AS1321

130mA Step-Up DC-DC Converter

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1 General Description

The AS1321 is a high-efficiency step-up DC-DC con-

verter designed to generate a fixed output voltage of

+5.0V.

The AS1321 achieves an efficiency of up to 96%. The

minimum input voltage is +1.5V, the output voltage is

fixed at +5.0V, and output current is up to 130mA

In order to save power the AS1321 features a shutdown

mode, where it draws less than 1µA. In shutdown mode

the battery is connected directly to the output enabling

the supply of real-time-clocks.

The AS1321 provides a power-on reset output that goes

high-impedance when the output reaches 90% of its reg-

ulation point.

The SHDNN trip threshold of the AS1321 can be used

as an input voltage detector that disables the device

when the battery voltage falls to a predetermined level.

An internal synchronous rectifier is included, which is

parallel with the external Schottky diode.

The AS1321 is available in a 6-pin SOT23 package.

Figure 1. Application Diagram

2 Key Features

!

Fixed Output Voltage: +5.0V

!

!

Internal Synchronous Rectifier

!

Shutdown Mode Supply Current: Less Than 1µA

!

Efficiency: Up to 96%

!

Minimum Input Voltage: +1.5V

!

Accurate Shutdown Low-Battery Cutoff Threshold

!

Battery Input Connected to Pin OUT in Shutdown

Mode for Backup Power

!

6-pin SOT23 Package

3 Applications

The AS1321 is ideal for low-power applications where

ultra-small size is critical as in medical diagnostic equip-

ment, hand-held instruments, pagers, digital cameras,

remote wireless transmitters, cordless phones, and PC

cards.

The device is also perfect as a local +5.0V supply or as

a battery backup.

AS1321

+1.5 to +5.0V

Battery

+5.0V

Output

22µF

22µF

L1

10µH

RESETN

Output

100k

Ω

On

Off

4

LX

3

GND

2

BATT

6

RESETN

1

SHDNN

5

OUT