Dual 5V Synchronous Buck Pulse-Width Modulator (PWM) Controller for DDRAM Memory VDDQ and VTT Termination

The ISL6531 provides complete control and protection for dual DC-DC converters optimized for high-performance DDRAM memory applications. It is designed to drive low cost N-channel MOSFETs in synchronous-rectified buck topology to efficiently generate 2.5V VDDQ for powering DDRAM memory, VREF for DDRAM differential signalling, and VTT for signal termination. The ISL6531 integrates all of the control, output adjustment, monitoring and protection functions into a single package.

Features

• Provides VDDQ, VREF, and VTT voltages for one- and twochannel DDRAM memory systems

• Excellent voltage regulation

- VDDQ = 2.5V ±2 over full operating range

- VREF = 1/2 • VDDQ ±1 over full operating range

- VTT = VREF ± 30mV

• Supports ‘S3’ sleep mode

- VTT is held at 1/2 • VDDQ via a low power window regulator to minimize wake-up time

• Fast transient response

- Full 0 to 100 duty ratio

• Operates from +5V Input

• VTT regulator internally compensated

• Overcurrent fault monitor on VDD

- Does not require extra current sensing element

- Uses MOSFET’s rDS(ON)

• Drives inexpensive N-Channel MOSFETs

• Small converter size

- 300kHz fixed frequency oscillator

• 24 Lead, SOIC or 32 Lead, 5mm×5mm QFN

• Pb-Free Plus Anneal Available (RoHS Compliant)

Applications

• VDDQ, VTT, and VREF regulation for DDRAM memory systems

- Main memory in AMD® Athlon™ and K8™, Pentium® III, Pentium IV, Transmeta, PowerPC™, AlphaPC™, and UltraSparc® based computer systems

• High-power tracking DC-DC regulators