ISL54105A Datasheet, PDF (10/16 Pages) Intersil Corporation – TMDS Regenerator

ISL54105A
Next, a 15m DualLink DVI cable was attached and
terminated into a female TPA2 adapter and the eye captured
in Figure 4.
FIGURE 4. CHROMA EYE DIAGRAM AFTER 15m CABLE
The eye is not meeting the minimum requirements of either
the HDMI or DVI standards and the Dell Monitor is unable to
recover the data and display an image.
Setup B inserts an ISL54105A and an additional 15m cable
between the pattern generator and the monitor:
CHROMA 2326
VIDEO PATTERN
GENERATOR
FIGURE 3
15m DUAL-LINK
DVI CABLE
FIGURE 4
FIGURE 7
ISL54105A
15m DUAL-LINK
DVI CABLE
DELL 2000FP
UXGA MONITOR
FIGURE 6
FIGURE 5. TEST SETUP B
Given the input signal shown in Figure 4, the ISL54105A’s
TMDS output signal (Figure 6) is extremely clean. The
output is an improvement over the original signal coming
from the pattern generator in both amplitude and jitter.
10
FIGURE 6. EYE DIAGRAM AT OUTPUT OF ISL54105A
The cleaner signal generated at the output of the ISL54105A
results in an improved eye at the end of another 15m cable
(Figure 7). The eye is open enough that the Dell 2000FP can
now display a UXGA image with no visible sparkle or other
artifacts.
FIGURE 7. ISL54105A EYE DIAGRAM AFTER 15m CABLE
Tx Loading Considerations
When the ISL54105A is powered-up and its Tx outputs are
disabled, via either the PD (power down) pin, the
power-down register bit (register 0x02[5]), or the tri-state
outputs bits (register 0x05[1:0]), the Tx pins are high
impedance. In this state they will draw no current from the
Rx pins of any TMDS receiver they may be connected to.
However, if power to the ISL54105A is removed, the Tx pins
are no longer high-impedance. Figure 8 shows the relevant
equivalent circuit, including the internal ESD protection
diodes. For simplicity’s sake, only one of the eight Tx
outputs, ESD protection diodes, and Rx termination resistors
are shown.
When V_D to the ISL54105A drops below ~2.7V and power is
applied to the external TMDS receiver, ESD protection
diodes inside the ISL54105A can become forward-biased,
FN6716.0
June 4, 2008