MAXIM MAX3158 Technical data

General Description

The MAX3158 is a high CMRR RS-485/RS-422 data-com­munications interface providing ±60V isolation in a
hybrid microcircuit. A single +5V supply on the logic side
powers both sides of the interface, with external 100V
capacitors transferring power from the logic side to the
isolated side. Each MAX3158 contains one transmitter
and one receiver and is guaranteed to operate at data
rates up to 250kbps. Drivers are short-circuit current lim­ited and protected against excessive power dissipation
by thermal shutdown circuitry that places the driver out­puts into a high-impedance state. The receiver input has
a fail-safe feature that guarantees a logic-high receiver
output if the inputs are open, shorted, or connected to a
terminated transmission line with all drivers disabled.

The MAX3158 typically draws 25mA of supply current
when unloaded or when fully loaded with the driver dis­abled. Supply current drops to 25µA when the device is
placed in shutdown mode. The device is pin selectable
between half- and full-duplex mode and also features
an independently programmable receiver and transmit­ter output phase through separate pins. The MAX3158
is a low-cost replacement for opto-isolated trans­ceivers. For fully isolated RS-485/RS-422 transceivers,
refer to the MAX1480 family data sheet.

________________________Applications

Industrial Controls Telecommunications

Level Translators Local Area Networks

Features

♦ ±60V Isolated Data Interface

♦ +5V Single Supply

♦ Low-Cost Replacement for Opto-Isolated

Transceivers

♦ True Fail-Safe Receiver While Maintaining

EIA/TIA-485 Compliance

♦ Pin-Selectable Full/Half-Duplex Operation

♦ Phase Controls to Correct for Twisted-Pair

Reversal

♦ 25µA Low-Power Shutdown Mode

♦ Thermal Shutdown for Driver Overload Protection

♦ 28-Pin SSOP Package

♦ Slew-Rate-Limited Reduced EMI

MAX3158

High CMRR RS-485 Transceiver

with ±60V Isolation

________________________________________________________________ Maxim Integrated Products 1

Typical Operating Circuit

19-2778; Rev 0; 2/03

Ordering Information

Pin Configurations appear at end of data sheet.

PART TEMP RANGE

PIN-PACKAGE

MAX3158CAI 0°C to +70°C 28 SSOP
MAX3158CPI 0°C to +70°C 28 PDIP
MAX3158EAI -40°C to +85°C 28 SSOP
MAX3158EPI -40°C to +85°C 28 PDIP

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.

V

CC

0.1µF

MICRO

V

CC

H/F
TXP
RXP

DE

MAX3158

DI
RE
RO

GND

C1HI C2LO C2HIC1LO

C1

0.047µFC20.047µF

ISOVCC

A
B
Y

Z
YR
ZR
AR
BR

ISOCOM

C3
1µF

RS-485

NODE

REMOTE GND

10nF

RT = 100Ω

RG

±60V

C4

GND OFFSET

REMOTE MICRO

MAX3158

High CMRR RS-485 Transceiver
with ±60V Isolation

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

(All voltages referenced to GND, unless otherwise noted.)

ELECTRICAL CHARACTERISTICS

(VCC= +5V ±5%, YR = ZR = AR = BR = ISOCOM, C1 = C2 = 0.047µF, C3 = C4 = 1µF, TA= T

MIN

to T

MAX

, unless otherwise noted.

Typical values are at V

CC

= +5V and TA= +25°C.) (Note 1)

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.

Supply Voltage (VCC).............................................................+7V

Cable Ground (ISOCOM) ....................................................±75V

Isolated Supply ISOVCC Relative to Cable Ground

(ISOCOM) ...........................................................................+7V

Digital Input, Output Voltage

(DI, DE, RE, TXP, RXP, RO).....................-0.3V to (V

CC

+ 0.3V)

Digital Inputs (H/F) Relative to Cable Ground

(ISOCOM) .........................................-0.3V to (ISOVCC + 0.3V)

Driver Output Voltage (Y, Z) Relative to Cable Ground

(ISOCOM)............................................................-8V to +12.5V

Receiver Input Voltage (A, B) Relative to Cable Ground

(ISOCOM)............................................................-8V to +12.5V

Termination Connections (YR, ZR, AR, BR) Relative to Cable

Ground (ISOCOM)...............................................-8V to +12.5V

Charge-Pump Capacitance Low

(C1LO, C2LO) .........................................-0.3V to (V

CC

+ 0.3V)

