Linear Technology LTC1482 Datasheet

FEATURES

LTC1482

Low Power RS485 Transceiver

with Carrier Detect and

Receiver Fail-Safe

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DESCRIPTIO

■

No Damage or Latchup to ±15kV (Human Body
Model), IEC1000-4-2 Level 4 (±8kV) Contact and
Level 3 (±8kV) Air Discharge

■

Active Low Carrier Detect Output

■

Guaranteed High Receiver Output State for
Floating, Shorted or Terminated Inputs with
No Signal Present

■

Drives Low Cost Residential Telephone Wires

■

Low Power: ICC = 700µA Max with Driver Disabled

■

ICC = 900µA Max in Driver Mode Without Load

■

20µA Max Quiescent Current in Shutdown Mode

■

Single 5V Supply

■

–7V to 12V Common Mode Range Permits ±7V
Ground Difference Between Devices on the Data Line

■

Maximum Data Rate of 4Mbps

■

Power Up/Down Glitch-Free Driver Outputs

■

Up to 32 Transceivers on the Bus

■

Available in 8-Lead MSOP, PDIP and SO Packages

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APPLICATIO S

■

Battery-Powered RS485/RS422 Applications

■

Low Power RS485/RS422 Transceiver

■

Level Translator

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

The LTC®1482 is a low power RS485 compatible trans­ceiver that offers an active low carrier detect output. The
open-drain carrier detect pin allows several transceivers
to share the same carrier detect line and can be used to
detect the insertion or removal of a driven RS485/RS422
cable.

Enhanced ESD protection allows the LTC1482 to with­stand ±15kV (human body model), IEC-1000-4-2 level 4
(±8kV) contact and level 3 (±8kV) air discharge ESD
without latchup or damage.

The LTC1482 receiver stays alive at all times except in
shutdown. The supply current is a maximum of 700µA
and 900µA when the driver is disabled and enabled
respectively. In shutdown, the quiescent current of the
LTC1482 drops to a maximum of 20µA.

When the driver is disabled or the LTC1482 is in shut­down, the driver outputs are three-stated and remain in
a high impedance state over the RS485 common mode
range.

Excessive power dissipation caused by bus contention or
faults is prevented by a thermal shutdown circuit, which
forces the driver outputs into a high impedance state.

The LTC1482 is fully specified over the commercial and
industrial temperature ranges and is available in 8-lead
MSOP, PDIP and SO packages.

TYPICAL APPLICATIO

RS485 Interface

RO1
CD1

DE1

DI1/SHDN1

LTC1482

R

D

B1

A1

V

CC1

120Ω 120Ω

GND1

U

V

CC2

GND2

Carrier Detect Output (2000 Foot STP Cable)

LTC1482

B2

A2

R

D

RO2
CD2
DE2
DI2/SHDN2

1482 TA01

DE1

A2
B2

CD2

DE1 ↑↓ Dl1 = V
DE2 = 0 Dl2 = V
1k PULL-UP AT CD

CC
CC

1482 TA01a

1

LTC1482

WW

W

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ABSOLUTE MAXIMUM RATINGS

(Note 1)

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

Control Input Voltages ................. –0.3V to (VCC + 0.3V)

Carrier Detect Voltage ................................. –0.3V to 8V

Driver Input Voltage ..................... –0.3V to (VCC + 0.3V)

Driver Output Voltages ................................. –7V to 10V

Receiver Input Voltages (Driver Disabled) .. –12V to 14V

Receiver Output Voltage ............... – 0.3V to (VCC + 0.3V)

U

W

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PACKAGE/ORDER INFORMATION

ORDER PART

NUMBER

RO

1

CD

2

DE

3

DI/SHDN

4

8-LEAD PLASTIC MSOP

T

= 125°C, θJA = 200°C/ W

JMAX

TOP VIEW

MS8 PACKAGE

8

V

CC

7

B

6

A

5

GND

LTC1482CMS8 LTC1482CN8

MS8 PART MARKING

LTCB

Junction Temperature .......................................... 125°C

Operating Temperature Range

LTC1482C ........................................ 0°C ≤ TA ≤ 70°C

LTC1482I...................................... –40°C ≤ TA ≤ 85°C

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

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

ORDER PART

RO

1

CD

2

DE

3

DI/SHDN

4

N8 PACKAGE
8-LEAD PDIP

T

= 125°C, θJA = 130°C/ W (N8)

JMAX

T

= 125°C, θJA = 135°C/W (S8)

JMAX

TOP VIEW

8-LEAD PLASTIC SO

V

8

CC

B

7

A

6

GND

5

S8 PACKAGE

NUMBER

LTC1482CS8
LTC1482IN8
LTC1482IS8

S8 PART MARKING

1482
1482I

Consult factory for Military grade parts.

