SC2620 Semtech Corporation, SC2620 Datasheet - Page 20

• Manufacturer Part Number: SC2620
• Description: 30V Step-down Regulator
• Manufacturer: Semtech Corporation

gain at high frequency. Placing p
Computed R
load transient responses in over half of the applications.
However in other cases empirically determined
compensation networks based on optimized load transient
responses may differ from those calculated by a factor of
3. Therefore checking the transient response of the
converter is imperative. Starting with calculated R
and C
expected load step to the converter at the maximum
operating V
converter while adjusting R
R
waveform does not show excessive ringing or overshoot
(see Figures 13(a), 13(b), 16(b) and 16(c)).
Feedforward capacitor C
limited frequency range and is sometimes used to improve
loop response. C
POWER MANAGEMENT
Applications Information
5
2008 Semtech Corp.
, the smallest C
C
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Figure 13. Load Transient Response of the Dual DC-DC Converter in Figure 1(a). I
6
Upper Trace : OUT1 Voltage, AC Coupled, 0.5V/div
Lower Trace : L
6
(using n=1 in Equations (11)-(13)), apply the largest
fR
1
IN
5
5
. Observe the load transient response of the
, C
5
11
and C
between 0.3A and 2A.
5
will be more effective if
and C
1
Inductor Current, 0.5A/div
6
can indeed result in near optimal
40 s/div
11
6
5
, C
boosts phase margin over a
(a)
so that the inductor current
5
and C
3
at about
6
. Choose the largest
V
V
IN
OUT
=16V
=3.3V
R
1
2
S
gives:
R
1
5
R
(13)
, C
2
.
5
20
Example: Determine the compensation components for
the 550kHz 9V-16V to 3.3V and 1.2V converter in Figure
1(a).
For both channels,
For the 3.3V output:
C
1
R
C
C
5
5
6
22
Upper Trace : OUT2 Voltage, AC Coupled, 0.5V/div
Lower Trace : L
11
11
1
F
3 .
. n is assumed to be 1 in (11) and (12).
3 .
(
550
k
30
k
13
1 .
2
k
k
60
10
5
2
10
3
5 .
Inductor Current, 0.5A/div
1
)
S
3
5 .
(
(
11
40 s/div
) 1
10
3
5 .
10
3 .
OUT1
(b)
5
(
) 8
Mrads
6
and I
10
1
2 (
22
5 .
3
8 .
nF
)
OUT2
1
,
10
V
V
10
47
IN
OUT
I
are switched
OUT
=16V
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=1.2V
SC2620
6
pF
(
4
MAX
)
)
2
A
and