
POWER MANAGEMENT
Description
The SC2447 is a versatile high-frequency dual phase PWM
step-down controller optimized for Philips and Renesas
DrMOS
TM
. Both phases are capable of sourcing or sink-
ing load currents, making the SC2447 suitable for net-
working system power and DDR applications.
1
www.semtech.com
SC2447
Dual-Phase, Single or Dual Output
Synchronous Step-Down Controller
REFOUT
GDH2
IN1-
SYNC
CS1+
COMP1
SS1/EN1
CS1-
SS2/EN2
COMP2
IN2-
REFIN
CS2-
CS2+
GDH1
GDL1
GDL2
REF
ROSC
AGND
AVCC
VDDG
CBN
CBP
VSSO
VSSC
DISABLE
VI
REG5V
VO
VDDO
VDDC
V
2.5V/20A
V
IN
12V
V
1.2V/25A
L
1
μ
H/1.8m
C
O1
100
μ
F
x 3
C
IN1
22
μ
F
x 4
C
SS1
0.1
μ
F
C
O2
100
μ
F
x 3
C
SS2
0.1
μ
F
R
OSC
, 51.1K
C
5
1
μ
F
C
3
1
μ
F
C
VCC
4.7
F
R
22.1K
R
22.1K
C
100nF
R
S1C
, 11K
PIP212-12M
R
FB1A
10K
R
FB1B
2.49K
R
24.9K
C
3.3nF
C
0.1uF
C
10pF
C
B1
100nF
R
1
10
R
VCC
10
L
0.4
μ
H/1m
C
6
1
μ
F
C
4
1
μ
F
R
S2B
200K
R
22.1K
C
68nF
R
S2C
, 20K
VDDG
CBN
CBP
VSSO
VSSC
DISABLE
VI
REG5V
VO
VDDO
VDDC
PIP212-12M
R
FB2A
10K
R
7.15K
R
A2
16.9K
C
A2
3.3nF
C
10pF
C
100nF
R
2
10
C
IN2
22
μ
F
x 4
SC2447
Revision: December 15, 2006
Features
2-Phase Step-down Controller optimized for Philips
or Renesas DrMOS
TM
Out of Phase Operation for Low Input Current Ripple
Outputs Source and Sink Current
Fixed Frequency Peak Current-Mode Control
Lossless Inductor DCR Current Sensing
Optional Resistor Current-Sensing for Precise Cur-
rent-Limit
Dual 30A Outputs or 2-Phase 60A Single Output
Operation
Wide Input Voltage Range: 4.65V to 15V
Individual Closed-Loop Soft-Start, Overload Shut-
down Timer and Enable
Output Voltage as Low as 0.5V
Starts into Pre-Bias Output
Tri-State PWM Output during Shutdown
Programmable Frequency Up to 1MHz Per Phase
External Synchronization
TSSOP-28 Lead-free Package. Fully WEEE and RoHS
Compliant
Typical Application Circuit
The SC2447 employs fixed frequency, continuous-con-
duction peak current-mode control for easy compensa-
tion and fast transient response.
The SC2447 can be used to generate two independent
outputs (up to 30A per output) or a single 60A output
with shared phase current. The PWM signals are 180°
out of phase to minimize input/output ripple.
Either inductor DC resistance or precision sense resistor
can be used for current-mode control. Inductor DC resis-
tance sensing has the advantage of being lossless.
Each phase has individual closed-loop soft-start and over-
load shutdown timer. The SC2447 powers up neatly with
pre-biased output. It has tri-state shutdown and hiccup
overload protection. In two-phase single-output configu-
ration, the master timer controls the soft-start and over-
load shutdown functions. The SC2447 is in a lead-free,
WEEE and RoHS compliant, TSSOP-28 package.
Applications
Telecommunication Power Supplies
DDR Memory Power Supplies
Graphic Power Supplies
Servers and Base Stations
Figure 1