Fairchild Semiconductor FAN5026 Dual DDR Dual-Output PWM Controller Data Sheet

FA 5026 D al D /D al-O tp t P tro ller

October 2005

FAN5026 Dual DDR/Dual-Output PWM Controller Features General Description Highly flexible dual synchronous switching PWM The FAN5026 PWM controller provides high efficiency controller includes modes for: and regulation for two output voltages adjustable in the

DDR mode with in-phase operation for reduced range from 0.9V to 5.5V that are required to power I/O, channel interference chip-sets, and memory banks in high-performance com- puters, set top boxes, and VGA cards. Synchronous rec-

90° phase shifted two-stage DDR Mode for reduced

tification contributes to high efficiency over a wide range

input ripple

of loads. Efficiency is even further enhanced by using

Dual Independent regulators 180° phase shifted

MOSFET’s R as a current sense component.

DS(ON)

Complete DDR Memory power solution

Feed-forward ramp modulation, average current mode

VTT Tracks VDDQ/2

control scheme, and internal feedback compensation

VDDQ/2 Buffered Reference Output

provide fast response to load transients. Out-of-phase

Lossless current sensing on low-side MOSFET or operation with 180° phase shift reduces input current Precision current sensing using sense resistor ripple. The controller can be transformed into a com-

VCC Under-voltage Lockout plete DDR memory power supply solution by activating a Wide power input range: 3 to 16V designated pin. In DDR mode of operation one of the channels tracks the output voltage of another channel

Excellent dynamic response with Voltage

and provides output current sink and source capability —

Feed-Forward and Average Current Mode control

features essential for proper powering of DDR chips. The

Power-Good Signal

buffered reference voltage required by this type of mem-

Supports DDR-II and HSTL

ory is also provided. The FAN5026 monitors these out-

TSSOP28 package puts and generates separate PGx (power good) signals

when the soft-start is completed and the output is within

Applications ±10% of its set point. A built-in over-voltage protection

prevents the output voltage from going above 120% of

DDR V and V voltage generation DDQ TT

the set point. Normal operation is automatically restored

Desktop computer

when the over-voltage conditions go away. Under-volt-

Graphics cards

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 Temperature Range Package Packing FAN5026MTC -40°C to 85°C TSSOP-28 Rails FAN5026MTCX -40°C to 85°C TSSOP-28 Tape and Reel

©2005 Fairchild Semiconductor Corporation www.fairchildsemi.com FAN5026 Rev. 1.0.5