AD8193
OUTPUT CHANNELS
Each high speed output differential pair is terminated to the
3.3 V VTTO power supply through two single-ended 50 Ω
on-chip resistors, as shown in Figure 20. These matched on-
chip back-terminations absorb reflections on the output TMDS
channels and improve the overall system signal integrity. These
termination resistors are always present in the outputs and they
cannot be switched out.
VTTO
50Ω
50Ω
OP[3:0]
ON[3:0]
IOUT
AVEE
Figure 20. High Speed Output Simplified Schematic
In a typical application, the AD8193 output is connected to the
input of an HDMI/DVI receiver, which provides a second set of
matched terminations in accordance with the HDMI 1.3
specification. If no receiver is connected, each of the AD8193
output pins should be tied to 3.3 V through a 50 Ω on-board
termination resistor.
Data Sheet
SWITCHING MODE
The source selector pin, S_SEL, is used to select which of the
two input groups is routed to the output. Source A is selected
when S_SEL is pulled up to logic high, and Source B is selected
when S_SEL is pulled down to logic low. Logic levels for this pin
are set in accordance with the specifications listed in Table 5. The
AD8193 can be used as a single-link TMDS buffer by setting
S_SEL to one fixed logic value.
S_SEL also controls the switch status of the input termination
resistors. The termination resistors for the selected input are
always connected, whereas the termination resistors for the
unselected input are always switched out (high-Z inputs).
Table 5. S_SEL Description
Selected
S_SEL Input
Input Termination Status
0
Input B
Input B terminations enabled, Input A
terminations disabled
1
Input A
Input A terminations enabled, Input B
terminations disabled
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