ISL62391_11 Datasheet, PDF (19/20 Pages) Intersil Corporation – High-Efficiency, Triple-Output System Power Supply Controller

ISL62391, ISL62392, ISL62391C, ISL62392C
R_OCSET to the phase-node side pad of the inductor, and
connect C_SEN to the output side pad of the inductor. The
ISEN resistor should also be connected to the output pad of
the inductor with a separate trace. Connect the OCSET pin
to the common node of node of R_OCSET and C_SEN.
For resistive current sensing, connect R_OCSET from the
OCSET pin to the inductor side of the resistor pad. The ISEN
resistor should be connected to the V_OUT side of the resistor
pad.
In both current-sense configurations, the resistor and
capacitor sensing elements, with the exclusion of the current
sense power resistor, should be placed near the
corresponding IC pin. The trace connections to the inductor
or sensing resistor should be treated as Kelvin connections.
FB (Pins 7 and 28), and VOUT (Pins 8 and 27)
The VOUT pin is used to generate the R³ synthetic ramp
voltage and for soft-discharge of the output voltage during
shutdown events. This signal should be routed as close to
the regulation point as possible. The input impedance of the
FB pin is high, so place the voltage programming and loop
compensation components close to the VOUT, FB, and GND
pins, keeping the high impedance trace short.
FSET (Pins 2 and 6)
This pin requires a quiet environment. The resistor R_FSET
and capacitor C_FSET should be placed directly adjacent to
this pin. Keep fast moving nodes away from this pin.
LGATE (Pins 15 and 20)
The signal going through this trace is both high dv/dt and
high di/dt, with high peak charging and discharging current.
Route this trace in parallel with the trace from the PGND pin.
These two traces should be short, wide, and away from
other traces. There should be no other weak signal traces in
proximity with these traces on any layer.
BOOT (Pins 14 and 21), UGATE (Pins 13 and 22), and
PHASE (Pins 12 and 23)
The signals going through these traces are both high dv/dt
and high di/dt, with high peak charging and discharging
current. Route the UGATE and PHASE pins in parallel with
short and wide traces. There should be no other weak signal
traces in proximity with these traces on any layer.
Copper Size for the Phase Node
The parasitic capacitance and parasitic inductance of the
phase node should be kept very low to minimize ringing. It is
best to limit the size of the PHASE node copper in strict
accordance with the current and thermal management of the
application. An MLCC should be connected directly across
the drain of the upper MOSFET and the source of the lower
MOSFET to suppress the turn-off voltage spike.
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FN6666.5
April 7, 2011