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at T

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

OD1

V

OD2

V

OD3

∆V

OD

V

OC

∆|VOC| Change in Magnitude of Driver Common Mode R = 22Ω, 27Ω or R = 50Ω, Figure 1 ● 0.2 V

V

IH

V

IL

I

IN1

I

IN2

V

THRO

Differential Driver Output Voltage (Unloaded) I
Differential Driver Output Voltage (with Load) R = 50Ω (RS422) ● 2V

Differential Driver Output Voltage V
(with Common Mode)

Change in Magnitude of Driver Differential R = 22Ω, 27Ω or R = 50Ω, Figure 1 ● 0.2 V
Output Voltage for Complementary Output States V

Driver Common Mode Output Voltage R = 22Ω, 27Ω or R = 50Ω, Figure 1 ● 3V

Output Voltage for Complementary Output States
Input High Voltage DE, DI/SHDN ● 2V
Input Low Voltage DE, DI/SHDN ● 0.8 V
Input Current DE, DI/SHDN ● ±2 µA
Input Current (A, B) with Driver Disabled DE = 0, VCC = 0 or 5V, VIN = 12V ● 1.0 mA

Differential Input Threshold Voltage for Receiver –7V ≤ VCM ≤ 12V, DE = 0 ● –0.20 –0.015 V

The ● denotes the specifications which apply over the full operating

= 25°C. VCC = 5V ±5% (Notes 2 and 3) unless otherwise noted.

A

= 0 ● V

OUT

R = 27Ω (RS485) Figure 1
R = 22Ω, Figure 1

= –7V to 12V, Figure 2 ● 1.5 5 V

TST

= –7V to 12V, Figure 2

TST

DE = 0, V

= 0 or 5V, VIN = –7V ● –0.8 mA

CC

● 1.5 5 V

● 1.5 5 V

CC

V

2

LTC1482

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at T

The ● denotes the specifications which apply over the full operating

= 25°C. VCC = 5V ±5% (Notes 2 and 3) unless otherwise noted.

A

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V
∆V
V

V
I

OZR

THCD

TH

OH

OL

Differential Input Threshold Voltage for CD = 1 –7V ≤ VCM ≤ 12V, DE = 0 ● –0.20 0.20 V
Receiver Input Hysteresis VCM = 0V, DE = 0 ±30 mV
CD Output High Voltage I
RO Output High Voltage I
RO and CD Output Low Voltage I
Three-State (High Impedance) Receiver Output VCC = Max, 0.4V ≤ V

= –10µA, (VA – VB) = 0V ● 3.4 V

OUT

= –4mA, (VA – VB) = 200mV ● 3.5 V

OUT

= 4mA, (VA – VB) = –200mV ● 0.4 V

OUT

≤ 2.4V ● ±1 µA

OUT

Current in Shutdown DI/SHDN = 0, DE = 0

R

IN

I

CC

I

SHDN

I

OSD1

I

OSD2

I

OS

I

PULL-UP

Receiver Input Resistance –7V ≤ VCM ≤ 12V ● 12 22 kΩ
Supply Current No Load, Driver Enabled (DE = VCC) ● 580 900 µA

No Load, Driver Disabled (DE = 0)

● 430 700 µA

Supply Current in Shutdown Mode DE = 0, DI = 0 ● 10 20 µA
Driver Short-Circuit Current, V
Driver Short-Circuit Current, V
RO and CD Short-Circuit Current 0V ≤ V

= High (Note 4) –7V ≤ V

OUT

= Low (Note 4) –7V ≤ V

OUT

≤ 10V 35 250 mA

OUT

≤ 10V 35 250 mA

OUT

OUT

≤ V

CC

● 785mA

CD Pull-Up Current CD = 0V ● 15 30 60 µA

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SWITCHING CHARACTERISTICS

temperature range, otherwise specifications are at T

The ● denotes the specifications which apply over the full operating

= 25°C. VCC = 5V ±5% (Notes 2 and 3) unless otherwise noted.

