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SDAn

Switch Box

TMDS341A

SDA_Sink

Source

Sink

Sink

TMDS341A

SDA_Sink

SDAn

Source

DVI/HDMI RX

TMDS341A

SLLS702 – MAY 2006

APPLICATION INFORMATION (continued)

Figure 38. DDC Link from Source to Sink With External Switch Box

allowable capacitance, C

C

should then be less than 704 pF.

Typical capacitance is 200 pF for a 28-AWG 5-m HDMI cable and 300 pF for a 28-AWG 5-m DVI cable. The

recommended total cable length is the length of cable 1, Lcable1, plus the length of cable 2, Lcable2. For a

28-AWG DVI cable, the total cable length is 11 m; and for a 28-AWG HDMI cable, the total cable length is 17

m.

Maximum Bus Lengths for DTV Applications

Figure 39 shows the TMDS341A being used as a switch in a DTV and being placed on the same PCB board as

the DVI/HDMI receiver. Unlike Figure 38, the output connector of the TMDS341A stand-alone switch and the

input connector of the sink are removed, which results in a lower capacitance in the DDC link and eliminates the

impedance discontinuity. However, the capacitance of the removed connectors is relatively small, relative to the

total allowable capacitance. The results from the previous section Maximum Bus Lengths for Switch Applications

can be reused if the pull-up resistors and capacitances have the same values. The recommended total cable

length is the length from source to sink.

Figure 39. DDC Link From Source to Sink Without External Switch Box

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