October 2005
FAN5026
Dual DDR/Dual-Output PWM Controller
Features
■ Highly flexible dual synchronous switching PWM
controller includes modes for:
– DDR mode with in-phase operation for reduced
channel interference
– 90° phase shifted two-stage DDR Mode for reduced
input ripple
– Dual Independent regulators 180° phase shifted
■ Complete DDR Memory power solution
– VTT Tracks VDDQ/2
– VDDQ/2 Buffered Reference Output
■ Lossless current sensing on low-side MOSFET or
Precision current sensing using sense resistor
■ VCC Under-voltage Lockout
■ Wide power input range: 3 to 16V
■ Excellent dynamic response with Voltage
Feed-Forward and Average Current Mode control
■ Power-Good Signal
■ Supports DDR-II and HSTL
■ TSSOP28 package
Applications
■ DDR VDDQ and VTT voltage generation
■ Desktop computer
■ Graphics cards
General Description
The FAN5026 PWM controller provides high efficiency
and regulation for two output voltages adjustable in the
range from 0.9V to 5.5V that are required to power I/O,
chip-sets, and memory banks in high-performance com-
puters, set top boxes, and VGA cards. Synchronous rec-
tification contributes to high efficiency over a wide range
of loads. Efficiency is even further enhanced by using
MOSFET’s RDS(ON) as a current sense component.
Feed-forward ramp modulation, average current mode
control scheme, and internal feedback compensation
provide fast response to load transients. Out-of-phase
operation with 180° phase shift reduces input current
ripple. The controller can be transformed into a com-
plete DDR memory power supply solution by activating a
designated pin. In DDR mode of operation one of the
channels tracks the output voltage of another channel
and provides output current sink and source capability —
features essential for proper powering of DDR chips. The
buffered reference voltage required by this type of mem-
ory is also provided. The FAN5026 monitors these out-
puts and generates separate PGx (power good) signals
when the soft-start is completed and the output is within
±10% of its set point. A built-in over-voltage protection
prevents the output voltage from going above 120% of
the set point. Normal operation is automatically restored
when the over-voltage conditions go away. Under-volt-
age protection latches the chip off when either output
drops below 75% of its set value after the soft-start
sequence for this output is completed. An adjustable
over-current function monitors the output current by
sensing the voltage drop across the lower MOSFET. If
precision current-sensing is required, an external cur-
rent-sense resistor may optionally be used.
Ordering Information
Part Number
FAN5026MTC
FAN5026MTCX
Temperature Range
-40°C to 85°C
-40°C to 85°C
Package
TSSOP-28
TSSOP-28
Packing
Rails
Tape and Reel
©2005 Fairchild Semiconductor Corporation
1
FAN5026 Rev. 1.0.5
www.fairchildsemi.com