March 2011
FAN5026
Dual DDR / Dual-Output PWM Controller
Features
Description
The FAN5026 PWM controller provides high efficiency
and regulation for two output voltages adjustable in the
range of 0.9V to 5.5V required to power I/O, chipꢀsets,
and memory banks in highꢀperformance computers,
setꢀtop boxes, and VGA cards. Synchronous
rectification and hysteretic operation at light loads
contribute to high efficiency over a wide range of loads.
Efficiency is enhanced by using MOSFET RDS(ON) as a
currentꢀsense component.
ꢀ
Highly Flexible, Dual Synchronous Switching PWM
Controller that Includes Modes for:
-
-
-
DDR Mode with Inꢀphase Operation for
Reduced Channel Interference
90° Phaseꢀshifted, Twoꢀstage DDR Mode
for Reduced Input Ripple
Dual Independent Regulators, 180° Phase
Shifted
ꢀ
ꢀ
Complete DDR Memory Power Solution
Feedforward ramp modulation, averageꢀcurrent mode
control, and internal feedback compensation provide
fast response to load transients. Outꢀofꢀphase operation
with 180ꢀdegree phase shift reduces input current
ripple. The controller can be transformed into a
complete DDR memory power supply solution by
activating a designated pin. In DDR Mode, one of the
channels tracks the output voltage of another channel
and provides output current sink and source capability
— essential for proper powering of DDR chips. The
buffered reference voltage required by this type of
memory is also provided. The FAN5026 monitors these
outputs and generates separate PGx (power good)
signals when the softꢀstart is completed and the output
is within ±10% of the set point.
-
-
VTT Tracks VDDQ/2
VDDQ/2 Buffered Reference Output
Lossless Current Sensing on LowꢀSide MOSFET or
Precision OverꢀCurrent Using Sense Resistor
ꢀ
ꢀ
ꢀ
VCC UnderꢀVoltage Lockout
Wide Input Range: 3V to 16V
Excellent Dynamic Response with Voltage
Feedforward and Average CurrentꢀMode Control
ꢀ
ꢀ
ꢀ
PowerꢀGood Signal
Supports DDRꢀII and HSTL
28ꢀLead ThinꢀShrink SmallꢀOutline Package
Overꢀvoltage protection prevents the output voltage
from exceeding 120% of the set point. Normal operation
is automatically restored when overꢀvoltage conditions
cease. Underꢀvoltage protection latches the chip off
when output drops below 75% of the set value after the
softꢀstart sequence for this output is completed. An
adjustable overꢀcurrent function monitors the output
current by sensing the voltage drop across the lower
MOSFET. If precision currentꢀsensing is required, an
external currentꢀsense resistor may be used.
Applications
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
DDR VDDQ and VTT Voltage Generation
PC Dual Power Supply
Server DDR Power
Desktop Computer
Graphics Cards
Related Resources
ꢀ
Application Note — AN-6002 Component
Calculations and Simulation Tools
Ordering Information
Operating
Part Number
Temperature
Range
Package
28ꢀLead ThinꢀShrink SmallꢀOutline Package (TSSOP)
Packing Method
Tape and Reel
FAN5026MTCX
ꢀ40 to +85°C
© 2005 Fairchild Semiconductor Corporation
FAN5026 • Rev. 1.0.8
www.fairchildsemi.com
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