SC475A Datasheet, PDF (1/27 Pages) Semtech Corporation – Synchronous Buck Controller with Dual-Level VOUT Transition Support

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SC475A
Synchronous Buck Controller with
Dual-Level VOUT Transition Support
Description
Features
The SC475A is a versatile, constant on-time synchronous
buck, pseudo-fixed-frequency, PWM controller intended for
notebook computers and other battery operated portable
devices. The SC475A contains all the features needed to
provide cost-effective control of system elements needing
voltage slewing. An integrated switch provides two resistor-
programmable DC output voltages controlled by the G0
input.
The output voltage is adjustable from 0.75V to 5V.
Additional features 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 SC475A
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
SC475A 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 SC475A
frequency for improved efficiency.
V_OUT Programmable 0.75V to 5.25V with Integrated
Transition Support
V Range 3V to 25V
BAT
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 MLP Package
Low External Part Count
Industrial Temperature Range
0.85% Internal Reference
1A/3A Non-Overlapping Gate Drive with
SmartDriver™ Technology
High Efficiency > 90%
Device is Fully WEEE and RoHS Compliant
†_{Patent Pending}
Applications
Notebook/Sub-Notebook Graphics Voltage
Controllers
Tablet PCs
Embedded Applications
September 25, 2006
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