AS1330 datasheet(9/18 Pages) AMSCO

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AS1330

Datasheet - D e t a i l e d D e s c r i p t i o n

8 Detailed Description

The AS1330 can operate from a single-cell input voltage (VIN) below 1V, and features fixed frequency (4MHz) and current mode PWM control for

exceptional line- and load-regulation. With low RDS(ON) and gate charge internal NMOS 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 AS1330 is ideal for portable devices since it 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 AS1330 includes an automatic 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.

Figure 19. AS1330 - Block Diagram

Low-Voltage Start-Up

The AS1330 requires VIN of only 0.85V (typ) or higher to start up. The low-voltage start-up circuitry controls the internal NMOS switch up to a

maximum peak inductor current of 650mA (typ), with 1.5ms (approx.) off-time during start-up, allowing the devices to start up into an output load.

With a VOUT > 1.65V, the start-up circuitry is disabled and normal fixed-frequency PWM operation is initiated. In this mode, the AS1330 operates

independent of VIN, allowing extended operating time as the battery can drop to several 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.

Low-Noise Fixed-Frequency Operation

Oscillator

The AS1330 switching frequency is internally fixed at 4MHz allowing the use of very small external components.

AS1330

–

Start Up

OSC

PWM

Control

A/B

MUX

Slope

Compensator

4MHz

Ramp

Generator

–

Powersave

Operation

Control

–

Shutdown

Control

PWM

Comp

–

0.8V

Ref

Sync Drive

Control

VOUT

Good

1.65V

gm Error

Amp

Shutdown

Powersave

0.25

Ω

0.35

Ω

4.7µF

1.8V

Output

4.7µF

AA Battery

Current

Sense

CP2

GND

VIN

VOUT

1µH

Sense & POK

Logic

SENSE

POK

Off

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