Charge-Pump Capacitance High (C1HI, C2HI) Relative

to Cable Ground (ISOCOM) .............-0.3V to (ISOVCC + 0.3V)

Continuous Power Dissipation (T

A

= +70°C)

28-Pin SSOP (derate 10.8mW/°C above +70°C) ..........860mW

28-Pin PDIP (derate 14.3mW/°C above +70°C)..........1143mW

Operating Temperature Ranges

MAX3158C_I .......................................................0°C to +70°C

MAX3158E_I ....................................................-40°C to +85°C

Junction Temperature......................................................+150°C

Storage Temperature Range ............................-65°C to +160°C

Lead Temperature (soldering, 10s) ................................+300°C

DRIVER

Differential Driver Output,
No Load

Differential Driver Output,
Loaded

Change in Magnitude of
Differential Output Voltage
(Note 2)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

V

V

∆V

OD1

OD2

Figure 1, R = 10MΩ 6V

Figure 1, R = 50Ω (RS-422) 2.0

Figure 1, R = 27Ω (RS-485) 1.5

Figure 1, R = 50Ω or R = 27Ω 0.2 V

OD

V

Driver Common-Mode Voltage V

Change in Magnitude of
Common-Mode Voltage
(Note 2)

Input High Voltage V

Input Low Voltage V

DI Input Hysteresis V

OC

∆V

HYS

Figure 1, R = 50Ω or R = 27Ω,

relative to ISOCOM

V

OC

Figure 1, R = 50Ω or R = 27Ω 0.2 V

OC

DE, DI, RE, TXP, RXP, relative to GND,

IH

H/F relative to ISOCOM

DE, DI, RE, TXP, RXP, relative to GND,

IL

H/F relative to ISOCOM

2.0 V

100 mV

3.5 V

0.8 V

MAX3158

High CMRR RS-485 Transceiver

with ±60V Isolation

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VCC= +5V ±5%, YR = ZR = AR = BR = ISOCOM, C1 = C2 = 0.047µF, C3 = C4 = 1µF, TA= T

MIN

to T

MAX

, unless otherwise noted.

Typical values are at V

CC

= +5V and TA= +25°C.) (Note 1)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Input Current

Input Current (A and B) I

Output Leakage (Y and Z)
Full Duplex

Driver Short-Circuit Output
Current (Note 3)

