AAT1187A Advanced Analog Technology, Inc., AAT1187A Datasheet - Page 22

• Manufacturer Part Number: AAT1187A
• Description: Boost Converter For Wled Driver
• Manufacturer: Advanced Analog Technology, Inc.

The Voltage-Loop Gain with Current Loop
Closed
The control to output voltage transfer function T
The voltage-loop gain with current loop closed is:
Where
The compensator transfer function
Where
L
T (s)
T (s)
s
d
c
vi
(
g
) s
w
m
s
zi
R
Figure 5. Voltage Loop Compensator
V (s)
V (s)
V
V
w
c
s (
O
w
C
T
C
fb
c
s
2
c
V
1 z
Vo
s (
FB
s
T )
R
w
sw
g R
s
m c
c
d
c
1
T (s)T (s)
C
(
s
icl
w
) s
h
12
c
R
z
s w
cs
2
f
12
s
2
T
s
p
Advanced Analog Technology, Inc.
T
f
pi
s
p
c
2
0
0
)
,
–
–
Advanced Analog Technology, Inc . –
台 灣 類 比 科 技 股 份 有 限 公 司
d
is :
Page 22 of 28
Version 1.00
Compensator design guide:
1. Crossover frequency
2. Gain margin>10dB
3. Phase margin>45
4. The
the compensator resistance, R
5. The output filter capacitor is chosen so C R
cancels R
Example 3:
V
V
r
R
R
C
R
IN
FB
C
c
= 9.13m
c
= 7.6k , C = 38.5cF, = 3, R
= 5V, V
1 (
= 1.233V, L = 6.65µH, g
C
21.533µF
25.079µF
32.587µF
36.312µF
38.469µF
c
V
~
V
FB
O
) 3
L
C
–
vi
C
C
2 f CR
O
(



C
) s
R
,
= 13.3V, I
C
2
ci
g k
R
L
Table 3. K Factor Table
m
zero
F
1
= 0.7667 , C
r
cs
c
at crossover frequency, Therefore,



∘




, and
O
1 D R
Best Corner
23.740kHz
21.842kHz
20.095kHz
15.649kHz
13.247kHz
Frequency
f
= 300mA, f
ci
C
R
m
c
L
1
2
= 85µS, R
L
C
f
C
s
= 1.95nF,
2r
CS
is determined by:
R
C
c
1 D
= 0.23V/A.
c
s
AAT1187A
r



= 1,190kHz,
R
2
L
l




= 76.689m
September 2009
K Factor
r
c
4.692
5.083
6.042
5.230
4.703



L
pole