Datasheet LTC1334 Datasheet (Linear Technology)

FEATURES

LTC1334

Single 5V RS232/RS485

Multiprotocol Transceiver

U

DESCRIPTIO

■

Four RS232 Transceivers or Two RS485
Transceivers on One Chip

■

Operates from a Single 5V Supply

■

Withstands Repeated ±10kV ESD Pulses

■

Uses Small Charge Pump Capacitors: 0.1µF

■

Low Supply Current: 8mA Typical

■

10µA Supply Current in Shutdown

■

Self-Testing Capability in Loopback Mode

■

Power-Up/Down Glitch-Free Outputs

■

Driver Maintains High Impedance in Three-State,
Shutdown or with Power Off

■

Thermal Shutdown Protection

■

Receiver Inputs Can Withstand ±25V

U

APPLICATIO S

■

Low Power RS485/RS422/RS232/EIA562 Interface

■

Software-Selectable Multiprotocol Interface Port

■

Cable Repeaters

■

Level Translators

The LTC®1334 is a low power CMOS
ceiver featuring two

reconfigurable interface ports. It can

bidirectional trans-

be configured as two RS485 differential ports, as two dual
RS232 single-ended ports or as one RS485 differential
port and one dual RS232 single-ended port. An onboard
charge pump requires four 0.1µF capacitors to generate
boosted positive and negative supplies, allowing the RS232
drivers to meet the RS232 ±5V output swing requirement
with only a single 5V supply. A shutdown mode reduces
the ICC supply current to 10µA.

The RS232 transceivers are in full compliance with RS232
specifications. The RS485 transceivers are in full compli­ance with RS485 and RS422 specifications. All interface
drivers feature short-circuit and thermal shutdown pro­tection. An enable pin allows RS485 driver outputs to be
forced into high impedance, which is maintained even
when the outputs are forced beyond supply rails or power
is off. Both driver outputs and receiver inputs feature
±10kV ESD protection. A loopback mode allows the driver
outputs to be connected back to the receiver inputs for
diagnostic self-test.

, LTC and LT are registered trademarks of Linear Technology Corporation.

TYPICAL APPLICATIO

12

3

LTC1334

DR IN

DR IN
DR IN

26
24

23

22

21

5V

20

5V

19
18
17
16
15

V

CC1

5V

RX OUT

DR ENABLE

RX OUT
RX OUT

U

2728

LTC1334

4
5

6
7
8
9
11
10
13
12

14

120Ω

5V
0V

ALL CAPACITORS: 0.1µF MONOLITHIC CERAMIC TYPE

RS485 INTERFACE

4000-FT 24-GAUGE TWISTED PAIR

RS232 INTERFACE

120Ω

13
12

11
10

9

5V

8

0V

4
5
6
7

14

212827

3

26
17

18

19

21
20
24
25
22
23
15

RX OUT

DR ENABLE

DR IN

5V
5V
RX OUT
RX OUT
DR IN
DR IN

V

CC2

5V

LTC1334 • TA01

1

LTC1334

A

S

(Note 1)

W

O

LUTEXI TIS

A

WUW

U

ARB

G

Supply Voltage (VCC) ............................................. 6.5V

Input Voltage

Drivers ................................... –0.3V to (VCC + 0.3V)

Receivers ............................................. – 25V to 25V

ON/OFF, LB, SEL1, SEL2 ........ –0.3V to (VCC + 0.3V)

Output Voltage

Drivers ................................................. – 18V to 18V

Receivers ............................... –0.3V to (VCC + 0.3V)

Short-Circuit Duration

Output ........................................................ Indefinite

VDD, VEE, C1+, C1–, C2+, C2–.......................... 30 sec

Operating Temperature Range

Commercial........................................... 0°C to 70°C

Industrial............................................ –40°C to 85°C

Storage Temperature Range ................ –65°C to 150°C

Lead Temperature (Soldering, 10 sec)................ 300°C

PACKAGE

+

1

C1

–

2

C1

3

V

DD

4

A1

5

B1

6

Y1

7

Z1

8

SEL1

9

SEL2

10

Z2

11

Y2

12

B2

13

A2

14

GND

G PACKAGE

28-LEAD PLASTIC SSOP

28-LEAD PLASTIC SO WIDE

T

= 125°C, θJA = 90°C/W (G)

JMAX

T

= 125°C, θJA = 56°C/W (NW)

JMAX

T

= 125°C, θJA = 85°C/W (SW)

JMAX

/

O

RDER I FOR ATIO

TOP VIEW

28-LEAD PDIP WIDE

SW PACKAGE

28

C2

27

C2

26

V

CC

25

R

B1

24

R

A1

23

DZ1/DE1

22

D

Y1

21

LB

20

ON/OFF

19

D

Y2

18

DZ2/DE2

17

R

A2

16

R

B2

15

V

EE

NW PACKAGE

+
–

ORDER PART

LTC1334CG
LTC1334CNW
LTC1334CSW
LTC1334IG
LTC1334ISW

WU

U

NUMBER

Consult factory for Military grade parts.

