 4. Receiver Timing Test Load

Y

R

L

V

V

OD

Z

OC

R

L

Y/Z

C

L

500Ω

500Ω

V

CC2

GND2

HIGH

DE

DI

GND

R

Y

Z

R

C

L

L

L

GND2

C

L

ST2 V

V

CC1

RO1

ST1

TRANSFORMER

RE

0.1μF

+3.0V TO +5.5V

10μF

DRIVER

RO1/RO2

C

TGM-240

1/2

BAT54C

10μF

1/2

BAT54C

GND2

VOLTAGE

REGULATOR

0.1μF

RECEIVER

CC2

V

CC1/VCC2

1kΩ

1kΩ

L

GND1/GND2

CONTROL GROUND

RS-485 GROUND

A

B

RO2

GND1

DE

DI

MAX3535E

BARRIER

TRANSCEIVER

ISOLATION BARRIER

BARRIER

TRANSCEIVER

V

CC2

DRIVER

Y

Z

SLO

C

C

L

L

2R

L

+3V to +5V, 2500V

RMS

Isolated RS-485/RS-422

Transceivers with ±15kV ESD Protection

______________________________________________________________________________________ 15

MAX3535E/MXL1535E

Switching Waveforms

Figure 6. Driver Propagation Delay

Figure 7. Driver Enable and Disable Times

Figure 8. Receiver Propagation Delays

Figure 9. Receiver Enable and Disable Times

80%

t

J

tR < 10ns, tF < 10ns

V

OD

DI

1.5V

t

DD

Z

V

DOH

Y

V

DOH

0V

-V

DOH

1/2 V

DOH

20%

t

TD

= VY - V

V

RO1H

t

PLH1

tR < 10ns, tF < 10ns

/2

OUTPUT

INPUT

0V

20%

t

PLH1

V

RO1H

t

J

80%

t

PLH2

t

R

1.5V

t

DD

80%

Z

20%

t

TD

V

RO1

RO2

V

A

V

- V

RO1H

RO1L

0V

B

t

PHL1

t

J

80%

t

PLH2

20%

t

F

/2

< 10ns, tF < 10ns

t

R

V

/2

DOH

OUTPUT NORMALLY LOW

OUTPUT NORMALLY HIGH

/2

V

DOH

2 x t

J

t

1.5V

t

PZL

PZH

DE

V

DOH

Y, Z

V

DOL

V

DOH

Y, Z

0V

t

1.5V

t

PLZ

PHZ

RE

V

V

V

RO1H

RO1

RO1L

RO1H

RO1

0V

V

+ 0.5V

DOL

- 0.5V

V

DOH

t

J

1.5V

t

ZL

t

ZH

tR < 10ns, tF < 10ns

OUTPUT NORMALLY LOW

OUTPUT NORMALLY HIGH

t

t

1.5V

LZ

HZ

V

RO1L

V

RO1H

+ 0.5V

- 0.5V

MAX3535E/MXL1535E

+3V to +5V, 2500V

RMS

Isolated RS-485/RS-422

Transceivers with ±15kV ESD Protection

16 ______________________________________________________________________________________

Detailed Description

The MAX3535E/MXL1535E isolated RS-485/RS-422 full­duplex transceivers provide 2500V

RMS

of galvanic isola­tion 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 poten­tials) on either side of the barrier are subject to large dif­ferences. The isolation barrier consists of two parts. The
first part is a capacitive isolation barrier (integrated high­voltage 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 transmit­ted 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-sec­ondary 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 capaci­tors (see the

Typical Application Circuit

).

The MAX3535E/MXL1535E include one differential dri­ver, one receiver, and internal circuitry to send the RS­485 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 ter­minated bus with all transmitters disabled, the receiv­er’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 con­tention. The first, a foldback current limit on the output
stage, provides immediate protection against short cir­cuits 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 tempera­ture 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 pull­down 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 capabili­ty to overcome the internal drive.

