AAT2513 datasheet(10/22 Pages) ANALOGICTECH

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AAT2513

Dual 600mA Step-Down

Converter with Synchronization

2513.2007.04.1.1

Functional Description

The AAT2513 is a peak current mode pulse width

modulated (PWM) converter with internal compen-

sation. Each channel has independent input,

enable, feedback, and ground pins with a 1.7MHz

clock. Both converters operate in either a fixed fre-

quency (PWM) mode or a more efficient light load

(LL) mode. A phase shift pin programs the convert-

ers to operate in phase or 180° out of phase. The

converter can also be synchronized to an external

clock during PWM operation.

The input voltage range is 2.7V to 5.5V. An exter-

nal resistive divider as shown in Figure 1 programs

the output voltage up to the input voltage. The con-

verter MOSFET power stage is sized for 600mA

load capability with up to 96% efficiency. Light load

efficiency is up to 90% at a 1mA load.

Soft Start / Enable

The AAT2513 soft start control prevents output volt-

age overshoot and limits inrush current when either

the input power or the enable input is applied.

When pulled low, the enable input forces the con-

verter into a low power non-switching state with a

bias current of less than 1µA.

Low Dropout Operation

For conditions where the input voltage drops to the

output voltage level, the converter duty cycle

increases to 100%. As the converter approaches

the 100% duty cycle, the minimum off time initially

forces the high side on time to exceed the 1.7MHz

clock cycle and reduce the effective switching fre-

quency. Once the input drops below the level

where the converter can regulate the output, the

high side P-channel MOSFET is enabled continu-

ously for 100% duty cycle. At 100% duty cycle the

output voltage tracks the input voltage minus the

I*R drop of the high side P-channel MOSFET.

Functional Block Diagram

EN1

LX1

PGND1

VIN1

FB1

EN2

LX2

PGND2

Comp.

Control

Logic

Control

Logic

VIN2

AGND

Voltage

Reference

Voltage

Reference

Comp

Oscillator

MODE/SYNC

VCC

Logic

Err.

Amp.

Err.

Amp.

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