DC ELECTRICAL CHARACTERISTICS

The ● denotes specifications which apply over the full operating

temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, C1 = C2 = C3 = C4 = 0.1µF (Notes 2, 3)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
RS485 Driver (SEL1 = SEL2 = High)

V

OD1

V

OD2

∆V

OD

V

OC

∆VOC Change in Magnitude of Driver Common Mode Figure 1, R = 27Ω or R = 50Ω ● 0.2 V

I

OSD

I

OZD

RS232 Driver (SEL1 = SEL2 = Low)

V

O

I

OSD

Driver Inputs and Control Inputs

V

IH

V

IL

I

IN

Differential Driver Output Voltage (Unloaded) IO = 0 ● 6V
Differential Driver Output Voltage (With Load) Figure 1, R = 50Ω (RS422) ● 2.0 6 V

Figure 1, R = 27Ω (RS485) ● 1.5 6 V

Change in Magnitude of Driver Differential Figure 1, R = 27Ω or R = 50Ω ● 0.2 V
Output Voltage for Complementary Output States

Driver Common Mode Output Voltage Figure 1, R = 27Ω or R = 50Ω ● 3V

Output Voltage for Complementary Output States
Driver Short-Circuit Current –7V ≤ VO ≤ 12V, VO = High ● 35 250 mA

–7V ≤ V

Three-State Output Current (Y, Z) –7V ≤ VO ≤ 12V ● ±5 ±500 µA

Output Voltage Swing Figure 4, RL = 3k, Positive ● 5 6.5 V

Figure 4, R

Output Short-Circuit Current VO = 0V ● ±60 mA

Input High Voltage D, DE, ON/OFF, SEL1, SEL2, LB ● 2V
Input Low Voltage D, DE, ON/OFF, SEL1, SEL2, LB ● 0.8 V
Input Current D, SEL1, SEL2 ● ±10 µA

DE, ON/OFF, LB

≤ 12V, VO = Low (Note 4) ● 10 250 mA

O

= 3k, Negative ● –5 –6.5 V

L

● –4 –15 µA

2

LTC1334

DC ELECTRICAL CHARACTERISTICS

The ● denotes specifications which apply over the full operating

temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, C1 = C2 = C3 = C4 = 0.1µF (Notes 2, 3)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
RS485 Receiver (SEL1 = SEL2 = High)

V

TH

∆V

TH

I

IN

R

IN

RS232 Receiver (SEL1 = SEL2 = Low)

V

TH

∆V

TH

R

IN

Receiver Output

V

OH

V

OL

I

OSR

I

OZR

R

OB

Power Supply Generator

V

DD

V

EE

Power Supply

I

CC

Differential Input Threshold Voltage –7V ≤ VCM ≤ 12V, LTC1334C ● –0.2 0.2 V

–7V ≤ V

≤ 7V, LTC1334I ● –0.3 0.3 V

CM

Input Hysteresis VCM = 0V 70 mV
Input Current (A, B) VIN = –7V ● – 0.8 mA

= 12V ● 1.0 mA

V

IN

Input Resistance –7V ≤ VIN ≤ 12V ● 12 24 kΩ

Receiver Input Threshold Voltage Input Low Threshold ● 0.8 V

Input High Threshold

● 2.4 V

Receiver Input Hysteresis 0.6 V
Receiver Input Resistance VIN = ±10V 3 5 7 kΩ

Receiver Output High Voltage IO = –3mA, VIN = 0V, SEL1 = SEL2 = Low ● 3.5 4.6 V
Receiver Output Low Voltage IO = 3mA, VIN = 3V, SEL1 = SEL2 = Low ● 0.2 0.4 V
Short-Circuit Current 0V ≤ VO ≤ V

CC

● 785mA

Three-State Output Current ON/OFF = Low ● ±10 µA
Inactive “B” Output Pull-Up Resistance (Note 5) ON/OFF = High, SEL1 = SEL2 = High 50 kΩ

VDD Output Voltage No Load, ON/OFF = High 8.5 V

= –10mA, ON/OFF = High 7.6 V

I

DD

VEE Output Voltage No Load, ON/OFF = High – 7.7 V

= 10mA, ON/OFF = High –6.9 V

I

EE

VCC Supply Current No Load, SEL1 = SEL2 = High ● 825 mA

No Load Shutdown, ON/OFF = 0V

● 10 100 µA

AC ELECTRICAL CHARACTERISTICS

The ● denotes specifications which apply over the full operating

temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, C1 = C2 = C3 = C4 = 0.1µF (Notes 2, 3)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
RS232 Mode (SEL1 = SEL2 = Low)

SR Slew Rate Figure 4, RL = 3k, CL = 15pF ● 30 V/µs

t
t
t
t
t

T

PLH

PHL

PLH

PHL

Figure 4, R
Transition Time Figure 4, RL = 3k, CL = 2500pF ● 0.22 1.9 3.1 µs
Driver Input to Output Figures 4, 9, RL = 3k, CL = 15pF ● 0.6 4 µs
Driver Input to Output Figures 4, 9, RL = 3k, CL = 15pF ● 0.6 4 µs
Receiver Input to Output Figures 5, 10 ● 0.3 6 µs
Receiver Input to Output Figures 5, 10 ● 0.4 6 µs

= 3k, CL = 1000pF ● 4V/µs

L

RS485 Mode (SEL1 = SEL2 = High)

t

PLH

t

PHL

t

SKEW

tr, t

f

Driver Input to Output Figures 2, 6, RL = 54Ω, CL = 100pF ● 20 40 70 ns
Driver Input to Output Figures 2, 6, RL = 54Ω, CL = 100pF ● 20 40 70 ns
Driver Output to Output Figures 2, 6, RL = 54Ω, CL = 100pF ● 515 ns
Driver Rise and Fall Time Figures 2, 6, RL = 54Ω, CL = 100pF ● 31540 ns

3

LTC1334

AC ELECTRICAL CHARACTERISTICS

The ● denotes specifications which apply over the full operating

temperature range, otherwise specifications are at TA = 25°C. VCC = 5V, C1 = C2 = C3 = C4 = 0.1µF (Notes 2, 3)

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
RS485 Mode (SEL1 = SEL2 = High)

t

ZL

t

ZH

t

LZ

t

HZ

t

PLH

t

PHL

t

SKEW

Note 1: Absolute Maximum Ratings are those values beyond which the
safety of the device cannot be guaranteed.

