AAT1162 查看數據表（PDF） - Analog Technology Inc

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AAT1162

Voltage-Scaling Step-Down Converter

Analog Technology Inc 

AAT1162

12V, 1.5A Step-Down DC/DC Converter

Short-Circuit Protection

The AAT1162 uses a cycle-by-cycle current limit to

protect itself and the load from an external fault

condition. When the inductor current reaches the

internally set 3.0A current limit, the P-channel

MOSFET switch turns off and the N-channel syn-

chronous rectifier is turned on, limiting the inductor

and the load current.

During an overload condition, when the output volt-

age drops below 50% of the regulation voltage

(0.3V at FB), the AAT1162 switching frequency

drops by a factor of 4. This gives the inductor cur-

rent ample time to reset during the off time to pre-

vent the inductor current from rising uncontrolled in

a short-circuit condition.

Thermal Protection

The AAT1162 includes thermal protection that dis-

ables the regulator when the die temperature

reaches 140ºC. It automatically restarts when the

temperature decreases by 25ºC or more.

Applications Information

Setting the Output Voltage

Figure 1 shows the basic application circuit for the

AAT1162 and output setting resistors. Resistors

R1 and R2 program the output to regulate at a volt-

age higher than 0.6V. To limit the bias current

required for the external feedback resistor string

while maintaining good noise immunity, the mini-

mum suggested value for R2 is 5.9kΩ. Although a

larger value will further reduce quiescent current, it

will also increase the impedance of the feedback

node, making it more sensitive to external noise

and interference. Table 1 summarizes the resistor

values for various output voltages with R2 set to

either 5.9kΩ for good noise immunity or 59kΩ for

reduced no load input current.

VIN 4.5V -13.2V

C1

22µF

R4

10Ω

C6

0.1µF

C7

1µ F

EP2

3 EN

4

IN

5

IN

7

AIN

LX

LX 1

LX 2

AAT1162 FB 9

COMP 10

6 DGND

AGND 11

13

DGND

16

PGND

DGND 14

8

DGND LDO

EP1

C5

1µF

L1

3.8µH

C3

100pF

R3

50kΩ

C4

270pF

VOUT

5V, 2A

R1

43.2kΩ C2

22µF

R2

5.9kΩ

Figure 1: Typical Application Circuit.

The adjustable feedback resistors, combined with

an external feed forward capacitor (C3 in Figure 1),

deliver enhanced transient response for extreme

pulsed load applications. The addition of the feed

forward capacitor typically requires a larger output

capacitor C2 for stability. Larger C3 values reduce

overshoot and undershoot during startup and load

changes. However, do not exceed 470pF to main-

tain stable operation.

1162.2007.09.1.2

11

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