ISL6269_06 Datasheet, PDF (1/17 Pages) Intersil Corporation – High-Performance Notebook PWM Controller with Bias Regulator and Audio-Frequency Clamp

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Data Sheet
August 7, 2006
ISL6269
FN9177.1
High-Performance Notebook PWM
Controller with Bias Regulator and
Audio-Frequency Clamp
The ISL6269 IC is a Single-Phase Synchronous-Buck PWM
controller featuring Intersil's Robust Ripple Regulator (R³)
technology that delivers truly superior dynamic response to
input voltage and output load transients. Integrated
MOSFET drivers, 5V LDO, and bootstrap diode result in
fewer components and smaller implementation area.
Intersil’s R³ technology combines the best features of fixed-
frequency PWM and hysteretic PWM while eliminating many
of their shortcomings. R³ technology employs an innovative
modulator that synthesizes an AC ripple voltage signal V_R,
analogous to the output inductor ripple current. The AC
signal V_R enters a hysteretic comparator where the lower
threshold is the error amplifier output V_COMP, and the upper
threshold is a programmable voltage reference V_W, resulting
in generation of the PWM signal. The voltage reference V_W
sets the steady-state PWM frequency. Both rising and falling
edges of the PWM are modulated, providing faster response
to input voltage transients and output load transients than
conventional fixed-frequency PWM controllers. Unlike a
conventional hysteretic converter, the ISL6269 has an error
amplifier that provides ±1% voltage regulation at the FB pin.
The ISL6269 has a 1.5ms digital soft-start and can be
started into a pre-biased output voltage. A resistor divider is
used to program the output voltage setpoint. The ISL6269
can be configured to operate in forced-continuous-
conduction-mode (FCCM) or in diode-emulation-mode
(DEM), which improves light-load efficiency. In FCCM the
controller always operates as a synchronous rectifier,
switching the low-side MOSFET regardless of the output
load, however with DEM enabled, the low-side MOSFET is
disabled preventing negative current flow from the output
inductor during low load operation. An audio filter prevents
the PWM switching frequency from entering the audible
spectrum due to extremely light load while in DEM.
A PGOOD pin indicates when the converter is capable of
supplying regulated voltage. The ISL6269 features a unique
fault-identification capability that can drastically reduce
trouble-shooting time and effort. The pull-down resistance of
the PGOOD pin is 30Ω for an overcurrent fault, 60Ω for an
overvoltage fault, or 90Ω for either an undervoltage fault or
during soft-start. The overcurrent protection is accomplished
by measuring the voltage drop across the r_DS(ON) of the
low-side MOSFET. A single resistor programs the
overcurrent and short-circuit points. Overvoltage and
undervoltage protection is monitored at the FB voltage
feedback pin.
Features
• High performance synthetic ripple regulation
• Extremely fast transient response
• External type-two loop compensation
• ±1% regulation accuracy: -10°C to +100°C
• Starts into a pre-biased output
• Wide input voltage range: +7.0V to +25.0V
• Wide output voltage range: +0.6V to +3.3V
• Wide output load range: 0A to 25A
• Programmable PWM frequency: 200kHz to 600kHz
• Power good monitor
• Fault identification by PGOOD pull-down resistance
• Integrated MOSFET drivers with shoot-through protection
• Internal digital soft-start
• Internal 5V LDO for self-biasing from up to 25V
• Configure forced continuous conduction or diode
emulation for increased light load efficiency
• PWM minimum frequency above audible spectrum
• Integrated boot-strap diode
• Low-side MOSFET r_DS(ON) overcurrent protection
• Undervoltage protection
• Soft crowbar overvoltage protection
• Over-temperature protection
• Pb-free plus anneal available (RoHS compliant)
Applications
• PCI express graphical processing unit
• Auxiliary power rail
• VRM
• Network adapter
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CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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