Note 2: All currents into device pins are positive; all currents out of device
pins are negative. All voltages are referenced to device ground unless
otherwise specified.

Note 3: All typicals are given at VCC = 5V, C1 = C2 = C3 = C4 = 0.1µF
and T

Driver Enable to Output Low Figures 3, 7, CL = 100pF, S1 Closed ● 50 90 ns
Driver Enable to Output High Figures 3, 7, CL = 100pF, S2 Closed ● 50 90 ns
Driver Disable from Low Figures 3, 7, CL = 15pF, S1 Closed ● 50 90 ns
Driver Disable from High Figures 3, 7, CL = 15pF, S2 Closed ● 60 90 ns
Receiver Input to Output Figures 2, 8, RL = 54Ω, CL = 100pF ● 20 60 140 ns
Receiver Input to Output Figures 2, 8, RL = 54Ω, CL = 100pF ● 20 70 140 ns
Differential Receiver Skew, t

PLH

– t

 Figures 2, 8, R

PHL

= 54Ω, CL = 100pF 10 ns

L

Note 4: Short-circuit current for RS485 driver output low state folds back
above VCC. Peak current occurs around VO = 3V.

Note 5: The “B” RS232 receiver output is disabled in RS485 mode
(SEL1 = SEL2 = high). The unused output driver goes into a high
impedance mode and has a resistor to VCC. See Applications Information
section for more details.

= 25°C.

A

W

U

TYPICAL PERFORMANCE CHARACTERISTICS

Receiver Output High Voltage
vs Temperature

5.0
I

= 3mA

OUT

4.9

4.8

4.7

4.6

4.5

4.4

4.3

OUTPUT VOLTAGE (V)

4.2

4.1

4.0

–50

= 5V

V

CC

–25

0

TEMPERATURE (°C)

50

25

75

100

LTC1334 • TPC01

125

Receiver Output Low Voltage
vs Temperature

0.5
I

= 3mA

OUT

V

= 5V

CC

0.4

0.3

0.2

OUTPUT VOLTAGE (V)

0.1

0

–50

0

–25

TEMPERATURE (°C)

50

25

75

100

LTC1334 • TPC02

125

RS485 Receiver Skew
t

– t

PLH

VCC = 5V

–25

PHL

0

TEMPERATURE (°C)

20
18
16
14
12
10

TIME (ns)

8
6
4
2
0

–50

 vs Temperature

50

25

75

100

LTC1334 • TPC03

125

4

W

TEMPERATURE (°C)

–50

INPUT THRESHOLD VOLTAGE (V)

2.0

1.8

1.6

1.4

1.2

1.0

0.8
25 75

LTC1334 • TPC06

–25 0

50 100 125

INPUT HIGH

INPUT LOW

VCC = 5V

TEMPERATURE (°C)

–50

SUPPLY CURRENT (mA)

10

9
8
7
6
5
4
3
2
1
0

0

50

75

LTC1334 • TPC09

–25

25

100

125

VCC = 5V
NO LOAD
SEL 1 = SEL 2 = HIGH

U

TYPICAL PERFORMANCE CHARACTERISTICS

LTC1334

Receiver Output Current
vs Output High Voltage

20
18
16
14
12
10

8
6

OUTPUT CURRENT (mA)

4
2
0

2.0

2.5

3.5 4.0

3.0

OUTPUT VOLTAGE (V)

Charge Pump Output Voltage
vs Temperature

10

8

VDD (–10mA LOAD)

6
4
2

VCC = 5V

0
–2
–4

OUTPUT VOLTAGE (V)

–6
–8

–10

–50

–25

VDD (NO LOAD)

VEE (10mA LOAD)

VEE (NO LOAD)

0

TEMPERATURE (°C)

50

25

TA = 25°C
V

CC

75

= 5V

4.5

LTC1334 • TPC04

100

LTC1334 • TPC07

125

5.0

Receiver Output Current
vs Output Low Voltage

40

TA = 25°C

= 5V

V

35

CC

30

25

20

15

OUTPUT CURRENT (mA)

10

5

0

0 0.5

1.0 2.01.5

OUTPUT VOLTAGE (V)

Supply Current
vs Temperature (RS485)

25

VCC = 5V
NO LOAD

20

SEL 1 = SEL 2 = HIGH

15

10

SUPPLY CURRENT (mA)

5

0

–50

–25

25

0

TEMPERATURE (°C)

RS232 Receiver Input Threshold
Voltage vs Temperature

2.5

3.0

LTC1334 • TPC05

Supply Current
vs Temperature (RS232)

50

75

100

LTC1334 • TPC08

125

RS485 Driver Differential Output
Voltage vs Temperature

2.6
RL = 54Ω

2.5

2.4

2.3

2.2

2.1

2.0

1.9

1.8

DIFFERENTIAL OUTPUT VOLTAGE (V)

1.7

1.6

= 5V

V

CC

–50

–25

25

50

0

TEMPERATURE (°C)

75

100

LTC1334 • TPC10

125

RS485 Driver Differential Output
Current vs Output Voltage

70

60

50

40

30

20

10

DIFFERENTIAL OUTPUT CURRENT (mA)

0

12 5

0

DIFFERENTIAL OUTPUT VOLTAGE (V)

34

TA = 25°C

= 5V

V

CC

LTC1334 • TPC11

RS485 Driver Skew
vs Temperature

15

VCC = 5V

12

9

TIME (µs)

