SC412A_1 Datasheet, PDF (1/22 Pages) Semtech Corporation – Synchronous Buck Controller

SC412A
Synchronous Buck Controller
POWER MANAGEMENT
Description
The SC412A is a versatile, constant on-time synchronous
buck, pseudo fixed-frequency, PWM controller intended
for notebook computers and other battery operated
portable devices. The SC412A contains all the features
needed to provide cost-effective control of switch-mode
power outputs.
The output voltage is programmable from 0.75 to 5.25
volts using external resistors. Switching frequency is
internally preset to 325kHz. Additional features cycle-
by-cycle current limit, voltage soft-start, under-voltage
protection, programmable over-current protection, soft
shutdown, automatic power save and non-overlapping
gate drive. The SC412A also provides an enable input
and a power good output.
The constant on-time topology provides fast, dynamic
response. The excellent transient response means that
SC412A based solutions require less output capacitance
than competing fixed-frequency converters. Switching
frequency is constant until a step in load or line voltage
occurs, at which time the pulse density and frequency
will increase or decrease to counter the change in
output voltage. After the transient event, the controller
frequency returns to steady state operation. At light loads,
the automatic power save mode reduces the switching
frequency for improved efficiency.
Features
‹ V_BAT Range 3V to 25V
‹ Soft-Shutoff at Output
‹ Current Sense Using Low-Side R_DS(ON) or Resistor
Sensing with Adjustable Cycle-by-Cycle Current Limit
‹ Fixed-Frequency 325kHz
‹ Constant On-Time for Fast Dynamic Response and
Reduced Output Capacitance
‹ Automatic Smart Power Save^†
‹ Internal Soft-Start
‹ Over-Voltage/Under-Voltage Fault Protection
‹ Power Good Output
‹ 1μA Typical Shutdown Current
‹ Tiny 3x3mm, 16 Pin MLP, Lead-free Package
‹ Low External Part Count
‹ Industrial Temperature Range
‹ 1% Internal Reference
‹ 1A/3A Non-Overlapping Gate Drive with SmartDrive™
‹ High Efficiency > 90%
‹ Fully WEEE and RoHS Compliant
†_{Patent pending}
Applications
‹ Notebook and Sub-Notebook Voltage Controllers
‹ Tablet PCs
‹ Embedded Applications
Typical Application Circuit
VCC
VBAT
VOUT
C1
D1
CIN
Q1
C2
L1
COUT
Q2
VCC
VCC
RLIM
R1
1 _LX
EN ¹²
2
BST
U1 11
PGOOD
3 _VCC
VOUT ¹⁰
4 _DL ^SC412A _FB 9
EN
PGOOD
VOUT
FB
R2
October 25, 2007
R3
1
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