RECEIVER

Receiver Differential Threshold
Voltage

Receiver Input Hysteresis ∆V

Receiver Output High Voltage V

Receiver Output Low Voltage V

Three-State Output Current at
Receiver

Receiver Input Resistance R

Receiver Output Short-Circuit
Current

SUPPLY CURRENT

Supply Current I

Supply Current in Shutdown
Mode

Maximum Ground Differential ∆V

I

I

IN1

IN2

DE, DI, RE ±2
H/F, TXP, RXP internal pulldown 10 40

DE = GND, VCC = GND or 5.25V, -7V ≤ (VIN ­V

IN3

DE = GND, VCC = GND or 5.25V, -7V ≤ (VIN ­V

DE = GND, VCC = GND or 5.25V, -7V ≤ (VIN -

I

V

O

DE = GND, VCC = GND or 5.25V, -7V ≤ (VIN ­V

I

OSD1

I

OSD2

V

OH

I

OZR

V

V

-7V ≤ VCM - V

TH

TH

IO = -4mA, VID = -50mV V CC - 1.5 V

IO = 4mA, VID = -200mV 0.4

OL

0.4V ≤ VO ≤ 2.4V ±1µA

-7V ≤ VCM - V
ISOCOM

IN

-7V ≤ VCM - V
BR open

I

OSR

CC

I

SHDN

GND

0V ≤ VRO ≤ V

No load, RE = DE = DI = GND or V
DE = GND, RE = VCC, V
DE = GND, RE = VCC, V

DE = GND, RE = VCC,
| ISOCOM leakage | ≤ 650µA

) ≤ +12V, AR = BR = ISOCOM

ISOCOM

) ≤ +12V, AR open, BR open

ISOCOM

) ≤ +12V, YR = ZR = ISOCOM

ISOCOM

) ≤ +12V, YR open, ZR open

ISOCOM

ISOCOM

ISOCOM

- 7V ≤ V

- 7V ≤ V

CC

≤ V

OUT

≤ V

OUT

≤ +12V -200 -125 -50 m V

ISOCOM

≤ +12V, AR = BR =

ISOCOM

≤ +12V, AR open,

ISOCOM

ISOVCC

+ 12V 250

ISOCOM

CC

= GND 25 60

ISOCOM

ISOCOM

= ±60V ±650

-5.0 +8.0

-0.58 +1.0

-5.0 +8.0

-0.58 +1.0

-250

25 mV

1.5

12

±7 ±100 mA

25 85 mA

±60 V

µA

mA

mA

mA

V

kΩ

µA

MAX3158

High CMRR RS-485 Transceiver
with ±60V Isolation

4 _______________________________________________________________________________________

SWITCHING CHARACTERISTICS

(VCC= +5V ±5%, YR = ZR = AR = BR = ISOCOM, C1 = C2 = 0.047µF, C3 = C4 = 1µF. Typical values are at VCC= +5V and TA= +25°C.)

Note 1: All currents into the device are positive; all currents out of the device are negative. All voltages are referred to device

ground unless otherwise noted.

Note 2: ∆V

OD

and ∆VOCare the changes in VODand VOC, respectively, when the DI input changes state.

Note 3: Current level applies to peak current just prior to foldback-current limiting.
Note 4: The device is put into shutdown by bringing RE high and DE low. If the enable inputs are in this state for less than 50ns,

the device is guaranteed not to enter shutdown. If the enable inputs are in this state for at least 700ns, the device is guaran­teed to have entered shutdown.

Driver Input to Output

Driver Output Skew
| t

Driver Rise or Fall Time tDR, t

Maximum Data Rate f

Driver Enable to Output High t

Driver Enable to Output Low t

Driver Disable Time from Low t

Driver Disable Time from High t

Receiver Input to Output

Differential Receiver Skew
| t

Receiver Enable to Output Low t

Receiver Enable to Output High t

Receiver Disable Time from Low t

Receiver Disable Time from High t

Time to Shutdown t

Driver Enable from Shutdown to
Output High

Driver Enable from Shutdown to
Output Low

Receiver Enable from Shutdown
to Output High

Receiver Enable from Shutdown
to Output Low

Charge-Pump Oscillating
Frequency

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

DPLH

RPLH

- t

- t

DPHL

RPHL

t

DPLH

t

DPHL

t

|

|

DSKEW

MAX

DZH

DZL

DLZ

DHZ

t

RPLH

t

RPHL

t

RSKEW

RZL

RZH

RLZ

RHZ

SHDN

t

DZH

(SHDN)

t

DZL

(SHDN)

t

RZH

(SHDN)

t

RZL

(SHDN)

f

OSC

Figures 3 and 5, R
C

= CL2 = 100pF

L1

Figures 3 and 5, R
C

= CL2 = 100pF

L1

Figures 3 and 5, R
C

= CL2 = 100pF

L1

Figures 3 and 5, R

DF

C

= CL2 =100pF

L1

Figures 4 and 6, CL = 100pF, S2 closed 3500 ns

Figures 4 and 6, CL = 100pF, S1 closed 3500 ns

Figures 4 and 6, CL = 15pF, S1 closed 300 ns

Figures 4 and 6, CL = 15pF, S2 closed 300 ns

,

Figures 7 and 9; | VID | ≥ 2.0V 440 600 ns

Figures 7 and 9; | VID | ≥ 2.0V 20 ns

Figures 2 and 8, CL = 100pF, S1 closed 20 50 ns

Figures 2 and 8, CL = 100pF, S2 closed 20 50 ns

Figures 2 and 8, C

Figures 2 and 8, C

(Note 4) 50 200 700 ns

Figures 4 and 6, C

Figures 4 and 6, C

Figures 2 and 8, C

Figures 2 and 8, C

= 54Ω,

DIFF

DIFF

DIFF

DIFF

= 54Ω,

= 54Ω,

= 54Ω,

400 1400 2000

400 1400 2000

200 1200 2200 ns

250 kbps

= 100pF, S1 closed 200 500 ns

L

= 100pF, S2 closed 200 500 ns

L

= 15pF, S2 closed 0.2 1 ms

L

= 15pF, S1 closed 0.2 1 ms

L

= 100pF, S2 closed 0.2 1 m s

L

= 100pF, S1 closed 0.2 1 ms

L

1.3 MHz

250 ns

ns

MAX3158

High CMRR RS-485 Transceiver

with ±60V Isolation

_______________________________________________________________________________________ 5

Typical Operating Characteristics

(VCC= +5V, YR = ZR = AR = BR = ISOCOM, C1 = C2 = 0.047µF, C3 = 1µF, C4 = 10nF, TA= +25°C, unless otherwise noted.)

