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MAX3681

+3.3V, 622Mbps, SDH/SONET 1:4 Deserializer with LVDS Outputs

Maxim Integrated 

+3.3V, 622Mbps, SDH/SONET

1:4 Deserializer with LVDS Outputs

Low-Voltage Differential-Signal (LVDS)

Inputs and Outputs

The MAX3681 features LVDS inputs and outputs for

interfacing with high-speed digital circuitry. The LVDS

standard is based on the IEEE 1596.3 LVDS specifica-

tion. This technology uses 250mVp-p to 400mVp-p, dif-

ferential low-voltage swings to achieve fast transition

times, minimized power dissipation, and noise immunity.

The parallel clock and data LVDS outputs (PCLK+,

PCLK-, PD_+, PD_-) require 100Ω differential DC termi-

nation between the inverting and noninverting outputs

for proper operation. Do not terminate these outputs to

ground.

The synchronization LVDS inputs (SYNC+, SYNC-) are

internally terminated with 100Ω of differential input

resistance, and therefore do not require external termi-

nation.

PECL Inputs

The serial data and clock PECL inputs (SD+, SD-,

SCLK+, SCLK-) require 50Ω termination to (VCC - 2V)

when interfacing with a PECL source (see the

Alternative PECL Input Termination section).

__________Applications Information

Alternative PECL Input Termination

Figure 4 shows alternative PECL input-termination

methods. Use Thevenin-equivalent termination when a

(VCC - 2V) termination voltage is not available. If AC

coupling is necessary, such as when interfacing with

an ECL-output device, use the ECL AC-coupling termi-

nation.

Layout Techniques

For best performance, use good high-frequency layout

techniques. Filter voltage supplies and keep ground

connections short. Use multiple vias where possible.

Also, use controlled impedance transmission lines to

interface with the MAX3681 data inputs and outputs.

THEVENIN-EQUIVALENT TERMINATION

+3.3V

130Ω

ZO = 50Ω

130Ω

MAX3681

ZO = 50Ω

PECL

INPUTS

82Ω

82Ω

+3.3V

ZO = 50Ω

ECL AC-COUPLING TERMINATION

1.6k

1.6k

MAX3681

50Ω

ZO = 50Ω -2V

PECL

INPUTS

50Ω

2.7k

2.7k

-2V

Figure 4. Alternative PECL Input Termination

6 _______________________________________________________________________________________

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