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AS1302

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

Switch Configuration

The AS1302 has nine built-in power switches in the shape of two coupled H-bridge topologies. The system features

1:2 and 2:3 operation modes as well as a 1:1 operation where the input is directly connected to the output.

In 2:3 operation mode two flying capacitors are placed in series and each capacitor is charged to the half of the input

voltage. In pumping phase the flying capacitors are placed in parallel. The bottom-plates of the parallel flying

capacitors CFLY1 and CFLY2 are connected to the input voltage so that the voltage at the top-plates of the flying

capacitors is boosted to a voltage equal to VBATT + VBATT/2. By connecting the top-plates of the capacitors to the

output, the output voltage in the 2:3 mode can be up to one and a half of VBATT. If the top-plate voltage is higher than

5V, the regulation loop adapts the power transistor’s on-resistance to drop some voltage.

In 1:2 operation both flying capacitors are placed in parallel to the input voltage, and therefore charged to the input

voltage. During pumping phase the input voltage is connected to the bottom of the charged flying capacitors. The

voltage at the top-plates of the parallel capacitors is now boosted to 2VBATT. By connecting the top-plates of the

capacitors to the output, the output can be charged to twice the voltage of VBATT. If the top-plate voltage is higher than

5V the regulation loop limits the charge transfer to the output.

Figure 33. 2:3 Operating Mode

VBATT

+2.9V to 5.15V

SW1

CFLY1

CFLY2

SW3

SW2

SW4

Charging Phase

VOUT

+5V

VBATT

+2.9V to 5.15V

SW1

CFLY1

CFLY2

SW3

SW2

SW4

Pumping Phase

VOUT

+5V

Figure 34. 1:2 Operating Mode

VBATT

+2.9V to 5.15V

SW1

CFLY1

CFLY2

SW3

SW2

SW4

VOUT

+5V

Charging Phase

VBATT

+2.9V to 5.15V

SW1

CFLY1

CFLY2

SW3

SW2

SW4

Pumping Phase

VOUT

+5V