Sunnyvale, Calif. - Maxim Integrated Products' MAX8523/8525 chip set meets the requirements of Intel Corp.'s VRD/VRM-10 power specifications. The MAX8525 is an interleaved two- to eight-phase, scalable PWM controller while the MAX8523 is a high-current, high-speed, dual-phase gate driver.
The chip set offers two options for current sensing: high accuracy using sense resistors or low-cost, lossless, temperature-compensated current sensing. The peak-current-mode architecture simplifies compensation using ceramic, polymer or electrolytic capacitors. The 150-kHz to 1.2-MHz phase-switching frequency optimizes size, cost and efficiency.
Maxim claims several firsts for the MAX8525, calling it the first controller that combines the current-sharing accuracy of an average-current-mode controller and transient response of a peak-current-mode controller. The controller uses a Rapid Active Average control scheme for instant average-current information (cycle by cycle) to provide fast voltage positioning. It also has been designed to cancel the ripple current inaccuracy component out of voltage positioning, while providing single-cycle response.
The controller also features pin-selectable two-, three- and four-phase operation, as well as true six- and eight-phase operation in master-slave mode, providing output-current scalability for server, workstation, desktop and networking applications. The two- to eight-phase interleaved operation also offers 5 percent current balance.
The device has a 0.4 percent accurate reference (over temperature) and only 8-millivolt initial accuracy error over temperature. This provides fast, accurate voltage positioning and reduces the need for output capacitors, Maxim said, while the peak-current-mode control and finite-gain precision error amplifier provide fast transient response.
Each MOSFET driver in the MAX8523 is capable of driving 3,000-picofarad capacitive loads with only 15-nanosecond propagation delay and 11-ns typical rise and fall times, allowing operations up to 1.2 MHz per phase. Adaptive dead time controls low-side MOSFET turn-on and user-programmable dead time controls high-side MOSFET turn-on.
Packaged in a compact, 16-pin QSOP, the MAX8523 dual-phase driver permits high-frequency, small-form-factor VRM designs. The MAX8525 VRD/VRM-10 controller is packaged in a 28-pin QSOP. Adjustable dead time for the high-side driver, adaptive dead time for the low-side driver, and its 4.5- to 6.5-volt gate voltage range optimize design with a variety of MOSFETs. The MAX8524 PWM controller is also available for legacy VRD/VRM9.1 designs.
The MAX8552 single-phase, wide-input gate driver is scheduled for release in July. Used with the MAX8524/MAX8525 controllers, it provides greater layout flexibility and addresses desk-note and LCD PC applications. All products are specified for the extended-industrial temperature range of -40 degrees C to 85 degrees C. Evaluation kits are available.
In lots of 1,000 pieces, the per piece price for the MAX8523 is 78 cents and for the MAX8525, $1.58.
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