Linear Technology LTC1485 Datasheet

LTC1485

Differential Bus Transceiver

EATU

F

■

ESD Protection over ±10kV

■

Low Power: ICC = 1.8mA Typ

■

28ns Typical Driver Propagation Delays with

RE

S

4ns Skew

■

Designed for RS485 or RS422 Applications

■

Single 5V Supply

■

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

■

Thermal Shutdown Protection

■

Power-Up/Down Glitch-Free Driver Outputs

■

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

■

Combined Impedance of a Driver Output and
Receiver Allows up to 32 Transceivers on the Bus

■

60mV Typical Input Hysteresis

■

Pin Compatible with the SN75176A, DS75176A, and
SN75LBC176

U

O

PPLICATI

A

■

Low Power RS485/RS422 Transceiver

■

Level Translator

S

DUESCRIPTIO

The LTC®1485 is a low power differential bus/line trans­ceiver designed for multipoint data transmission standard
RS485 applications with extended common-mode range
(12V to –7V). It also meets the requirements of RS422.

The CMOS with Schottky design offers significant power
savings over its bipolar counterpart without sacrificing
ruggedness against overload or ESD damage.

The driver and receiver feature three-state outputs, with
the driver outputs maintaining high impedance over the
entire 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. I/O pins are protected against
multiple ESD strikes of over ±10kV.

The receiver has a fail-safe feature which guarantees a
high output state when the inputs are left open.

Both AC and DC specifications are guaranteed from – 40°C
to 85°C and 4.75V to 5.25V supply voltage range.

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

A

U

O

PPLICATITYPICAL

5V

8

6

7

5

DRIVER

RECEIVER

RE

DE

3

4

DI

1

RO

2

1485 TA01

RO

DE

3

4

DI

DRIVER

1

RECEIVER

RE

5V

8

LTC1485 LTC1485

2

6

120Ω

7

4000 FT 24 GAUGE TWISTED PAIR

5

120Ω

1

LTC1485

WU

U

PACKAGE

/

O

RDER I FOR ATIO

W

O

A

(Note 1)

LUTEXI T

S

Supply Voltage (VCC) .............................................. 12V

Control Input Voltages ................... – 0.5V to VCC + 0.5V

Control Input Currents ........................ – 50mA to 50mA

Driver Input Voltages ..................... – 0.5V to VCC + 0.5V

Driver Input Currents .......................... –25mA to 25mA

Driver Output Voltages ......................................... ±14V

Receiver Input Voltages ........................................ ±14V

Receiver Output Voltages .............. – 0.5V to VCC + 0.5V

Operating Temperature Range

LTC1485C............................................... 0°C to 70°C

A

WUW

ARB

U
G

I

S

TOP VIEW

1

RO

2

RE

3

DE

45

DI

N8 PACKAGE

8-LEAD PLASTIC DIP

T

= 125°C, θJA = 100°C/ W (N)

JMAX

= 150°C, θJA = 150°C/ W (S)

T

JMAX

8

R

7

D

6

S8 PACKAGE

8-LEAD PLASTIC SOIC

V

CC

B
A

GND

ORDER PART

NUMBER

LTC1485CN8
LTC1485IN8
LTC1485CS8
LTC1485IS8

S8 PART MARKING

1485
1485I

LTC1485I .......................................... – 40°C to 85°C

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

Consult factory for Military grade parts.

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

LECTRICAL C CHARA TERIST

E

V

= 5V (Notes 2, 3), unless otherwise noted.

CC

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

OD1

V

OD2

∆V

OD

V

OC

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

V

INH

V

INL

I

IN1

I

IN2

V

TH

∆V

TH

V

OH

V

OL

I

OZR

I

CC

R

IN

I

OSD1

I

OSD2

I

OSR

Differential Driver Output Voltage (Unloaded) IO = 0 ● 5V
Differential Driver Output Voltage (With Load) R = 50Ω, (RS422) ● 2V

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

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

Output Voltage for Complementary Output States
Input High Voltage DI, DE, RE ● 2.0 V
Input Low Voltage DI, DE, RE ● 0.8 V
Input Current DI, DE, RE ● ±2 µA
Input Current (A, B) VCC = 0V or 5.25V, VIN = 12V ● 1.0 mA

Differential Input Threshold Voltage for Receiver – 7V ≤ VCM ≤ 12V ● – 0.2 0.2 V
Receiver Input Hysteresis VCM = 0V ● 60 mV
Receiver Output High Voltage IO = – 4mA, VID = 0.2V ● 3.5 V
Receiver Output Low Voltage IO = 4mA, VID = – 0.2V ● 0.4 V
Three-State Output Current at Receiver VCC = Max 0.4V ≤ VO ≤ 2.4V ● ±1 µA
Supply Current No Load; DI = GND or V

Receiver Input Resistance – 7V ≤ VCM ≤ 12V ● 12 kΩ
Driver Short-Circuit Current, V
Driver Short-Circuit Current, V
Receiver Short-Circuit Current 0V ≤ VO ≤ V

= High VO = – 7V ● 250 mA

OUT

= Low VO = 10 V ● 250 mA

OUT

ICSCD

R = 27Ω, (RS485) (Figure 1) ● 1.5 5 V

VCC = 0V or 5.25V, VIN = – 7V ● – 0.8 mA

Outputs Enabled ● 1.8 2.3 mA
Outputs Disabled ● 1.7 2.3 mA

CC

CC

● 785mA

2

LTC1485

U

S

WI

VCC = 5V (Notes 2, 3), unless otherwise noted.

