SC4502H Semtech Corporation, SC4502H Datasheet - Page 13

• Manufacturer Part Number: SC4502H
• Description: 1.4 Amp, 2 Mhz Step-up Switching Regulator With Soft-start | Semtech
• Manufacturer: Semtech Corporation

Therefore
and
The spacing between p
converter is delivering the maximum output current from
the lowest V
compensation condition. Ignoring C
moment, C
equivalent output resistance R
Applications Information
POWER MANAGEMENT
2005 Semtech Corp.
D
R
z2
p2
O
1
1
10
Amplifier
10
12
12
Transcondu
4
0.3
5.3
5
1
forms a low frequency pole with the
0.5
0.5
2
IN
10
. This represents the worst-case
0.62
H
Open
F
0.62
Figure 8. Suggested PCB Layout for the SC4502/SC4502H. Notice that there is no
2
Loop
ctance
2
SHDN
SHDN
SHDN
SHDN
20Krads
and z
VOUT
VOUT
VOUT
VOUT
272
GND
GND
GND
GND
C4
C4
C4
C4
Gain
via directly under the device. All vias are 12mil in diameter.
Krads
2
O
R1
R1
R1
R1
is the closest when the
of the error amplifier:
1
60
1
R3
R3
R3
R3
C6
C6
C6
C6
R2
R2
R2
R2
49dB
C5
C5
C5
C5
3.18KHz
5
43.4KHz
and C
1
4.7M
6
for the
C2
C2
C2
C2
U1
U1
U1
U1
C3
C3
C3
C3
13
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 crossover frequency
should not be higher than
effect and maximizes loop bandwidth. Thus
R
Increasing R
crossover frequency. However it reduces the phase
margin. The values of R
4
3
R4
R4
R4
R4
and R
R
C1
C1
C1
C1
determines the mid-band loop gain of the converter.
p1
3
z1
C
D1
D1
D1
D1
4
R
R
380
30.3
3
3
O
also forms a zero with angular frequency:
2
1
1
C
V
C
1
OUT
, p
4
I
4
rads
OUT(MAX)
Krads
3
2
increases the mid-band gain and the
59K
C
and the RHP zero z
4.7M
1
2
1
L1
L1
L1
L1
VIN
VIN
VIN
VIN
60Hz
1
1
560pF
4.8
SC4502/SC4502H
560pF
3
z
3
KHz
2
and C
. Placing z
4
can be determined
2
all increase phase
1
near p
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2
nulls its
(15)