A

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

t

PLH

t

PHL

t

SKEW

tr, t

f

t

ZH

t

ZL

t

LZ

t

HZ

t

ZH(SHDN)

Driver Input to Output R

= 54Ω, CL1 = CL2 = 100pF ● 10 28 60 ns

DIFF

Driver Input to Output (Figures 4, 6) ● 10 30 60 ns
Driver Output to Output ● 210 ns
Driver Rise or Fall Time ● 31540 ns
Driver Enable to Output High CL = 100pF (Figures 5, 7) S2 Closed ● 40 70 ns
Driver Enable to Output Low CL = 100pF (Figures 5, 7) S1 Closed ● 40 100 ns
Driver Disable Time from Low CL = 15pF (Figures 5, 7) S1 Closed ● 40 70 ns
Driver Disable Time from High CL = 15pF (Figures 5, 7) S2 Closed ● 40 70 ns
Driver Enable from Shutdown to Output High CL = 100pF (Figures 5, 7) S2 Closed ● 40 100 ns

(Note 5)

t

ZL(SHDN)

t

HZ(SHDN)

t

LZ(SHDN)

f

MAX

t

PLH

Driver Enable from Shutdown to Output Low CL = 100pF (Figures 5, 7) S1 Closed ● 40 100 ns
Driver Disable on Shutdown from Output High CL = 15pF (Figures 5, 7) S2 Closed ● 40 100 ns
Driver Disable on Shutdown from Output Low CL = 15pF (Figures 5, 7) S1 Closed ● 40 100 ns
Maximum Data Rate (Note 6) ● 4 5 Mbps
Receiver Input to Output (Note 7) R

= 54Ω, CL1 = CL2 = 100pF, ● 30 138 200 ns

DIFF

(Figures 4, 8)

t

PHL

Receiver Input to Output R

= 54Ω, CL1 = CL2 = 100pF, ● 30 122 200 ns

DIFF

(Figures 4, 8)

t

SKD

|t

– t

PLH

| Differential Receiver Skew R

PHL

= 54Ω, CL1 = CL2 = 100pF, 16 ns

DIFF

(Figures 4, 8)

t

t

CDH

CDL

Receiver Input to CD Output High (Note 7) R

Receiver Input to CD Output Low (Note 7) R

= 54Ω, CL1 = CL2 = 100pF, ● 2900 5000 ns

DIFF

(Figures 4, 10) DI/SHDN = V

= 54Ω, CL1 = CL2 = 100pF, ● 150 300 ns

DIFF

(Figures 4, 10) DI/SHDN = V

CC

CC

3

LTC1482

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SWITCHING CHARACTERISTICS

temperature range, otherwise specifications are at T

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

t

CDH(SHDN)

t

CDL(SHDN)

t

ZH(SHDN)

t

ZL(SHDN)

t

HZ(SHDN)

t

LZ(SHDN)

Receiver Input to CD Output High at Shutdown R

Receiver Input to CD Output Low from Shutdown R

Receiver Enable from Shutdown to Output High CL = 15pF (Figures 3, 9) S2 Closed, ● 30 600 ns

Receiver Enable from Shutdown to Output Low CL = 15pF (Figures 3, 9) S1 Closed, ● 2600 5000 ns

Receiver Disable from High on Shutdown CL = 15pF (Figures 3, 9) S2 Closed, ● 200 600 ns

Receiver Disable from Low on Shutdown CL = 15pF (Figures 3, 9) S1 Closed, ● 200 600 ns

The ● denotes the specifications which apply over the full operating

= 25°C. VCC = 5V ±5% (Notes 2 and 3) unless otherwise noted.

A

= 54Ω, CL1 = CL2 = 100pF, ● 2600 5000 ns

DIFF

(Figures 4, 11) DI/SHDN = DE

= 54Ω, CL1 = CL2 = 100pF, ● 2600 5000 ns

DIFF

(Figures 4, 11) DI/SHDN = DE

A = 750mV, B = –750mV, DE = 0,
DI/SHDN =

A = –750mV, B = 750mV, DE = 0,
DI/SHDN =

A = 750mV, B = –750mV, DE = 0,
DI/SHDN =

A = –750mV, B = 750mV, DE = 0,
DI/SHDN =

Note 1: Absolute Maximum Ratings are those values beyond which the life of
a device may be impaired.

Note 2: All typicals are given for V

= 5V and TA = 25°C.

CC

Note 3: 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 4: For higher ambient temperatures, the part may enter thermal
shutdown during short-circuit conditions.

Note 5: Both driver input and driver enable pins are pulled high
simultaneously.

Note 6: Guaranteed by design.
Note 7: Measured with an external LTC1485 driver.

