ISL6228
High-Performance Dual-Output Buck Controller for Notebook Applications

Key Features

• High performance R³ technology
• Fast transient response
• ±1% regulation accuracy: -10°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 available (RoHS compliant)

Description

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 V_R, analogous to the output inductor ripple current. The AC signal V_R enters a window comparator where the lower threshold is the error amplifier output VCOMP, 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 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.

Applications

• General purpose switching buck regulators
• PCI express graphical processing unit
• Auxiliary power rail
• VRM
• Network adapter