User Guide 046
4
UG046.0
August 28, 2015
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When designing for >6A of output current place a Schottky
clamp diode as close as possible to the LXx and PGNDx pins of
the IC. A small series R-C snubber connected from the LXx pins to
the PGNDx pins may be used to damp high-frequency ringing on
the LXx pins if desired.
LXx Connection
Use a small island of copper to connect the LXx pins of the IC to
the output inductor on layers 1 and 4. Void the copper on layers 2
and 3 adjacent to the island to minimize capacitive coupling to
the power and ground planes. Place most of the island on layer 4
to minimize the amount of copper that must be voided from the
ground plane (layer 2).
Keep all other signal traces as short as possible.
High Current Protection Clamp
When using the ISL70003ASEH to output current levels >6A it is
highly recommended to implement a LX to PGND Schottky diode
clamp to prevent damage to the lower power FET devices. The
MBRS320T3G diode is used on the ISL70003ASEHEV1Z
evaluation platform but is not on this evaluation platform.
Lead Strain Relief
The package leads protrude from the bottom of the package and
the leads need forming to provide strain relief. On the heatsink
package R64.C, the lead forming should be made so that the
bottom of the heatsink and the formed leads are flush.
Heatsink Mounting Guidelines
The R64.C package has a heatsink mounted on the underside of
the package. The following JESD-51x series guidelines may be
used to mount the package:
1. Place a thermal land on the PCB under the heatsink.
2. The land should be approximately the same size as to 1mm
larger than the 10.16x10.16mm heatsink.
3. Place an array of thermal vias below the thermal land.
- Via array size: ~9x9 = 81 thermal vias.
- Via diameter: ~0.3mm drill diameter with plated copper on
the inside of each via.
- Via pitch: ~1.2mm.
- Vias should drop to and contact as much metal area as
feasible to provide the best thermal path.
Heatsink Electrical Potential
The heatsink is connected to pin 50 within the package; thus the
PCB design and potential applied to pin 50 will therefore define
the heatsink potential.
Heatsink Mounting Materials
In the case of electrically conductive mounting methods
(conductive epoxy, solder, etc) the thermal land, vias and
connected plane(s) below must be the same potential as pin 50.
In the case of electrically nonconductive mounting methods
(nonconductive epoxy), the heatsink and pin 50 could have
different electrical potential than the thermal land, vias and
connected plane(s) below.
