www.ams.com/DC-DC_Step-Up/AS1322

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L o w Vo l t a g e , M i c r o p o w e r, D C - D C S t e p - U p C o n v e r t e r s

1 General Description

The AS1322A and the AS1322B are synchronous, fixed frequency,

very high-efficiency DC-DC boost converters capable of supplying

3.3V at 150mA from a single AA-supply. Compact size and minimum

external parts requirements make these devices perfect for modern

portable devices.

High-speed switching frequency (1.2MHz) and internally

compensated PWM current mode design provide highly-reliable DC-

DC conversion, especially when driving white LEDs.

The converters are available as the standard products listed in Table

1.

The devices contain two internal MOSFET switches: one NMOS

switch and one PMOS synchronous rectifier.

Anti-ringing control circuitry reduces EMI by damping the inductor in

discontinuous mode, and the devices exhibit extremely low

quiescent current (< 1µA) in shutdown.

The AS1322 is available in a 6-pin TSOT-23 package.

Figure 1. Typical Application Diagram – Single Cell to 3.3V

Synchronous Boost Converter

2 Key Features

95% Efficiency

Single-Cell Operation

Delivers 160mA @ 3.3V (from Single AA Cell)

Delivers 220mA @ 5.0V (from Two AA Cells)

Delivers 570mA @ 3.3V (from Two AA Cells)

Low Start-Up Voltage: 0.85V

High-Speed Fixed-Frequency: 1.2MHz

Internal PMOS Synchronous Rectifier

Automatic Powersave Operation (AS1322A)

Continuous Switching at Light Loads (AS1322B)

Anti-Ringing Control Minimizes EMI

Logic Controlled Shutdown (< 1µA)

Output Range: 2.5 to 5.0V

6-pin TSOT-23 Package

3 Applications

The AS1322 is ideal for low-power applications where ultra-small

size is critical as in medical diagnostic equipment, hand-held

instruments, pagers, digital cameras, remote wireless transmitters,

MP3 players, LCD bias supplies, cordless phones, GPS receivers,

and PC cards.

Table 1. Standard Products

Model

Light Load Switching

AS1322A

Automatic Powersave Operation

AS1322B

Continuous Switching

AA Battery

AS1322

10µF

604k

Ω

1%

1.02M

Ω

1%

On

Off

L1

4.7µH

10µF

GND

2

SW

1

3.3V

160mA

4

SHDNN

3

FB

6

5