NX2141CMTR MICROSEMI [Microsemi Corporation], NX2141CMTR Datasheet - Page 16

• Manufacturer Part Number: NX2141CMTR
• Description: SINGLE CHANNEL MOBILE PWM CONTROLLER WITH FEEDFORWARD AND ENABLE
• Manufacturer: MICROSEMI [Microsemi Corporation]

B. Type II compensator design
stage output capacitors, usually the Type II compensa-
tor can be used to compensate the system.
F
RC circuit without feedback as shown in figure 15. R
and C
C
Rev. 1.6
05/15/07
LC
2
<F
introduces a pole to suppress the switching noise.
loop gain
Figure 20 - Bode plot of Type II compensator
Choose R
8. Calculate R
Choose R
If the electrolytic capacitors are chosen as power
For this type of compensator, F
Type II compensator can also be realized by simple
R
R =
ESR
1
power stage
compensator
introduce a zero to cancel the double pole effect.
1
2
<<F
V
F
R
3.2k
2
2
OUT
Z
2
O
<1/10F
F
1
2
-V
V
1
LC
=12.7k
1
=4k .
REF
REF
15nF
C
F
1
ESR
3
s.
.
40dB/decade
1.05V-0.8V
(
20dB/decade
4k
F
1
(
Z2
2.4kHz
F F
O
1
F
0.8V
Gain
1
P1
P
)
O
8.8kHz
has to satisfy
12.8k
1
)
3
The following equations show the compensator pole zero
location and constant gain.
tor design. Input voltage is 12V, output voltage is 2.5V,
output inductor is 2.2uH, output capacitors are two 680uF
with 41m
and ESR zero F
Figure 21 - Type II compensator with
The following is parameters for type II compensa-
1.Calculate the location of LC double pole F
R2
R1
F
F
F =
F
Gain=g
Vout
LC
ESR
p
z
electrolytic capacitors.
2
2
2.9kHz
2
2
5.7kHz
transconductance amplifier
2
2
Vref
m
Fb
ESR
1
R
R +R
.
1
R
3
1
R
3
ESR C
2.2uH 1360uF
20.5m
L
1
1
OUT
C
gm
1
C
2
1
1
2
1
R
C
3
OUT
OUT
1360uF
... (16)
...(15)
... (17)
R3
C1
Ve
NX2141
C2
LC
16