NCP3012
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25
Compensation Type II
This compensation is suitable for electrolytic capacitors.
Components of the Type II compensation (Figure 36)
network can be specified by the following equations:
Figure 36. Type II Compensation
R
C1
+
2 @ p @ f
0
@ L @ V
RAMP
@ V
OUT
ESR @ V
IN
@ V
ref
@ gm
(eq. 43)
C
C1
+
1
0.75 @ 2 @ p @ f
P0
@ R
C1
(eq. 44)
C
C2
+
1
p @ R
C1
@ f
S
(eq. 45)
R1 +
V
OUT
* V
ref
V
ref
@ R2
(eq. 46)
V
RAMP
is the peaktopeak voltage of the oscillator ramp
and gm is the transconductance error amplifier gain.
Capacitor C
C2 is optional.
Compensation Type III
Tantalum and ceramics capacitors have lower ESR than
electrolytic, so the zero of the output LC filter goes to a
higher frequency above the zero crossover frequency. This
requires a Type III compensation network as shown in
Figure 37.
There are two methods to select the zeros and poles of this
compensation network. Method I is ideal for tantalum
output capacitors, which have a higher ESR than ceramic:
Figure 37. Type III Compensation
f
Z1
+ 0.75 @ f
P0
(eq. 47)
f
Z2
+ f
P0
(eq. 48)
f
P2
+ f
Z0
(eq. 49)
f
P3
+
f
S
2
(eq. 50)
Method II is better suited for ceramic capacitors that
typically have the lowest ESR available:
f
Z2
+ f
0
@
1 * sinq max
1 ) sin q max
Ǹ
(eq. 51)
f
P2
+ f
0
@
1 ) sin q max
1 * sin q max
Ǹ
(eq. 52)
f
Z1
+ 0.5 @ f
Z2
(eq. 53)
f
P3
+ 0.5 @ f
S
(eq. 54)
qmax is the desired maximum phase margin at the zero
crossover frequency, ƒ
0
. It should be 45° 75°. Convert
degrees to radians by the formula:
q max + q max
degress
@
ǒ
2 @ p
360
Ǔ
:Units+ radians
(eq. 55)
The remaining calculations are the same for both methods.
R
C1
uu
2
gm
(eq. 56)
C
C1
+
1
2 @ p @ f
Z1
@ R
C1
(eq. 57)
C
C2
+
1
2 @ p @ f
P3
@ R
C1
(eq. 58)
C
FB1
+
2 @ p @ f
0
@ L @ V
RAMP
@ C
OUT
V
IN
@ R
C1
(eq. 59)
R
FB1
+
1
2p @ C
FB1
@ f
P2
(eq. 60)
(eq. 61)
R1 +
1
2 @ p @ C
FB1
@ f
Z2
* R
FB1
R2 +
V
ref
V
OUT
* V
ref
@ R1
(eq. 62)
If the equation in Equation 63 is not true, then a higher value
of R
C1
must be selected.
R1 @ R2 @ R
FB1
R1 @ R
FB1
) R2 @ R
FB1
) R1 @ R2
u
1
gm
(eq. 63)
NCP3012
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26
PACKAGE DIMENSIONS
TSSOP14
CASE 948G01
ISSUE B
DIM MIN MAX MIN MAX
INCHESMILLIMETERS
A 4.90 5.10 0.193 0.200
B 4.30 4.50 0.169 0.177
C −−− 1.20 −−− 0.047
D 0.05 0.15 0.002 0.006
F 0.50 0.75 0.020 0.030
G 0.65 BSC 0.026 BSC
H 0.50 0.60 0.020 0.024
J 0.09 0.20 0.004 0.008
J1 0.09 0.16 0.004 0.006
K 0.19 0.30 0.007 0.012
K1 0.19 0.25 0.007 0.010
L 6.40 BSC 0.252 BSC
M 0 8 0 8
NOTES:
1. DIMENSIONING AND TOLERANCING PER
ANSI Y14.5M, 1982.
2. CONTROLLING DIMENSION: MILLIMETER.
3. DIMENSION A DOES NOT INCLUDE MOLD
FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH OR GATE BURRS SHALL NOT
EXCEED 0.15 (0.006) PER SIDE.
4. DIMENSION B DOES NOT INCLUDE
INTERLEAD FLASH OR PROTRUSION.
INTERLEAD FLASH OR PROTRUSION SHALL
NOT EXCEED 0.25 (0.010) PER SIDE.
5. DIMENSION K DOES NOT INCLUDE DAMBAR
PROTRUSION. ALLOWABLE DAMBAR
PROTRUSION SHALL BE 0.08 (0.003) TOTAL
IN EXCESS OF THE K DIMENSION AT
MAXIMUM MATERIAL CONDITION.
6. TERMINAL NUMBERS ARE SHOWN FOR
REFERENCE ONLY.
7. DIMENSION A AND B ARE TO BE
DETERMINED AT DATUM PLANE W.
____
S
U0.15 (0.006) T
2X L/2
S
U
M
0.10 (0.004) V
S
T
L
U
SEATING
PLANE
0.10 (0.004)
T
SECTION NN
DETAIL E
J
J1
K
K1
DETAIL E
F
M
W
0.25 (0.010)
8
14
7
1
PIN 1
IDENT.
H
G
A
D
C
B
S
U0.15 (0.006) T
V
14X REFK
N
N
7.06
14X
0.36
14X
1.26
0.65
DIMENSIONS: MILLIMETERS
1
PITCH
SOLDERING FOOTPRINT
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