NX2142A MICROSEMI [Microsemi Corporation], NX2142A Datasheet - Page 15

• Manufacturer Part Number: NX2142A
• Description: SINGLE CHANNEL PWM CONTROLLER WITH FEEDFORWARD AND 5V BIAS REGULATOR
• Manufacturer: MICROSEMI [Microsemi Corporation]

voltage, using equation 21, the final selection of R
8k
at 75% of the LC double pole.
at half the swithing frequency.
Rev. 1.1
10/28/07
R =
2.Set crossover frequency F
3. Set R
4.Calculate R
Choose R
5. Calculate C
Choose C
6. Calculate C
Choose C
F
F
C =
C =
3
=
= 3 6 k
LC
ESR
1
2
=
=2.7nF
1 0
=
= 1 4 p F
V
1
2
2
1.94kHz
V
2
2
O S C
5.6kHz
2
2
in
2
equal to 4k . Based on output
2
1
2
1
R
R
3
37.4k
3 7 . 4 k
=2.7nF.
=15pF.
3
=37.4k
1
3
ESR C
2
1.5uH 4500uF
6.33m
3
L
1
2
F
1
value by the following equation.
OUT
1
z
by setting compensator zero F
by setting compensator pole
F
1
s
E S R
6 . 3 3 m
6 0 k H z
1
1
1
0.75 1.94kHz
C
OUT
OUT
F
6 0 0 k H z
O
4500uF
L
O
1 . 5 u H
=60kHz>>F
R
2
4 k
ESR
.
F
1
p
is
Z
Case 2:
simple RC circuit without feedback as shown in figure
15. R
pole effect. C
ing noise. The following equations show the compen-
sator pole zero location and constant gain.
sator 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 14 - Type II compensator with
Type II compensator can also be realized by
The following is parameters for type II compen-
1.Calculate the location of LC double pole F
3
R2
R1
and C
F
F =
F
Gain=g
Vout
LC
p
z
2
2
2
2.9kHz
2
2
1
introduces a pole to suppress the switch-
transconductance amplifier(case 2)
Vref
introduce a zero to cancel the double
m
Fb
ESR
1
R
R +R
1
R
.
3
1
R
3
2.2uH 1360uF
L
1
1
OUT
gm
C
electrolytic capacitors.
C
2
1
1
2
NX2142/2142A
R
C
3
OUT
... (19)
... (18)
... (20)
R3
C1
Ve
C2
LC
15