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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 up-switching to achieve the highest possible efficiency. The regulation of the

output voltage is achieved by a regulation loop, which modulates the on-resistance 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, including loop-

filter and compensation ramp, takes feedback and reference as inputs and generates the error voltage signal. The

error voltage is then used as the gate voltage of the power transistor which modulates the on-resistance of the latter.

The modulated transistor on-resistance controls the charge transferred from the input to the output and therefore the

regulation of the output is realized. Based on adjusting of 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