nx2142 Microsemi Corporation, nx2142 Datasheet - Page 12

• Manufacturer Part Number: nx2142
• Description: Single Channel Pwm Controller With Feedforward And 5v Bias Regulator
• Manufacturer: Microsemi Corporation

ESR POSCAP, OSCON)
in which the crossover frequency is selected as
F
following steps. Here two X5R 22uF ceramic capacitor
wi t h 3m
is 6.8uH.
and ESR zero F
Rev. 1.1
10/28/07
LC
Case 1:
<F
Typical design example of type III compensator
1. Calculate the location of LC double pole F
F
O
F
Figure 10 - Bode plot of Type III compensator
<F
ESR
LC
loop gain
power stage
compensator
is chosen as output capacitor, output inductor
ESR
9.2kHz
2
2
241kHz
2
2
F
F
and F
Z1
LC
(F
ESR
<F
F
LC
Z2
.
F
O
ESR C
1.5m
O
<F
<F
LC
6.8uH 44uF
L
<=1/10~1/5F
1
1
OUT
O
ESR
1
1
<F
40dB/decade
(for most ceramic or low
F
ESR
C
O
OUT
44uF
OUT
20dB/decade
)
F
F
P1
ESR
s
is shown as the
F
P2
LC
double pole by equation (11).
half the switching frequency.
1/10~ 1/5 of the switching frequency. Set F
late R
2. Set R
3. Calculate C2 with zero Fz1 at 50% of the LC
Choose C
4. Calculate C
Choose C
5. Calculate C
Choose C
6. Set zero F
Choose R
7. Calculate R
R
Choose R
C
R =
C
2.
C =
3
2
2
1
3
=
=18k
=
=1.1nF
2
2
221
2
2
2
10
V
2
3.5nF
53pF
2
2
1
V
OSC
1
in
4
1
equal to 10k
C
1.2nF
3
2
1
3
2
2
=3.9nF.
=52pF.
=1.2nF.
=20k
600kHz 1.2nF
3
1
F
=300 .
P1
0.5 9.2kHz 10k
R
1
10k
2
1
F
Z2
(
1
Z1
3
3
4
1
F
= 0.75F
by equation (14) with pole F
with the crossover frequency at
by equation (13) with F
1
C
z2
(
1
60kHz 6.8uH
F
R
3
0.75*9.2kHz 300kHz
-
R
10k
P2
1
4
F
F
1
4
p1
O
300kHz
NX2142/2142A
)
LC
1
L
and F
C
out
-
p1
=0.5F
1
44uF
O
)
=60kHz.
p1
s
, calcu-
=F
p2
s
.
at
12