Dual 180° Out-of-Phase PWM Step-Down Controllers with POR

 

Part Number	Replacement	Explanation

Description

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The MAX1875/MAX1876 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 MAX1875/MAX1876 or a system clock. One MAX1875/MAX1876 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°. These devices also feature soft-start and soft-stop.

The MAX1875/MAX1876 eliminate 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 conditions. The MAX1876 includes a power-on reset output to signal the system when both outputs reach regulation.

The MAX1875/MAX1876 are available in a 24-pin QSOP package. An evaluation kit is available to speed designs.

MAX1875, MAX1876: Typical Operating Circuit Enlarge+

Key Features

Two Independent Output Voltages

180° Out-of-Phase Operation

90° Out-of-Phase Operation (Using Two MAX1875/MAX1876s)

Foldback Current Limit

4.75V to 23V Input Supply Range

0 to 18V Output-Voltage Range (Up to 10A)

>90% Efficiency

Fixed-Frequency Pulse-Width Modulation (PWM) Operation

Adjustable 100kHz to 600kHz Switching Frequency

External SYNC Input

Clock Output for Master/Slave Synchronization

Soft-Start and Soft-Stop

Active-low RST Output with 140ms Minimum Delay (MAX1876)

Lossless Current Limit (No Sense Resistor)

Applications/Uses

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