Renesas Electronics Corporation High-Performance Dual-Output Buck Controller for Notebook Applications ISL6228IRTZ

The ISL6228 IC is a dual channel synchronous-buck PWM controller featuring Intersil's Robust Ripple Regulator (Rsup3/sup) 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.brbr Intersil's Rsup3/sup technology combines the best features of fixedfrequency and hysteretic PWMs while eliminating many of their shortcomings. Rsup3/sup technology employs an innovative modulator that synthesizes an AC ripple voltage signal VsubR/sub, analogous to the output inductor ripple current. The AC signal VsubR/sub enters a window comparator where the lower threshold is the error amplifier output VCOMP, and the upper threshold is a programmable voltage reference VsubW/sub, resulting in generation of the PWM signal. The voltage reference VsubW/sub 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.brbr 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-conductio n-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.