ADP5135

Data Sheet

Rev. 0 | Page 18 of 24

Table 9. Suggested 2.2 μH Inductors

Vendor

Model

Dimensions (mm)

DCR (mΩ)

Wurth Electronics

74438335022

3.0 ×3.0 × 1.5

3500

108

TDK

VLCF5020T-2R2N2R6-1

5.0 × 5.0 × 2.0

2620

71

Taiyo Yuden

NP04SZB2R2N

5.0 × 5.0 × 2.0

2700

42

Coilcraft

XFL4020-222ME

4.0 × 4.0 × 2.1

3500

23.5

The peak-to-peak output voltage ripple for the selected output

capacitor and inductor values is calculated using the following

equation:



OUT

SW

IN

OUT

SW

RIPPLE

RIPPLE

C

L

f

V

C

f

I

V

















2

2

8

Capacitors with lower effective series resistance (ESR) are

preferred to guarantee low output voltage ripple, as shown in

the following equation:

RIPPLE

RIPPLE

COUT

I

V

ESR



temperature and dc bias effects, is a minimum of 7 μF and a

maximum of 40 μF.

The buck regulators require 10 μF output capacitors to guaran-

tee stability and response to rapid load variations. To transition

into and out of the PWM/PSM modes, a 22 μF output capacitor

can be used for applications that require larger load steps. A list of

suggested capacitors is shown in Table 10. In certain applications

where one or all buck regulators power a processor, the operat-

ing state is known because it is controlled by software. In this

condition, the processor can drive the MODE pin according to the

operating state; consequently, it is possible to reduce the output

capacitor from 10 μF to 4.7 μF because the regulator does not

expect a large load variation when working in PSM mode.

Input Capacitor

Higher value input capacitors help to reduce the input voltage

ripple and improve transient response. The maximum input

capacitor current is calculated using the following equation:

IN

OUT

IN

OUT

MAX

LOAD

CIN

V

V

V

V

I

I

)

(

)

(





To minimize supply noise, place the input capacitor as close as

possible to the VINx pin of the buck regulator. As with the

output capacitor, a low ESR capacitor is recommended.

The effective capacitance needed for stability, which includes

temperature and dc bias effects, is a minimum of 3 μF and a

maximum of 10 μF. A list of suggested capacitors is shown in

Table 11 and Table 12.

Table 10. Suggested 22 μF Capacitors

Vendor

Type

Model

Case

Size

Voltage

Rating (V)

Murata

X5R

GRM188R60G226MEA0D

0603

6.3

TDK

X5R

C1608X5R0J226M080AC

0603

6.3

Taiyo

Yuden

X5R

LMK212BJ226MG-T

0805

10.0

Table 11. Suggested 10 μF Capacitors

Vendor

Type

Model

Case

Size

Voltage

Rating (V)

Murata

X5R

GRM188R60J106

0603

6.3

TDK

X5R

C1608JB0J106K

0603

6.3

Taiyo Yuden

X5R

JMK107BJ106MA-T

0603

6.3

Panasonic

X5R

ECJ1VB0J106M

0603

6.3

Table 12. Suggested 4.7 μF Capacitors

Vendor

Type

Model

Case

Size

Voltage

Rating (V)

Murata

X5R

GRM188R60J475ME19D

0402

6.3

Taiyo Yuden

X5R

JMK107BJ475

0402

6.3

Panasonic

X5R

ECJ-0EB0J475M

0402

6.3

Table 13. Suggested 1.0 μF Capacitors

Vendor

Type

Model

Case

Size

Voltage

Rating (V)

Murata

X5R

GRM155B30J105K

0402

6.3

Murata

X5R

GRM155R61A105KE15D

0402

10.0

TDK

X5R

C1005JB0J105KT

0402

6.3

Panasonic

X5R

ECJ0EB0J105K

0402

6.3

Taiyo

Yuden

X5R

LMK105BJ105MV-F

0402

10.0