AP7335_1009 Datasheet, PDF (12/17 Pages) Diodes Incorporated – 300mA, Low Quiescent Current, Fast Transient

AP7335
300mA, Low Quiescent Current, Fast Transient
Low Dropout Linear Regulator
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:
P_D = (V_IN - V_OUT) X I_OUT
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:
P_D
(max@T_A)
=
(
+145°C -
R _θJA
TA
)
AP7335
Document number: DS32259 Rev. 2 - 2
12 of 17
www.diodes.com
September 2010
© Diodes Incorporated