SC4501 Semtech Corporation, SC4501 Datasheet - Page 14

• Manufacturer Part Number: SC4501
• Description: 2MHz Step-Up Switching Regulator
• Manufacturer: Semtech Corporation

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Therefore
and
The spacing between p
converter is delivering the maximum output current from
the lowest V
condition. Ignoring C
low frequency pole with the equivalent output resistance
R
Application Information
POWER MANAGEMENT
O
2005 Semtech Corp.
D
R
of the error amplifier:
O
Z
p
2
2
1
1
Amplifier
6
6
12
12
8 .
Transcondu
IN
8 .
SHDN
SHDN
SHDN
. This represents the worst-case compensation
0
5
3 .
4
0
0
7 .
2
1
5 .
5 .
Open
10
H
. 0
5
. 0
and C
62
Loop
c
F
Figure 9. Suggested PCB Layout for the SC4501. Notice that there is no via
GND
GND
VOUT
VOUT
62
2
tan
and z
2
29
ce
C4
C4
6
Gain
209
for the moment, C
4 .
2
R1
R1
Krads
directly under the device. All vias are 12mil in diameter.
is the closest when the
Krads
60
R3
R3
C6
C6
R2
R2
49
1
C5
C5
dB
1
1
. 4
33
68
4
3 .
KHz
7 .
4
KHz
forms a
M
C2
C2
U1
U1
U1
U1
14
C3
C3
C
The poles p
shift in the loop response. For stable operation, the overall
loop gain should cross 0dB with -20dB/decade slope. Due
to the presence of the RHP zero, the 0dB crossover frequency
should not be higher than
effect and maximizes loop bandwidth. Thus
R
Increasing R
4
3
R
and R
determines the mid-band loop gain of the converter.
3
p
Z
1
1
C
4
R4
R4
C1
C1
3
260
39
R
I 2
also forms a zero with angular frequency:
R
V
3
O
1
3
OUT
1
D1
D1
1
, p
OUT
5 .
C
increases the mid-band gain and the crossover
C
4
4
rads
(
Krads
2
C
MAX
2
and the RHP zero z
)
1
4
30
7 .
1
9 .
M
K
41
1
6
z
3
Hz
1
L1
L1
2
3 .
820
820
. Placing z
KHz
VIN
VIN
pF
pF
2
all increase phase
1
near p
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SC4501
2
nulls its
(15)