AAT1106 Ver la hoja de datos (PDF) - Skyworks Solutions

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componentes Descripción

Fabricante

AAT1106

600mA Step-Down Converter

Skyworks Solutions 

Part

Sumida

CR43

Sumida

CDRH4D18

Toko

D312C

L (μH)

1.4

2.2

3.3

4.7

1.0

2.2

3.3

4.7

1.5

2.2

3.3

4.7

Max

DCR

(m)

56.2

71.2

86.2

108.7

4.5

75

110

162

120

140

180

240

Rated DC

Current

(A)

2.52

1.75

1.44

1.15

1,72

1.32

1.04

0.84

1.29

1.14

0.98

0.79

Size

WxLxH

(mm)

4.5x4.0x3.5

4.7x4.7x2.0

3.6x3.6x1.2

Table 2: Typical Surface Mount Inductors.

For output voltages above 2.0V, when light-load effi-

ciency is important, the minimum recommended induc-

tor size is 2.2μH. For optimum voltage-positioning load

transients, choose an inductor with DC series resistance

in the 50m to 150m range. For higher efficiency at

heavy loads (above 200mA), or minimal load regulation

(with some transient overshoot), the resistance should

be kept below 100m. The DC current rating of the

inductor should be at least equal to the maximum load

current plus half the ripple current to prevent core satu-

ration (600mA + 105mA). Table 2 lists some typical

surface mount inductors that meet target applications

for the AAT1106.

Manufacturer's specifications list both the inductor DC

current rating, which is a thermal limitation, and the

peak current rating, which is determined by the satura-

tion characteristics. The inductor should not show any

appreciable saturation under normal load conditions.

Some inductors may meet the peak and average current

ratings yet result in excessive losses due to a high DCR.

Always consider the losses associated with the DCR and

its effect on the total converter efficiency when selecting

an inductor. For example, the 2.2μH CR43 series induc-

tor selected from Sumida has a 71.2mΩ DCR and a

1.75ADC current rating. At full load, the inductor DC loss

is 25mW which gives a 2.8% loss in efficiency for a

600mA, 1.5V output.

Slope Compensation

The AAT1106 step-down converter uses peak current

mode control with a unique adaptive slope compensation

scheme to maintain stability with lower value inductors

DATA SHEET

AAT1106

600mA Step-Down Converter

for duty cycles greater than 50%. Using lower value

inductors provides better overall efficiency and also

makes it easier to standardize on one inductor for differ-

ent required output voltage levels. In order to do this

and keep the step-down converter stable when the duty

cycle is greater than 50%, the AAT1106 separates the

slope compensation into 2 phases. The required slope

compensation is automatically detected by an internal

circuit using the feedback voltage VFB before the error

amp comparison to VREF.

VREF

VFB

Error Amp

When below 50% duty cycle, the slope compensation is

0.284A/μs; but when above 50% duty cycle, the slope

compensation is set to 1.136A/μs. The output inductor

value must be selected so the inductor current down slope

meets the internal slope compensation requirements.

Below 50% duty cycle, the slope compensation require-

ment is:

m = 1.25 = 0.284A/µs

2·L

Therefore:

L = 0.625 = 2.2µH

m

Above 50% duty cycle,

m = 5 = 1.136A/µs

2·L

Therefore:

L = 2.5 = 2.2µH

m

With these adaptive settings, a 2.2μH inductor can be

used for all output voltages from 0.6V to 5V.

Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

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201970B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 15, 2013

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