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AS1301

Data Sheet - Deta iled Description

Switch Configuration

The AS1301 has nine built-in power switches in the shape of two coupled H-bridge topologies. The system features

1:2 and 2:3 operation mode as well as an 1:1 operation where the input is directly connected to the output. This

feedthrough mode is suitable for input voltages higher than the output voltage.

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

voltage. In pumping phase the flying capacitors are place in parallel. The bottom-plate of the parallel flying capacitors

CFLY1 and CFLY2 is then connected to the input voltage so that the voltage at the top-plate of the flying capacitors is

boosted to a voltage equal to VBATT+ VBATT/2. By connecting the top-plate of the capacitors to the output, the output

voltage in 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. The 2:3 operation mode runs in single-phase

operation only.

In 1:2 operation mode just one of both flying capacitors is placed in series 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 capacitor

CFLY. The voltage at the top-plate of the capacitor is now boosted to 2VBATT. By connecting the top-plate of the

capacitor to the output, the output can be charged to double of VBATT. If the top-plate voltage is higher than 5V the

regulation loop limits the charge transfer to the output. In collaboration with the second flying capacitor this mode

features dual-phase operation.

Figure 27. 2:3 Single Phase Operating Mode

VBATT

SW1

CFLY1

CFLY2

SW3

SW2

SW4

Charging Flying Capacitors

VOUT

VBATT

SW1

CFLY1

CFLY2

SW3

SW2

SW4

Generating Output Voltage

VOUT

Figure 28. 1:2 Dual Phase Operating Mode

VBATT

SW1

CFLY1

CFLY2

SW3

SW2

SW4

VOUT

VBATT

SW1

CFLY1

CFLY2

SW3

SW2

SW4

VOUT

Charging CFLY1, CFLY2 used for output voltage

Charging CFLY2, CFLY1 used for output voltage

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