?2010 Semtech Corporation
1
SC417/SC427
10A EcoSpeed
TM
Integrated FET
Regulator with Programmable LDO
Features
Power system:
Input voltage 3V to 28V
Integrated bootstrap switch
Programmable LDO output 200mA
1% reference tolerance -40 to +85 癈
Selectable internal/external bias power supply
EcoSpeed
TM
architecture with pseudo-fixed fre-
quency adaptive on-time control
Logic input/output control
Independent control EN for LDO and switcher
Programmable V
IN
UVLO threshold
Power good output
Selectable ultrasonic/power save methods
Protections
Over-voltage/under-voltage
TC compensated R
DS(ON)
sensed current limit
Thermal shutdown
Output capacitor types
High ESR SP, POSCAP, OSCON
Ceramic capacitors
Package 5x5mm, 32-pin MLPQ
Lead-free and halogen free
RoHS and WEEE compliant
Applications
Office automation and computing
Networking and telecommunication equipment
Point-of-load power supplies and module replacement.
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Description
The SC417/SC427 is a stand-alone synchronous
EcoSpeed
TM
buck regulator which incorporates Semtechs
advanced, patented adaptive on-time control architecture
to provide excellent light-load efficiency and fast transient
response. It features integrated power MOSFETs, a boot-
strap switch, and a programmable LDO in a 5x5mm
package. The device is highly efficient and uses minimal
15x20mm PCB area for a total converter solution. Refer to
page 16 for information on the C-SIM simulation tool.
The SC417/SC427 supports using standard capacitor types
such as electrolytic or special polymer, in addition to
ceramic, at switching frequencies up to 1MHz. The pro-
grammable frequency, synchronous operation, and select-
able power-save provide high efficiency operation over a
wide load range. In power-save mode, the minimum oper-
ating frequency for the SC417 is 25kHz whereas the SC427
has no minimum.
Additional features include internal soft-start, program-
mable cycle-by-cycle over-current limit protection, under
and over-voltage protections and soft shutdown. The
device also provides separate enable inputs for the PWM
controller and LDO as well as a power good output for the
PWM controller.
The wide input voltage range, programmable frequency,
and programmable LDO make the device extremely flexible
and easy to use in a broad range of applications. Support is
provided for single cell or multi-cell battery systems in addi-
tion to traditional DC power supply applications.
May 20, 2010
POWER MANAGEMENT
SC417/SC427
V5V
BST
LX
PGOOD
ILIM
LXS
EN/PSV
TON
ENL
LXBST
RILIM
CBST
+
RFB1
RFB2
VOUT
COUT
1礔
L1
VEXT/LDO
CIN
PGND
AGND
VIN
VIN
VOUT
FB
PGOOD
ENABLE LDO
ENABLE/PSAVE
RTON
Typical Application Circuit
US Patent: 7,714,547 B2