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AS1301

8 Detailed Description

Operating Principle

Functional Description

The AS1301 is a high efficiency and low noise switched capacitor DC-DC converter that is capable of boost operation.

It is equipped with two built-in coupled H-bridge type switch configurations. Based on the value of the output voltage

the system automatically initiates mode-switching to achieve the highest possible efficiency. The regulation of the

output voltage is achieved by a regulation loop, which modulates the current drive capability of the power transistors so

that the amount of charge transferred from the input to the output at each clock cycle is controlled and is equal to the

charge needed by the load.

Regulation Loop

The AS1301 operates at constant frequency at any load. For the regulation loop power transistors, a resistor divider,

and an error amplifier is used to keep the output voltage within the allowed limits. The error amplifier takes the

feedback and reference signals as inputs and generates the error voltage signal. The error voltage controls a driver

that triggers the gate of the power transistor which modulates the current drive capability of the power transistors. The

modulated power transistors control the charge transferred from the input to the output and therefore the regulation of

the output voltage is realized. Based on adjusting the amount of charge transferred, this regulation concept delivers

the smallest voltage ripple possible.

Figure 26. Functional Block Diagram

+

VBATT

VOUT

C1+

C1-

C2+

C2-

EN

Double-H Bridge

Topology

Soft

Start

Vmode trig

Ref

POR

Temp

State Machine

&

Control Logic

Mode Select

GND

CLK

AS1301

On

Off