10-Bit Bus LVDS Serializers

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11

100

Ω

100

Ω

ASIC

ASIC

ASIC

100

Ω

100

Ω

MAX9205

MAX9207

MAX9150

REPEATER

MAX9206

MAX9208

MAX9206

MAX9208

Figure 13. Point-to-Point Broadcast Using MAX9150 Repeater

A point-to-point version of the multidrop bus is shown in

Figure 13. The low-jitter MAX9150 10-port repeater is

used to reproduce and transmit the serializer output

over 10 double-terminated point-to-point links.

Compared to the multidrop bus, more interconnect is

traded for more robust hot-plug capability.

The repeater eliminates nine serializers compared to 10

individual point-to-point serializer-to-deserializer con-

nections. Since repeater jitter subtracts from the serial-

izer-deserializer timing margin, a low-jitter repeater is

essential in most high data rate applications.

Multiple serializers and deserializers bused over a dif-

ferential serial connection on a backplane are shown in

Figure 14. The second serializer can be a backup to

the primary serializer. The typical close spacing (1in or

less) of cards on a backplane reduces the characteris-

tic impedance by as much as half the initial, unloaded

value. Termination resistors that match the loaded char-

acteristic impedance are required at each end of the

bus. The total loaded seen by the serializer is 27

Ω in

this case.

Board Layout

For bus LVDS applications, a four-layer PCB that pro-

vides separate power, ground, and input/output signals

is recommended. Separate LVTTL/LVCMOS and bus

LVDS signals from each other to prevent coupling into

the bus LVDS lines.