ISL6563 Datasheet, PDF (17/19 Pages) Intersil Corporation – Two-Phase Multiphase Buck PWM Controller with Integrated MOSFET Drivers

ISL6563
High frequency decoupling capacitors should be placed as
close to the power pins of the load, or for that reason, to any
decoupling target they are meant for, as physically possible.
Attention should be paid as not to add inductance in the
circuit board wiring that could cancel the usefulness of these
low inductance components. Consult with the manufacturer
of the load on specific decoupling requirements.
Use only specialized low-ESR capacitors intended for
switching-regulator applications for the bulk capacitors. The
bulk capacitor’s ESR determines the output ripple voltage
and the initial voltage drop following a high slew-rate
transient’s edge. In most cases, multiple capacitors of small
case size perform better than a single large case capacitor.
Bulk capacitor choices include aluminum electrolytic, OS-Con,
Tantalum and even ceramic dielectrics. An aluminum
electrolytic capacitor’s ESR value is related to the case size
with lower ESR available in larger case sizes. However, the
equivalent series inductance (ESL) of these capacitors
increases with case size and can reduce the usefulness of the
capacitor to high slew-rate transient loading. Unfortunately,
ESL is not a specified parameter. Consult the capacitor
manufacturer and/or measure the capacitor’s impedance with
frequency to help select a suitable component.
Output Inductor Selection
One of the parameters limiting the converter’s response to a
load transient is the time required to change the inductor
current. In a multiphase converter, small inductors reduce
the response time with less impact to the total output ripple
current (as compared to single-phase converters).
+12V_IN
+5V_IN
(C_F1)
DACSEL/VID12
VID4
VID3
VID2
VID1
VID0
VRM10
R_ISEN
ISEN
R’_OFS
R_OFS
SSEND
ENLL
OFS
VCC
L_IN
(C_F2)
(C_HFIN1)
C_BIN1
PVCC
BOOT1
UGATE1
C_BOOT1
Q1
PHASE1
L_OUT1
ISL6563
LGATE1
BOOT2
UGATE2
Q2
C_BOOT2
Q3
C_BIN2
(C_HFIN2)
C_BOUT
V_OUT
(C_HFOUT)
COMP
C₂
C₁
R₂
FB
R₁
PHASE2
LGATE2
PGND
GND
L_OUT2
Q4
LOCATE NEAR LOAD;
(MINIMIZE CONNECTION PATH)
LOCATE NEAR SWITCHING TRANSISTORS;
(MINIMIZE CONNECTION PATH)
LOCATE CLOSE TO IC
(MINIMIZE CONNECTION PATH)
KEY
HEAVY TRACE ON CIRCUIT PLANE LAYER
ISLAND ON POWER PLANE LAYER
ISLAND ON CIRCUIT PLANE LAYER
VIA CONNECTION TO GROUND PLANE
FIGURE 9. PRINTED CIRCUIT BOARD POWER PLANES AND ISLANDS
17
FN9126.8
June 10, 2010