SC2446 Semtech Corporation, SC2446 Datasheet

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SC2446

Manufacturer Part Number
SC2446
Description
Dual-Phase Single or Two Output Synchronous Step-Down Controller
Manufacturer
Semtech Corporation
Datasheet

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The SC2446 is a high-frequency dual synchronous step-
down switching power supply controller. It provides out-
of-phase high-current output gate drives to all N-chan-
nel MOSFET power stages. The SC2446 operates in syn-
chronous continuous-conduction mode. Both phases are
capable of maintaining regulation with sourcing or sink-
ing load currents, making the SC2446 suitable for gen-
erating both V
tions.
The SC2446 employs fixed frequency peak current-mode
control for the ease of frequency compensation and fast
transient response.
The dual-phase step-down controllers of the SC2446 can
be configured to provide two individually controlled and
regulated outputs or a single output with shared current
in each phase. The Step-down controllers operate from an
input of at least 4.7V and are capable of regulating out-
puts as low as 0.5V
The step-down controllers in the SC2446 have the pro-
vision to sense a synthesized MOSFET R
rent-mode control. This sensing scheme (U.S. patent
6,441,597) eliminates the need of the current-sense re-
sistor and is more noise-immune than direct sensing of
the high-side or the low-side MOSFET voltage. Precise cur-
rent-sensing with sense resistor is optional.
Individual soft-start and overload shutdown timer is in-
cluded in each step-down controller. The SC2446 imple-
ments hiccup overload protection. In two-phase single-
output configuration, the master timer controls the soft-
start and overload shutdown functions of both control-
lers.
POWER MANAGEMENT
Revision: September 9, 2004
Typical Application Circuit
Description
Figure 1
DDQ
C99
VO2
and the tracking V
+
C95
R79
R81
RCS+
C96
L11
R83
R75
C103
C101
CFILTER
RFILTER
TT
Q21
Q23
for DDR applica-
DS(ON)
R73
R77
C106
RCS-
REF
VIN
SYNC
Dual Independant Outputs
for cur-
C93
D11
C107
PVCC
BST2
GDH2
GDL2
VPN2
CS2+
CS2-
IN2-
COMP2
REFIN
VIN2
SYNC
SS1/EN1
SS2/EN2
C92
SC2446
VIN
U1
Synchronous Step-Down Controllers
REFOUT
1
COMP1
PGND
AGND
GDH1
AVCC
BST1
GDL1
VPN1
CS1+
CS1-
Rosc
REF
IN1-
Features
Applications
C108
Dual-Phase Single or Two Output
C104
R85
2-Phase synchronous continuous conduction mode
for high efficiency step-down converters
Out of phase operation for low input current ripples
Output source and sink currents
Fixed frequency peak current-mode control
75mV/-110mV maximum current sense voltage
Synthesized MOSFET R
low-cost applications
Optional resistor current-sensing for precise current-
limit
Dual outputs or 2-phase single output operation
Excellent current sharing between individual phases
Wide input voltage range: 4.7V to 16V
Individual soft-start, overload shutdown and enable
Duty cycle up to 88%
0.5V feedback voltage for low-voltage outputs
External reference input for DDR applications
Buffered V
Programmable frequency up to 1 MHz per phase
External synchronization
Industrial temperature range
28-lead TSSOP - EDP package
Telecommunication power supplies
DDR memory power supplies
Graphic power supplies
Servers and base stations
RCS-
C94
D12
C109
R74
R78
C105
C102
VIN
Q22
Q24
DDQ
CFILTER
RFILTER
R84
/2 output
U.S. Patent No. 6,441,597, www.semtech.com
R76
L12
RCS+
C97
DS(ON)
R80
R82
www.DataSheet4U.com
current-sensing for
C98
VO1
+
C100
SC2446

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