LTC1689 데이터 시트보기 (PDF) - Linear Technology

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LTC1689

100Mbps RS485 Hot Swapable Quad Drivers

Linear Technology 

LTC1688/LTC1689

UW

W

SWITCHI G TI E WAVEFOR S

3V

DI

0V

B

VO

A

VO

– VO

1.5V

tPLH

f = 1MHz; tr < 3ns; tf < 3ns

1/2 VO

90%

10%

tr

tSKEW

VDIFF = V(A) – V(B)

Figure 4. Driver Propagation Delays

1.5V

tPHL

1/2 VO

tSKEW

90%

10%

tf

3V

EN

0V

5V

A, B

VOL

VOH

A, B

0V

1.5V

tZL

1/2 VDD

f = 1MHz; tr ≤ 3ns; tf ≤ 3ns

OUTPUT NORMALLY LOW

1/2 VDD

OUTPUT NORMALLY HIGH

tZH

Figure 5. Driver Enable and Disable Times

1.5V

tLZ

0.5V

0.5V

tHZ

1688/89 F04

1688/89 F05

APPLICATIONS INFORMATION

The LTC1688/LTC1689 family of RS485 quad differential

drivers employs a novel architecture and fabrication pro-

cess that allows ultra high speed operation (100Mbps)

and Hot Swap capability while maintaining the ruggedness

of RS485 operation (three-state outputs can float from

– 7V to 12V with a single 5V supply). Unlike typical CMOS

drivers whose propagation delay can vary as much as

500%, the propagation delay of the LTC1688/LTC1689

drivers will only vary by ±50% (a narrow ±4ns window).

This performance is achieved by designing the input stage

of each driver to have minimum propagation delay shift

over temperature and from part to part.

The LTC1688/LTC1689 have an ESD rating of 6kV human

body model.

Electrical Characteristics table for 3V DC and AC specifica-

tions). Figure 6 shows waveforms of an LTC1689 driving

a receiver using 100 feet of Category 5 UTP. Both parts are

operating at 3V supply.

2V/DIV

LTC1689 OUTPUT

FAR END OF CABLE

2V/DIV

5V/DIV

RECEIVER OUTPUT

50Mbps with 3V Operation

The LTC1688/LTC1689 are designed to operate with a 3V

power supply and still achieve 50Mbps operation (see

20ns/DIV

1688/89 F06

Figure 6. 3V High Speed Data Transmission

16889fa

6

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