Datasheet

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 amplifi er with the
Type I compensation is given by:
f
UG
=
1
2•π •R1•C
P1
Hz
referring to Figure 7.
Most applications demand an improved transient response
to allow a smaller output fi lter capacitor. To achieve a higher
bandwidth, Type III compensation is required, providing
two zeros to compensate for the double-pole response of
the output fi lter. Referring to Figure 8, the location of the
poles and zeros are given by:
f
POLE1
≅
1
2•π •32e
3
•R1•CP1
Hz
(which is extremely close to DC)
f
ZERO1
=
1
2•π •R
Z
•C
P1
Hz
f
ZERO2
=
1
2•π •R1•C
Z1
Hz
f
POLE2
=
1
2•π •R
Z
•C
P2
Hz
where resistance is in ohms and capacitance is in far-
ads.
1.22V
R1
R2
3532 F07
FB
9
V
C
C
P1
V
OUT
10
–
+
ERROR
AMP
1.22V
R1
R2
3532 F08
FB
9
V
C
C
P1
C
Z1
R
Z
V
OUT
10
C
P2
–
+
ERROR
AMP
Figure 7. Error Amplifi er with Type l Compensation Figure 8. Error Amplifi er with Type lll Compensation
APPLICATIO S I FOR ATIO
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