Linear Technology LTC1687, LTC1686 Datasheet

FEATURES

■

Precision Propagation Delay Over Temperature:

Receiver/Driver: 18.5ns ±3.5ns

■

High Data Rate:

■

Low t

PLH/tPHL

52Mbps

Skew:

Receiver/Driver: 500ps Typ

■

–7V to 12V RS485 Input Common Mode Range

■

Guaranteed Fail-Safe Operation Over the Entire
Common Mode Range

■

High Input Resistance: ≥22k, Even When Unpowered

■

Short-Circuit Protected

■

Thermal Shutdown Protected

■

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

■

Single 5V Supply

■

Pin Compatible with LTC490/LTC491

■

45dB CMRR at 26MHz

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APPLICATIONS

■

High Speed RS485/RS422 Full Duplex Transceivers

■

Level Translator

■

Backplane Transceiver

■

STS-1/OC-1 Data Transceiver

■

Signal Repeaters

LTC1686/LTC1687

52Mbps Precision Delay

RS485 Fail-Safe Transceivers

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DESCRIPTION

The LTC®1686/LTC1687 are high speed, precision delay,
full-duplex RS485 transceivers that can operate at data
rates as high as 52Mbps. The devices also meet the
requirements of RS422.

A unique architecture provides very stable propagation
delays and low skew over a wide common mode and
ambient temperature range.

The driver and receiver feature three-state outputs, with
disabled driver outputs maintaining high impedance over
the entire common mode range. A short-circuit feature
detects shorted outputs and substantially reduces driver
output current. A similar feature also protects the receiver
output from short circuits. Thermal shutdown circuitry
protects from excessive power dissipation.

The receiver has a fail-safe feature that guarantees a high
output state when the inputs are shorted or are left floating.
The LTC1686/LTC1687 RS485 transceivers guarantee
receiver fail-safe operation over the
range (–7V to 12V). Receiver input resistance remains
≥ 22k when the device is unpowered or disabled.

The LTC1686/LTC1687 operate from a single 5V supply
and draw only 7mA of supply current.

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

entire

common mode

TYPICAL APPLICATION

LTC1686 LTC1686

3

D

R

DRIVER

2

RECEIVER

5

100Ω 100Ω

6

8

100Ω 100Ω

7

400 FT OF CATEGORY 5 UTP

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RECEIVER

DRIVER

LTC1686/87 • TA01

10Mbps Data Pulse

400 Feet Category 5 UTP

1686/87 TA02

DRIVER INPUT

RECEIVER
INPUT

RECEIVER
OUTPUT

2V/DIV

R

1V/DIV

D

5V/DIV

CABLE DELAY



100ns/DIV

1

LTC1686/LTC1687

S8 PACKAGE

8-LEAD PLASTIC SO

1
2
3
4

8
7
6
5



TOP VIEW

V

DD


R
D

GND

A
B
Z
Y

R

D

A

W

O

LUTEXI T

S

A

WUW

ARB

U
G

I

S

(Note 1)

Supply Voltage (VDD).............................................. 10V

Control Input Currents .................... –100mA to 100mA

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

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

Driver Output Voltages ................................. +12V/– 7V

Receiver Input Voltages ................................ +12V/–7V

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

Receiver Input Differential ...................................... 10V

PACKAGE

/

O

RDER I FOR ATIO

WU

U

ORDER PART

NUMBER

LTC1686CS8

S8 PART MARKING

T

= 125°C, θ

JMAX

Consult factory for Industrial and Military grade parts.

