5962F0153601QYA View Datasheet(PDF) - Aeroflex UTMC

Part Name

Description

Manufacturer

5962F0153601QYA

Octal 400 Mbps Bus LVDS Repeater

Aeroflex UTMC 

APPLICATIONS INFORMATION

The UT54LVDM328 provides the basic bus repeater

function. The device operates as a 9 channel LVDS buffer.

Repeating the signal restores the LVDS amplitude, allowing

it to drive another media segment. This allows for isolation

of segments or long distance applications.

The intended application of these devices and signaling

technique is for both point-to-point baseband (single

termination) and multipoint (double termination) data

transmissions over controlled impedance media. The

transmission media may be printed-circuit board traces,

backplanes, or cables. (Note: The ultimate rate and distance

of data transfer is dependent upon the attenuation

characteristics of the media, the noise coupling to the

environment, and other application specific characteristics.)

Input Fail-Safe:

The UT54LVDM328 also supports OPEN, shorted and

terminated input fail-safe. Receiver output will be HIGH for

all fail-safe conditions.

PCB layout and Power System Bypass:

Circuit board layout and stack-up for the UT54LVDM328

should be designed to provide noise-free power to the device.

Good layout practice also will separate high frequency or high

level inputs and outputs to minimize unwanted stray noise

pickup, feedback and interference. Power system

performance may be greatly improved by using thin

dielectrics (4 to 10 mils) for power/ground sandwiches. This

increases the intrinsic capacitance of the PCB power system

which improves power supply filtering, especially at high

frequencies, and makes the value and placement of external

bypass capacitors less critical. External bypass capacitors

should include both RF ceramic and tantalum electrolytic

types. RF capacitors may use values in the range 0.01µF to

0.1µ F. Tantalum capacitors may be in the range of 2.2µF to

10µF. Voltage rating for tantalum capacitors should be at

least 5X the power supply voltage being used. It is

recommended practice to use two vias at each power pin of

the UT54LVDM328, as well as all RF bypass capacitor

terminals. Dual vias reduce the interconnect inductance and

extends the effective frequency range of the bypass

components.

The outer layers of the PCB may be flooded with additional

ground plane. These planes will improve shielding and

isolation, as well as increase the intrinsic capacitance of the

power supply plane system. Naturally, to be effective, these

planes must be tied to the ground supply plane at frequent

intervals with vias. Frequent via placement also improves

signal integrity in signal transmission lines by providing short

paths for image currents which reduces signal distortion. The

planes should be pulled back from all transmission lines and

component mounting pads a distance equal to the width of

the widest transmission line from the internal power or

ground plane(s) whichever is greater. Doing so minimizes

effects on transmission line impedances and reduces

unwanted parasitic capacitances at component mounting

pads.

Compatibility with LVDS standard:

In backplane multidrop configurations, with closely spaced

loads, the effective differential impedance of the line is

reduced. If the mainline has been designed for 50Ω

differential impedance, the loading effects may reduce this

to the 35Ω range depending upon spacing and capacitance

load. Terminating the line with a 35Ω load is a better match

than with 50Ω and reflections are reduced.

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