LM3668_15 Datasheet, PDF(14/30 Page) Texas Instruments – 1-A, High-Efficiency Dual-Mode Single-Inductor Buck-Boost DC-DC Converter

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LM3668_15 Datasheet, PDF (14/30 Pages) Texas Instruments – 1-A, High-Efficiency Dual-Mode Single-Inductor Buck-Boost DC-DC Converter

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LM3668

SNVS449O â JUNE 2007 â REVISED APRIL 2015

8.2 Functional Block Diagram

www.ti.com

PVIN

Switch

buffer

Sw1

Sw2

Switch

buffer

VOUT

VDD

SYNC/

MODE

Buffer

Soft

Start

Control Logic

PFM_hi PFM

Generator

PFM_low

PWM

Comparator

2 MHz

Oscillator

Ramp

Generator

Error

Amp

VREF

VSEL

PGND

SGND

8.3 Feature Description

8.3.1 Buck Operation

When the input voltage is greater than the output voltage, the device operates in buck mode where switch P2 is

always ON and P1 and N1 control the output. Figure 41 shows the simplified circuit for buck mode operation.

P1 SW1

SW2 P2

VIN

Load

Figure 41. Simplified Circuit for Buck Operation

8.3.2 Boost Operation

When the input voltage is smaller than the output voltage, the device enters boost mode operation where P1 is

always ON, while switches N2 and P2 control the output. Figure 42 shows the simplified circuit for boost mode

operation.

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