+3V to +5V, 2500V

RMS

Isolated RS-485/RS-422

Transceivers with ±15kV ESD Protection

______________________________________________________________________________________ 17

MAX3535E/MXL1535E

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 V

CC1

is below its undervoltage-lock-

out threshold (2.69V nominal)

2) The voltage on V

CC2

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 con­dition, 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 terminat­ed 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 harmon­ics at the output. Floating SLO or connecting it to V

CC2

selects the fast slew rate, which allows high-speed
operation.

Figure 10. Reading a Fault Condition

TRI-STATED BUFFER/

BIDIRECTIONAL MICROCONTROLLER I/O

RO1

V

CC1

V

CC1

RE

OE

FAULT

D

R

RE

DE

DI

OE

DRIVER OUTPUT BECOMES HIGH IMPEDANCE

MAX3535E
MXL1535E

FAULT

FAULT DETECTED

GND1

MAX3535E/MXL1535E

+3V to +5V, 2500V

RMS

Isolated RS-485/RS-422

Transceivers with ±15kV ESD Protection

18 ______________________________________________________________________________________

Functional Tables

Table 1. Transmitting Logic

Table 2. Receiving Logic

Table 3. Fault Mode

TRANSMITTING LOGIC

INPUTS OUTPUTS

DE DI Y Z

1110

1001

0 X High impedance High impedance

RECEIVING LOGIC

INPUTS OUTPUTS

RE VA - V

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

B

RO1 RO2

NORMAL

FUNCTION

Transformer

driver

(ST1, ST2)

RE = 0 Active High High High High High

RE = V

RO1

RE = floating Active

Driver outputs (Y, Z) Active

Internal barrier

communication

Fault indicator on RE

CC1

RO2 Active Active Active Active Active Active

V

CC1

V

CC2

impedance

(60µA pull-

MODE

> V

UVH1

> V

UVH2

On On On On Off On

High

Active Disabled Disabled Disabled Disabled

Low

down)

V

< V

CC1

V

(100µA pullup)

UVL1

> V

CC2

UVH2

High

impedance

High

impedance

High

impedance

High

V

> V

CC1

V

(100µA pullup)

UVH1

< V

CC2

UVL2

High

impedance

High

impedance

High

impedance

High

FAULT MODES

V

< V

CC1

V

(100µA pullup)

UVL1

< V

CC2

UVL2

High

impedance

High

impedance

High

impedance

High

THERMAL

SHUTDOWN

High

impedance

High

impedance

High

impedance

High

(100µA pullup)

INTERNAL

COMMUNICATION

High impedance

High impedance

High impedance

Communication

attempted

(100µA pullup)

FAULT

High

+3V to +5V, 2500V

RMS

Isolated RS-485/RS-422

Transceivers with ±15kV ESD Protection

______________________________________________________________________________________ 19

MAX3535E/MXL1535E

Applications Information

Typical Applications

The MAX3535E/MXL1535E transceivers facilitate bi­directional 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 charac­teristic impedance. Keep stub lengths off the main line
as short as possible.

Figure 11. Typical Half-Duplex Multidrop RS-485 Network

BA

R

D

RO

DI

DE

RERE

TGM-240

B

120Ω

A

BA

R

D

DE

1/2

BAT54C

10μF

DI

CONTROL GROUND

0.1μF
RS-485 GROUND

RO

R

RE

DI

D

DE

RO

ST1

ST2 V

TRANSFORMER

DRIVER

MAX3535E

BARRIER

TRANSCEIVER

ISOLATION BARRIER

0.1μF

+3.3V

10μF

V

CC1

RO1

GND1

RE

DE

DI

1/2

BAT54C

BARRIER

TRANSCEIVER

GND2

VOLTAGE

REGULATOR

R

RECEIVER

DRIVER

D

V

CC2

CC2

A

B

RO2

Y

Z

SLO

120Ω

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 transform­ers designed for the MAX845 and MAX253. The 420kHz
transformer driver operates with single primary and cen­ter-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 = V

MAX

/ (2 x f

MIN

)

where, V

MAX

is the worst-case maximum supply voltage,

and f

MIN

is the minimum frequency at that supply voltage.

