SW

VCON

FB

EN

VIN

PGND

OSCILLATOR

RAMP

GENERATOR

OUTPUT SHORT

PROTECTION

THERMAL

SHUTDOWN

DRIVER

CONTROL LOGIC

PWM

COMP.

Ref3

Ref2

NCP

OVER-VOLTAGE

DETECTOR

DELAY

ERROR

AMP

OLP

Ref4

LIGHT-LOAD

CHECK COMP

ECO COMP

BYPASS

VCON

BPEN

FB

2/5

Ref1

+

+

SGND

STANDBY COMP

Ref5

1.5V

-

LM3262

SNVS875O – AUGUST 2012 – REVISED DECEMBER 2015

www.ti.com

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 Circuit Operation

Referring to the Functional Block Diagram, the LM3262 operates as follows. During the first part of each

switching cycle, the control block in the LM3262 turns on the internal top-side PFET switch. This allows current to

flow from the input through the inductor to the output filter capacitor and load. The inductor limits the current to a

each cycle, the controller turns the PFET switch off, blocking current flow from the input, and then turns the

bottom-side NFET synchronous rectifier on. In response, the magnetic field of the inductor collapses, generating

a voltage that forces current from ground through the synchronous rectifier to the output filter capacitor and load.

As the stored energy is transferred back into the circuit and depleted, the inductor current ramps down with a

when low, smoothing the voltage across the load.

The output voltage is regulated by modulating the PFET switch on time to control the average current sent to the

load. The effect is identical to sending a duty-cycle modulated rectangular wave formed by the switch and

synchronous rectifier at SW to a low-pass filter formed by the inductor and output filter capacitor. The output

voltage is equal to the average voltage at the SW pin.

12

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