AAT1112 데이터 시트보기 (PDF) - Analog Technology Inc

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AAT1112

1.5A, 1.4MHz Step-Down Converter

Analog Technology Inc 

Functional Block Diagram

FB

AAT1112

1.5A, 1.4MHz Step-Down Converter

VIN

VP

Err.

Amp

VREF

EN

MODE/SYNC

Input

GND

DH

Logic

DL

LX

PGND

Functional Description

The AAT1112 is a high performance 1.5A monolith-

ic step-down converter operating at 1.4MHz switch-

ing frequency. It minimizes external component

size and optimizes efficiency over the complete

load range. Apart from the small bypass input

capacitor, only a small L-C filter is required at the

output. Typically, a 3.3µH inductor and a 22µF

ceramic capacitor are recommended for a 3.3V

output (see table of recommended values).

At dropout, the converter duty cycle increases to

100% and the output voltage tracks the input volt-

age minus the RDS(ON) drop of the P-channel high-

side MOSFET (plus the DC drop of the external

inductor). The device integrates extremely low

RDS(ON) MOSFETs to achieve low dropout voltage

10

during 100% duty cycle operation. This is advan-

tageous in applications requiring high output volt-

ages (typically > 2.5V) at low input voltages.

The integrated low-loss MOSFET switches can

provide greater than 95% efficiency at full load.

PFM operation maintains high efficiency under light

load conditions (typically <150mA). The MODE/

SYNC pin allows optional "PWM only" mode. This

maintains constant frequency and low output ripple

across all load conditions. Alternatively, the IC can

be synchronized to an external clock via the

MODE/ SYNC input. External synchronization is

maintained between 0.6MHz and 3.0MHz.

In battery-powered applications, as VIN decreases,

the converter dynamically adjusts the operating fre-

quency prior to dropout to maintain the required duty

cycle and provide accurate output regulation.

1112.2007.01.1.1

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