AFS090 datasheet(228/334 Pages) MICROSEMI

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Device Architecture

2- 21 2

R e v isio n 2

Timing Characteristics

BLVDS/M-LVDS

Bus LVDS (BLVDS) and Multipoint LVDS (M-LVDS) specifications extend the existing LVDS standard to

high-performance multipoint bus applications. Multidrop and multipoint bus configurations can contain

any combination of drivers, receivers, and transceivers. Microsemi LVDS drivers provide the higher drive

current required by BLVDS and M-LVDS to accommodate the loading. The driver requires series

terminations for better signal quality and to control voltage swing. Termination is also required at both

ends of the bus, since the driver can be located anywhere on the bus. These configurations can be

implemented using TRIBUF_LVDS and BIBUF_LVDS macros along with appropriate terminations.

Multipoint designs using Microsemi LVDS macros can achieve up to 200 MHz with a maximum of 20

loads. A sample application is given in Figure 2-133. The input and output buffer delays are available in

the LVDS section in Table 2-171.

Example: For a bus consisting of 20 equidistant loads, the following terminations provide the required

differential voltage, in worst-case industrial operating conditions at the farthest receiver: RS =60 Ω and

RT =70 Ω, given Z0 =50 Ω (2") and Zstub =50 Ω (~1.5").

Table 2-169 • AC Waveforms, Measuring Points, and Capacitive Loads

Input Low (V)

Input High (V)

Measuring Point* (V)

VREF (typ.) (V)

1.075

1.325

Cross point

–

Note:

*Measuring point = Vtrip. See Table 2-90 on page 2-168 for a complete table of trip points.

Table 2-170 • LVDS

Commercial Temperature Range Conditions: TJ = 70°C, Worst-Case VCC = 1.425 V,

Worst-Case VCCI = 2.3 V

Applicable to Pro I/Os

Speed Grade

tDOUT

tDP

tDIN

tPY

Units

Std.

0.66

2.10

0.04

1.82

–1

0.56

1.79

0.04

1.55

–2

0.49

1.57

0.03

1.36

Note:

For the derating values at specific junction temperature and voltage supply levels, refer to Table 3-7 on

page 3-9.

Figure 2-133 • BLVDS/M-LVDS Multipoint Application Using LVDS I/O Buffers

...

BIBUF_LVDS

Receiver

Transceiver

Receiver

Transceiver

Driver

RS RS

Zstub

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