6

3

0

–50

–25

0

TEMPERATURE (°C)

50

25

75

100

LTC1334 • TPC12

5

125

LTC1334

TEMPERATURE (

°C)

–50

OUTPUT SHORT-CIRCUIT CURRENT (mA)

160

140

120

100

80

60

40

25 75

LTC1334 • TPC15

–25 0

50 100 125

SOURCE

(V

OUT

= 0V)

SINK
(V

OUT

= 5V)

VCC = 5V

TEMPERATURE (

°C)

–50

OUTPUT LEAKAGE CURRENT (µA)

500
450
400
350
300
250
200
150
100

50

0

0

50

75

LTC1334 • TPC18

–25

25

100

125

VCC = 5V

W

U

TYPICAL PERFORMANCE CHARACTERISTICS

RS485 Driver Output High Voltage
vs Output Current

–80

–70

–60

–50

–40

–30

OUTPUT CURRENT (mA)

–20

–10

0

12 4

0

OUTPUT VOLTAGE (V)

3

RS232 Driver Output Voltage
vs Temperature

10

8

= 3k

OUTPUT HIGH

OUTPUT LOW

0

TEMPERATURE (

50

25

75

°C)

6
4
2

VCC = 5V

0

R

L

–2
–4

OUTPUT VOLTAGE (V)

–6
–8

–10

–50

–25

TA = 25°C
V

= 5V

CC

LTC1334 • TPC13

100

LTC1334 • TPC16

125

RS485 Driver Output Low Voltage
vs Output Current

120

TA = 25°C
V

= 5V

CC

100

80

60

40

OUTPUT CURRENT (mA)

20

0

1234

5

0

RS232 Driver Short-Circuit
Current vs Temperature

30

V

= 0V

OUT

= 5V

V

CC

25

20

15

10

5

OUTPUT SHORT-CIRCUIT CURRENT (mA)

0

–50

–25 0

OUTPUT VOLTAGE (V)

SOURCE

SINK

50 100 125

25 75

TEMPERATURE (

°C)

RS485 Driver Output Short-Circuit
Current vs Temperature

5

LTC1334 • TPC14

Driver Output Leakage Current
(Disable/Shutdown) vs Temperature

LTC1334 • TPC17

PIN FUNCTIONS

C1+ (Pin 1): Commutating Capacitor C1 Positive Terminal.
Requires 0.1µF external capacitor between Pins 1 and 2.

C1– (Pin 2): Commutating Capacitor C1 Negative Terminal.
VDD (Pin 3): Positive Supply Output for RS232 Drivers.

Requires an external 0.1µF capacitor to ground.

A1 (Pin 4): Receiver Input.
B1 (Pin 5): Receiver Input.
Y1 (Pin 6): Driver Output.
Z1 (Pin 7): Driver Output.

6

UUU

SEL1 (Pin 8): Interface Mode Select Input.
SEL2 (Pin 9): Interface Mode Select Input.
Z2 (Pin 10): Driver Output.
Y2 (Pin 11): Driver Output.
B2 (Pin 12): Receiver Input.
A2 (Pin 13): Receiver Input.
GND (Pin 14): Ground.
VEE (Pin 15): Negative Supply Output. Requires an exter-

nal 0.1µF capacitor to ground.

LTC1334

U

UU

PI FU CTIO S

RB2 (Pin 16): Receiver Output.
RA2 (Pin 17): Receiver Output.
DZ2/DE2 (Pin 18): RS232 Driver Input in RS232 Mode.

RS485 Driver Enable with internal pull-up in RS485 mode.

D

(Pin 19): Driver Input.

Y2

ON/OFF (Pin 20): A high logic input enables the transceiv-

ers. A low puts the device into shutdown mode and
reduces ICC to 10µA. This pin has an internal pull-up.

LB (Pin 21): Loopback Control Input. A low logic level
enables internal loopback connections. This pin has an
internal pull-up.

DY1 (Pin 22): Driver Input.
DZ1/DE1 (Pin 23): RS232 Driver Input in RS232 Mode.

RS485 Driver Enable with internal pull-up in RS485 mode.

RA1 (Pin 24): Receiver Output.
RB1 (Pin 25): Receiver Output.
VCC (Pin 26): Positive Supply; 4.75V ≤ VCC ≤ 5.25V

C2– (Pin 27): Commutating Capacitor C2 Negative Termi-

nal. Requires 0.1µF external capacitor between Pins 27
and 28.

C2+ (Pin 28): Commutating Capacitor C2 Positive Terminal.

1 28

+

C1

2

–

C1

3

V

DD

4

A1

5

B1

6

Y1

7

Z1

8

SEL1

9

SEL2

10

Z2

11

Y2

12

B2

13

A2

14 15

GND

27

26

25

24

23

22

21

20

19

18

17

16

+

C2

–

C2

V

CC

R

B1

R

A1

DZ1/DE1

D

Y1

LB

ON/OFF

D

Y2

DZ2/DE2

R

A2

R

B2

V

EE

UU

FU CTIO TABLES

RS485 Driver Mode

INPUTS OUTPUTS

ON/OFF SEL DE D CONDITIONS Z Y

1 1 1 0 No Fault 0 1
1 1 1 1 No Fault 1 0
1 1 1 X Thermal Fault Z Z
110X X ZZ
01XX X ZZ

RS485 Receiver Mode

INPUTS OUTPUTS

ON/OFF SEL B – A R

1 1 < – 0.2V 0 1
1 1 > 0.2V 1 1
1 1 Inputs Open 1 1
01 XZZ

*See Note 5 of Electrical Characteristics table.

