Dual 180° Out-of-Phase PWM Step-Down Controller with Power Sequencing and POR

The MAX1858 dual, synchronized, step-down controller generates two outputs from input supplies ranging from 4.75V to 23V. Each output is adjustable from sub-1V to 18V and supports loads of 10A or higher. Input voltage ripple and total RMS input ripple current are reduced by synchronized 180° out-of-phase operation.

The switching frequency is adjustable from 100kHz to 600kHz with an external resistor. Alternatively, the controller can be synchronized to an external clock generated to another MAX1858 or a system clock. One MAX1858 can be set to generate an in-phase, or 90° out-of-phase, clock signal for synchronization with additional controllers. This allows two controllers to operate either as an interleaved two- or four-phase system with each output shifted by 90°. The device also features “first-on/last-off” power sequencing for compatibility with DSPs, ASICs, and FPGAs, as well as soft-start and soft-stop to ensure reliable and repeatable power sequencing.

The MAX1858 eliminates the need for current-sense resistors by utilizing the low-side MOSFET's on-resistance as a current-sense element. This protects the DC-DC components from damage during output-overload conditions or when output short-circuit faults without requiring a current-sense resistor. Adjustable foldback current limit reduces power dissipation during short-circuit condition. A power-on reset output signals the system when both outputs reach regulation.

The MAX1858 is available in a 24-pin QSOP package. An evaluation kit is available to speed designs.

Applications

* Broadband Routers * DSP, ASIC, and FPGA Power Supplies * Network-Power Supplies * Servers * Set-Top Boxes * Telecom Power Supplies