Dual-Output Buck Controller for Notebook Applications ISL6228

The ISL6228 IC is a dual channel 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 and bootstrap diodes result in fewer

components and smaller implementation area.

Intersil’s R3 technology combines the best features of fixedfrequency

and hysteretic PWMs while eliminating many of

their shortcomings. R3 technology employs an innovative

modulator that synthesizes an AC ripple voltage signal VR,

analogous to the output inductor ripple current. The AC signal

VR enters a window comparator where the lower threshold is

the error amplifier output VCOMP, and the upper threshold is a

programmable voltage reference VW, resulting in generation

of the PWM signal. The voltage reference VW sets the

steady-state PWM frequency. Both edges of the PWM can be

modulated in response to input voltage transients and output

load transients, much faster than conventional fixedfrequency

PWM controllers. Unlike a conventional hysteretic

converter, each channel of the ISL6228 has an error amplifier

that provides ±1% voltage regulation at the FB pin.

The ISL6228 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 ISL6228

operates in continuous-conduction-mode (CCM) in heavy

load, and in diode-emulation-mode (DEM) in light load to

improve light-load efficiency. In CCM, the controller always

operates as a synchronous rectifier. In DEM, the low-side

MOSFET is permitted to stay off, blocking negative current

flow into the low-side MOSFET from the output inductor.

Features

• High performance R3 technology

• Fast transient response

• ±1% regulation accuracy: -40°C to +100°C

• Individual power stage input rail for each channel

• Wide input voltage range: +3.3V to +25V

• Output voltage range: +0.6V to +5V

• Diode emulation mode for increased light load efficiency

• Programmable PWM frequency: 200kHz to 600kHz

• Pre-biased output start-up capability

• Integrated MOSFET drivers and bootstrap diode

• Internal digital soft-start

• Power good monitor

• Fault protection

- Undervoltage protection

- Soft crowbar overvoltage protection

- Inductor DCR overcurrent protection

- Over-temperature protection

- Fault identification by PGOOD pull-down resistance

• Pb-free (RoHS compliant)

Applications

• General purpose switching buck regulators

• PCI express graphical processing unit

• Auxiliary power rail

• VRM

• Network adaptor