ADV3002-EVALZ AD [Analog Devices], ADV3002-EVALZ Datasheet - Page 16

• Manufacturer Part Number: ADV3002-EVALZ
• Description: 4:1 HDMI/DVI Switch with Equalization, DDC/CEC Buffers and EDID Replication
• Manufacturer: AD [Analog Devices]

ADV3002
LOSS OF SIGNAL DETECT
The TMDS clock line of each HDMI input has a loss of signal (LOS)
monitor attached to it. The purpose of the LOS monitor is to
determine if there is activity in the HDMI link. A simplified
circuit diagram of the LOS detector is shown in Figure 27. The
LOS monitors are disabled by default. The LOS monitors can be
enabled by programming the LOS_EN bit of the LOS detect control
register. When enabled, the status of each HDMI input can be
read in the LOS detect status register. A logic high LOS_STATUS
bit of a given HDMI input indicates an inactive input; a logic low
LOS_STATUS bit indicates an active input. Three conditions need
to be fulfilled for an HDMI input to be considered active:
•
•
•
The TMDS input termination resistors must be enabled. By
default, the ADV3002 TMDS input termination resistors are
enabled only on the selected input.
The TMDS clock frequency exceeds the frequency cutoff
(LOS_FC). Refer to Table 1 for the value of the LOS fre-
quency cutoff.
TMDS clock differential amplitude exceeds the LOS threshold
set in the LOS detect control register. Refer to Table 1 for the
value of the LOS amplitude threshold.
Rev. 0 | Page 16 of 28
LOS Autosquelch
The LOS detect circuit can be used to automatically disable the
TMDS signal path. Setting the LOS_RX_EN bit in the LOS
control register causes the selected TMDS input to be disabled
when an LOS event occurs on that input. In this case, the TMDS
signal path is enabled when the active signal conditions listed
previously are met.
TMDS CLOCK
INPUT[x]
Figure 27. Loss of Signal Detect Simplified Circuit Diagram
FREQUENCY
FREQUENCY
DETECTOR
DETECTOR
1
0
1
0
FD
AD
LOS_THR
LOS_FC
LOS_STATUS[3:0]