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Receiver Output Voltage vs Input
Voltage

6

TA = 25°C

5

4

3

2

1

RECEIVER OUTPUT VOLTAGE (V)

V

THRO(LOW)

0

–0.16 –0.12 –0.08 –0.04 0

–0.2

INPUT VOLTAGE (V)

V

THRO(HIGH)

1482 G01

Receiver Input Threshold Voltage
(Output High) vs Temperature

0
–0.02
–0.04
–0.06
–0.08

–0.1
–0.12
–0.14
–0.16
–0.18

RECEIVER INPUT THRESHOLD VOLTAGE (mV)

–0.20

–55 –35 –15 5 25 45 65 85 105 125

VCM = 12V

VCM = 0V

TEMPERATURE (°C)

VCC = 5V
V

VCM = –7V

THRO(HIGH)

1482 G02

Receiver Input Threshold Voltage
(Output Low) vs Temperature

0
–0.02
–0.04
–0.06
–0.08

–0.1
–0.12
–0.14
–0.16
–0.18

RECEIVER INPUT THRESHOLD VOLTAGE (mV)

–0.20

–55 –35 –15 5 25 45 65 85 105 125

VCM = 12V

VCM = 0V

TEMPERATURE (°C)

VCC = 5V
V

VCM = –7V

THRO(LOW)

1482 G03

4

UW

TEMPERATURE (°C)

CARRIER DETECT THRESHOLD VOLTAGE (V)

1482 G09

0.25

0.20

0.15

0.10

0.05
0

–0.05
–0.10
–0.15
–0.20
–0.25

VCC = 5V

POSITIVE
V

THCD(LOW)

NEGATIVE
V

THCD(LOW)

–55 –35 –15 5 25 45 65 85 105 125

VCM = 12V

VCM = –7V

VCM = 12V

VCM = –7V

VCM = 0V

VCM = 0V

TYPICAL PERFOR A CE CHARACTERISTICS

LTC1482

Receiver Input Offset Voltage vs
Temperature

0

VCC = 5V

–20
–40
–60

–80
–100
–120
–140
–160
–180

RECEIVER INPUT OFFSET VOLTAGE (mV)

–200

–55 –35 –15 5 25 45 65 85 105 125

VCM = 0V

TEMPERATURE (°C)

VCM = 12V

VCM = –7V

Carrier Detect Output Voltage vs
Receiver Input Voltage

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

CARRIER DETECT OUTPUT VOLTAGE (V)

0
–0.25

THCD(LOW)

NEGATIVE

V

–0.15 –0.05 0.05 0.15 0.25

RECEIVER INPUT VOLTAGE (V)

THCD(HIGH)

THCD(HIGH)

NEGATIVE, V

POSITIVE, V

1482 G04

THCD(LOW)

POSITIVE

V

1482 G07

Receiver Hysteresis vs
Temperature

100

VCC = 5V

90
80
70
60
50
40

HYSTERESIS (mV)

30
20
10

0

–55 –35 –15 5 25 45 65 85 105 125

VCM = –7V TO 12V

TEMPERATURE (°C)

Carrier Detect Threshold Voltage
(Output High) vs Temperature

0.25

0.20
POSITIVE

0.15
V

THCD(HIGH)

0.10

0.05
NEGATIVE

0

V

–0.05
–0.10
–0.15
–0.20

CARRIER DETECT THRESHOLD VOLTAGE (V)

–0.25

THCD(HIGH)

VCC = 5V

–55 –35 –15 5 25 45 65 85 105 125

VCM = 0V

VCM = 0V

TEMPERATURE (°C)

VCM = 12V

VCM = –7V

VCM = 12V

VCM = –7V

1482 G05

1482 G08

Receiver Input Threshold Voltage
vs Supply Voltage

0

TA = 25°C

–0.02
–0.04
–0.06
–0.08
–0.10
–0.12
–0.14
–0.16
–0.18

RECEIVER INPUT THRESHOLD VOLTAGE (V)

–0.20

4.5

V

THRO(HIGH)

V

THRO(LOW)

4.75 5 5.25 5.5
SUPPLY VOLTAGE (V)

Carrier Detect Threshold Voltage
(Output Low) vs Temperature

1482 G06

Receiver Output High Voltage vs
Temperature

4.5
VCC = 4.75V

4.4

4.3

4.2

4.1

4.0

3.9

3.8

3.7

RECEIVER OUTPUT HIGH VOLTAGE (V)

3.6

3.5

= –8mA

I

OUT

–55 –35 –15 5 25 45 65 85 105 125

TEMPERATURE (°C)

1482 G10

Carrier Detect Output High
Voltage vs Output Current

5.0
VCC = 4.75V

4.5

= 25°C

T

A

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

CARRIER DETECT OUTPUT HIGH VOLTAGE (V)

0

–35 –30 –25 –20 –15 –10 –5 0

OUTPUT CURRENT (µA)

1482 G11

Receiver and Carrier Detect
Output Low Voltage vs Output
Current

40

TA = 25°C

35

= 4.75

V

CC

30

25

20

15

OUTPUT CURRENT (mA)

10

5

0

0

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
OUTPUT LOW VOLTAGE (V)

1482 G12

5