Cable TMDS Equalizer

The MAX3814 is useful in providing equalization for

cables losses at location ZZ, at the input DVI/HDMI

connector of the remote display. It can equalize cable

lengths of 15 meters of 26 AWG wire and 12 meters of

28 AWG wire. Again, the 200

Ω resistor placed at the

output of the MAX3814 absorbs reflections from the

imperfect termination of the ASIC or imperfect transmis-

sion-line interconnect.

Layout Considerations

The TMDS CML inputs are the most critical paths for

the MAX3814 and great care should be taken to mini-

mize discontinuities on these transmission lines

between the connector and the IC. Here are some sug-

gestions for maximizing the performance of the

MAX3814.

• The data and clock inputs should be wired direct-

ly between the cable connector and IC without

stubs.

• The 4-channel implementation treats all channels

identically. Input and output data channel designa-

tions are only a guide. Polarity assignments can be

swapped and channel paths can be interchanged.

• An uninterrupted ground plane should be posi-

tioned beneath the high-speed I/Os.

• Ground-path vias should be placed close to the

IC and the input/output interfaces to allow a return

current path to the IC and the DVI and HDMI

inputs.

• Maintain a 100

Ω differential transmission line

impedance into and out of the MAX3814.

• To minimize possible reflections, choose the

200

Ω back termination option. Place this resistor

as close to the MAX3814 as possible.

• Use good high-frequency layout techniques and

multilayer boards with an uninterrupted ground

plane to minimize EMI and crosstalk. Refer to the

schematic and board layers of the MAX3814EVKIT.

DVI/HDMI TMDS FR-4 and

Cable Equalizer/Driver

______________________________________________________________________________________

11

LAPTOP

DOCK

EXTERNAL DVI/HDMI

CABLE

DVI/HDMI

CONNECTOR

DVI/HDMI

CONNECTOR

MXM

CONNECTOR

DOCKING

CONNECTOR

REMOTE DISPLAY

GRAPHICS

BOARD

ASIC

ASIC

200

Ω

50

Ω

3.3V

50

Ω

3.3V

50

Ω

3.3V

50

Ω

3.3V

50

Ω

3.3V

50

Ω

3.3V

200

Ω

CMOS

ROUTING

SWITCH

50

Ω

3.3V

50

Ω

3.3V

200

Ω

MAX3814

MAX3814

MAX3814

Typical Application Circuits