RB*

A

RS232 Driver Mode

INPUTS

ON/OFF SEL D CONDITIONS Y, Z

1 0 0 No Fault 1
1 0 1 No Fault 0
1 0 X Thermal Fault Z
00X X Z

OUTPUTS

RS232 Receiver Mode

INPUTS

ON/OFF SEL A, B R

10 0 1
10 1 0
1 0 Inputs Open 1
00 X Z

OUTPUTS

, R

A

B

7

LTC1334

W

BLOCK DIAGRA SM

Interface Configuration with Loopback Disabled

V

DD

SEL1 = 0V

SEL2 = 0V

GND

PORT 1 = RS232 MODE
PORT 2 = RS232 MODE

2
3

4

A1

5

B1

6

Y1

7

Z1

8

9

10

Z2

11

Y2

12

B2

13

A2

14

PORT 1 = RS485 MODE

281

C2C1

27
26

V

V

CC

DD

25

R

B1

24

R

A1

23

D

Z1

22

D

Y1

21

20
19

18

17

16
15

SEL1 = 5V

LB

ON

SEL2 = 0V

D

Y2

D

Z2

R

A2

R

B2

V

EE

PORT 2 = RS232 MODE

2
3

4

A1

5

B1

6

Y1

7

Z1

8

9

10

Z2

11

Y2

12

B2

13

A2

14

GND

281

C2C1

27
26

25
24

23

22

21

20
19

18

17

16
15

V

R
R

DE1

D

LB

ON
D

D

R

R

V

CC

B1

A1

Y1

Y2

Z2

A2

B2

EE

V

DD

SEL1 = 0V

SEL2 = 5V

PORT 1 = RS232 MODE
PORT 2 = RS485 MODE

2
3

4

A1

5

B1

6

Y1

7

Z1

8

9

10

Z2

11

Y2

12

B2

13

A2

14

GND

PORT 1 = RS485 MODE

281

C2C1

27
26

25

24

23

22

21

20
19

18

17

16
15

V

R

R

D

D

LB

ON
D

DE2

R

R

V

CC

B1

A1

Z1

Y1

Y2

A2

B2

EE

V

DD

SEL1 = 5V

SEL2 = 5V

PORT 2 = RS485 MODE

2
3

4

A1

5

B1

6

Y1

7

Z1

8

9

10

Z2

11

Y2

12

B2

13

A2

14

GND

LTC1334 • BD01

281

C2C1

27
26

V

CC

25

R

B1

24

R

A1

23

DE1

22

D

Y1

21

LB

20

ON

19

D

Y2

18

DE2

17

R

A2

16

R

B2

15

V

EE

Interface Configuration with Loopback Enabled

V

DD

SEL1 = 0V

SEL2 = 0V

GND

PORT 1 = RS232 MODE
PORT 2 = RS232 MODE

2
3

6

Y1

7

Z1

8

9

10

Z2

11

Y2

14

PORT 1 = RS485 MODE

2
3

V

DD

6

Y1

7

Z1

8

9

10

Z2

11

Y2

14

GND

PORT 2 = RS232 MODE

281

C2C1

27
26

V

CC

25

R

B1

24

R

A1

23

DE1

22

D

Y1

21

20
19

18

17

16
15

SEL1 = 0V

ON

SEL2 = 5V

D

Y2

D

Z2

R

A2

R

B2

V

EE

281

C2C1

27
26

V

CC

25

R

B1

24

R

A1

23

D

Z1

22

D

Y1

21

20

19

18

17

16
15

SEL1 = 5V

ON

SEL2 = 0V

D

Y2

D

Z2

R

A2

R

B2

V

EE

V

DD

Y1

Z1

10

Z2

11

Y2

14

GND

PORT 1 = RS232 MODE
PORT 2 = RS485 MODE

2
3

6

7
8

9

PORT 1 = RS485 MODE

2
3

V

DD

6

Y1

7

Z1

8

9

10

Z2

11

Y2

14

GND

PORT 2 = RS485 MODE

LTC1334 • BD02

281

C2C1

27
26

V

CC

25

R

B1

24

R

A1

23

DE1

22

D

Y1

21

LBLBLBLB

20

ON

19

D

Y2

18

DE2

17

R

A2

16

R

B2

15

V

EE

281

C2C1

27
26

V

CC

25

R

B1

24

R

A1

23

D

Z1

22

D

Y1

ON
D

DE2

R

R

V

SEL1 = 5V

SEL2 = 5V

Y2

A2

B2

EE

21

20
19

18

17

16
15

8

TEST CIRCUITS

Z

R

V

OD

V

OC

R

Y

LTC1334 • F01

LTC1334

V

CC

3V

SEL

Z

D

DE

3V

R

L

Y

C

C

3V

B

A

LTC1334 • F02

SEL

R

15pF

DR OUT

L

L

500Ω

C

L

S1

S2

LTC1334 • F03

Figure 1. RS422/RS485
Driver Test Load

0V

D

SEL

Y, Z

C

L

LTC1334 • F04

Figure 2. RS485 Driver/Receiver
Timing Test Circuit

R

L

Figure 4. RS232 Driver
Swing/Timing Test Circuit

U

W

SWITCHI G WAVEFOR S

3V

1.5V

t

PLH

10%

O

Z – Y

D

0V

V

O

–V

O

Y

V

Z

50%

f = 1MHz: t

90%

t

r

t

SKEW

≤ 10ns: tf ≤ 10ns

r

V

= V(Z) – V(Y)

