March 2006
FAN5240
Multi-Phase PWM Controller for AMD Mobile Athlon™
and Duron™
Features
General Description
■ CPU Core power: 0.925V to 2.0V output range
■ ±1% reference precision over temperature
■ Dynamic voltage setting with 5-bit DAC
■ 6V to 24V input voltage range
The FAN5240 is a single output 2-Phase synchronous
buck controller to power AMD’s mobile CPU core. The
FAN5240 includes a 5-bit digital-to-analog converter
(DAC) that adjusts the core PWM output voltage from
0.925VDC to 2.0VDC, which may be changed during
operation. Special measures are taken to allow the out-
put to transition with controlled slew rate to comply with
AMD’s Power Now technology. The FAN5240 includes
a precision reference, and a proprietary architecture with
integrated compensation providing excellent static and
dynamic core voltage regulation. The regulator includes
special circuitry which balances the 2 phase currents for
maximum efficiency.
■ 2 phase interleaved switching
■ Active droop to reduce output capacitor size
■ Differential remote voltage sense
■ High efficiency:
>90% efficiency over wide load range
>80% efficiency at light load
■ Excellent dynamic response with Voltage
Feed-Forward and Average Current Mode control
At light loads, when the filter inductor current becomes
discontinuous, the controller operates in a hysteretic
mode, dramatically improving system efficiency. The hys-
teretic mode of operation can be inhibited by the FPWM
control pin.
■ Dynamic duty cycle clamp minimizes inductor current
build up
■ Lossless current sensing on low-side MOSFET or
Precision current sensing using sense resistor
■ Fault protections: Over-voltage, Over-current, and
The FAN5240 monitors the output voltage and issues a
PGOOD (Power-Good) when soft start is completed and
the output is in regulation. A pin is provided to add delay
to PGOOD with an external capacitor.
Thermal Shut-down
■ Controls: Enable, Forced PWM, Power Good, Power
Good Delay
■ QSOP28, TSSOP28
A built-in over-voltage protection (OVP) forces the lower
MOSFET on to prevent the output from exceeding a set
voltage. The PWM controller's overcurrent circuitry moni-
tors the converter load by sensing the voltage drop
across the lower MOSFET. The overcurrent threshold is
set by an external resistor. If precision overcurrent pro-
tection is required, an optional external current-sense
resistor may be used.
Applications
■ AMD Mobile Athlon CPU V
Regulator
CORE
■ Graphic chip V
Regulator
CORE
Ordering Information
Part Number
FAN5240QSC
FAN5240QSCX
FAN5240MTC
FAN5240MTCX
Temperature Range
-10°C to 85°C
Package
QSOP-28
QSOP-28
TSSOP-28
TSSOP-28
Packing
Rails
-10°C to 85°C
Tape and Reel
Rails
-10°C to 85°C
-10°C to 85°C
Tape and Reel
©2006 Fairchild Semiconductor Corporation
FAN5240 Rev. 1.2.0
1
www.fairchildsemi.com