19-2431; Rev 0; 7/02
Dual 180° Out-of-Phase PWM Step-
Down Controllers with POR
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 con-
troller can be synchronized to an external clock gener-
ated 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 synchro-
nization 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.
Network Power Supplies
Telecom Power Supplies
DSP, ASIC, and FPGA Power Supplies
Typical Operating Circuit appears at end of data sheet.
o Two Independent Output Voltages
o 180° Out-of-Phase Operation
o 90° Out-of-Phase Operation
(Using Two MAX1875/MAX1876s)
o Foldback Current Limit
o 4.75V to 23V Input Supply Range
o 0 to 18V Output-Voltage Range (Up to 10A)
o >90% Efficiency
o Fixed-Frequency Pulse-Width Modulation (PWM)
o Adjustable 100kHz to 600kHz Switching
o External SYNC Input
o Clock Output for Master/Slave Synchronization
o Soft-Start and Soft-Stop
o RST Output with 140ms Minimum Delay (MAX1876)
o Lossless Current Limit (No Sense Resistor)
-40°C to +85°C
-40°C to +85°C
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.