DIFF

1/2 V

O

Figure 3. RS485 Driver Output
Enable/Disable Timing Test Load

0V

SEL

Y, Z

D

V

0V

A, B

IN

Figure 5. RS232 Receiver
Timing Test Circuit

1.5V

t

PHL

90%

50%

10%

t

f

t

LTC1334 • F06

SKEW

SEL

R

V

OUT

15pF

LTC1334 • F05

Figure 6. RS485 Driver Propagation Delays

9

LTC1334

U

W

SWITCHI G WAVEFOR S

3V

1.5V

t

ZL

t

ZH

Figure 7. RS485 Driver Enable and Disable Times

0V

t

PLH

B – A

Y, Z

Z, Y

R

DE

–V

0V

5V

V

OL

V

OH

0V

V

OD2

OD2

V

OH

V

OL

f = 1MHz: t

2.3V

2.3V

f = 1MHz: t

1.5V

≤ 10ns: tf ≤ 10ns

r

OUTPUT NORMALLY LOW

OUTPUT NORMALLY HIGH

≤ 10ns: tf ≤ 10ns

r

INPUT

OUTPUT

1.5V

t

t

HZ

0V

LZ

0.5V

0.5V

LTC1334 • F07

t

PHL

1.5V

LTC1334 • F08

A, B

Y, Z

Figure 8. RS485 Receiver Propagation Delays

3V

D

0V

V

O

–V

O

1.5V

t

PHL

0V

1.5V

t

PLH

0V

LTC1334 • F09

Figure 9. RS232 Driver Propagation Delays

V

IH

1.3V

V

IL

V

OH

R

V

OL

t

PHL

0.8V

1.7V

t

PLH

2.4V

LTC1334 • F10

Figure 10. RS232 Receiver Propagation Delays

10

LTC1334

PPLICATI

A

U

O

S

I FOR ATIO

WU

U

Basic Theory of Operation

The LTC1334 has two interface ports. Each port may be
configured as a pair of single-ended RS232 transceivers
or as a differential RS485 transceiver by forcing the
port’s selection input to a low or high, respectively. The
LTC1334 provides two RS232 drivers and two RS232
receivers or one RS485 driver and one RS485 receiver
per port. All the interface drivers feature three-state
outputs. Interface outputs are forced into high imped­ance when the driver is disabled, in the shutdown mode
or with the power off.

All the interface driver outputs are fault-protected by a
current limiting and thermal shutdown circuit. The ther­mal shutdown circuit disables both the RS232 and RS485
driver outputs when the die temperature reaches 150°C.
The thermal shutdown circuit reenables the drivers when
the die temperature cools to 130°C.

In RS485 mode, shutdown mode or with the power off, the
input resistance of the receiver is 24k. The input resistance
drops to 5k in RS232 mode.

In RS485 mode, an internal 4µA current source pulls the
driver enable pin high if left open. The RS485 receiver has
a 4µA current source at the noninverting input. If both the
RS485 receiver inputs are open, the output goes to a high
state. Both the current sources are disabled in the RS232
mode. The receiver output B is inactive in RS485 mode
and has a 50k pull-up resistor to provide a known output
state in this mode.

A loopback mode enables internal connections from driver
outputs to receiver inputs for self-test when the LB pin has
a low logic state. The driver outputs are not isolated from
the external loads. This allows transmitter verification
under the loaded condition. An internal 4µA current source
pulls the LB pin high if left open and disables the loopback
configuration.

RS232/RS485 Applications

The LTC1334 can support both RS232 and RS485 levels
with a single 5V supply as shown in Figure 11.

Multiprotocol Applications

A logic low at the ON/OFF pin shuts down the device and
forces all the outputs into a high impedance state. A logic
high enables the device. An internal 4µA current source to
VCC pulls the ON/OFF pin high if it is left open.

1

0.1µF

RS485 I/O

≥ ±5V INTO

3kΩ LOAD

V

DD

120Ω

RS232 DR OUT

RS232 DR OUT

C1

5V

RS232 RX IN

RS232 RX IN

LTC1334

2

3
4
5

6
7

8
9

11
10
13
12

14

The LTC1334 is well-suited for software controlled inter­face mode selection. Each port has a selection pin as
shown in Figure 12. The single-ended transceivers sup­port both RS232 and EIA562 levels. The differential trans­ceivers support both RS485 and RS422.

28

LTC1334 • F11

C2

0.1µF

V

CC

5V

27

26

24

23

22

21
20

19
18
17
16
15

0.1µF0.1µF

RX OUT

DR ENABLE

DR IN

5V
5V

DR IN
DR IN
RX OUT
RX OUT
V

EE

0.1µF

Figure 11. RS232/RS485 Interfaces

11

LTC1334

PPLICATI

A

PORT 1

INTERFACE

5V

K1*

TX2A-5V

FMMT619**

PORT 2

INTERFACE

5V

K2*

TX2A-5V

FMMT619**

U

O

S

I FOR ATIO

1

0.1µF 0.1µF

VDD

INPUT A

K1A

120Ω

INPUT B

OUTPUT A

K1B

120Ω

OUTPUT B

360k

TERM1

7.5k

K2A

120Ω

K2B

120Ω

TERM2

13

12

11

10
14

INPUT A

INPUT B

OUTPUT A

OUTPUT B

360k

7.5k

LTC1334

2
326

4

5

6

7

AROMAT CORP [phone]

*

ZETEX [phone]

**

WU

28
27

0.1µF0.1µF

25

RX OUT

24

RX OUT

22

DR IN

8

SEL1

23

DR IN/ENABLE

21

LB

20

ON/OFF

16

RX OUT

17

RX OUT

19

DR IN

9

SEL2

18

DR IN/ENABLE

15

0.1µF

Figure 12. Multiprotocol Interface
with Optional, Switchable Terminations

U

C2C1

V

EE

LTC1334 • F12

Each receiver in the LTC1334 is designed to present one

V
5V

unit load (5kΩ nominal for RS232 and 12kΩ minimum for

CC

RS485) to the cable. Some RS485 and RS422 applications
call for terminations, but these are only necessary at two
nodes in the system and they must be disconnected when
operating in the RS232 mode. A relay is the simplest, low­est cost method of switching terminations. In Figure 12
TERM1 and TERM2 select 120Ω terminations as needed.
If terminations are needed in all RS485/RS422 applica­tions, no extra control signals are required; simply con­nect TERM1 and TERM2 to SEL1 and SEL2.