SUPPLY CURRENT vs. TEMPERATURE

160

140

RL = 54Ω

120

100

80

60

SUPPY CURRENT (mA)

40

NO LOAD

20

0

-40 -20 -10 0 10 20 30-30 40 50 60 70 80 90
TEMPERATURE (°C)

MAX3158 toc01

-100

SUPPY CURRENT (µA)

-200

-300

RECEIVER OUTPUT CURRENT

vs. RECEIVER OUTPUT HIGH VOLTAGE

20

18

16

14

12

10

8

6

OUTPUT CURRENT (mA)

4

2

0

0 2.0 2.51.51.00.5 3.0 3.5 4.0 4.5 5.0 5.5

OUTPUT HIGH VOLTAGE (V)

MAX3158 toc04

OUTPUT LOW VOLTAGE (V)

SHUTDOWN SUPPLY CURRENT

vs. TEMPERATURE

300

V

= -50V

ISOCOM

200

100

0

V

= 0V

ISOCOM

V

= +50V

ISOCOM

-40 -20 -10 0 10 20 30-30 40 50 60 70 80 90
TEMPERATURE (°C)

RECEIVER OUTPUT LOW VOLTAGE

vs. TEMPERATURE

0.50

IRO = 8mA

0.45

0.40

0.35

0.30

0.25

0.20

0.15

0.10

0.05

0

-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)

MAX3158 toc02

OUTPUT CURRENT (mA)

4.40

4.35

MAX3158 toc05

4.30

4.25

4.20

4.15

4.10

OUTPUT VOLTAGE (V)

4.05

4.00

3.95

RECEIVER OUTPUT CURRENT

vs. RECEIVER OUTPUT LOW VOLTAGE

45

40

35

30

25

20

15

10

5

0

021 3456

OUTPUT LOW VOLTAGE (V)

RECEIVER OUTPUT HIGH VOLTAGE

vs. TEMPERATURE

IRO = -8mA

-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)

MAX3158 toc03

MAX3158 toc06

DRIVER OUTPUT CURRENT

vs. DRIVER OUTPUT LOW VOLTAGE

160

140

120

100

80

60

OUTPUT CURRENT (mA)

40

20

0

042 6 8 101214

OUTPUT VOLTAGE (V)

0

-10

-20

MAX3158 toc07

-30

-40

-50

-60

-70

-80

OUTPUT CURRENT (mA)

-90

-100

-110

-120

DRIVER OUTPUT CURRENT

vs. DRIVER OUTPUT HIGH VOLTAGE

MAX3158 toc08

-8 -4-6 -20246
OUTPUT HIGH VOLTAGE (V)

DRIVER OUTPUT CURRENT

vs. DIFFERENTIAL OUTPUT VOLTAGE

100

10

1

OUTPUT CURRENT (mA)

0.1

0.01
01 32546

DIFFERENTIAL OUTPUT VOLTAGE (V)

MAX3158 toc09

MAX3158

High CMRR RS-485 Transceiver
with ±60V Isolation

6 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(VCC= +5V, YR = ZR = AR = BR = ISOCOM, C1 = C2 = 0.047µF, C3 = 1µF, C4 = 10nF, TA= +25°C, unless otherwise noted.)