= 150°C/ W

JA

1686

Driver Short-Circuit Duration

(V

: –7V to 10V)...................................... Indefinite

OUT

Receiver Short-Circuit Duration

(V

: 0V to VDD) ........................................ Indefinite

OUT

Operating Temperature Range .................... 0°C to 70°C

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

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

1

NC

2

R

3

RE

4

DE

5

D

6

GND
GND

14-LEAD PLASTIC SO

T

JMAX

TOP VIEW

R

S PACKAGE

= 125°C, θ

D

JA

14
13
12
11
10

9
87

= 90°C/W

V

DD

NC
A
B
Z

Y

NC

ORDER PART

NUMBER

LTC1687CS

DC ELECTRICAL CHARACTERISTICS

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

OD1

V

OD2

∆V

OD

V

OC

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

V

IH

V

IL

I

IN1

I

IN2

V

TH

∆V

TH

V

OH

2

Differential Driver Output (Unloaded) I
Differential Driver Output (With Load) R = 50Ω (RS422) 2.0 V

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

Driver Common Mode Output Voltage R = 27Ω or 50Ω, VDD = 5V, Figure 1 ● 23V

Mode Output Voltage for Complementary
Output States

Input High Voltage D, DE, RE ● 2V
Input Low Voltage D, DE, RE ● 0.8 V
Input Current D, DE, RE ● –1 1 µA
Input Current (A, B) VA, VB = 12V, VDD = 0V or 5.25V ● 500 µA

Differential Input Threshold Voltage –7V ≤ VCM ≤ 12V ● –0.3 0.3 V
for Receiver

Receiver Input Hysteresis VCM = 0V 25 mV
Receiver Output High Voltage I

= 0 ● V

OUT

R = 27Ω (RS485), Figure 1 ● 1.5 V

, VB = –7V, VDD = 0V or 5.25V ● –500 µA

V

A

= –4mA, VID = 300mV ● 3.5 4.8 V

OUT

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

DD

DD

V

V

LTC1686/LTC1687

DC ELECTRICAL CHARACTERISTICS

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

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V
I

OL

OZR

Receiver Output Low Voltage I

= 4mA, VID = –300mV ● 0.4 V

OUT

Three-State (High Impedance) Output 0.4V ≤ V

≤ 2.4V ● –1 1 µA

OUT

Current at Receiver

I

OZD

Three-State (High Impedance) Output V

= –7V to 12V ● –200 200 µA

OUT

Current at Driver

C

LOAD

I

DD

I

OSD1

I

OSD2

I

OSR

R

IN

C

IN

Receiver and Driver Output Load Capacitance (Note 4) ● 500 pF
Supply Current No Load, Pins D, DE, RE = 0V or V
Driver Short-Circuit Current, V
Driver Short-Circuit Current, V
Receiver Short-Circuit Current V

= HIGH V

OUT

= LOW V

OUT

= –7V or 10V (Note 5) ● 20 mA

OUT

= –7V or 10V (Note 5) ● 20 mA

OUT

OUT

= 0V or V

(Note 5) ● 20 mA

DD

● 712 mA

DD

Input Resistance –7V ≤ VCM ≤ 12V ● 22 kΩ
Input Capacitance A, B, D, DE, RE Inputs (Note 4) 3 pF
Open-Circuit Input Voltage VDD = 5V (Note 4), Figure 5 ● 3.2 3.3 3.4 V

Fail-Safe Time to Detect Fail-Safe Condition 2 µs
Time

CMRR Receiver Input Common Mode VCM = 2.5V, f = 26MHz 45 dB

Rejection Ratio

U

SWITCHING CHARACTERISTICS

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

t

, t

PLH

t

SKEW

tr, t

f

t

ZH

t

ZL

t

LZ

t

HZ

t

PLH

t

SQD

t

ZL

t

ZH

t

LZ

t

HZ

t

PKG-PKG

Driver Input-to-Output Propagation Delay R

PHL

Figures 3, 5

Driver Output A-to-Output B Skew R

Figures 3, 5

Driver Rise/Fall Time R

Figures 3, 5
Driver Enable to Output High CL = 100pF, S2 Closed, Figures 4, 6 ● 25 50 ns
Driver Enable to Output Low CL = 100pF, S1 Closed, Figures 4, 6 ● 25 50 ns
Driver Disable from Low CL = 15pF, S1 Closed, Figures 4, 6 ● 25 50 ns
Driver Disable from High CL = 15pF, S2 Closed, Figures 4, 6 ● 25 50 ns

