HIP6301VCBZ datasheet(16/20 Pages) RENESAS

16 / 20 page

HIP6301V, HIP6302V

FN9034 Rev 3.00

Page 16 of 20

May 5, 2008

A multi-layer printed circuit board is recommended.

Figure 13 shows the connections of the critical components

for one output channel of the converter. Note that capacitors

CIN and COUT could each represent numerous physical

capacitors. Dedicate one solid layer, (usually the middle

layer of the PC board), for a ground plane and make all

critical component ground connections 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 LO1

short. The power plane should support the input power and

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

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 reduce

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

VCORE

+12V

VIA CONNECTION TO GROUND PLANE

ISLAND ON POWER PLANE LAYER

ISLAND ON CIRCUIT PLANE LAYER

LO1

COUT

CIN

+5VIN

KEY

PHASE

VCC

USE INDIVIDUAL METAL RUNS

COMP

HIP6301V

PWM

RIN

RFB

CBP

VSEN

ISEN

RSEN

HIP6601

CBOOT

CBP

VCC

FS/DIS

PVCC

LOCATE NEXT TO IC PIN

LOCATE NEXT

TO FB PIN

LOCATE NEXT TO IC PIN(S)

ISOLATE OUTPUT STAGES

FOR EACH CHANNEL TO HELP

LOCATE NEAR TRANSISTOR

FIGURE 13. PRINTED CIRCUIT BOARD POWER PLANES AND ISLANDS

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