LM10506 datasheet(32/43 Pages) TI2

32 / 43 page

VROUT = IRIPPLE x ESRCOUT and VCOUT =

8 x FS x COUT

IRIPPLE

VOUT-RIPPLE-PP =

ROUT + V

COUT

8 x FS x COUT

üI

RIPPLE

where üIRIPPLE =

VOUT

VIN

2 x L x FS

D x (VIN - VOUT)

and D =

VOUT-RIPPLE-PP =

VOUT1/2/3

SW1/2/3

OUTPUT

CAPACITOR

LM10506

SNVS729F – SEPTEMBER 2011 – REVISED AUGUST 2014

www.ti.com

9.2.2.3.2.3.1

Output Capacitor Selection

The output capacitor of a switching converter absorbs the AC ripple current from the inductor and provides the

initial response to a load transient. The ripple voltage at the output of the converter is the product of the ripple

current flowing through the output capacitor and the impedance of the capacitor. The impedance of the capacitor

can be dominated by capacitive, resistive, or inductive elements within the capacitor, depending on the frequency

of the ripple current. Ceramic capacitors have very low ESR and remain capacitive up to high frequencies. Their

inductive component can usually be neglected at the frequency ranges at which the switcher operates.

The output-filter capacitor smooths out the current flow from the inductor to the load and helps maintain a steady

output voltage during transient load changes. It also reduces output voltage ripple. These capacitors must be

selected with sufficient capacitance and low enough ESR to perform these functions.

Note that the output voltage ripple increases with the inductor current ripple and the Equivalent Series

Resistance of the output capacitor (ESRCOUT). Also note that the actual value of the capacitor’s ESRCOUT is

frequency and temperature dependent, as specified by its manufacturer. The ESR should be calculated at the

applicable switching frequency and ambient temperature.

(3)

Output ripple can be estimated from the vector sum of the reactive (capacitance) voltage component and the real

(ESR) voltage component of the output capacitor where:

(4)

where:

•

VOUT-RIPPLE-PP: estimated output ripple,

•

VROUT: estimated real output ripple,

•

VCOUT: estimated reactive output ripple.

(5)

The device is designed to be used with ceramic capacitors on the outputs of the buck regulators. The

recommended dielectric type of these capacitors is X5R, X7R, or of comparable material to maintain proper

tolerances over voltage and temperature. The recommended value for the output capacitors is 22

μF, 6.3V with

an ESR of 2 m

Ω or less. The output capacitors need to be mounted as close as possible to the output/ground

pins of the device.

Table 5. Recommended Output Capacitors

MODEL

TYPE

VENDOR

VOLTAGE RATING (V)

CASE SIZE

08056D226MAT2A

Ceramic, X5R

AVX Corporation

6.3

0805, (2012)

C0805L226M9PACTU

Ceramic, X5R

Kemet

6.3

0805, (2012)

ECJ-2FB0J226M

Ceramic, X5R

Panasonic - ECG

6.3

0805, (2012)

JMK212BJ226MG-T

Ceramic, X5R

Taiyo Yuden

6.3

0603, (1608)

C2012X5R0J226M

Ceramic, X5R

TDK Corporation

6.3

0603, (1608)

Submit Documentation Feedback

Product Folder Links: LM10506

LM10506 Datasheet(PDF) 32 Page - Texas Instruments

LM10506 Datasheet(HTML) 32 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43

Datasheet Download

Link URL