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AS1331

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

8 Detailed Description

The synchronous buck-boost converter AS1331 uses a Power Save Mode control technique to reach a high efficiency

over a wide dynamic range of load currents. The output voltage is monitored by a comparator with 3% accuracy. The

Meaning, the switching is stopped and only quiescent current is drawn from the power source. The switching is started

The numbers of current pulses which are necessary to load the output capacitor are set by the value of the output

capacitor, the load current, and the comparator hysteresis (~1%).

Figure 23. AS1331 - Block Diagram - Fixed Output Voltage

Modes of Operation

inductor current reaches approximately 400mA. In the next step SW A and SW D are closed and depending on the

and SW D are closed until the inductor current is 600mA.

Note:

The 4-switch-mode (SW A+SW C => SW B+SW D => SW A + SW C...) and also the buck-mode (SW A+SW D

=> SW B+SW D => SW A+SW D...) are never used.

Start-Up Mode

reaches approximately 2.15V. The inductor current is controlled by an alternate algorithm during start-up.

Note:

VIN

SW1

SW2

SW A

SW B

SW C

SW D

1.6V

600mA

VOUT

PGND

GND

EN

Peak

Current

Limit

UVLO

State

Machine

and

Logic

Gate Drivers

and

Anticross

Conduction

IZERO

Detect

1.25V

Thermal Shutdown

Shutdown

R1

R2

FB

VOUT

Comp

AS1331