Datasheet

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TMDS Outputs
TMDS442
V
CC
GND
TMDS
Driver
AV
CC
Z
O
= R
T
Z
O
= R
T
R
T
R
T
TMDS
Receiver
HPD Pins
DDC Channels
Dual-Link 2-to-1 Switch Configurations
TMDS442
SLLS757A – AUGUST 2006 – REVISED MARCH 2007
A 1% precision resister, 4.64-k Ω , connected from VSADJ to ground is recommended to allow the differential
output swing to provide TMDS signal levels. The differential output driver provides a typical 10-mA current sink
capability, which provides a typical 500-mV voltage drop across a 50- Ω termination resistor. A 10% accuracy
resistor is allowed to be connected when the output swing is not strictly required to meet the TMDS signal levels.
A 10% resistor provides differential output voltages in the range of 438 mV and 532 mV.
Figure 31. TMDS Driver and Termination Circuit
Referring to Figure 31 , if both V
CC
(TMDS442 supply) and AV
CC
(sink termination supply) are both powered, the
TMDS output signals are high impedance when OE = high. Both supplies being active is the normal operating
condition.
Again refer to Figure 31 , if V
CC
is on and AV
CC
is off, the TMDS outputs source a typical 5-mA current through
each termination resistor to ground. A total of 10-mW of power is consumed by the terminations independent of
the OE logical selection. When AV
CC
is powered on, normal operation ( OE controls output impedance) is
resumed.
When the power source of the device is off and the power source to termination is on, the I
O(off)
, output leakage
current, specification ensures the leakage current is limited 10- μ A or less.
The PRE pin provides 3dB de-emphasis, allowing output signal pre-conditioning to offset interconnect losses
from the TMDS442 outputs to a TMDS receiver. PRE is recommended to be set low while connecting to a
receiver throw short PCB route.
The HPD signals (HPD1, HPD2, HPD3) have an output impedance of 47- Ω typically. In certain applications, a
931- Ω resistor from the HPD output to the connector pin is recommended, to increase the output resistance to
1-K Ω +/- 20%.
The DDC channels are designed using I
2
C drivers with 5-V signal tolerance, allowing direct connection to
standard I
2
C buses.
TMDS442 can be simply configured to operate as a dual-link DVI/HDMI, 2-to-1 switch, by configuring the device
as follows, see Figure 32 :
1. Set SA1 = low and SA2 = high
2. Set SB1 = SB2
3. When the 5V_SINK1, HPD_SINK1, SCL_SINK1, and SDA_SINK1 are selected as the control channels
from/to the SINK, connect the 5V_PWR1, HPD1, SCL1, and SDA1 to the dual-link source 1, and connect the
5V_PWR3, HPD3, SCL3, and SDA3 to the dual-link source 2.
4. When the 5V_SINK2, HPD_SINK2, SCL_SINK2, and SDA_SINK2 are selected as the control channels
from/to the SINK, connect the 5V_PWR2, HPD2, SCL2, and SDA2 to the dual-link source 1, and connect the
5V_PWR4, HPD4, SCL4, and SDA4 to the dual-link source 2.
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Product Folder Link(s): TMDS442