ISL6211 Datasheet, PDF (14/16 Pages) Intersil Corporation – Crusoe™ Processor Core-Voltage Regulator

ISL6211
Layout Considerations
Switching converters, even during normal operation,
produce short pulses of current which could cause
substantial ringing and be a source of EMI pollution if layout
constrains are not observed.
There are two sets of critical components in a DC-DC
converter. The switching power components process large
amounts of energy at high rate and are noise generators.
The low power components responsible for bias and
feedback functions are sensitive to noise.
A multi-layer printed circuit board is recommended. Dedicate
one solid layer for a ground plane. Dedicate another solid
layer as a power plane and break this plane into smaller
island of common voltage levels.
Notice all the nodes that are subjected to high dV/dt voltage
swing such as PHASE, UGATE and LGATE, for example. All
surrounding circuitry will tend to couple the noise from these
nodes through stray capacitance. Do not oversize copper
traces connected to these nodes. Do not place traces
connected to the feedback components adjacent to these
traces. It is not recommended to use High Density
Interconnect Systems, or micro-vias on these signals. The
use of blind or buried vias should be limited to the low
current signals only. The use of normal thermal vias is left to
the discretion of the designer.
Keep the wiring traces from the control IC to the MOSFET
gate and source as short as possible and capable of
handling peak currents of 2A. Minimize the area within the
gate-source path to reduce stray inductance and eliminate
parasitic ringing at the gate.
Locate small critical components like the soft-start capacitor
and current sense resistors as close as possible to the
respective pins of the IC.
The ISL6211 utilizes advanced packaging technology that
will have lead pitch of 0.6mm. High performance analog
semiconductors utilizing narrow lead spacing may require
special considerations in PWB design and manufacturing. It
is critical to maintain proper cleanliness of the area
surrounding these devices. It is not recommended to use
any type of rosin or acid core solder, or the use of flux in
either the manufacturing or touch up process as these may
contribute to corrosion or enable electromigration and/or
eddy currents near the sensitive low current signals. When
chemicals such as these are used on or near the PWB, it is
suggested that the entire PWB be cleaned and dried
completely before applying power.
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