Using +5.5V and 290kHz gives a required minimum ET

MAX3535E/MXL1535E

+3V to +5V, 2500V

RMS

Isolated RS-485/RS-422

Transceivers with ±15kV ESD Protection

20 ______________________________________________________________________________________

Figure 12. Using the MAX3535E/MXL1535E as an RS-422 Line Repeater

Figure 13. Transformer Driver Output Stage

1/2

TGM-250

BAT54C

CONTROL GROUND

GND2

10μF

1/2

BAT54C

BARRIER

TRANSCEIVER

ISOLATION BARRIER

0.1μF

V

CC2

VOLTAGE

REGULATOR

A

120Ω

RO2

120Ω

SLO

B

Y

Z

RECEIVER

DRIVER

RD

DR

V

CC2

TRANSFORMER

DRIVER

BARRIER

TRANSCEIVER

ST2

MAX3535E
MXL1535E

ST1

RS-422 GROUND

V

CC1

RO1

RE

DE

DI

GND1

10μF

+5V

0.1μF

DI

RO

MAX488

D

R

Y

Z

A

B

TRANSFORMER DRIVER OUTPUT STAGE

V

CC1

R

OH

ST1 ST2

TRANSFORMER

PRIMARY

R

OL

R

R

GND1

OH

OL

+3V to +5V, 2500V

RMS

Isolated RS-485/RS-422

Transceivers with ±15kV ESD Protection

______________________________________________________________________________________ 21

MAX3535E/MXL1535E

product of 9.5V-µs. The commercially available trans­formers 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 pri­mary ET product is 6.2V-µs. All of the previously men­tioned 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 trans­former, 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 V

CC2

(+3.13V) under worst-case,

high-temperature, low-V

CC1

, and full-load conditions. For
light loads on the isolated side, ensure that the voltage at
V

CC2

does not exceed +7.5V. For example, the CTX01-

14659 transformer results in 85mA (typ) V

CC1

supply cur­rent with full load on the RS-485 driver. Using a TGM250
1:1:1 transformer lowers the V

CC1

supply current to 65mA

(typ), while maintaining good margin on the V

CC2

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
V

CC1

supply current of 51mA (typ).

Table 4. Transformers for the MXL1535E/MAX3535E

Table 5. Transformers for MAX3535E at +5V

MANUFACTURER PART NUMBER ISOLATION VOLTAGE (1s) PHONE NUMBER

Cooper Electronic Technologies, Inc. CTX01-14659 500V 561-241-7876

Cooper Electronic Technologies, Inc. CTX01-14608 3750V

EPCOS AG (Germany)
(USA)

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

B78304-A1477-A3 500V

RMS

561-241-7876

0 89-626-2-80-00
800-888-7724

MANUFACTURER

HALO Electronics, Inc.

BH Electronics, Inc. 500-1749 3750V

Coilcraft, Inc. U6982-C 1500V

Newport/C&D Technologies

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 1800V

Premier Magnetics, Inc. PM-SM15 1500V

PART

NUMBER

TGM-010 500V

TGM-250 2000V

TGM-350 3000V

TGM-450 4500V

7825355

7625335 4000V

ISOLATION

VOLTAGE (1s)

RMS

RMS

RMS

RMS

RMS

RMS

1500V

RMS

RMS

PHONE

NUMBER

650-903-3800 www.haloelectronics.com/6pin.html

952-894-9590

800-322-2645
44-1236-730595

520-295-4300 www.dc-dc.com/products/productline.asp?ED=9

714-898-0960 www.rhombus-ind.com/pt-cat/maxim.pdf

949-452-0511 www.premiermag.com/pdf/pmsm15.pdf

www.bhelectronics.com/PDFs/DC­DCConverterTransformers.pdf

www.coilcraft.com/minitrans.cfm

WEBSITE

±15kV ESD Protection

As with all Maxim devices, ESD-protection structures
are incorporated on all pins to protect against electro­static discharges encountered during handling and
assembly. The driver outputs and receiver inputs have
extra protection against static electricity. Maxim’s engi­neers have developed state-of-the-art structures to pro­tect 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 pro­tection 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

1.5kΩ resistor.

