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AS1329

8 Detailed Description

and PMOS switches, the device maintains high-efficiency from light to heavy loads.

Modern portable devices frequently spend extended time in low-power or standby modes, switching to high power-

drain only when certain functions are enabled. The AS1329A, AS1329B and AS1329C are ideal for portable devices

since they maintain high-power conversion efficiency over a wide output power range, thus increasing battery life in

these types of devices.

In addition to high-efficiency at moderate and heavy loads, the AS1329A as well as the AS1329B includes an auto-

matic powersave mode that improves efficiency of the power converter at light loads. The powersave mode is initiated

if the output load current falls below a factory programmed threshold (see Figure 3 on page 5).

Note: The AS1329C does not support powersave mode and provides continuous operation at all loads, eliminating

Figure 15. Block Diagram

Low-Voltage Start-Up

NMOS switch up to a maximum peak inductor current of 850mA (typ), with 1.5ms (approx.) off-time during start-up,

allowing the devices to start up into an output load.

tenths of a volt without affecting output regulation. The limiting factor for the application is the ability of the battery to

supply sufficient energy to the output.

AS1329

+

–

Start Up

OSC

PWM

Control

A/B

MUX

Slope

Compensator

1.2MHz

Ramp

Generator

+

–

Powersave

Operation

Control

–

Shutdown

Control

PWM

Comp

Σ

+

–

1.23V

Ref

Sync Drive

Control

A

B

Good

2.3V

Amp

Shutdown

Powersave

0.35

Ω

0.45

Ω

640k

Ω

1%

1.02M

Ω

1%

4.7µF

3.3V

Output

1µF

1.5V

Single

Cell

* Optional

Current

Sense

80k

Ω

2.5pF

150pF

GND

2

SW

1

4

SHDNN

3

FB

6

5

L1

4.7µH