AAT1154 Ver la hoja de datos (PDF) - Analog Technology Inc

Número de pieza

componentes Descripción

Fabricante

AAT1154

1MHz 3A Step-Down DC/DC Converter

Analog Technology Inc 

SwitchRegTM

Functional Block Diagram

VCC

PRODUCT DATASHEET

AAT1154

1MHz 3A Step-Down DC/DC Converter

VP = 2.7V to 5.5V

REF

FB

OP. AMP

CMP

DH

LOGIC

LX

OSC

Temp.

Sensing

GND

EN

Applications Information

Main Control Loop

The AAT1154 is a peak current mode step-down con-

verter. The inner wide bandwidth loop controls the

inductor peak current. The inductor current is sensed as

it flows through the internal P-channel MOSFET. A fixed

slope compensation signal is then added to the sensed

current to maintain stability for duty cycles greater than

50%. The inner loop appears as a voltage-programmed

current source in parallel with the output capacitor.

The voltage error amplifier output programs the current

loop for the necessary inductor current to force a con-

stant output voltage for all load and line conditions. The

feedback resistive divider is internal, dividing the output

voltage to the error amplifier reference voltage of 1V.

The error amplifier has a limited DC gain. This eliminates

the need for external compensation components, while

still providing sufficient DC loop gain for good load regu-

lation. The crossover frequency and phase margin are

set by the output capacitor value.

Duty cycle extends to 100% as the input voltage

approaches the output voltage. Thermal shutdown pro-

tection disables the device in the event of a short-circuit

or overload condition.

Soft Start/Enable

Soft start controls the current limit when the input volt-

age or enable is applied. It limits the current surge seen

at the input and eliminates output voltage overshoot.

When pulled low, the enable input forces the device into

a low-power, non-switching state. The total input current

during shutdown is less than 1μA.

Power and Signal Source

Separate small signal ground and power supply pins iso-

late the internal control circuitry from switching noise. In

1154.2007.11.1.7

www.analogictech.com

9

Share Link: