www.ams.com/LDO

Revision 1.9

8 - 19

AS1363

Datasheet - Detailed Descr i p ti on

8 Detailed Description

The AS1363 is a low-dropout, low-quiescent-current linear regulator specifically designed for battery-powered devices. The regulator supplies

loads of up to 500mA and can deliver a factory-preset output voltage or user-adjustable output voltage.

Figure 15. Block Diagram

Figure 15 shows the block diagram of the AS1363. It identifies the basics of a series linear regulator employing a P-Channel MOSFET as the

control element. A stable voltage reference (1.2VREF in Figure 15) is compared with an attenuated sample of the output voltage. Any difference

between the two voltages (reference and sample) creates an output from the error amplifier that drives the series control element to reduce the

difference to a minimum. The error amplifier incorporates additional buffering to drive the relatively large gate capacitance of the series pass P-

channel MOSFET, when additional drive current is required under transient conditions.. Input supply variations are absorbed by the series

element, and output voltage variations with loading are absorbed by the low output impedance of the regulator.

The device features a 1.2V reference, error amplifier, P-channel pass transistor, and internal feedback voltage-divider (see Figure 15). Additional

blocks include an output current limiter, thermal sensor, and shutdown logic.

8.1 Shutdown

If pin EN is connected to GND the AS1363 is disabled. In shutdown mode all internal circuits are turned off, reducing supply current to 30nA

typical. For normal operation pin EN must be connected to IN. During shutdown, POK is low.

2

AS1363-AD

+

–

Shutdown

Logic

+

–

+

–

100mV

+

–

+

–

MOSFET

Driver

Thermal

Sensor

1

IN

6

OUT

3

EN

POK

5

SET

4

GND

1µF

2.0V to 5.5V

Voltage

To Controller

Error

Amplifier

On

Off

1.2V

Reference

1.2V to 5.3V