DRIVER DIFFERENTIAL OUTPUT

VOLTAGE vs. TEMPERATURE

1.98
RL = 54Ω

1.96

1.94

1.92

1.90

1.88

1.86

OUTPUT VOLTAGE (V)

1.84

1.82

1.80

-40 0-20 20 40 60 80
TEMPERATURE (°C)

MAX3158 toc10

PROPAGATION DELAY (ns)

RECEIVER PROPAGATION DELAY

vs. TEMPERATURE

490

480

470

460

450

440

430

420

410

-40 0-20 20 40 60 80
TEMPERATURE (°C)

MAX3158 toc11

DRIVER PROPAGATION DELAY

vs. TEMPERATURE

1.52
RL = 54Ω

1.50

1.48

1.46

1.44

1.42

1.40

1.38

PROPAGATION DELAY (µs)

1.36

1.34

1.32

-40 0-20 20 40 60 80
TEMPERATURE (°C)

MAX3158 toc12

DRIVER ENABLE TIME

vs. TEMPERATURE

1.500

1.475

1.450

1.425

1.400

1.375

DRIVER ENABLE TIME (µs)

1.350

1.325

1.300

-40 0-20 20 40 60 80 100
TEMPERATURE (°C)

DRIVER PROPAGATION DELAY

0V

0V

MAX3158 toc16

250

MAX3158 toc13

200

150

100

DRIVER DISABLE TIME (ns)

50

DI

2V/div

VY - VZ

DRIVER DISABLE TIME

vs. TEMPERATURE

0

-40 0-20 20 40 60 80 100
TEMPERATURE (°C)

POWER-UP DELAY

= 0V)

(V

ISOCOM

MAX3158 toc17

MAX3158 toc14

DE
10V/div

VY
5V/div

RECEIVER PROPAGATION DELAY

0V

0V

POWER-UP DELAY

(V

ISOCOM

0V

-50V

2µs/div

= -50V)

MAX3158 toc15

MAX3158 toc18

V

- V

A

5V/div

R

O

DE
5V/div

VY
10V/div

B

R

= 54Ω

DIFF

CL1 = CL2 = 100pF

2µs/div

40µs/div

100µs/div

MAX3158

High CMRR RS-485 Transceiver

with ±60V Isolation

_______________________________________________________________________________________ 7

Test Circuits and Timing Diagrams

Figure 1. Driver DC Test Load

Figure 3. Driver Timing Test Circuit

Figure 2. Receiver Enable/Disable Timing Test Load

Figure 4. Driver Enable/Disable Timing Test Load

Typical Operating Characteristics (continued)

(VCC= +5V, YR = ZR = AR = BR = ISOCOM, C1 = C2 = 0.047µF, C3 = 1µF, C4 = 10nF, TA= +25°C, unless otherwise noted.)

+50V

POWER-UP DELAY

= +50V)

(V

ISOCOM

0V

100µs/div

MAX3158 toc19

DE
5V/div

VY
10V/div

MAXIMUM COMMON-MODE VOLTAGE TO

GROUND vs. COMMON-MODE FREQUENCY

70

MAXIMUM COMMON-MODE
VOLTAGE TO ISOCOM

60

50

40

30

20

10

COMMON-MODE VOLTAGE TO GROUND (V)

0

0.1 1 10

COMMON-MODE VOLTAGE TO
ISOCOM = 7V PEAK

COMMON-MODE FREQUENCY (kHz)

MAX3158 toc20

Y

R

V

OD

R

V

OC

3V

DE

DI

Y

V

ID

Z

C

L1

R

DIFF

C

L2

Z

RECEIVER

OUTPUT

TEST POINT

C

100pF

L

1kΩ

1kΩ

S1

S2

V

CC

OUTPUT

UNDER TEST

500Ω

C

L

S1

S2

V

CC

MAX3158

High CMRR RS-485 Transceiver
with ±60V Isolation

8 _______________________________________________________________________________________

Figure 5. Driver Propagation Delays

Figure 6. Driver Enable and Disable Times

Figure 7. Receiver Propagation Delays

Figure 8. Receiver Enable and Disable Times

Figure 9. Receiver Propagation Delay Test Circuit

Test Circuits and Timing Diagrams (continued)

3V

DI

V

DIFF

1.5V

0V

Z

V

O

Y

1/2 V

O

V

O

0V

-V

10%

O

t

DR

90%

3V

DE

Y, Z

V

Y, Z

1.5V 1.5V

0V

t

DZL(SHDN)

OL

0V

2.3V

2.3V

t

DZH(SHDN)

t

DPLH

V

DIFF

t

DSKEW = | tDPLH

OUTPUT NORMALLY LOW

OUTPUT NORMALLY HIGH

t

= V (Y) - V (Z)

