ISL59446 Datasheet, PDF (12/13 Pages) Intersil Corporation – 500MHz Triple 4:1 Gain-of-2, Multiplexing Amplifier

ISL59446
• Match Channel-Channel analog I/O trace lengths and
layout symmetry. This will minimize propagation delay
mismatches.
• Maximize use of AC decoupled PCB layers. All signal I/O
lines should be routed over continuous ground planes (i.e.
no split planes or PCB gaps under these lines). Avoid vias
in the signal I/O lines.
• Use proper value and location of termination resistors.
Termination resistors should be as close to the device as
possible.
• When testing use good quality connectors and cables,
matching cable types and keeping cable lengths to a
minimum.
• Minimum of 2 power supply decoupling capacitors are
recommended (1000pF, 0.01µF) as close to the devices
as possible - avoid vias between the cap and the device
because vias add unwanted inductance. Larger caps can
be farther away. When vias are required in a layout, they
should be routed as far away from the device as possible.
• The NIC pins are placed on both sides of the input pins.
These pins are not internally connected to the die. It is
recommended these pins be tied to ground to minimize
crosstalk.
The QFN Package Requires Additional PCB Layout
Rules for the Thermal Pad
The thermal pad is electrically connected to V- supply
through the high resistance IC substrate. Its primary function
is to provide heat sinking for the IC. However, because of the
connection to the V- supply through the substrate, the
thermal pad must be tied to the V- supply to prevent
unwanted current flow to the thermal pad. Do not tie this pin
to GND as this could result in large back biased currents
flowing between GND and V-. The ISL59446 the package
with pad dimensions of D2 = 2.48mm and E2 = 3.4mm.
Maximum AC performance is achieved if the thermal pad is
attached to a dedicated decoupled layer in a multi-layered
PC board. In cases where a dedicated layer is not possible,
AC performance may be reduced at upper frequencies.
• The thermal pad requirements are proportional to power
dissipation and ambient temperature. A dedicated layer
eliminates the need for individual thermal pad area. When
a dedicated layer is not possible a 1” x 1” pad area is
sufficient for the ISL59446 that is dissipating 0.5W in
+50°C ambient. Pad area requirements should be
evaluated on a case by case basis.
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FN6261.1
August 26, 2010