Typical Applications

A typical RS232/EIA562 interface application is shown in
Figure 13 with the LTC1334.

A typical connection for a RS485 transceiver is shown in
Figure 14. A twisted pair of wires connects up to 32 drivers
and receivers for half duplex multipoint data transmission.
The wires must be terminated at both ends with resistors
equal to the wire’s characteristic impedance. An optional
shield around the twisted pair helps to reduce unwanted
noise and should be connected to ground at only one end.

1/2 LTC1334 1/2 LTC1334

DR IN

DR IN
RX OUT
RX OUT

19
18
17
16

9

11
10
13
12

RS232/

EIA562

INTERFACE

LINES

Figure 13. Typical Connection for RS232/EIA562 Interface

4
5
6
7

LTC1334 • F13

24
25
22
23
8

RX OUT
RX OUT
DR IN
DR IN

12

RX OUT

DR ENABLE

DR IN

5V

1/2 LTC1334

24

23

22

8

4
5

6
7

120Ω

76 54

22

23 24 8

DR IN RX OUT

DR ENABLE

5V

120Ω

1/2
LTC1334

Figure 14. Typical Connection for RS485 Interface

1/2 LTC1334
13
12

11
10

17

18

19

9

RX OUT

DR ENABLE

DR IN

5V

LTC1334 F14

LTC1334

PPLICATI

A

U

O

S

I FOR ATIO

WU

U

A typical RS422 connection (Figure 15) allows one driver
and ten receivers on a twisted pair of wires terminated with
a 100Ω resistor at one end.

A typical twisted-pair line repeater is shown in Figure 16.
As data transmission rate drops with increased cable
length, repeaters can be inserted to improve transmission
rate or to transmit beyond the RS422 4000-foot limit.

The LTC1334 can be used to translate RS232 to RS422
interface levels or vice versa as shown in Figure 17. One

1/2 LTC1334

RX OUT

5V

1/2 LTC1334

22

8

24

23

6

7

4

100Ω

5

DR ENABLE

DR IN

RX OUT

port is configured as an RS232 transceiver and the other
as an RS485 transceiver.

Using two LTC1334s as level translators, the RS232/
EIA562 interface distance can be extended to 4000 feet
with twisted-pair wires (Figure 18).

AppleTalk®/LocalTalk® Applications

Two AppleTalk applications are shown in Figure 19 and 20
with the LTC1323 and the LTC1334.

AppleTalk and LocalTalk are registered trademarks of Apple Computer, Inc.

24

8

5V

5

4

100Ω

1/2 LTC1334

13

12

11

10

LTC1334 • F15

17

RX OUT

8

18

DR ENABLE

19

DR IN

5V

Figure 15. Typical Connection for RS422 Interface

5V

23

8

6

7

RX IN

2224

4

100Ω

5

1/2 LTC1334

Figure 16. Typical Cable Repeater for RS422 Interface

5V

232217

8

13

RX IN

RS232/EIA562

DR OUT

11

9

LTC1334

19 24

5V

232217

8

6

7

4

100Ω

5

TX OUT

RS422RS232/EIA562

RX IN

LTC1334 • F17

LTC1334 • F16

TX OUT

RX IN

TX OUT

13

LTC1334

11

9

19 24

Figure 17. Typical RS232/EIA562 to RS422 Level Translator

19

8

LTC1334

23

24

22

175V9

11

DR OUT

RS232/EIA562

13

RX IN

LTC1334 • F18

RS422

6

100Ω

7

4

100Ω

5

4

5

6

7

Figure 18. Typical Cable Extension for RS232/EIA562 Interface

13

LTC1334

PPLICATI

A

1

0.33µF

TXD

TXDEN

SHDN

RXEN

RXDO

2

3

4

5

6

7

8

O

LTC1323CS-16

CHARGE

PUMP

U

S

I FOR ATIO

16

5V

15

TXD

TXD

RXD

RXD

–

+

–

+

EMI

0.33µF

EMI

EMI

EMI

EMI

14

13

12

11

10

9

WU

1µF

1k

1k

5Ω TO

5Ω TO

22Ω

= OR OR

U

120Ω

22Ω

100pF 100pF

120Ω

FERRITE

BEAD

0.1µF

FERRITE

BEAD

100pF

1k

1k

SEL1, 5V
SEL2, 5V

EMI

EMI
EMI

EMI

NC

NC
NC

NC

1
2
3

4

5
6

7

8
9

10

11
12

13

14

Figure 19. AppleTalk/LocalTalk Implemented Using the LTC1323CS-16 and LTC1334 Transceivers

