AP7335 datasheet(12/17 Pages) DIODES

12 / 17 page

AP7335

300mA, Low Quiescent Current, Fast Transient

Low Dropout Linear Regulator

AP7335

Document number: DS32259 Rev. 2 - 2

12 of 17

www.diodes.com

September 2010

Application Note (Continued)

Ultra Fast Start-up

After enabled, the AP7335 is able to provide full power in

as little as tens of microseconds, typically 220µs, without

sacrificing low ground current. This feature will help load

circuitry move in and out of standby mode in real time,

eventually extend battery life for mobile phones and other

portable devices.

Fast Transient Response

Fast transient response LDO can extend battery life.

TDMA-based cell phone protocols such as Global System

for Mobile Communications (GSM) have a transmit/receive

duty factor of only 12.5 percent, enabling power savings

by putting much of the baseband circuitry into standby

mode in between transmit cycles. In baseband circuits, the

load often transitions virtually instantaneously from 100µA

to 100mA. To meet this load requirement, the LDO must

react very quickly without a large voltage drop or

overshoot — a requirement that cannot be met with

conventional, general-purpose LDO.

The AP7335’s fast transient response from 0 to 300mA

provides stable voltage supply for fast DSP and GSM

chipset with fast changing load.

Low Quiescent Current

The AP7335, consuming only around 35µA for all input

range, provides great power saving in portable and low

power applications.

Wide Output Range

The AP7335, with a wide output range of 0.8V to 5.0V,

provides a versatile LDO solution for many portable

applications.

Power Dissipation

The device power dissipation and proper sizing of the

thermal plane that is connected to the thermal pad is

critical to avoid thermal shutdown and ensure reliable

operation. Power dissipation of the device depends on

input voltage and load conditions and can be calculated by:

PD = (VIN - VOUT) X IOUT

The maximum power dissipation, handled by the device,

depends on the maximum junction to ambient thermal

resistance, maximum ambient temperature, and maximum

device junction temperature, which can be calculated by

the equation in the following:

PD (max@TA) =

)

145

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