ISL6211
Crusoe™ Processor Core-Voltage Regulator

Key Features

• High Efficiency Over Wide Load Range
• Loss-Less Current-Sense Scheme
• Uses MOSFET's RDS(ON)
• Optional Current-Sense Resistor for Higher Tolerance Overcurrent Protection
• Powerful Gate Drivers with Adaptive Dead Time
• Summing Current-Mode Control and On-Chip Active Droop for Optimum Transient Response
• TTL-Compatible 5-Bit Digital Output Voltage Selection
• Wide Range - 0.6VDC to 1.0VDC in 25mV Steps, and from 1.0VDC to 1.75VDC in 50mV Steps
• "On-the-Fly" VID code change with customer programmable slew rate
• Alternative Input to Set Output Voltage During Start-up or Power Saving Modes
• Selectable Forced Continuous Conduction Mode of Operation
• Power-Good Output Voltage Monitor
• No Negative Core Voltage on Turn-off
• Over-Voltage, Under-Voltage and Over-Current Fault Monitors
• 300/600kHz Selectable Switching Frequency

Description

The ISL6211 is a single-output power-controller to power core of Transmeta's Crusoe™ CPU. The ISL6211 includes a 5-bit digital-to-analog converter (DAC) that adjusts the core PWM output voltage from 0.6VDC to 1.75VDC. The DAC settings may be changed during operation. Special measures are taken to allow such a transition with controlled slew rate to comply with Transmeta's LongRun™ technology. A precise reference and a proprietary architecture with integrated compensation provide excellent static and dynamic core voltage regulation.

In nominal currents, the controller operates at a selectable frequency of 300kHz or 600kHz. When the filter inductor current becomes discontinuous, the controller operates in a hysteretic mode dramatically improving system efficiency. The hysteretic mode of operation can be inhibited by a designated control pin.

The ISL6211 monitors the output voltage. A Power-Good signal is issued when soft start is completed and the output is in regulation. A built-in over-voltage protection prevents the load from seeing output voltages higher than 1.9V. Under-voltage protection latches the chip off when the output drops below 75% of the set value. The PWM controller's over-current circuitry monitors the converter load by sensing the voltage drop across the lower MOSFET. The overcurrent threshold is set by an external resistor. If precision overcurrent protection is required, an external current-sense resistor may optionally be used.

Applications

• Mobile PCs
• Web Tablets
• Internet Appliances