ADP2127 datasheet(14/20 Pages) AD

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ADP2126/ADP2127

Rev. A | Page 14 of 20

APPLICATIONS INFORMATION

The low-profile ADP2126/ADP2127 are compatible with chip

inductors and multilayer ceramic capacitors that are ideal for

use in portable applications due to their small footprint and low

height. The recommended components for low-profile applications

may change as this technology advances. Table 5 and Table 6 list

compatible inductors and capacitors.

This section describes the selection of external components.

The component value ranges are limited to optimize efficiency

and transient performance while maintaining stability over the

full operating range.

INDUCTOR SELECTION

The high switching frequency of the ADP2126/ADP2127 allows for

minimal output voltage ripple, even with small inductors. Inductor

sizing is a trade-off between efficiency and transient response.

A small value inductor leads to a larger inductor current ripple,

which provides excellent transient response but degrades efficiency.

A small footprint and low height chip inductor can be used for an

overall smaller solution size but has a higher dc resistance (DCR)

value and lower current rating that can degrade performance.

Shielded ferrite core inductors are advantageous for their low core

losses and low electromagnetic interference (EMI). For optimal

performance and stability, use inductor values between 1.5 μH

and 0.5 μH. Recommended inductors are shown in Table 5.

The inductor peak-to-peak current ripple, ΔIL, is calculated from

(

)

OUT

−

(2)

where:

fSW is the switching frequency.

L is the inductor value.

It is important that the minimum dc current rating of the inductor

be greater than the peak inductor current (IPK) in the application.

IPK is calculated from

IPK = ILOAD(MAX) + ΔIL/2

(3)

The dc current rating of the inductor should be greater than the

calculated IPK to prevent core saturation.

INPUT CAPACITOR SELECTION

The input capacitor must be rated to support the maximum input

operating voltage. Higher value input capacitors reduce the input

voltage ripple caused by the switch currents on the VIN pin.

Maximum rms input current for the application is calculated using

()

OUT

MAX

LOAD

CIN

MAX

RMS

−

)

(

)

(

(4)

Place the input capacitor as close as possible to the VIN pin to

minimize supply noise.

In principle, different types of capacitors can be considered, but

for battery-powered applications, the best choice is the multilayer

ceramic capacitor, due to its small size, low equivalent series

resistance (ESR), and low equivalent series inductance (ESL).

It is recommended that the VIN pin be bypassed with at least a

2.2 μF input capacitor. For a 0.22 mm height solution using the

ADP2127, at least 2 × 1.0 μF capacitors will be necessary on the

input. The input capacitor can be increased without any limit for

better input voltage filtering. X5R or X7R dielectrics with a voltage

rating of 6.3 V or higher are recommended.

Table 5. Inductor Selection

Manufacturer

Series

Inductance (μH)

DCR (mΩ) (typ)

Current Rating (mA)

Size (L × W × H) (mm)

Package

Murata

LQM18PN1R0-A52

1.0

520

500

1.6 × 0.8 × 0.33

0603

Taiyo Yuden

CKP1608S1R5M

1.5

420

500

1.6 × 0.8 × 0.33

0603

Table 6. Input/Output Capacitor Selection

Manufacturer

Part Number

Capacitance (μF)

Voltage Rating (V)

Temperature

Coefficient

Size (L × W × H) (mm)

Package

Murata

GRM153R60J225ME95

2.2

6.3

X5R

1.0 × 0.5 × 0.33

0402

GRM153R60G225M

2.2

X5R

1.0 × 0.5 × 0.33

0402

Taiyo Yuden

JMK105BJ225MP

2.2

6.3

X5R

1.0 × 0.5 × 0.33

0402

AMK105BJ225MP

2.2

X5R

1.0 × 0.5 × 0.33

0402

AMK105BJ105MC

1.0

X5R

1.0 × 0.5 × 0.22

0402

ADC105BJ105ME

1.0

X5R

1.0 × 0.5 × 0.20

0402

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