參數(shù)資料
型號(hào)： SC2440TETRT
廠商： Semtech Corporation
英文描述： 2.5 MHz Dual Switching Regulator with Integrated 2A Switches
中文描述： 2.5 MHz雙開(kāi)關(guān)穩(wěn)壓器集成甲開(kāi)關(guān)
文件頁(yè)數(shù)： 12/26頁(yè)
文件大?。?/td> 643K
代理商： SC2440TETRT
12
2005 Semtech Corp.
www.semtech.com
SC2440
POWER MANAGEMENT
Applications Information
in size and DCR. Setting
V
45
.
V
D
=
and
V
CESAT
=
A
6
=
)
=
I
L
,
V
25
.
in (3),
f
)(
2
+
V
(
)
25
.
V
V
)(
45
.
+
V
L
IN
OUT
In
OUT
=
(4)
where L is in
μ
H and f is in MHz.
Equation (3) shows that for a given
,
V
OUT
L
I
increases
as D decreases. If
choose L based on the nominal input voltage. Always
verify converter operation at the input voltage extremes.
IN
V
varies over a wide range, then
The peak current limits of both SC2440 power transistors
are internally set at 2.6A. The peak current limits are
duty-cycle invariant and are guaranteed higher than 2A.
The maximum load current is therefore conservatively
2
I
A
2
2
I
I
I
L
L
LM
)
MAX
(
OUT
=
=
(5)
If
LM
I
L
3
I
=
, then
LM
I
LM
LM
I
L
LM
I
)
MAX
(
OUT
I
85
.
2
I
2
I
=
=
=
.
The saturation current of the inductor should be 20-30%
higher than the peak current limit (2A). Low-cost powder
iron cores are not suitable for high-frequency switching
power supplies due to their high core losses. Inductors
with ferrite cores should be used.
Input Capacitor
A buck converter draws pulse current with peak-to-peak
amplitude equal to its output current I
from its input
supply. An input capacitor placed between the supply
and the buck converter filters the AC current and keeps
the current drawn from the supply to a DC constant. The
input capacitance C
should be high enough to filter the
pulse input current. Its equivalent series resistance (ESR)
should be low so that power dissipated in the capacitor
does not result in significant temperature rise and
degrade reliability. For a single channel buck converter,
the RMS ripple current in the input capacitor is
)
D
1
D
I
I
OUT
RMS
)
CIN
(
=
. (6)
Power dissipated in the input capacitor is
)
ESR
(
I
2
RMS
)
CIN
(
.
Equation (6) has a maximum value of
2
I
OUT
( at
2
1
D
=
),
corresponding to the worst-case power dissipation
I
2
in C
IN
.
4
ESR
OUT
A dual-channel step-down converter with interleaved
switching reduces the RMS ripple current in the input
capacitor to a fraction of that of a single-phase buck
converter. If both power transistors in the SC2440 were
to switch on in phase, the current drawn by the SC2440
would consist of current pulses with amplitude equal to
the sum of the channel output currents. If each channel
were delivering I
and operating at 50% duty cycle, then
the input current would switch from zero to 2I
. The
RMS ripple current in the input capacitor would then be
I
OUT
. Power dissipated in C
IN
would be
that of a single-channel converter. The SC2440 produces
the highest RMS ripple current in C
when only one
channel is running and delivering the maximum output
current (
A
2
5
≈
). The input capacitor therefore should
have a RMS ripple current rating of at least 1A.
ESR
I
2
OUT
, 4 times
Multi-layer ceramic capacitors, which have very low ESR
(a few m
) and can easily handle high RMS ripple current,
are the ideal choice for input filtering. A single 4.7
μ
F or
10
μ
F X5R ceramic capacitor is adequate. For high voltage
applications, a small ceramic (1
μ
F or 2.2
μ
F) can be placed
in parallel with a low ESR electrolytic capacitor to satisfy
both the ESR and bulk capacitance requirements.
Output Capacitor
The output ripple voltage
V
OUT
of a buck converter can
be expressed as
+
=
OUT
L
OUT
V
fC
8
1
ESR
I
(7)
where C
OUT
is the output capacitance.
Inductor ripple current
I
increases as D decreases
(Equation (3)). The output ripple voltage is therefore the
highest when V
IN
is at its maximum. The first term in (7)
相關(guān)PDF資料
PDF描述
SC2441A 1.8V to 20V Input 2-Phase Synchronous Step-down Controllers with Step-up Converter
SC2441AEVB 1.8V to 20V Input 2-Phase Synchronous Step-down Controllers with Step-up Converter
SC2441ATETRT 1.8V to 20V Input 2-Phase Synchronous Step-down Controllers with Step-up Converter
SC2441 Very Low Input Voltage 2-Phase Synchronous Step-down Controllers with Step-up Converter
SC2441EVB Very Low Input Voltage 2-Phase Synchronous Step-down Controllers with Step-up Converter
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
SC2441 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Very Low Input Voltage 2-Phase Synchronous Step-down Controllers with Step-up Converter
SC2441A 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:1.8V to 20V Input 2-Phase Synchronous Step-down Controllers with Step-up Converter
SC2441A_09 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:1.8V to 20V Input 2-Phase Synchronous Step-down Controllers with Step-up Converter
SC2441AEVB 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:1.8V to 20V Input 2-Phase Synchronous Step-down Controllers with Step-up Converter
SC2441ATETRT 制造商:Semtech Corporation 功能描述:
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