Applications Information

Differential Inputs

The MAX9390/MAX9391 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 MAX9390 or to GND for the MAX9391.

Expanding the Number of LVDS Output

Ports

Cascade devices to make larger switches. Consider

the total propagation delay and total jitter when deter-

mining the maximum allowable switch size.

Power-Supply Bypassing

mount ceramic 0.1µF and 0.01µF capacitors in parallel

as close to the device as possible. Install the 0.01µF

capacitor closest to the device.

Differential Traces

Input and output trace characteristics affect the perfor-

mance of the MAX9390/MAX9391. Connect each input

and output to a 50

Ω characteristic impedance trace.

Maintain the distance between differential traces and

eliminate sharp corners to avoid discontinuities in dif-

ferential impedance and maximize common-mode

noise immunity. Minimize the number of vias on the dif-

ferential input and output traces to prevent impedance

discontinuities. Reduce reflections by maintaining the

50

Ω characteristic impedance through connectors and

across cables. Minimize skew by matching the electri-

cal length of the traces.

Output Termination

Terminate LVDS outputs with a 100

Ω resistor between

the differential outputs at the receiver inputs. LVDS out-

puts require 100

Ω termination for proper operation.

Ensure that the output currents do not exceed the cur-

rent limits specified in the Absolute Maximum Ratings.

Observe the total thermal limits of the MAX9390/

MAX9391 under all operating conditions.

Cables and Connectors

Use matched differential impedance for transmission

media. Use cables and connectors with matched differ-

ential impedance to minimize impedance discontinu-

ities. Avoid the use of unbalanced cables. Balanced

cables such as twisted pair offer superior signal quality

and tend to generate less EMI due to canceling effects.

Board Layout

Use a four-layer printed circuit (PC) board providing

separate signal, power, and ground planes for high-

close to the device as possible. Install termination

resistors as close to receiver inputs as possible. Match

the electrical length of the differential traces to minimize

signal skew.

Anything-to-LVDS Dual 2 x 2

Crosspoint Switches

10

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Table 1. Input/Output Function Table

_SEL0

_SEL1

OUT_0 /

OUT_0

OUT_1 /

OUT_1

MODE

0

0

IN_0 / IN_0

IN_0 / IN_0

1:2 splitter

0

1

IN_0 / IN_0

IN_1 / IN_1

Repeater

1

0

IN_1 / IN_1

IN_0 / IN_0

Switch

1

1

IN_1 / IN_1

IN_1 / IN_1

1:2 splitter