Description:
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.
Description:
Two Independent Output Voltages
180° Out-of-Phase Operation
90° Out-of-Phase Operation(Using Two MAX1858s)
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
Power-On/-Off Sequencing with Soft-Start and
Soft-Stop
RST Output with 140ms Minimum Delay
Lossless Current Limit (No Sense Resistor)
