
HPD Pins
1kW
TMDS361
HPD_SINK
VCC/5V_source
1 k
(internal
W
series resistor)
VCC
HPD_SINK
HPD[1:3]
HPD_SOURCE
ON
L
H
L
ON
H
L
H
OFF
X
Z
H
VCC
HPD[1:3]
HPD_SOURCE
S0387-01
1kW
10kW
5V_Source (5VcomingfromHDMI source)
Layout Considerations
Using the TMDS361 in Systems with Different CEC Link Requirements
www.ti.com............................................................................................................................................ SLLS919A – DECEMBER 2008 – REVISED JANUARY 2009
The HPD circuits are powered by the 3.3-V VCC supply. This provides maximum VOH = VCC and maximum
VOL= 0.4-V output signals to the SOURCE with a typical 1-k output resistance. An external 1-k resistor is not
needed here. The HPD output of the selected source port follows the logic level of the HPD_SINK input.
Unselected HPD outputs are kept low. When the device is in standby mode, all HPD outputs follow HPD_SINK.
If VOH greater than VCC is desired, then an external circuit as shown in Figure 33 can be used. In this case, the max VOH can be equal to the 5 V coming from the HDMI source.
Figure 33. External Circuit to Drive 5-V VOH on HPD[1:3]
The high-speed differential TMDS inputs are the most critical paths for the TMDS361. There are several
considerations to minimize discontinuities on these transmission lines between the connectors and the device:
Maintain 100- differential transmission line impedance into and out of the TMDS361.
Keep an uninterrupted ground plane beneath the high-speed I/Os.
Keep the ground-path vias to the device as close as possible to allow the shortest return current path.
Keep the trace lengths of the TMDS signals between connector and device as short as possible.
The TMDS361 supports a DTV with up to three HDMI inputs when used in conjunction with a signal-port HDMI
receiver.
Figure 34 and
Figure 35 show simplified application block diagrams for the TMDS361 in different DTVs
with different consumer electronic control (CEC) requirements. The CEC is an optional feature of the HDMI
interface for centralizing and simplifying user control instructions from multiple audio/video products in an
interconnected system, even when all the audio/video products are from different manufacturers. This feature
minimizes the number of remote controls in a system, as well as reducing the number of times buttons must be
pressed.
Copyright 2008–2009, Texas Instruments Incorporated
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