nx2119 Microsemi Corporation, nx2119 Datasheet - Page 9

• Manufacturer Part Number: nx2119
• Description: Synchronous Pwm Controller With Current Limit Protection
• Manufacturer: Microsemi Corporation

order. The crossover frequency has to be selected as
F
and ESR zero F
Rev.3.2
04/10/08
Case 1:
LC
Figure 4 - Bode plot of Type III compensator
<F
Design example for type III compensator are in
1.Calculate the location of LC double pole F
2. Set R
R =
O
F
F
<F
ESR
1
LC
loop gain
power stage
compensator
ESR,
V
R
F
6.2kHz
OUT
2
2
2
F
60.3kHz
Z1
2
2
and F
2
LC
equal to 10k .
F
-V
<F
ESR
V
Z2
REF
F
REF
O
.
O
LC
<F
1.5uH 440uF
ESR C
6m
<=1/10~1/5F
L
1
OUT
1
ESR
1
40dB/decade
1
10k
F
1.8V-0.8V
O
C
440uF
20dB/decade
OUT
F
OUT
F
P1
ESR
0.8V
s.
F
P2
8k
LC
frequency at 1/10~ 1/5 of the switching frequency. Set
F
double pole by equation (11).
half the switching frequency.
O
=30kHz.
4. Calculate R
3. Set zero F
Choose C
5. Calculate C
C
Choose C
6. Calculate C
Choose C
7. Calculate R
R
Choose R
C =
C
R =
Choose R
3
2
1
3
4
=
=2.3nF
=
=16.9k
1.2k
2
2
2
2
1.5V 2
2
V
2nF
2
2
63pF
2
5V
V
OSC
in
1
2
1
3
3
1
=68pF.
=2.2nF, R
=2.2nF.
=1.2k
60.3kHz 2.2nF
R
10k
1
1
F
0.75 6.2kHz 16.9k
=8k
1
F
2
R
1
P1
16.9k
2
Z2
Z1
4
4
2
1
3
and C
1
= F
by equation (14) with pole F
by equation (13).
with zero F
C
(
C
R
F
F
1
3
1
P2
z2
F
3
30kHz 1.5uH
4
LC
(
O
1
2.2nF
6.2kHz 60.3kHz
4
-
3
and F
=16.9k
NX2119/2119A
F
150kHz
with the crossover
L
1
p1
1
)
C
z1
p1
out
-
at 75% of the LC
=F
ESR
1
440uF
.
)
p2
at
9