AP7335

300mA, Low Quiescent Current, Fast Transient

Low Dropout Linear Regulator

AP7335

Document number: DS32259 Rev. 1 - 2

13 of 18

www.diodes.com

July 2010

© Diodes Incorporated

Thermal Shutdown Protection

Thermal protection disables the output when the junction temperature rises to approximately +145°C, allowing the

device to cool down. When the junction temperature reduces to approximately +130°C the output circuitry is

enabled again. Depending on power dissipation, thermal resistance, and ambient temperature, the thermal

protection circuit may cycle on and off. This cycling limits the heat dissipation of the regulator, protecting it from

damage due to overheating.

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:

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:

JA

R

)

A

T

-

C

145

(

θ

°

+