SG2524, SG3524

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SLVS077E – APRIL 1977 – REVISED JANUARY 2015

9 Detailed Description

9.1 Overview

SGx524 is a fixed-frequency pulse-width-modulation (PWM) voltage-regulator control circuit. The regulator

comparator, providing linear control of the output pulse duration (width) by the error amplifier.

The SGx524 contains an onboard 5-V regulator that serves as a reference, as well as supplying the SGx524

internal regulator control circuitry. The internal reference voltage is divided externally by a resistor ladder network

to provide a reference within the common-mode range of the error amplifier as shown in Figure 11, or an external

reference can be used.

The output is sensed by a second resistor divider network and the error signal is amplified. This voltage is then

steered to the appropriate output pass transistor (Q1 or Q2) by the pulse-steering flip-flop, which is

synchronously toggled by the oscillator output. The oscillator output pulse also serves as a blanking pulse to

ensure both outputs are never on simultaneously during the transition times. The duration of the blanking pulse is

The outputs may be applied in a push-pull configuration in which their frequency is one-half that of the base

oscillator, or paralleled for single-ended applications in which the frequency is equal to that of the oscillator. The

output of the error amplifier shares a common input to the comparator with the current-limiting and shut-down

circuitry and can be overridden by signals from either of these inputs. This common point is pinned out externally

via the COMP pin, which can be employed to either control the gain of the error amplifier or to compensate it. In

addition, the COMP pin can be used to provide additional control to the regulator.

9.2 Functional Block Diagram

A.

Resistor values shown are nominal.

Copyright © 1977–2015, Texas Instruments Incorporated

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Product Folder Links: SG2524 SG3524