LTC1334

LTC1334 • F19

28

5V
NC

R

DE1

D

5V

5V

NC

NC

NC
NC

0.1µF0.1µF

A1

Y1

0.1µF

27
26

25
24

23

22

21
20

19

18

17
16

15

0.33µF

CPEN

TXD

TXI

TXDEN

SHDN

RXEN

RXO

RXO

RXDO

5Ω TO

5Ω TO

22Ω

= OR OR

LTC1323CS

1

CHARGE

2

3

4

5

6

7

8

9

10

11

12

PUMP

EMI

24

5V

23

0.33µF

22

21

–

20

TXD

EMI

+

19

TXD

TXO

RXI

RXI

RXD

RXD

EMI

EMI

EMI

EMI

–

EMI

+

EMI

18

17

16

15

14
13

22Ω

100pF 100pF

1µF

120Ω

120Ω

FERRITE

BEAD

FERRITE

BEAD

100pF

SEL2

120Ω

120Ω

0.1µF

EMI

EMI
EMI

EMI

SEL1

5V

EMI

EMI

NC

EMI

1
2

LTC1334

3

4

5
6

7

8
9

10

11
12

13

14

LTC1334 • F20

28

5V

NC
R

DE1

D

5V

5V

D

D

R
NC

0.1µF0.1µF

A1

Y1

Y2

Z2

A2

0.1µF

27

26

25
24

23

22

21

20

19

18

17

16

15

14

Figure 20. AppleTalk Direct Connect Using the LTC1323 DTE and the LTC1334 for DCE Transceivers

PACKAGE DESCRIPTION

5.20 – 5.38**
(0.205 – 0.212)

U

Dimensions in inches (millimeters) unless otherwise noted.

G Package

28-Lead Plastic SSOP (0.209)

(LTC DWG # 05-08-1640)

10.07 – 10.33*

(0.397 – 0.407)

2526 22 21 20 19 181716 1523242728

12345678 9 10 11 12 1413

1.73 – 1.99

(0.068 – 0.078)

° – 8°

0

7.65 – 7.90

(0.301 – 0.311)

LTC1334

0.13 – 0.22

(0.005 – 0.009)

NOTE: DIMENSIONS ARE IN MILLIMETERS

*

DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.152mm (0.006") PER SIDE

**

DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.254mm (0.010") PER SIDE

0.600 – 0.625

(15.240 – 15.875)

0.55 – 0.95

(0.022 – 0.037)

(12.827 – 14.224)

0.505 – 0.560*

0.150 ± 0.005

(3.810 ± 0.127)

0.65

(0.0256)

BSC

0.25 – 0.38

(0.010 – 0.015)

NW Package

28-Lead PDIP (Wide 0.600)

(LTC DWG # 05-08-1520)

27

12

252628

3

4

5

0.045 – 0.065

(1.143 – 1.651)

0.05 – 0.21

(0.002 – 0.008)

G28 SSOP 1098

1.455*

(36.957)

MAX

23

7

6

20212224

19

9

8

10

1718

11 12 13 14

15

16

0.015

(0.381)

0.009 – 0.015

(0.229 – 0.381)

+0.035

0.625
–0.015

+0.889

15.87

()

–0.381

*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)

MIN

0.125

(3.175)

MIN

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen­tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

0.035 – 0.080

(0.889 – 2.032)

0.100
(2.54)

BSC

0.018 ± 0.003

(0.457 ± 0.076)

0.070

(1.778)

TYP

N28 1098

15

LTC1334

PACKAGE DESCRIPTION

U

Dimensions in inches (millimeters) unless otherwise noted.

SW Package

28-Lead Plastic Small Outline (Wide 0.300)

(LTC DWG # 05-08-1690)

0.697 – 0.712*
(17.70 – 18.08)

2526

2728

NOTE 1

0.291 – 0.299**
(7.391 – 7.595)

0.010 – 0.029

(0.254 – 0.737)

0.009 – 0.013

(0.229 – 0.330)

NOTE:

1. PIN 1 IDENT, NOTCH ON TOP AND CAVITIES ON THE BOTTOM OF PACKAGES ARE THE MANUFACTURING OPTIONS.
THE PART MAY BE SUPPLIED WITH OR WITHOUT ANY OF THE OPTIONS

DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE

*

DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE

**

NOTE 1

× 45°

0.016 – 0.050

(0.406 – 1.270)

0° – 8° TYP

0.093 – 0.104

(2.362 – 2.642)

0.050

(1.270)

BSC

2345

1

0.014 – 0.019

(0.356 – 0.482)

TYP

6

22 21 20 19 18

910

78

11 12

17

16 152324

1413

0.394 – 0.419

(10.007 – 10.643)

0.037 – 0.045

(0.940 – 1.143)

0.004 – 0.012

(0.102 – 0.305)

S28 (WIDE) 1098

RELATED PARTS

PART NUMBER DESCRIPTION COMMENTS

LTC485 Low Power RS485 Interface Transceiver Single 5V Supply, Wide Common Mode Range
LT®1137A Low Power RS232 Transceiver ±15kV IEC-1000-4-2 ESD Protection, Three Drivers, Five Receivers
LTC1320 AppleTalk Transceiver AppleTalk/Local Talk Compliant
LTC1321/LTC1322/LTC1335 RS232/EIA562/RS485 Transceivers Configurable, 10kV ESD Protection
LTC1323 Single 5V AppleTalk Transceiver LocalTalk/AppleTalk Compliant 10kV ESD
LTC1347 5V Low Power RS232 Transceiver Three Drivers/Five Receivers, Five Receivers Alive in Shutdown
LTC1387 Single 5V RS232/RS485 Transceiver Single Port, Configurable, 10kV ESD

1334fa LT/TP 1099 2K REV A • PRINTED IN USA

 LINEAR TECHNOLOGY CORPORATION 1995

16

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

[phone] ● FAX: [phone]

●

www.linear-tech.com