ADP3026 データシートの表示（PDF） - Analog Devices

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ADP3026

High Efficiency Dual Power Supply Controller

Analog Devices 

Table 7. Recommended Inductor Manufacturers

Coilcraft

Phone: 847/639-6400

Fax: 847/639-1469

Web: www.coilcraft.com

SMT Power Inductors

Series 1608, 3308, 3316, 5022, 5022HC,

DO3340

Low Cost Solution

SMT Shielded Power Inductors

Series DS5022, DS3316, DT3316

Best for Low EMI/RFI

Power Inductors and Chokes,

Series DC1012, PCV-0, PCV-1, PCV-2, PCH-27,

PCH-45

Low Cost

Coiltronics

Phone: 561/241-7876

Fax: 561/241-9339

Web: www.coiltronics.com

SMT Power Inductors

Series UNI-PAC2, UNI-PAC3 and UNI-PAC4

Low Cost Solution

SMT Power Inductors

Series, ECONO-PAC, VERSA-PAC

Best for Low Profile or Flexible Design

Power Inductors CTX Series

Low EMI/RFI

Low Cost Toroidal Inductors but Not

Miniature

Murata Electronics

North America Inc.

Phone: 770/436-1300

Fax: 770/436-3030

Web: www.murata.com

SMT Power Inductors

Series LQT2535

Best for Low EMI/RFI

Chip Inductors

LQN6C, LQS66C

ADP3026

CIN and COUT Selection

In continuous conduction mode, the source current of the

upper MOSFET is approximately a square wave of duty cycle

VOUT/VIN. To prevent large voltage transients use a low ESR

input capacitor sized for the maximum rms current. The

maximum rms capacitor current is given by

I RMS = V OUT × (V IN − V OUT) × I OUT(MAX)

(7)

V IN

This formula has a maximum at VIN = 2 × VOUT, where IRMS =

IOUT(MAX)/2. Note that the capacitor manufacturer’s ripple current

ratings are often based on only 2000 hours of life. It is therefore

advisable to further derate the capacitor, or to choose a

capacitor rated at a higher temperature than required. Several

capacitors may also be connected in parallel to meet size or

height requirements in the design. If electrolytic or tantalum

capacitors are used, place an additional 0.1 µF to 1 µF ceramic

bypass capacitor in parallel with CIN.

The selection of the output capacitor, COUT, is driven by the

required effective series resistance (ESR) and the desired output

ripple. A good guideline is to limit the ripple voltage to 1% of

the nominal output voltage. It is assumed that the total ripple is

caused by two factors: 25% comes from the COUT bulk

capacitance value, and 75% comes from the capacitor ESR.

The value of COUT is determined by

COUT

=

2×

I RIPPLE

f ×V RIPPLE

(8)

where IRIPPLE = 0.3 × IOUT and VRIPPLE = 0.01 × VOUT. The

maximum acceptable ESR of COUT is found using

ESR ≤ 0.75 × V RIPPLE

(9)

I RIPPLE

Manufacturers such as Vishay, AVX, Elna, WIMA, and Sanyo

provide good high performance capacitors. Sanyo’s OSCON

semiconductor dielectric capacitors have lower ESR for a given

size, at a somewhat higher price. Choosing sufficient capacitors

to meet the ESR requirement for COUT normally exceeds the

amount of capacitance needed to meet the ripple current

requirement.

In surface-mount applications, multiple capacitors may have to

be paralleled to meet the capacitance, ESR, or rms current

handling requirements. Aluminum electrolytic and dry

tantalum capacitors are available in surface-mount

configurations. In the case of tantalum, it is critical that

capacitors are surge tested for use in switching power supplies.

Recommendations for output capacitors are shown in Table 8.

Rev. 0 | Page 13 of 20

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