cv

S

R

R

Q

GND

FB

SW

VIN

EN

+

-

DRIVER

Artificial

Ramp

SHDN

Thermal

SHDN

OVP

1.6 MHz

Comp

Internal -

SENSE

I

LIMIT

I

LDO

Internal -

START

SOFT -

PFET

SENSE

I

ENABLE and UVLO

15

.

1

x

REF

V

Control Logic

LM2831

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SNVS422D – AUGUST 2006 – REVISED SEPTEMBER 2015

7 Detailed Description

7.1 Overview

The LM2831 device is a constant-frequency PWM buck regulator IC that delivers a 1.5-A load current. The

regulator has a preset switching frequency of 550 kHz, 1.6 MHz, or 3 MHz. This high-frequency allows the

LM2831 to operate with small surface mount capacitors and inductors, resulting in a DC-DC converter that

requires a minimum amount of board space. The LM2831 is internally compensated, so the device is simple to

use and requires few external components.

7.2 Functional Block Diagram

7.3 Feature Description

7.3.1 Theory of Operation

The LM2831 uses current-mode control to regulate the output voltage. The following operating description of the

LM2831 will refer to Functional Block Diagram and to the waveforms in Figure 18. The LM2831 supplies a

regulated output voltage by switching the internal PMOS control switch at constant-frequency and variable duty

cycle. A switching cycle begins at the falling edge of the reset pulse generated by the internal oscillator. When

this pulse goes low, the output control logic turns on the internal PMOS control switch. During this on-time, the

sense signal is summed with the regulator’s corrective ramp and compared to the error amplifier’s output, which

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