LTC3532 LINER [Linear Technology], LTC3532 Datasheet - Page 13

• Manufacturer Part Number: LTC3532
• Description: Micropower Synchronous Buck-Boost DC/DC Converter
• Manufacturer: LINER [Linear Technology]

APPLICATIO S I FOR ATIO
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:
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
f
UG
Figure 7. Error Amplifi er with Type l Compensation
=
2 • π • R1• C
1
ERROR
AMP
U
P1
+
–
Hz
U
V
FB
10
9
C
1.22V
C
P1
W
V
OUT
R1
R2
3532 F07
U
the output fi lter. Referring to Figure 8, the location of the
poles and zeros are given by:
where resistance is in ohms and capacitance is in far-
ads.
(which is extremely close to DC)
f
f
f
f
POLE1
POLE2
ZERO1
ZERO2
Figure 8. Error Amplifi er with Type lll Compensation
≅
=
=
=
2 • π • 32e
2 • π • R
2 • π • R
2 • π • R1• C
ERROR
AMP
+
–
1
1
1
Z
Z
1
• C
• C
3
• R1• CP1
FB
V
10
9
P1
Z1
P2
C
1.22V
Hz
Hz
Hz
R
Z
C
P2
Hz
C
P1
LTC3532
3532 F08
V
OUT
R1
R2
13
C
Z1
3532fc