ISL54100A_14 Datasheet, PDF (17/21 Pages) Intersil Corporation – TMDS Regenerators with Multiplexers

ISL54100A, ISL54101A, ISL54102A
• Minimize capacitance on all TMDS lines. The lower the
capacitance, the sharper the rise and fall times.
• Maintain a constant, solid ground (or power) plane under
the 3 high speed TMDS signals. Do not route the signals
over gaps in the ground plane or over other traces.
VIA TO
POWER
PLANE
V⁺
CBYPASS
IC
VIAS
TO
GND
GND
EQUIVALENT CIRCUIT
POWER PLANE
RVIA
RTRACE
RTRACE
V⁺
V⁺
CBYPASS
IC
GND
GROUND PLANE
FIGURE 12. SUB-OPTIMAL BYPASS CAPACITOR LAYOUT
• Ideally each supply should be bypassed to ground with a
0.1µF capacitor. Minimize trace length and vias to
minimize inductance and maximize noise rejection.
Figure 12 demonstrates a common but non-ideal PCB
layout and its equivalent circuit. The additional trace
resistance between the bypass capacitor and the power
supply/IC reduces its effectiveness. Figure 13
demonstrates a better layout. In this case there is still
series trace resistance (it is impossible to completely
eliminate it), but now it is being put to good use, as part of
a “T” filter, attenuating supply noise before it gets to the IC,
and reducing the amount of IC-generated noise that gets
injected into the supply. Follow the good supply bypassing
rules shown in Figure 13 to the extent possible.
VIA TO
POWER
PLANE
V⁺
CBYPASS
IC
GND
VIAS
TO
GND
EQUIVALENT CIRCUIT
POWER PLANE
RVIA
RTRACE
RTRACE
V⁺
V⁺
CBYPASS
IC
GND
GROUND PLANE
FIGURE 13. OPTIMAL (“T”) BYPASS CAPACITOR LAYOUT
ISL5410xA Serial Communication
Overview
The ISL5410xA uses a 2-wire serial bus for communication
with its host. SCL is the Serial Clock line, driven by the host
and SDA is the Serial Data line, which can be driven by all
devices on the bus. SDA is open drain to allow multiple
devices to share the same bus simultaneously.
Communication is accomplished in three steps:
1. The Host selects the ISL5410xA it wishes to
communicate with.
2. The Host writes the initial ISL5410xA Configuration
Register address it wishes to write to or read from.
3. The Host writes to or reads from the ISL5410xA’s
Configuration Register. The ISL5410xA’s internal
address pointer auto increments, so to read registers
0x00 through 0x1B, for example, one would write 0x00 in
step 2, then repeat step three 28 times, with each read
returning the next register value.
17
FN6725.0
June 17, 2008