AAT1126 查看數據表（PDF） - Advanced Analogic Technologies

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AAT1126

600mA, 1MHz Step-Down Converter

Advanced Analogic Technologies 

AAT1126

600mA, 1MHz Step-Down Converter

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 = 59kΩ

R1 (kΩ)

19.6

29.4

39.2

49.9

59.0

68.1

78.7

88.7

118

124

137

187

267

R2 = 221kΩ

R1 (kΩ)

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,

conduction 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 conduction 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 converter switching losses.

For the condition where the step-down converter is

in dropout at 100% duty cycle, the total device dis-

sipation reduces to:

PTOTAL = IO2 · RDSON(HS) + IQ · VIN

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.

1126.2006.05.1.1

13

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