SC2447 Datasheet, PDF (1/26 Pages) Semtech Corporation – Dual-Phase, Single or Dual Output Synchronous Step-Down Controller

SC2447
Dual-Phase, Single or Dual Output
Synchronous Step-Down Controller
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.
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.
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
Applications
Telecommunication Power Supplies
DDR Memory Power Supplies
Graphic Power Supplies
Servers and Base Stations
Typical Application Circuit
V_IN
12V
V_OUT1
2.5V/20A
C_O1
100µF
x3
R_FB1A
10KΩ
R_FB1B
2.49KΩ
Figure 1
C_IN1
22µF
x4
C_B1
L₁ ^100nF
1µH/1.8mΩ
R_S1B
22.1KΩ
R_S1A
22.1KΩ
C_CS1
100nF
R_S1C , 11KΩ
VDDO
CBP
VDDC
VDDG
CBN
VO
REG5V
VI
DISABLE
VSSO VSSC
PIP212-12M
R₁
10Ω
C₃
C₅
1µF
1µF
C_VCC
4.7µF
C_CMP1
10pF
R_A1
24.9KΩ
C_A1
3.3nF
C_REF
0.1uF
R_VCC
10Ω
AVCC
R₂
10Ω
C₄
1µF
C₆
1µF
GDH1
GDL1
GDH2
GDL2
SC2447
VDDC
VDDG
VDDO
CBP
REG5V
VI
CBN
VO
DISABLE
VSSC VSSO
PIP212-12M
C_IN2
22µF
x4
C_B2
100nF
L₂
0.4µH/1mΩ
R_S2B
200KΩ
R_S2A
22.1KΩ
CS1+
CS2+
C_CS2
68nF
CS1-
IN1-
CS2-
IN2-
R_S2C , 20KΩ
COMP1
REFOUT
REF
REFIN
COMP2
R_OSC , 51.1KΩ
ROSC
AGND
SS1/EN1
R_A2
16.9KΩ
C_A2
3.3nF
C_CMP2
10pF
SYNC
SS2/EN2
C_SS2
C_SS1
0.1µF 0.1µF
V_OUT2
1.2V/25A
C_O2
100µF
x3
R_FB2A
10KΩ
R_FB2B
7.15KΩ
Revision: December 15, 2006
1
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