ACT86600 datasheet(53/56 Pages) QORVO

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ACT86600

Hybrid PMIC for Enterprise

Storage and Computing

Data Sheet Rev. B, February 2, 2023

Subject to change without notice

53 of 56

www.qorvo.com

can only go up with maximum 50mA load current. After

start-up, more load (up to “Maximum Output Current”)

can be added. This is the most common case. If VCC5

starts up with output voltage higher than 2.6V (in case

of starting up with pre-bias), it can go up with more than

50mA load current.

Compensation

VCC5 utilizes a proprietary internal compensation

scheme to simultaneously simplify external component

selection while optimizing transient performance over

their full operating range. No external compensation de-

sign is required. Simply follow a few simple guidelines

described below when choosing the output capacitor

and inductor.

Input Capacitor Selection

The input requires a high quality, low-ESR, ceramic

input capacitor. VCC5 can be connected to the same or

a different voltage rail from the other converters. Even if

it is connected to the same voltage rail, it must have a

dedicated input capacitor. A 10µF capacitor is typically

suitable, but this value can be increased without limit.

Smaller capacitor values can be used with lighter output

loads. Choose the input capacitor value to keep the

input voltage ripple less than 50mV. When in buck-mode,

the following equation calculates the input ripple.

Vripple

=��∗��∗�1−��

��∗��

Be sure to consider the capacitor’s DC bias effects and

maximum ripple current rating when using capacitors

smaller than 0805.

A capacitor’s actual capacitance is strongly affected by

its DC bias characteristics. The input capacitor is

typically an X5R, X7R, or similar dielectric. Use of Y5V,

Z5U, or similar dielectrics is not recommended. Input

capacitor placement is critical for proper operation. The

input capacitor must be placed as close to the IC as

possible. The traces from AVIN to the capacitor and

from the capacitor to PGND should as short and wide

as possible.

Inductor Selection

VCC5

uses

proprietary

internal

compensation

scheme to simultaneously simplify external component

selection and optimize transient performance over its

full operating range. It requires a 1µH inductor. Choose

inductors with a low DC-resistance, or DCR, for higher

efficiency and avoid inductor saturation by choosing

inductors with DC ratings that exceed the maximum

inductor peak current by at least 30%. Additionally, the

inductor peak-to-peak current ripple must be carefully

considered along with the selected switching frequency

before selecting appropriate inductor values with

adequate

current

rating.

The

following

equation

calculates the inductor ripple current.

∆�� =�1−��∗��

��∗��

Where VOUT is the output voltage, VIN is the input voltage,

FSW is the switching frequency, and L is the inductor

value.

Output Capacitor Selection

VCC5 is designed to take advantage of the benefits of

ceramic capacitors, namely small size and very-low

ESR capacitors. It is designed to operate with greater

than 10µF of capacitance. To ensure stability, ensure

that the actual output capacitance is greater than 10µF.

Design for an output ripple voltage less than 1% of the

output

voltage. The

output

capacitance

can

increased to reduce output voltage ripple and improve

load transients if needed. The following equation

calculate the output voltage ripple

VRIPPLE

= ∆��

8∗��∗��

Where

ΔIL is the inductor ripple current, FSW is the

switching frequency, and COUT is the output capacitance

after taking DC bias into account.

The 10µF capacitor is the output capacitor of the buck

topology. Note that an additional 0.22µF must be

connected directly to the VCC5 pin. This capacitor is a

high frequency bypass capacitor that minimizes noise

entering the IC.

Two of the most common dielectrics are Y5V and X5R.

Whereas Y5V dielectrics are inexpensive and can

provide high capacitance in small packages, their

capacitance varies greatly over their voltage and

temperature ranges and are not recommended for

DC/DC applications. X5R and X7R dielectrics are more

suitable for output capacitor applications. Be sure to

consider the capacitor’s DC bias effects and maximum

ripple current rating when using capacitors smaller than

0805.

VCC5 PCB Layout Considerations

High switching frequencies and large peak currents

make PC board layout an important part of step-down

DC/DC converter design. A good design minimizes

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