nx2154 Microsemi Corporation, nx2154 Datasheet - Page 9

• Manufacturer Part Number: nx2154
• Description: 300khz Synchronous Pwm Controller
• Manufacturer: Microsemi Corporation

Case 1:
capacitors, typical design example of type III
compensator in which the crossover frequency is
selected as F
as the following steps. Here one SANYO 6ME1000WG
with 30 m
and ESR zero F
Rev.1.2
02/26/07
Figure 4 - 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
1.3kHz
is chosen as output capacitor.
2
2
5.3kHz
2
2
LC
F
LC
Z1
<F
<F
ESR
(F
F
ESR
ESR
Z2
LC
.
ESR C
F
30m
F
15uH 1000uF
L
<F
<F
ESR
<F
LC
1
1
OUT
O
F
1
ESR
1
O
P1
40dB/decade
and F
<F
C
1000uF
OUT
F
OUT
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
Choose C
8. Calculate C
Choose C
C
1
C =
C
=
=9.9k
3
2
3
1.5V 2
1
V
33V
V
=
=9.2nF
R
V
OSC
OUT
in
2
2
2
3k
2
2
2
12.2nF
2
2
106pF
2
-V
V
2
REF
1
2
REF
equal to 10k
1
3
4
2
1
3
1
=10nF.
=10k .
=12nF.
=100pF.
=1.91k
R
10k
=3k .
5.3kHz 10nF
1
F
0.75 1.3kHz 10k
ESR
1
F
R
Z2
2
1
10k
P1
Z1
4
2
1
3
3
10k
4
1
= F
F
by equation (14) with pole F
.
.
with F
30kHz 15uH 10k
with zero F
(
30m
5V-0.8V
O
C
F
1
R
F
1
z2
LC
(
3
P2
1
L R
4
1.3kHz 5.3kHz
-
and F
NX2154/2154A
150kHz
O
0.8V
F
=30kHz.
1
p1
1
R
2
2
)
z1
p1
R
R
-
1.91k
at 75% of the LC
=F
3
3
10k
ESR
1
.
)
3k
3k
p2
at
9