Interleaved High-Efficiency, Dual Power-Supply Controllers for Notebook Computers

The MAX8716/MAX8717/MAX8756/MAX8757 are dual, step-down, interleaved, fixed-frequency, switch-mode power-supply (SMPS) controllers with synchronous rectification. The MAX8716/MAX8717/MAX8756/MAX8757 are intended for main (5V/3.3V) power generation, while the MAX8756 is optimized for I/O power rails in battery-powered systems.

Fixed-frequency operation with optimal interleaving minimizes input ripple current from the lowest input voltages up to the 26V maximum input. Optimal 40/60 interleaving allows the input voltage to go down to 8.3V before duty-cycle overlap occurs in 5V/3.3V applications, compared to 180° out-of-phase regulators where the duty-cycle overlap occurs when the input drops below 10V.

Accurate output current limit is achieved using a sense resistor. Alternatively, power dissipation can be reduced using lossless inductor current sensing. Independent ON/OFF controls and power-good signals allow flexible power sequencing. Soft-start reduces inrush current, while soft-stop gradually ramps the output voltage down preventing negative voltage dips.

A low-noise mode maintains high light-load efficiency while keeping the switching frequency out of the audible range.

The MAX8716 is available in a 24-pin thin QFN package, and the MAX8717/MAX8756/MAX8757 are available in a 28-pin thin QFN package.

Applications

* 2 to 4 Li+ Cell Battery-Powered Devices * Main or I/O Power Supplies * Notebook and Subnotebook Computers * PDAs and Mobile Communicators

* Fixed Switching Frequency

* 200kHz, 300kHz, or 500kHz

* 250kHz, 300kHz, or 400kHz (MAX8756 Only)

* No Current-Sense Resistor Required

* 40/60 Optimal Interleaving

* Reduced Input-Capacitor Requirement

* Output Voltage Fixed or Adjustable Outputs (Dual Mode™)

* 3.3V/5V Fixed or 1V to 5.5V Adjustable

* 1.5V/1.8V Fixed or 1V to 2.3V Adjustable (MAX8756 Only)

* 4V to 26V Input Range

* Independently Selectable PWM, Skip, and Low-Noise Mode Operation

* Soft-Start and Soft-Stop

* 2V Precision Reference with 0.75% Accuracy

* Independent Power-Good Outputs