SC412A
Synchronous Buck Controller
POWER MANAGEMENT
Description
The SC412A is a versatile, constant on-time synchronous
buck, pseudo
fi
xed-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
fi
xed-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
C1
D1
VBAT
CIN
Q1
16
15
14
13
VCC
RLIM
R1
DH
L1
VOUT
1
2
ILIM
NC
NC
C2
LX
BST
VCC
DL
PAD
EN
12
11
10
9
EN
PGOOD
VOUT
FB
U1
PGOOD
VOUT
FB
COUT
Q2
VCC
3
4
SC412A
GND
RTN
NC
NC
R2
17
7
5
6
8
R3
September 19, 2006
1
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