ISL6530
Dual 5V Synchronous Buck Pulse-Width Modulator (PWM) Controller for DDRAM Memory V_DDQ and V_TTTermination

Key Features

• Provides V_DDQ, Vsub>REF, and V_TT voltages for one- and two-channel DDRAM memory systems
• Excellent voltage regulation
• V_DDQ = 2.5V ±2% over full operating range
• Vsub>REF = (V_DDQ÷2) ±1% over full operating range
• V_TT = Vsub>REF ± 30mV
• Supports 'S3' sleep mode
• V_TT is held at VDDQ÷2 via low power window regulator to minimize wake-up time
• Fast transient response
• Full 0% to 100% duty ratio
• Operates from +5V input
• Overcurrent fault monitor on VDD
• Does not require extra current sensing element
• Uses MOSFET's r_DS(ON)
• Drives inexpensive N-Channel MOSFETs
• Small converter size
• 300kHz fixed frequency oscillator
• 24 Lead, SOIC or 32 Lead, 5mm×5mm QFN

Description

The ISL6530 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 V_DDQ for powering DDRAM memory, V_REF for DDRAM differential signalling, and V_TT for signal termination. The ISL6530 integrates all of the control, output adjustment, monitoring and protection functions into a single package.

The VDDQ output of the converter is maintained at 2.5V through an integrated precision voltage reference. The Vsub>REF output is precisely regulated to 1/2 the memory power supply, with a maximum tolerance of ±1% over temperature and line voltage variations. V_TT accurately tracks Vsub>REF. During V2_SD sleep mode, the V_TT output is maintained by a low power window regulator.

The ISL6530 provides simple, single feedback loop, voltagemode control with fast transient response. It includes two phase-locked 300kHz triangle-wave oscillators which are displaced 90^o to minimize interference between the two PWM regulators. The regulators feature error amplifiers with a 15MHz gain-bandwidth product and 6V/µs slew rate which enables high converter bandwidth for fast transient performance. The resulting PWM duty ratio ranges from 0% to 100%.

The ISL6530 protects against over-current conditions by inhibiting PWM operation. The ISL6530 monitors the current in the V_DDQ regulator by using the r_DS(ON) of the upper MOSFET which eliminates the need for a current sensing resistor.

Applications

• V_DDQ, V_TT, and Vsub>REF regulation for DDRAM memory systems
• Main Memory in AMD® Athlon™ and K8™, Pentium® III, Pentium IV, Transmeta, PowerPC™, AlphaPC™, and UltraSparc® based computer systems
• Video memory in graphics systems
• High-power tracking DC-DC regulators