, t

Receiver Input-to-Output Propagation Delay CL = 15pF, Figures 3, 7 ● 15 18.5 22 ns

PHL

Receiver Skew t

PLH

– t

 C

PHL

Receiver Enable to Output Low CL = 15pF, S1 Closed, Figures 2, 8 ● 25 50 ns
Receiver Enable to Output High CL = 15pF, S2 Closed, Figures 2, 8 ● 25 50 ns
Receiver Disable from Low CL = 15pF, S1 Closed, Figures 2, 8 ● 25 50 ns
Receiver Disable from High CL = 15pF, S2 Closed, Figures 2, 8 ● 25 50 ns
Maximum Receiver Input (Note 4) ● 2000 ns

Rise/Fall Times
Package-to-Package Skew CL = 15pF, Same Temperature (Note 4) 1.5 ns
Minimum Input Pulse Width VDD = 5V ±5% (Note 4) ● 17 19.2 ns
Maximum Data Rate VDD = 5V ±5% (Note 4) ● 52 60 Mbps
Maximum Input Frequency VDD = 5V ±5% (Note 4) ● 26 30 MHz

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

= 54Ω, CL1 = CL2 = 100pF, ● 15 18.5 22 ns

DIFF

= 54Ω, CL1 = CL2 = 100pF, 500 ps

DIFF

= 54Ω, CL1 = CL2 = 100pF, 3.5 ns

DIFF

= 15pF, Figures 3, 7 500 ps

L

3

LTC1686/LTC1687

TEMPERATURE (°C)

–25

SUPPLY CURRENT (mA)

53

54

55

50

100

1686/87 G03

52

51

50

025 75

56

57

58

BOTH DRIVER AND RECEIVER
ENABLED AND LOADED
25Mbps DATA RATE

RECEIVER INPUT OVERDRIVE (V)

0.3 0.5

0

RECEIVER PROPAGATION DELAY (ns)

10

25

0.7

1.25

1.5

1686/87 G06

5

20

15

1.0

2.0

2.5

TA = 25°C

ELECTRICAL CHARACTERISTICS

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

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

Note 2: All currents into the device pins are positive; all currents out of the
device pins are negative.

Note 3: All typicals are given for V
Note 4: Guaranteed by design, but not tested.
Note 5: Short-circuit current does not represent output drive capability.

When the output detects a short-circuit condition, output drive current is
significantly reduced (from hundreds of mA to 20mA max) until the short
is removed.

UW

TYPICAL PERFORMANCE CHARACTERISTICS

Receiver Input CMRR

46.5

46.0

45.5

45.0

44.5

44.0

43.5

43.0

42.5

COMMON MODE REJECTION RATIO (dB)

TA = 25°C

42.0
10

1k 100k 1M

FREQUENCY (Hz)

1686/87 G01

Supply Current vs Data Rate

70

BOTH DRIVER AND RECEIVER
ENABLED AND LOADED

60

= 25°C

T

A

50

40

30

20

SUPPLY CURRENT (mA)

10

0

10 20 50

1

DATA RATE (Mbps)

4030

1686/87 G02

= 5V, TA = 25°C.

DD

Supply Current vs Temperature

Receiver Propagation Delay
vs Load Capacitance

30

TA = 25°C

25

20

15

10

PROPAGATION DELAY (ns)

5

0

5

15

LOAD CAPACITANCE (pF)

4

25 35 55

105 205

1686/87 G04

Receiver Propagation Delay
vs Common Mode

25

TA = 25°C

20

15

10

PROPAGATION DELAY (ns)

5

0

–4 0

–2

–7

RECEIVER COMMON MODE (V)

2

Receiver Propagation Delay
vs Input Overdrive

8

412

10

6

1686/87 G05