- t

, t

DZL

, t

DZH

DPHL

DPHL

t

DLZ

t

DHZ

t

1.5V

1/2 V

O

90%

DF

|

10%

3V

RE

0V

V

CC

RO

RO

0V

1.5V 1.5V

t

, t

RZL(SHDN)

1.5V

OUTPUT NORMALLY LOW

OUTPUT NORMALLY HIGH

1.5V

t

, t

RZH(SHDN)

RZL

RZH

t

RLZ

t

RHZ

V

V

OL

OH

+ 0.5V

- 0.5V

V

V

OL

OH

+ 0.5V

- 0.5V

ATE

B

V

ID

R

R

A

RECEIVER
OUTPUT

V

OH

-1V

RO

V

OL

A

1V

B

1.5V 1.5V

t

t

RSKEW = | tRPLH

RPHL

INPUT

OUTPUT

- t

RPHL

t

RPLH

|

MAX3158

High CMRR RS-485 Transceiver

with ±60V Isolation

_______________________________________________________________________________________ 9

Pin Description

PIN

SSOP

PDIP

NAME FUNCTION

12 RO

Receiver Output. When RE is low and A - B > -50mV, RO will be high; if A - B ≤ -200mV,
RO will be low.

23 RE Receiver Output Enable. Drive RE low to enable RO.

3 4 DE Driver Output Enable. Drive DE high to enable driver outputs.

45 DI

Driver Input. With DE high, a low on DI forces the noninverting output low and the inverting
output high; with DI high, outputs reverse.

5 6 C1LO Connect to the negative terminal of C1 (0.047µF, 100V).

6, 7,

12, 22,

23

1, 12,

14, 15,

28

N.C. No Connection. Not internally connected.

8 7 C1HI Connect to the positive terminal of C1 (0.047µF, 100V).

9 8 ISOVCC

Internally generated power-supply voltage, referenced to the cable ground (ISOCOM).
Connect a 1µF capacitor to ISOCOM.

10 9 H/F

Half/Full-Duplex Selector Pin. Leave open, or connect to ISOCOM to select Full Duplex,
or connect to ISOVCC to select Half Duplex.

11 10 ZR

Connect to ISOCOM for a 1.5kΩ input impedance on Z. Leave open for a 12kΩ input
impedance on Z.

13 11 YR

Connect to ISOCOM for a 1.5kΩ input impedance on Y. Leave open for a 12kΩ input
impedance on Y.

14 13

Cable Ground

15 16 Z Inverting Driver Output (and Inverting Receiver Input in Half-Duplex Mode)

16 17 Y Noninverting Driver Output (and Noninverting Receiver Input in Half-Duplex Mode)

17 18 B Inverting Receiver Input in Full-Duplex Mode

18 19 A Noninverting Receiver Input in Full-Duplex Mode

19 20 BR

Connect to ISOCOM for a 1.5kΩ input impedance on B. Leave open for a 12kΩ input
impedance on B.

20 21 AR

Connect to ISOCOM for a 1.5kΩ input impedance on A. Leave open for a 12kΩ input
impedance on A.

21 22 C2HI Connect to the positive terminal of C2 (0.047µF, 100V).

24 23 C2LO Connect to the negative terminal of C2 (0.047µF, 100V).

25 24 GND Ground

26 25 TXP

Transmitter Phase. Leave open, or connect to GND for normal transmitter polarity, or connect
to V

CC

to invert the transmitter polarity.

27 26 RXP

Receiver Phase. Leave open, or connect to GND for normal receiver polarity, or connect to
V

CC

to invert the receiver polarity.

28 27 V

CC

+4.75V to +5.25V Positive Supply. Connect a 0.1µF capacitor to GND.

ISOCOM

MAX3158

High CMRR RS-485 Transceiver
with ±60V Isolation

10 ______________________________________________________________________________________

Detailed Description

The MAX3158 is a high CMRR RS-485/RS-422 data­communications interface providing ±60V isolation in a
hybrid microcircuit. A single +5V supply on the logic
side powers both sides of the interface, with external
100V capacitors transferring power from the logic side
to the isolated side (see Block Diagram). The MAX3158
typically draws 25mA of supply current when unloaded
or when fully loaded with the driver disabled. Supply
current drops to 25µA when the device is placed in
shutdown mode (see Low-Power Shutdown Mode sec­tion). The MAX3158 transceiver for RS-485/RS-422
communication contains one driver and one receiver.