MAX3535E/MXL1535E

+3V to +5V, 2500V

RMS

Isolated RS-485/RS-422

Transceivers with ±15kV ESD Protection

22 ______________________________________________________________________________________

Table 6. Transformers for MAX3535E at +3.3V

Figure 14. Human Body ESD Test Model

MANUFACTURER

HALO Electronics, Inc.

BH Electronics, Inc. 500-2582 2000V

Coilcraft, Inc. Q4470-C 1500V

Newport/C&D Technologies

Midcom, Inc.

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 1800V

PART

NUMBER

TGM-040 500V

TGM-240 2000V

TGM-340 3000V

TGM-340 4500V

78253335 1500V

76253335 4000V

95062 1250V

95063 1250V

ISOLATION

VOLTAGE (1s)

RMS

RMS

RMS

RMS

RMS

RMS

RMS

PHONE

NUMBER

650-903-3800 www.haloelectronics.com/6pin.html

952-894-9590

800-322-2645
44-1236-730595

520-295-4300 www.dc-dc.com/products/productline.asp?ED=9

605-886-4385 www.midcom-inc.com

714-898-0960 www.rhombus-ind.com/pt-cat/maxim.pdf

www.bhelectronics.com/PDFs/DC­DCConverterTransformers.pdf

www.coilcraft.com/minitrans.cfm

WEBSITE

Premier Magnetics Inc. PM-SM16 1500V

RMS

949-452-0511 www.premiermag.com/pdf/pmsm15.pdf

1MΩ RD 1500Ω

R

C

DISCHARGE

RESISTANCE

STORAGE

s

CAPACITOR

HIGH-

VOLTAGE

DC

SOURCE

CHARGE-CURRENT-

LIMIT RESISTOR

C

100pF

DEVICE
UNDER

TEST

+3V to +5V, 2500V

RMS

Isolated RS-485/RS-422

Transceivers with ±15kV ESD Protection

______________________________________________________________________________________ 23

MAX3535E/MXL1535E

Machine Model

The Machine Model for ESD tests all pins using a
200pF storage capacitor and zero discharge resis­tance. 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 excel­lent 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 com­bined. 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 sys­tem can tolerate a 25% data skew, (the difference
between t

PLH1

and t

PHL1

), 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 interfer­ence 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.

Figure 15. Human Body Current Waveform

Figure 16. Data Skew vs. Data Rate Graph

IP 100%

90%

AMPERES

36.8%

10%

0

0

t

RL

TIME

t

DL

CURRENT WAVEFORM

PEAK-TO-PEAK RINGING

I

r

(NOT DRAWN TO SCALE)

50

45

40

35

30

25

20

DATA SKEW (%)

15

10

DATA SKEW vs. DATA RATE

TYP SKEW
MAX SKEW

5

0

0 500 750250 1000 1250 1500 1750 2000

DATA RATE (kbps)

MAX3535E/MXL1535E

+3V to +5V, 2500V

RMS

Isolated RS-485/RS-422

Transceivers with ±15kV ESD Protection

24 ______________________________________________________________________________________

Chip Information

PROCESS: BiCMOS

TRANSISTOR COUNT: 7379

Typical Application Circuit

ST1

+3.3V

V

CC1

0.1μF

μC

10μF

RO1

RE

DE

DI

ST2 V

TRANSFORMER

DRIVER

TGM-240

1/2

BAT54C

10μF

1/2

BAT54C

GND2

VOLTAGE

REGULATOR

0.1μF

RECEIVER

DRIVER

V

CC2

CONTROL GROUND

RS-485 GROUND

CC2

A

B

RO2

Y

Z

MAX3535E

GND1

BARRIER

TRANSCEIVER

ISOLATION BARRIER

BARRIER

TRANSCEIVER

SLO

+3V to +5V, 2500V

RMS

Isolated RS-485/RS-422

Transceivers with ±15kV ESD Protection

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________

25

© 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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

.)

MAX3535E/MXL1535E

28L 16L SOIC.EPS