AAT2614

DATA SHEET

Step-Down DC/DC Converter with Quad High PSRR LDOs

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Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com

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Synchronous Step-Down Converter

The AAT2614 contains one high performance 600mA,

1.7MHz synchronous step-down converter.

The step-

down converter operates to ensure high efficiency per-

formance over all load conditions.

The input voltage range is from 2.5V to 5.5V, and the

output voltage is fixed and can be trimmed as shown in

the Ordering Information section of this datasheet.

Power devices are sized for 600mA current capability

while maintaining over 85% efficiency at full load. High

efficiency is maintained at lower currents

A high DC gain error amplifier with internal compensa-

tion controls the output. It provides excellent transient

response and load/line regulation. The converter has soft

start control to limit inrush current.

Apart from the input capacitor, only a small L-C filter is

required at the output side for the step-down converter

to operate properly. Typically, a 2.2μH inductor and a

10μF ceramic capacitor are recommended for low output

voltage ripple and small component size.

Control Loop

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

verter. The inner, wide bandwidth loop controls the

inductor peak current. The inductor current is sensed

through the P-channel MOSFET (high side) and is also

used for short circuit and overload protection. A fixed

slope compensation signal is added to the sensed cur-

rent to maintain stability for duty cycles greater than

50%. The peak current mode loop appears as a voltage

programmed current source in parallel with the output

capacitor. The output of the voltage error amplifier pro-

grams the current mode loop for the necessary peak

inductor current to force a constant output voltage for all

load and line conditions. The voltage feedback resistive

divider is internal and the error amplifier reference volt-

age is 0.6V. The voltage loop has a high DC gain making

for excellent DC load and line regulation. The internal

voltage loop compensation is located at the output of the

transconductance voltage error amplifier.

Soft-Start

Soft start increases the inductor current limit point lin-

early when the input voltage or enable input is applied.

It limits the current surge seen at the input and elimi-

nates output voltage overshoot.

Current Limit and

Over-Temperature Protection

For overload conditions the peak input current is limited.

As load impedance decreases and the output voltage

falls closer to zero, more power is dissipated internally,

raising the device temperature. Thermal protection com-

pletely disables switching when internal dissipation

becomes excessive, protecting the device from damage.

The junction over-temperature threshold is 140°C with

15°C of hysteresis.

LDO Regulator

The advanced circuit design of the linear regulator is

specifically optimized for very fast start-up and shut-

down timing. This proprietary LDO is also tailored for

superior transient response characteristics. These traits

are particularly important for applications which require

fast power supply timing.

The high-speed turn-on capability is enabled through the

implementation of a fast start control circuit, which

accelerates the power up behavior of fundamental con-

trol and feedback circuits within the LDO regulator. Fast

turn-off time response is achieved by an active output

pull down circuit, which is enabled when the LDO regula-

tor is placed in the shutdown mode. This active fast

shutdown circuit has no adverse effect on normal device

operation. The LDO regulator output has been specifi-

cally optimized to function with low cost, low ESR ceram-

ic capacitors. However, the design will allow for operation

over a wide range of capacitor types.

The regulator comes with complete short circuit and ther-

mal protection. The combination of these two internal

protection circuits gives a comprehensive safety system

to guard against extreme adverse operating conditions.