Data Sheet

ADP2503/ADP2504

Rev. D | Page 13 of 16

APPLICATIONS INFORMATION

ADIsimPower DESIGN TOOL

The ADP2503/ADP2504 is supported by ADIsimPower design

tool set. ADIsimPower is a collection of tools that produce

complete power designs optimized for a specific design goal.

The tools enable the user to generate a full schematic, bill of

materials, and calculate performance in minutes. ADIsimPower

can optimize designs for cost, area, efficiency, and device count

while taking into consideration the operating conditions and

limitations of the IC and all real external components. For

more information about ADIsimPower design tools, refer to

www.analog.com/ADIsimPower. The tool set is available from

this website, and users can also request an unpopulated board

through the tool.

INDUCTOR SELECTION

The high 2.5 MHz switching frequency of the ADP2503/

ADP2504 allows for minimal output voltage ripple, while

minimizing inductor size and cost. Careful inductor selection

also optimizes efficiency and reduces electromagnetic interfe-

rence (EMI). The selection of the inductor value determines

the inductor current ripple and loop dynamics.

L

f

V

V

V

V

Buck

peak

I

OSC

IN

OUT

IN

OUT

L













)

(

)

(

,

L

f

V

V

V

V

Boost

peak

I

OSC

IN

OUT

IN

OUT

L











)

(

)

(

,

where:

L is the inductor value in henries.

A larger inductor value reduces the current ripple (and, therefore,

the peak inductor current), but is physically larger in size with

increased dc resistance. Inductor values between 1 μH and

1.5 μH are suggested. The maximum inductor value to ensure

stability is 2.0 μH. For increased efficiency with the ADP2504,

it is suggested that a 1.5 μH inductor be used.

The inductor peak current is at the maximum in boost mode.

To determine the actual maximum inductor current in boost

mode, estimate the input dc current.

η

V

V

I

I

IN

OUT

MAX

LOAD

MAX

IN

1

)

(

)

(



















where η is efficiency (assume η ≈ 0.85 to 0.90).

The saturation current rating of the inductor must be at least

Ceramic multilayer inductors can be used with lower current

designs for a reduced overall solution size and dc resistance

(DCR). These are available in low profile packages. Care must

be taken because these derate quickly as the inductor value is

increased, especially at higher operating temperatures.

Ferrite core inductors have good core loss characteristics as well as

reasonable dc resistance. A shielded ferrite inductor reduces the

EMI generated by the inductor.

Table 5. Sample of Recommended Inductors

Vendor

Value

(μH)

Device No.

DCR

(mΩ)

(A)

Dimensions

L × W × H

(mm)

Toko

1.2

DE2810C

55

1.7

2.8 × 2.8 × 1.0

Toko

1.5

DE2810C

60

1.5

2.8 × 2.8 × 1.0

Toko

1

MDT2520-CN

100

1.8

2.5 × 2 × 1.2

Murata

1

LQM2HP-G0

55

1.6

2.5 × 2 × 1

Murata

1.5

LQM2HP-G0

70

1.5

2.5 × 2 × 1

TDK

1.0

CPL2512T

90

1.5

2.5 × 1.5 × 1.2

TDK

1.5

CPL2512T

120

1.2

2.5 × 1.5 × 1.2

Coilcraft

1.0

LPS3010

85

1.7

3.0 × 3.0 × 0.9

Coilcraft

1.5

LPS3010

120

1.3

3.0 × 3.0 × 0.9

Taiyo

Yuden

1.5

NR3015T1

40

1.5

3.0 × 3.0 × 1.5

Output Capacitor Selection

The output capacitor selection determines the output voltage

ripple, transient response, and the loop dynamics of the

ADP2503/ADP2504. The output voltage ripple for a given

output capacitor is as follows:



OUT

OSC

IN

OUT

IN

OUT

OUT

C

f

L

V

V

V

V

Buck

peak

V

















2

8

)

(

)

(

,

OSC

OUT

OUT

IN

OUT

LOAD

OUT

f

V

C

V

V

I

Boost

peak

V













)

(

)

(

,

If the ADP2503/ADP2504 are operating in buck mode, the

worst-case voltage ripple occurs for the highest input voltage,

The maximum voltage overshoot, or undershoot, is inversely

proportional to the value of the output capacitor. To ensure

stability and excellent transient response, it is recommended

to use a minimum of 22 μF X5R 6.3 V or 2 × 10 μF X5R 6.3 V

capacitors at the output. The effective capacitance (includes

temperature and dc bias effects) needed for stability is 14 μF.