2- to 8-Phase VRM 10/9.1 PWM Controllers with Precise Current Sharing and Fast Voltage Positioning

Active: In Production.

The MAX8525 (VRM 10/VRD 10)/MAX8524 (VRM 9.1/VRD 9.1) current-mode step-down controllers, the MAX8523 high-speed, dual-phase MOSFET gate driver, and the MAX8552 wide-input, single-phase MOSFET gate driver provide flexible, low-cost, low-voltage CPU core supplies. The MAX8523 and MAX8552 high-speed, high-current gate drivers allow operation at high switching frequencies to reduce external component size and cost for small-footprint, low-profile designs. Pin-selectable 2-, 3-, and 4-phase operation and master-slave 6- and 8-phase operation provide output-current scalability for servers, workstations, desktops, desk notes, and networking applications.

The switching frequency of the MAX8524/MAX8525 is adjustable from 150kHz to 1.2MHz, permitting loop bandwidths of up to 200kHz. Peak current-mode control provides fast transient response and reduces cost. A proprietary current-sharing scheme reduces current imbalance between phases to less than 5% at full load.

The MAX8524/MAX8525 offer 0.4% initial accuracy and remote-sense functionality. Both controllers also feature programmable no-load offset and output-voltage positioning to adjust the output voltage as a function of the output current. The fast-active voltage positioning further reduces bulk output capacitors and cost.

Current-mode control also simplifies compensation with a variety of capacitors by eliminating the output-filter double pole associated with voltage-mode controllers. Both devices are compatible with electrolytic, tantalum, polymer, and ceramic capacitors. Output current sensing eliminates issues associated with controllers that use high-side current sense and ensure stable and jitter-free operation. Temperature-compensated, lossless inductor current sense eliminates the need for a current-sense resistor and further reduces cost, while maintaining voltage-positioning accuracy and reducing power dissipation.

The MAX8525 features control VID voltage transition for dynamic VID changes and eliminate both undervoltage and overvoltage overshoot. The PWRGD signal is accurate during VID code changes for the MAX8525 to avoid any false fault signal.

Adjustable foldback current-limit and overvoltage protection provide for a robust design.

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