Pin Name

Pin

Number

I/O

Description

POWER

V

CC

2, 8, 14,

20, 29, 35,

38, 44

PV

Each V

typically with a via located as close as possible to the landing pad of the V

It is recommended to have a 0.01 µF or 0.1 µF, X7R, size-0402 bypass capacitor from

each V

GND

5, 11, 17,

32, 41

P

Ground reference. Each ground pin should be connected to the ground plane through a low

inductance path, typically with a via located as close as possible to the landing pad of the

GND pin.

GND

DAP

P

Die Attach Pad (DAP) is the metal contact at the bottom side, located at the center of the

LLP-48 package. It should be connected to the GND plane with at least 4 via to lower the

ground impedance and improve the thermal performance of the package.

Note: I = Input, O = Output, P = Power

Functional Description

The DS42MB200 is a signal conditioning 2:1 multiplexer and

a 1:2 buffer designed to support port redundancy up to 4.25

Gb/s. Each input stage has a fixed equalizer that provides

equalization to compensate about 5 dB of transmission loss

from a short backplane trace (about 10 inches backplane).

The output driver has pre-emphasis (driver-side equaliza-

tion) to compensate the transmission loss of the backplane

that it is driving. The driver conditions the output signal such

that the lower frequency and higher frequency pulses reach

approximately the same amplitude at the end of the back-

plane, and minimize the deterministic jitter caused by the

amplitude disparity. The DS42MB200 provides 4 steps of

user-selectable pre-emphasis ranging from 0, -3, -6 and –9

dB to handle different lengths of backplane. Figure 1 shows

a driver pre-emphasis waveform. The pre-emphasis duration

is 200ps nominal, corresponds to 0.75 bit-width at 4 Gb/s.

The pre-emphasis levels of switch-side and line-side can be

individually programmed.

The high speed inputs are self-biased to about 1.5V and are

designed for AC coupling. The inputs are compatible to most

AC coupling differential signals such as LVDS, LVPECL and

CML.

TABLE 1. LOGIC TABLE FOR MULTIPLEX CONTROLS

MUX_S0

Mux Function

0

1 (default)

MUX_S1

Mux Function

0

1 (default)

TABLE 2. LOGIC TABLE FOR LOOPBACK Controls

LB0A

Loopback Function

0

1 (default)

Normal mode. Loopback disabled.

LB0B

Loopback Function

0

1 (default)

Normal mode. Loopback disabled.

LB1A

Loopback Function

0

1 (default)

Normal mode. Loopback disabled.

LB1B

Loopback Function

0

1 (default)

Normal mode. Loopback disabled.

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