2.5 MHz Dual Switching Regulator
with Integrated 2A Switches
POWER MANAGEMENT
Description
The SC2440 is an adjustable frequency dual current-
mode switching regulator with 2A integrated switches.
Its high frequency operation allows the use of small
inductors and capacitors, resulting in very compact power
supplies. The SC2440 is suitable for next generation XDSL
modems requiring operating frequencies in excess of 1.5
MHz. The two channels operate at 180° out of phase
for reduced input voltage ripples. Separate soft start/
shutdown pins allow independent control and output
sequencing for latch-up prevention. The SC2440 can also
be externally synchronized up to 2.5 MHz per channel.
Current-mode PWM control allows fast transient
response with simple loop compensation. Cycle-by-cycle
current limiting and hiccup overload protection reduce
power dissipation during overload.
SC2440
Features
u
Up to 2.5 MHz/Channel Programmable Switching
u
u
u
u
u
u
u
u
u
u
u
u
u
u
u
u
u
Frequency
Fixed Frequency Current-mode Control
Wide Input Voltage Range 2.8V to 20V
Out of Phase Switching Reduces Ripple
Cycle-by-cycle Current-limiting
Independent Shutdown/soft-start Pins
Independent Hiccup Overload Protection
Independent Power-Good Indicators
Two 2A Integrated Switches
External Synchronization
Thermal Shutdown
Thermally Enhanced 16-pin TSSOP Package
XDSL and Cable Modems
Set-up Boxes
Point of Load Applications
CPE Equipment
DSP Power Supplies
Disk Drives
Applications
Typical Application Circuit
R6
100K
FB1
PGOOD1 BOOST1
D3
C2
1N4148
0.1µF
L1
COMP1
C7 10pF
SS1
22nF
R9
ROSC
C10
22nF C9
COMP2
R7 10pF C8
24.3K
220pF
FB2
GND
BOOST2
R8
PGOOD2
100K
1N4148
SW2
C4
0.1µF
15K
SS2
SYNC
SW1
VIN
12V
C15
IN
10µF
D2
UPS120
L2
4.4µH
D4
C3
10µF
R4
10K
R3
40.2K
OUT2
5V/2A
3.3µH
D1
UPS120
C1
10µF
R1
23.3K
R2
10K
R5
C5
Efficiency vs Load Current
95
OUT1
3.3V/2A
15.4K C6 470pF
90
85
Efficiency (%)
80
75
70
65
60
55
50
0
V
IN
= 12V
V
OUT2
= 5V
SC2440
V
OUT1
= 3.3V
0.5
1
1.5
2
L1: Sumida CR43
L2: F alco D04012
Load Current (A)
Figure 1. 1.3MHz 12V to 3.3V and 5V Step-down Converter
Revision: March 5, 2007
1
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