This device features fail-safe circuitry, which guaran­tees a logic-high receiver output when the receiver
inputs are open or shorted, or when they are connected
to a terminated transmission line with all drivers dis­abled (see Fail-Safe section). The MAX3158 is selec­table between half- and full-duplex communication by
connecting a selector pin to ISOVCC or ISOCOM,
respectively. Drivers are output short-circuit current lim­ited. Thermal shutdown circuitry protects drivers
against excessive power dissipation. When activated,
the thermal shutdown circuitry places the driver outputs
into a high-impedance state. The device also features
independently programmable receiver and transmitter
output phase through separate pins. The MAX3158 is a
low-cost replacement for opto-isolated transceivers.

Fail-Safe

The MAX3158 guarantees a logic-high receiver output
when the receiver inputs are shorted or open, or when
they are connected to a terminated transmission line with
all drivers disabled. The receiver threshold is fixed
between -50mV and -200mV. If the differential receiver
input voltage (A - B) is greater than or equal to -50mV,
RO is logic high. If A - B is less than or equal to -200mV,
RO is logic low. In the case of a terminated bus with all
transmitters disabled, the receiver’s differential input volt­age is pulled to 0V by the termination. With the receiver
thresholds of the MAX3158, this results in a logic high
with a 50mV minimum noise margin. Unlike competitor’s
fail-safe devices, the -50mV to -200mV threshold com­plies with the ±200mV EIA/TIA-485 standard.

MAX3158 Programming

The MAX3158 has several programmable operating
modes. Occasionally, twisted-pair lines are reversed.
The MAX3158 has two pins that invert the phase of the
driver and the receiver to correct for this problem. For
normal operation, drive TXP and RXP low, connect
them to ground, or leave them unconnected (internal
pulldown). To invert the driver phase, drive TXP high or

connect it to VCC. To invert the receiver phase, drive
RXP high or connect it to VCC. Note that the receiver
threshold is positive when RXP is high.

The MAX3158 can operate in full- or half-duplex mode.
Connect H/F to ISOCOM for full-duplex mode, and con­nect it to ISOVCC for half-duplex operation. In half­duplex mode, the receiver inputs are switched to the
driver outputs, connecting outputs Y and Z to inputs A
and B, respectively. In half-duplex mode, the internal
full-duplex receiver input resistors are still connected to
pins A and B.

Low-Power Shutdown Mode

The low-power shutdown mode is initiated by bringing
both RE high and DE low. In shutdown, this device typi-
cally draws only 25µA of supply current, and no power
is transferred across the isolation capacitors in this
mode. RE and DE may be driven simultaneously; the
parts are guaranteed not to enter shutdown if RE is
high and DE is low for less than 50ns. If the inputs are
in this state for at least 700ns, the parts are guaranteed
to enter shutdown. Enable times t_ZHand t_ZLin the
Switching Characteristics table assume the part was
not in a low-power shutdown state. Enable times
t_

ZH

(SHDN)

and t_

ZL

(SHDN)

assume the parts were shut
down. It takes drivers and receivers longer to become
enabled from low-power shutdown mode t_

ZH

(SHDN)

,

t_

ZL

(SHDN)

than from driver/receiver-disable mode

(t_ZH, t_ZL).

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 whole common-mode voltage range (see
Typical Operating Characteristics). The second, a ther­mal shutdown circuit, forces the driver outputs into a
high-impedance state if the die temperature becomes
excessive—typically around +150°C.

Applications Information

Capacitor and Grounding Resistor

Selection

The value for the charge-pump capacitors C1 and C2
should be between 47nF and 100nF. Smaller values will
result in insufficient supply voltage on the isolated side.
Larger values are allowed but will not result in better
charge-pump capacity. The values for C1 and C2, as
well as that of C4, determine the maximum frequency
and amplitude of the voltage difference (under operat­ing conditions) between the local and isolated ground.
Besides the capacitor values, this maximum frequency

