CAT6613 데이터 시트보기 (PDF) - Unspecified

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CAT6613

HDMI 1.3 Transmitter

Unspecified 

CAT6613 Datasheet

C. TTL input traces from the decoder should be kept as short as possible

D. Depending on the TTL output specifications of the frontend decoder, 33Ω resistors might be

placed in series to its output pins. This slow down the signal rising edges, reduces current

spikes and lower the reflections.

E. The PCLK signal should be kept away from other signal traces to avoid crosstalk interference.

A general guideline is 2X the dielectric thickness. For example, if the dielectric layer between

the signal layer and the immediate power/ground layer is 7 mil, then the PCLK trace should

be kept at least 14 mil away from all other signal traces.

4. The characteristic impedance of all differential PCB traces should be kept at 100Ω all the way from

the HDMI connector to the CAT6613. This is crucial to the system performance at high speeds. When

layouting these differential transmission lines, the following guidelines should be followed:

A. The signals traces should be on the outside layers (TOP layer or BOTTOM layer) while

beneath it there should be a continuous ground plane in order to maintain the so-called

micro-strip transmission line structure, giving stable and well-defined characteristic

impedances.

B. Carefully choose the width and spacing of the differential transmission lines as their

characteristic impedance depends on various parameters of the PCB: trace width, trace

spacing, copper thickness, dielectric constant, dielectric thickness, etc. Careful 3D EM

simulation is the best way to derive a correct dimension that enables a nominal 100Ω

differential impedance.

C. Cornering, through holes, crossing and any irregular signal routing should be minimized so as

to prevent from disrupting the EM field and creating discontinuity in characteristic impedance.

D. The CAT6613 should be placed as close to the HDMI connector as possible. As a rule of

thumb, the lengths of the TMDS differential traces (from the TMDS output pins of the

CAT6613 to the HDMI connector) should be smaller than 1 cm (refer to Figure 20),

especially for applications that support TMDS data rates at more than 1.62 Gbps. This is

because at such high transmission rates, the source-side reflections would seriously impact

the output data eyes. Since PCB traces, even when carefully designed, suffer from large

impedance variations, it's a must that the reflection route be kept as short as possible.

5. Special care should be taken when adding discrete ESD devices to all differential PCB traces

(TX2P/M, TX1P/M, TX0P/M, TXCP/M). The CAT6613 is designed to provide ESD protection for up to

2kV at these pins, which is good enough to prevent damages during assembly. To meet the system

EMC specification, external discrete ESD diodes might be added. But note that adding discrete ESD

diodes inevitably add capacitive loads, therefore degrade the electrical performance at high speeds. If

not chosen carefully, these diodes coupled with less-than-optimal layout would degrade the output

data eyes, which might fail to pass the SOURCE Data Eye Diagram test in the HDMI Compliance Test

The CAT logo is a registered trademark of Chip Advanced Technology

2008 Chip Advanced Technology Inc. – All Right Reserved.

Mar-2010 Rev:1.0 33/37

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