AAT1126 데이터 시트보기 (PDF) - Skyworks Solutions

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AAT1126

600mA, 1MHz Step-Down Converter

Skyworks Solutions 

DATA SHEET

AAT1126

600mA, 1MHz Step-Down Converter

VOUT

C1

10μF

GND

JP1

1

2

3

Enable L1

4.7μH

R1

118K

R2

59K

LX

1

GND

2

EN

3

LX

VIN 5

OUT 4

AAT1126

VIN

C2

4.7μF

U1 AAT1126 SOT23-5

L1 CDRH3D16-4R7

C2 4.7μF 10V 0805 X5R

C1 10μF 6.3V 0805 X5R

Figure 5: AAT1126 Adjustable Evaluation Board Schematic.

VOUT (V)

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

1.8

1.85

2.0

2.5

3.3

R2 = 59k

R1 (k)

19.6

29.4

39.2

49.9

59.0

68.1

78.7

88.7

118

124

137

187

267

R2 = 221k

R1 (k)

75

113

150

187

221

261

301

332

442

464

523

715

1000

Table 2: Adjustable Resistor Values For Use With

0.6V Step-Down Converter.

Thermal Calculations

There are three types of losses associated with the

AAT1126 step-down converter: switching losses, con-

duction losses, and quiescent current losses. Conduction

losses are associated with the RDS(ON) characteristics of

the power output switching devices. Switching losses are

dominated by the gate charge of the power output

switching devices. At full load, assuming continuous con-

duction mode (CCM), a simplified form of the losses is

given by:

PTOTAL

=

IO2

·

(RDSON(HS)

·

VO

+ RDSON(LS)

VIN

·

[VIN

-

VO])

+ (tsw · F · IO + IQ) · VIN

IQ is the step-down converter quiescent current. The

term tsw is used to estimate the full load step-down con-

verter switching losses.

For the condition where the step-down converter is in

dropout at 100% duty cycle, the total device dissipation

reduces to:

PTOTAL = IO2 · RDSON(HS) + IQ · VIN

Since RDS(ON), quiescent current, and switching losses all

vary with input voltage, the total losses should be inves-

tigated over the complete input voltage range.

Given the total losses, the maximum junction tempera-

ture can be derived from the JA for the SOT23-5 pack-

age which is 150°C/W.

TJ(MAX) = PTOTAL · ΘJA + TAMB

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

201976B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 15, 2013

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