nx2154 Microsemi Corporation, nx2154 Datasheet - Page 10

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

order. The crossover frequency has to be selected as
F
voltage is 5V, output voltage is 1.8V, inductor is 1.5uH,
two POSCAP 2R5TPE220MC(220uF,12 m
as output capacitor.
and ESR zero F
Rev.1.2
02/26/07
Case 2:
LC
Figure 5 - 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
F
O
F
<F
ESR
LC
loop gain
power stage
compensator
ESR
F
6.2kHz
2
2
F
and F
60.3kHz
Z1
2
2
2
LC
equal to 10k .
F
<F
ESR
Z2
F
O
.
O
LC
<F
1.5uH 440uF
ESR C
<=1/10~1/5F
6m
L
1
OUT
1
ESR
1
40dB/decade
1
F
O
C
440uF
20dB/decade
OUT
F
OUT
F
P1
ESR
s.
F
In this case, input
P2
are chosen
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
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
1
2
1
3
4
=
=2.3nF
=
=16.9k
1.2k
2
2
V
2
2
1.5V 2
2
R
V
2nF
2
2
63pF
2
5V
OUT
V
OSC
2
in
1
2
1
3
3
1
-V
=68pF.
V
=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
REF
1
P1
16.9k
REF
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
(
10k
O
1
2.2nF
6.2kHz 60.3kHz
4
1.8V-0.8V
-
3
and F
=16.9k
NX2154/2154A
F
150kHz
with the crossover
L
1
p1
1
)
C
z1
p1
out
0.8V
-
at 75% of the LC
=F
ESR
1
440uF
.
8k
)
p2
at
10