Synchronous Buck Controller with
Multi-Level VOUT Transition Support
POWER MANAGEMENT
POWER MANAGEMENT
Description
The SC471/A is a versatile, constant on-time synchronous
buck, pseudo-fixed-frequency, PWM controller intended for
notebook computers and other battery operated portable
devices. The SC471/A contains all the features needed to
provide cost-effective control of system elements needing
voltage slewing. Two integrated switches provide four
resistor-programmable DC output voltages, controlled by
the G0 and G1 inputs.
The output voltage is adjustable from 0.75V to 5V.
Additional features for each output include 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 SC471/A provides an enable input and a power good
output which is automatically blanked during output
voltage transitions.
The constant on-time topology provides fast dynamic
response. The excellent transient response means that
SC471/A 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 SC471/A
frequency for improved efficiency.
SC471/SC471A
Features
V
OUT
Programmable 0.75V to 5.25V with Integrated
Transition Support
V
BAT
Range 3V to 25V
Soft Shutoff at Output
Current Sense Using Low-side R
DS(ON)
or Resistor
Sensing
Adjustable Cycle-by-Cycle Valley Current Limit
325kHz Fixed-Frequency
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 with Transition Blanking
1μA Typical Shutdown Current
500μA Typical Operating Current
Tiny 3×3mm, 16 Pin MLPQ Package
Low External Part Count
Industrial Temperature Range
0.85% Internal Reference
1A/3A Non-Overlapping Gate Drive with
SmartDriver™ Technology
High Efficiency > 90%
This Product is Fully WEEE and RoHS Compliant
†Patent Pending
Applications
Notebook/Sub-Notebook Graphics Voltage
Controllers
Tablet PCs
Embedded Applications
September 12, 2006
1
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SEMTECH [ SEMTECH CORPORATION ]
