AAT3236 查看數據表（PDF） - Advanced Analogic Technologies

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AAT3236

300mA CMOS High Performance LDO

Advanced Analogic Technologies 

AAT3236

300mA CMOS High Performance LDO

VOUT = 3.0V

IOUT = 500mA

IGND = 150μA

526mW + (3.0V × 500mA)

VIN(MAX) =

500mA + 150μA

VIN(MAX) = 4.05V

From the discussion above, PD(MAX) was deter-

mined to equal 526mW at TA = 25°C.

Thus, the AAT3236 can sustain a constant 3V output

at a 500mA load current as long as VIN is ≤ 4.05V at

an ambient temperature of 25°C.

Higher input-to-output voltage differentials can be

obtained with the AAT3236, while maintaining device

functions within the thermal safe operating area. To

accomplish this, the device thermal resistance must

be reduced by increasing the heat sink area or by

operating the LDO regulator in a duty-cycled mode.

For example, an application requires VIN = 4.2V

while VOUT = 3.0V at a 500mA load and TA = 25°C.

VIN is greater than 4.05V, which is the maximum

safe continuous input level for VOUT = 3.0V at

500mA for TA = 25°C. To maintain this high input

voltage and output current level, the LDO regulator

must be operated in a duty-cycled mode. Refer to

the following calculation for duty-cycle operation:

IGND = 150μA

IOUT = 500mA

VIN = 4.2V

VOUT = 3.0V

%DC =

100

PD(MAX)

(VIN - VOUT)IOUT + (VIN × IGND)

%DC =

100

(4.2V

-

526mW

3.0V)500mA + (4.2V

×

150μA)

%DC = 87.57%

PD(MAX) is assumed to be 526mW.

For a 500mA output current and a 1.2 volt drop

across the AAT3236 at an ambient temperature of

25°C, the maximum on-time duty cycle for the

device would be 87.57%.

The following family of curves show the safe oper-

ating area for duty-cycled operation from ambient

room temperature to the maximum operating level.

Device Duty Cycle vs. VDROP

(VOUT = 2.5V @ 25°C)

3.5

3

2.5

500 mA

200 mA

2

1.5

400 mA

1

300 mA

0.5

0

0 10 20 30 40 50 60 70 80 90 100

Duty Cycle (%)

Device Duty Cycle vs. VDROP

(VOUT = 2.5V @ 50°C)

3.5

3

2.5 500 mA

200 mA

100 mA

2

1.5

400 mA

1

300 mA

0.5

0

0 10 20 30 40 50 60 70 80 90 100

Duty Cycle (%)

Device Duty Cycle vs. VDROP

(VOUT = 2.5V @ 85°C)

3.5

3

2.5

2

200 mA

1.5

1 500 mA

0.5

400 mA

300 mA

0

0 10 20 30 40 50 60 70

Duty Cycle (%)

100 mA

80 90 100

12

3236.2007.03.1.4

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