LTC3532

13

3532fc

The loop gain is typically rolled off before the RHP zero

frequency.

A simple Type I compensation network can be incorpo-

rated to stabilize the loop, but at a cost of reduced band-

width and slower transient response. To ensure proper

phase margin using Type I compensation, the loop must

be crossed over a decade before the LC double pole.

The unity-gain frequency of the error amplifier with the

Type I compensation is given by:

1

Hz

referring to Figure 7.

Most applications demand an improved transient response

to allow a smaller output filter capacitor. To achieve a higher

bandwidth, Type III compensation is required, providing

two zeros to compensate for the double-pole response of

the output filter. Referring to Figure 8, the location of the

poles and zeros are given by:

1

Hz

(which is extremely close to DC)

1

Hz

1

Hz

1

Hz

where resistance is in ohms and capacitance is in far-

ads.

1.22V

R1

R2

3532 F07

FB

9

10

–

+

ERROR

AMP

1.22V

R1

R2

3532 F08

FB

9

10

–

+

ERROR

AMP

Figure 7. Error Amplifier with Type l Compensation

Figure 8. Error Amplifier with Type lll Compensation

APPLICATIO S I FOR ATIO