FAN5250 View Datasheet(PDF) - Fairchild Semiconductor

Part Name

Description

Manufacturer

FAN5250

Mobile Processor Core-Voltage Regulator

Fairchild Semiconductor 

www.fairchildsemi.com

FAN5250

Mobile Processor Core-Voltage Regulator

Features

• High efficiency over wide load range

• Non dissipative current-sense; uses MOSFET RDS(ON) or

can use optional Current-Sense resistor for greater

precision

• Overcurrent protection

• Powerful drivers for N-Channel MOSFETs with adaptive

dead time

• Precision core voltage control

• Remote “Kelvin” sensing

• Summing current-mode control with programmable

Active Droop for Optimum Transient Response and

Lower Processor Power Dissipation

• 5-Bit Digital Output Voltage Selection

• Wide Range output voltage: 0.6 VDC to 1.0 VDC in

25mV Steps, and from 1.0 VDC to 1.75 VDC in 50mV

Steps

• “On-the-Fly” VID code change with programmable slew

rate

• Alternative input to set output voltage during start-up or

power saving modes

• Forced continuous conduction mode of operation

• Output voltage (Power-Good) monitor

• No negative core voltage on turn-off

• Over-Voltage, Under-Voltage and Over-Current fault

monitors

• Selectable 300/600kHz Switching Frequency

Applications

• Transmeta’s Crusoe™ CPU core power

• Intel P3-M™ processor (IMVP-2)

Description

The FAN5250 is a single output power controller to power

mobile CPU cores. The FAN5250 includes a 5-bit digital-to-

analog converter (DAC) that adjusts the core PWM output

voltage from 0.6VDC to 1.75VDC, and may be changed

during operation. Special measures are taken to allow the

output to transition with controlled slew rate to comply with

Transmeta’s LongRun™ and Intel’s P3-M Speed-Step™

requirements. The FAN5250 includes a precision reference,

and a proprietary architecture with integrated compensation

providing excellent static and dynamic core voltage regula-

tion.

With nominal currents, the controller operates at a selectable

frequency of 300kHz or 600kHz. At light loads, 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 the FPWM control pin.

The FAN5250 monitors the output voltage and issues a

PGOOD (Power-Good) when soft start is completed and the

output is in regulation. A built-in over-voltage protection

(OVP) forces the lower MOSFET on to prevent output volt-

ages from exceeding 1.9V. Undervoltage protection latches

the chip off when the output drops below 75% of the set

value. The PWM controller's overcurrent 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 optional external current-sense resistor may

be used.

LongRun is a trademark of Transmeta Corporation.

REV. 1.1.6 3/12/03

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