Detailed Description

The LVDS interface standard provides a signaling

method for point-to-point communication over a con-

trolled-impedance medium as defined by the ANSI

TIA/EIA-644 standard. LVDS utilizes a lower voltage

swing than other communication standards, achieving

higher data rates with reduced power consumption,

while reducing EMI emissions and system susceptibility

to noise.

The MAX9394/MAX9395 high-speed, low-power 2:1

multiplexers and 1:2 demultiplexers with loopback pro-

vide signal redundancy switching in telecom and stor-

age applications. These devices select one of two

remote signal sources for local input and buffer a single

local output signal to two remote receivers.

The multiplexer section (channel B) accepts two differen-

tial inputs and generates a single LVDS output. The

demultiplexer section (channel A) accepts a single differ-

ential input and generates two parallel LVDS outputs. The

MAX9394/MAX9395 feature a loopback mode that con-

nects the input of channel A to the output of channel B

and connects the selected input of channel B to the out-

puts of channel A. LB_SELA and LB_SELB provide inde-

pendent loopback control for each channel.

Three LVCMOS/LVTTL logic inputs control the internal

connections between inputs and outputs, one for the

multiplexer portion of channel B (BSEL), and the other

two for loopback control of channels A and B (LB_SELA

and LB_SELB). Independent enable inputs for each dif-

ferential output pair provide additional flexibility.

Input Fail-Safe

The differential inputs of the MAX9394/MAX9395 pos-

sess internal fail-safe protection. Fail-safe circuitry

forces the outputs to a differential-low condition for

undriven inputs or when the common-mode voltage

exceeds the specified range. The MAX9394 provides

high-level input fail-safe detection for LVDS, HSTL, and

other GND-referenced differential inputs. The MAX9395

provides low-level input fail-safe detection for LVPECL,

Select Function

BSEL selects the differential input pair to transmit

through OUTB (OUTB) for LB_SELB = GND or through

the loopback function for each channel. Connect

LB_SEL_ to GND to select the normal inputs for each

back function. The loopback function routes the input of

channel A to the output of channel B, and the inputs of

channel B to the outputs of channel A. See Tables 1

and 2 for a summary of the input/output routing

between channels.

Enable Function

The EN_ _ logic inputs enable and disable each set of

OUT_0/OUT_0 differential output pair. Connect EN_0 to

GND to disable the OUT_0/OUT_0 differential output

pair. The differential output pairs assert to a differential

low condition when disabled.

Applications Information

Differential Inputs

The MAX9394/MAX9395 inputs accept any differential

signaling standard within the specified common-mode

voltage range. The fail-safe feature detects common-

mode input signal levels and generates a differential

output low condition for undriven inputs or when the

common-mode voltage exceeds the specified range

for the MAX9394 or to GND for the MAX9395.

2:1 Multiplexers and 1:2 Demultiplexers with

Loopback

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Figure 6. Output Channel-to-Channel Skew