hip6301vcbza-t Intersil Corporation, hip6301vcbza-t Datasheet - Page 16

• Manufacturer Part Number: hip6301vcbza-t
• Description: Microprocessor Core Voltage Regulator Multiphase Buck Pwm Controller
• Manufacturer: Intersil Corporation

with vias to this layer. Dedicate another solid layer as a power
plane and break this plane into smaller islands of common voltage
levels. Keep the metal runs from the PHASE terminal to inductor
L
output power nodes. Use copper filled polygons on the top and
bottom circuit layers for the phase nodes. Use the remaining
printed circuit layers for small signal wiring. The wiring traces from
the driver IC to the MOSFET gate and source should be sized to
carry at least one ampere of current.
Component Selection Guidelines
Output Capacitor Selection
The output capacitor is selected to meet both the dynamic
load requirements and the voltage ripple requirements. The
load transient for the microprocessor CORE is characterized
by high slew rate (di/dt) current demands. In general,
multiple high quality capacitors of different size and dielectric
are paralleled to meet the design constraints.
Modern microprocessors produce severe transient load rates.
High frequency capacitors supply the initially transient current
and slow the load rate-of-change seen by the bulk capacitors.
The bulk filter capacitor values are generally determined by
the ESR (effective series resistance) and voltage rating
requirements rather than actual capacitance requirements.
High frequency decoupling capacitors should be placed as
close to the power pins of the load as physically possible. Be
careful 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
O1
KEY
short. The power plane should support the input power and
LOCATE NEXT
ISLAND ON POWER PLANE LAYER
TO FB PIN
+5VIN
C
R
R
BP
C
FB
IN
T
16
FIGURE 13. PRINTED CIRCUIT BOARD POWER PLANES AND ISLANDS
LOCATE NEXT TO IC PIN(S)
V
COMP
FB
VSEN
CC
HIP6301V
FS/DIS
PWM
ISEN
R
LOCATE NEXT TO IC PIN
SEN
R
T
HIP6301V, HIP6302V
ISLAND ON CIRCUIT PLANE LAYER
CBP
+12V
VCC
HIP6601
PVCC
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 measure the capacitor’s
impedance with frequency to 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. Small inductors in a multi-phase converter reduces
the response time without significant increases in total ripple
current.
The output inductor of each power channel controls the
ripple current. The control IC is stable for channel ripple
current (peak-to-peak) up to twice the average current. A
single channel’s ripple current is approximately:
The current from multiple channels tend to cancel each other
and reduce the total ripple current. Figure 14 gives the total
ripple current as a function of duty cycle, normalized to the
parameter
the total ripple current from the number of channels and the
duty cycle, multiply the y-axis value by
∆I
=
V
------------------------------- -
PHASE
IN
F
SW
CBOOT
–
V
(
×
Vo
OUT
L
)
⁄
×
(
LxF
USE INDIVIDUAL METAL RUNS
FOR EACH CHANNEL TO HELP
ISOLATE OUTPUT STAGES
V
--------------- -
V
OUT
IN
SW
CIN
LO1
)
at zero duty cycle. To determine
VIA CONNECTION TO GROUND PLANE
COUT
LOCATE NEAR TRANSISTOR
VCORE
(
Vo
)
⁄
(
LxF
December 27, 2004
SW
)
.
FN9034.2