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

PLH

t

PHL

t

SKEW

t

ZL

t

ZH

t

LZ

t

HZ

The ● denotes specifications which apply over the operating temperature
range.

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

I

TCH

GC CHARA TERIST

Driver Input to Output R

Driver Input to Output R

Driver Output to Output R

Driver Rise or Fall Time R

Driver Enable to Output High CL = 100pF (Figures 4, 6) S2 Closed ● 40 70 ns
Driver Enable to Output Low CL = 100pF (Figures 4, 6) S1 Closed ● 40 70 ns
Driver Disable Time from Low CL = 15pF (Figures 4, 6) S1 Closed ● 40 70 ns
Driver Disable Time from High CL = 15pF (Figures 4, 6) S2 Closed ● 40 70 ns
Receiver Input to Output R
Receiver Input to Output R
| t

– t

PLH

Differential Receiver Skew
Receiver Enable to Output Low CL = 15pF (Figures 3, 8) S1 Closed ● 30 45 ns
Receiver Enable to Output High CL = 15pF (Figures 3, 8) S2 Closed ● 30 45 ns
Receiver Disable from Low CL = 15pF (Figures 3, 8) S1 Closed ● 30 45 ns
Receiver Disable from High CL = 15pF (Figures 3, 8) S2 Closed ● 30 45 ns

|R

PHL

ICS

= 54Ω, CL1 = CL2 = 100pF ● 10 30 50 ns

DIFF

(Figures 2, 5)

= 54Ω, CL1 = CL2 = 100pF ● 10 30 50 ns

DIFF

(Figures 2, 5)

= 54Ω, CL1 = CL2 = 100pF ● 410 ns

DIFF

(Figures 2, 5)

= 54Ω, CL1 = CL2 = 100pF ● 51525 ns

DIFF

(Figures 2, 5)

= 54Ω, CL1 = CL2 = 100pF (Figures 2, 7) ● 15 25 50 ns

DIFF

= 54Ω, CL1 = CL2 = 100pF (Figures 2, 7) ● 20 30 55 ns

DIFF

= 54Ω, CL1 = CL2 = 100pF (Figures 2, 7) ● 515 ns

DIFF

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 for V

= 5V and TA = 25°C.

CC

LPER

F

O

Receiver Output Low Voltage vs
Output Current

36

TA = 25°C

32

28

24

20

16

12

OUTPUT CURRENT (mA)

8

4

0

0.5 1.5

0

1.0

OUTPUT VOLTAGE (V)

R

ATYPICA

2.0

1485 G01

UW

CCHARA TERIST

E

C

Receiver Output High Voltage vs
Output Current

–18

TA = 25°C

–16

–14

–12

–10

–8

–6

OUTPUT CURRENT (mA)

–4

–2

0

5

ICS

43

OUTPUT VOLTAGE (V)

1485 G02

2

Receiver Output High Voltage vs
Temperature

4.8
I = 8mA

4.6

4.4

4.2

4.0

3.8

3.6

OUTPUT VOLTAGE (V)

3.4

3.2

3.0

–25 125

–50

0

TEMPERATURE (°C)

50

25

75 100

1485 G03

3

LTC1485

TEMPERATURE (°C)

–50

1.55

INPUT THRESHOLD VOLTAGE (V)

1.59

50

1485 G09

1.57

–25 125

1.61

1.63

0

25

75 100

LPER

F

O

R

ATYPICA

UW

CCHARA TERIST

E

C

ICS

Receiver Output Low Voltage
vs Temperature

0.9
I = 8mA

0.8

0.7

0.6

0.5

0.4

0.3

OUTPUT VOLTAGE (V)

0.2

0.1

0

–25 125

–50

0

TEMPERATURE (°C)

50

25

Driver Output Low Voltage vs
Output Current

TA = 25°C

80

60

75 100

1485 G04

Driver Differential Output Voltage
vs Output Current

64

48

32

OUTPUT CURRENT (mA)

16

0

13

0

2

OUTPUT VOLTAGE (V)

Driver Output High Voltage vs
Output Current

–96

–72

TA = 25°C

TA = 25°C

4

1485 G05

Driver Differential Output Voltage
vs Temperature

2.4

2.2

2.0

1.8

DIFFERENTIAL VOLTAGE (V)

1.6
–50

0

–25 125

25

TEMPERATURE (°C)

50

TTL Input Threshold vs
Temperature

RL =54Ω

75 100

1485 G06

40

OUTPUT CURRENT (mA)

20

0

0

Receiver | t
Temperature

5

4

3

TIME (ns)

2

1

–50

–25 125

13

2

OUTPUT VOLTAGE (V)

– t

PLH

0

TEMPERATURE (°C)

| vs

PHL

25

50

4

1485 G07

75 100

1485 G10

–48

OUTPUT CURRENT (mA)

–24

0

5

4

3

TIME (ns)

2

1

–50

13

0

OUTPUT VOLTAGE (V)

0

–25 125

TEMPERATURE (°C)

2

4

1485 G08

Supply Current vs TemperatureDriver Skew vs Temperature

1.8

DRIVER ENABLED

1.7

1.6

DRIVER DISABLED

SUPPLY CURRENT (mA)

1.5

50

75 100

1485 G11

25

1.4
–50

0

–25 125

25

TEMPERATURE (°C)

50

75 100

1485 G12

4