MAX3158

High CMRR RS-485 Transceiver

with ±60V Isolation

______________________________________________________________________________________ 11

and amplitude are also determined by the resistance
between the remote ground and the ISOCOM pin. The
receiver input resistors will cause the isolated common
voltage to go to the mean voltage of the receiver inputs,
which will be a direct function of the remote ground
potential. The receiver input resistance and the capaci­tors C1, C2, and C4 set up a time constant that limits
how fast the ISOCOM pin can follow variations in the
remote ground voltage. Connecting YR and ZR in half­duplex operation, or AR and BR in full-duplex operation,
to ISOCOM results in a relatively low input impedance of
the MAX3158 receiver inputs (2kΩ). This allows for a
60Hz sine wave with a 60V maximum amplitude (see
Typical Operating Characteristics). If YR, ZR, AR, and
BR are left open, the receiver input impedance is 12kΩ
allowing up to 32 transceivers on the bus. To guarantee
the same low time constant under those conditions, use
a shielded cable with a 1kΩ resistor connected between

the shield and ISOCOM. Using a lower value for this
resistor is not recommended because this could trigger
a holding current in the internal ESD protection device if
the ±75V isolation limit is exceeded.

A single point hard-ground connection for the shield is
recommended.

Communication Between

Two MAX3158s

If two MAX3158 devices are used to communicate with
each other, one of the devices must have ISOCOM
connected to local ground. Failure to do so will result in
floating ISOCOM pins, with both devices trying to adapt
to the isolated ground of the other.

Chip Information

TRANSISTOR COUNT: 1309

Block Diagram

TXP

RXP

V

DI

DE

RO

RE

MAX3158

CC

OSC

POWER

Y

Z

YR

ZR

A

B

AR

BR

H/F

H/F

ISOVCC

GND C1L C2L C1H C2H ISOCOM

MAX3158

High CMRR RS-485 Transceiver
with ±60V Isolation

12 ______________________________________________________________________________________

Pin Configurations

TOP VIEW

RO

RE

DE

DI

C1LO

N.C.

N.C.

C1HI

ISOVCC

H/F

ZR

N.C.

YR

ISOCOM

1

2

3

4

5

6

7

8

9

10

11

12

13

14

MAX3158

28 SSOP

28

V

CC

27

RXP

26

TXP

25

GND

24

C2LO

23

N.C.

22

N.C.

21

C2HI

20

AR

19

BR

18

A

17

B

16

Y

15

Z

N.C.

C1LO

C1HI

ISOVCC

H/F

N.C.

ISOCOM

N.C.

1

2

RO

3

RE

4

DE

5

DI

ZR

YR

MAX3157MAX3158

6

7

8

9

10

11

12

13

14

28

N.C.

V

27

CC

RXP

26

25

TXP

GND

24

C2LO

23

C2HI

22

AR

21

BR

20

A

19

B

18

Y

17

Z

16

N.C.

15

28 PDIP

MAX3158

High CMRR RS-485 Transceiver

with ±60V Isolation

______________________________________________________________________________________ 13

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

.)

e

D

12

MAX

0.078

0.008

0.015

0.008

0.212

0.311

0.037

8∞

MILLIMETERS

MAX

MIN

1.73 1.99

0.05

0.21

0.25

0.38

0.09

0.20

5.20

5.38

0.65 BSC

7.90

7.65

0.63

0.95

0∞

8∞

MAX

0.249

0.249

0.289

0.328

0.407

MILLIMETERS

MAX

MIN

6.07

6.33

6.07

6.33

7.07

7.33

8.07

8.33

10.07

10.33

N

14L
16L

20L

24L

28L

C

INCHES

MIN

D

0.239

D

0.239

D

0.278

D

0.317

0.397

D

INCHES

DIM

MIN

A

0.068

A1

0.002

B

0.010

C

HE

N

A

B

A1

D

E

e

H

L

0.004

SEE VARIATIONS

0.205

0.0256 BSC

0.301

0.025

0∞

L

SSOP.EPS

NOTES:

1. D&E DO NOT INCLUDE MOLD FLASH.

2. MOLD FLASH OR PROTRUSIONS NOT TO EXCEED .15 MM (.006").

3. CONTROLLING DIMENSION: MILLIMETERS.

4. MEETS JEDEC MO150.

5. LEADS TO BE COPLANAR WITHIN 0.10 MM.

PROPRIETARY INFORMATION

TITLE:

PACKAGE OUTLINE, SSOP, 5.3 MM

21-0056

REV.DOCUMENT CONTROL NO.APPROVAL

1

C

1

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.

14 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

© 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

MAX3158

High CMRR RS-485 Transceiver
with ±60V Isolation

Package Information (continued)

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages

.)

PDIPN.EPS