TMDS Digital Video Equalizer for

HDMI/DVI Cables

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Detailed Description

The MAX3815A TMDS equalizer accepts differential

CML input data at rates of 250Mbps up to 2.25Gbps

(individual channel data rate). It automatically adjusts

to skin-effect losses in copper cable. It consists of four

CML input buffers, a loss-of-clock signal detector, three

independent adaptive equalizers, four limiting amplifiers,

and four output buffers (Figure 1).

CML Input Buffers and Output Drivers

The input buffers and the output drivers are implemented

using current-mode logic (CML) (see Figures 4 and 5). The

output drivers are open-collector and can be turned off

with the OUTON pin. The OUTLEVEL pin sets the output

drive current to one of three levels; see the Applications

Information and Pin Description sections for more infor-

mation. For details on interfacing with CML, refer to

Application Note 291: HFAN-01.0: Introduction to LVDS,

PECL, and CML.

Loss-of-Clock Signal Detector

The loss-of-clock signal detector indicates a loss-of-

clock signal at the CLKLOS pin. This is an open-collector

external pullup. This resistor is required whether or not

the LOS output is used.

Adaptive Equalizer

The three data channels each contain an independent

adaptive equalizer. Each channel analyzes the incom-

ing signal and determines the amount of equalization to

apply.

Limiting Amplifier

The limiting amplifier amplifies the signal from the adap-

tive equalizer and truncates the top and bottom of the

waveform to provide a clean high- and low-level signal

to the output drivers.

Figure 1. Functional Diagram

INPUT

BUFFER

DRIVER

ADAPTIVE

EQ

LIMITING

AMPLIFIER

TERMINATED

3.3V CML

INPUT

BUFFER

DRIVER

ADAPTIVE

EQ

LIMITING

AMPLIFIER

TERMINATED

3.3V CML

INPUT

BUFFER

DRIVER

ADAPTIVE

EQ

LIMITING

AMPLIFIER

TERMINATED

3.3V CML

INPUT

BUFFER

DRIVER

LIMITING

AMPLIFIER

TERMINATED

3.3V CML

RXC_OUT+/-

OUTLEVEL

RX2_OUT+/-

RX1_OUT+/-

RX0_OUT+/-

RX0_IN+/-

RX1_IN+/-

RX2_IN+/-

RXC_IN+/-

CLKLOS

EQCONTROL

OUTON

CLOCK LOS

DETECTOR

MAX3815A