nx2119 Microsemi Corporation, nx2119 Datasheet - Page 10

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

Case 2:
capacitors, typical design example of type III
compensator in which the crossover frequency is
selected as F
as the following steps. Here two SANYO MV-WG1500
with 13 m
and ESR zero F
Rev.3.2
04/10/08
Figure 5 - Bode plot of Type III compensator
1. Calculate the location of LC double pole F
F
F
ESR
If electrolytic capacitors are used as output
LC
loop gain
power stage
compensator
F
2.3kHz
2
is chosen as output capacitor.
2
8.2kHz
2
2
LC
F
LC
Z1
<F
<F
ESR
(F
F
ESR
ESR
ESR C
Z2
LC
6.5m
.
F
F
1.5uH 3000uF
L
<F
<F
ESR
<F
1
LC
1
OUT
O
F
1
ESR
1
O
P1
40dB/decade
and F
<F
C
OUT
3000uF
OUT
F
O
O
)
O
<=1/10~1/5F
20dB/decade
F
P2
s
is shown
LC
double pole by equation (11).
half the switching frequency.
R =
R =
4
2. Set R
Choose R
3. Set zero F
4. Calculate C
Choose C
5. Calculate R
R
Choose R
6. Calculate R
Choose R
7. Calculate C
C
Choose C
8. Calculate C
Choose C
C =
C
1
=
=37.3k
3
2
1
3
1.5V 2
V
=
=4.76nF
5V
V
V
R
OSC
OUT
in
4.1k
2
2
2
2
2
2
2.4nF
2
2
28pF
2
-V
2
V
1
2
equal to 10k
REF
1
3
4
2
1
3
REF
1
=27pF.
=8.06k
=4.7nF.
=37.4k .
=2.2nF.
10k
R
8.2kHz 4.7nF
=4k .
0.75 2.3kHz 37.4k
1
F
1
F
1
R
ESR
37.4k
2
P1
Z2
Z1
4
4
2
1
3
3
1
F
= F
30kHz 1.5uH 10k
by equation (14) with pole F
.
.
with F
with zero F
10k
6.5m
(
O
C
R
F
1.8V-0.8V
F
1
P2
1
3
z2
4
LC
(
L R
1
2.3kHz 8.2kHz
-
and F
NX2119/2119A
O
150kHz
F
=30kHz.
1
R
p1
1
0.8V
2
2
)
z1
p1
R
R
-
at 75% of the LC
=F
3
3
8k
10k
ESR
1
.
)
4k
4k
p2
at
10