nx2154 Microsemi Corporation, nx2154 Datasheet - Page 11
nx2154
Manufacturer Part Number
nx2154
Description
300khz Synchronous Pwm Controller
Manufacturer
Microsemi Corporation
Datasheet
1.NX2154.pdf
(17 pages)
B. Type II compensator design
stage output capacitors, usually the Type II compensa-
tor can be used to compensate the system.
circuit without feedback as shown in figure 6. R
introduce a zero to cancel the double pole effect. C
introduces a pole to suppress the switching noise. The
following equations show the compensator pole zero lo-
cation and constant gain.
Rev.1.2
02/26/07
Figure 6 - Bode plot of Type II compensator
If the electrolytic capacitors are chosen as power
Type II compensator can be realized by simple RC
Gain=g
F =
F
z
p
loop gain
2
power stage
compensator
2
m
F
Z
1
R
R +R
1
R
3
1
F
R
3
LC
1
C
C
2
1
F
2
ESR
R
40dB/decade
3
20dB/decade
F F
... (16)
... (15)
... (17)
O
Gain
P
3
and C
1
2
F
tor design. Input voltage is 40V, output voltage is 5V,
output inductor is 6uH, output capacitor is one 1000uF
with 30m
and ESR zero F
swithing frequency, here F
LC
<F
Figure 7 - Type II compensator with
R =
For this type of compensator, F
The following is parameters for type II compensa-
1.Calculate the location of LC double pole F
2.Set R
Choose R
3. Set crossover frequency at 1/10~ 1/5 of the
4.Calculate R
F
ESR
R2
R1
1
ESR
Vout
<<F
V
F
R
LC
OUT
2
electrolytic capacitors.
5.3kHz
2
2
O
2
<=1/10~1/5F
transconductance amplifier
equal to 1k .
-V
V
1.3kHz
Vref
2
2
1
Fb
REF
ESR
=191
REF
.
ESR C
30m
3
value by the following equation.
1
1k
gm
15uH 1000uF
1
L
5V-0.8V
1
OUT
O
1
s.
NX2154/2154A
1000uF
=30kHz.
OUT
0.8V
C
OUT
R3
C1
Ve
191
O
has to satisfy
C2
LC
11