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AN1262 APPLICATION NOTE

Figure 8. Brownout protection circuit and timing diagram

15

CONTROL LOOP DESIGN

The control loop can be summarized as shown in figure 9, where each block is described by its transfer function

in the complex frequency domain represented by means of a Bode plot.

Figure 9. Control loop Block Diagram

The set PWM modulator + Power stage is what, in control theory terminology, is called the "plant", while the

compensated error amplifier is the "controller".

+

-

L6590A

L6590D

2.5 V

VinOK

50 µA

Vin

6.4 V

R1

R2

Vcc

VinOK

Vcc

PWM

Vout

OUTPUT

DIVIDER

+

-

Vref

Vo

COMPENSATED

ERROR AMPLIFIER

PWM MODULATOR

POWER STAGE

G2(j

Vin

D

G1(j