MAX1955

·Operates from a 1.6V to 5.5V Supply (MAX1956)
·0.5% Output Accuracy
·0.8V to 0.9VIN Output Range
·Up to 25A per Phase Output Current
·On-Chip Boost Regulator Provides 5V Gate Drive
·Up to 93% Efficiency
·180° Out-of-Phase Operation
·±4% Voltage Margining
·Lossless, Foldback Current Limit
·Selectable Voltage Sequencing
·Synchronizable to External Clock
·Digital Soft-Start and Soft-Stop
·Small 28-Pin, 5mm × 5mm Thin QFN Package

IN, AVDD, SYNC, EN, ILIM_, FB_, SEQ to GND.........-0.3V to +6V
COMP_, REF to GND................................-0.3V to (V_AVDD + 0.3V)
LXB to GND ..............................................-0.3V to (V_VDD + 0.3V)
DL_ to GND ...............................(V_PGND - 0.3V) to (V_VDD + 0.3V)
BST_ to GND .......................................................-0.3V to +12V
DH1 to LX1 .............................................-0.3V to (BST1 + 0.3V)
DH2 to LX2 .............................................-0.3V to (BST2 + 0.3V)
LX1 to BST1...........................................................-6V to +0.3V
LX2 to BST2...........................................................-6V to +0.3V
PGND to GND or VDD to AVDD............................-0.3V to +0.3V
REF Short-Circuit to GND.........................................Continuous
I_VDD................................................................................250mA
Continuous Power Dissipation* (T_A = +70)
28-Lead Thin QFN
(derate 20.8mW/ above +70)................................1667mW
Operating Temperature Range ...........................-40 to +85
Junction Temperature......................................................+150
Storage Temperature Range .............................-65 to +150
Lead Temperature (soldering 10s) ..................................+300
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

The MAX1955/MAX1956 are dual-output, fixed-frequency, voltage-mode, pulse-width modulated (PWM) step-down controllers with 0.5% output accuracy. Each controller switches at a constant 600kHz and is 180° out-of-phase with the other controller, reducing input ripple current and the number of input capacitors.

An on-chip bias supply of MAX1955/MAX1956 generates a 5V gate drive to deliver up to 25A output current per phase with low-cost N-channel MOSFETs at up to 93% efficiency. Lossless adjustable current limit eliminates expensive currentsense resistors and improves efficiency. Foldback current limit reduces power dissipation during short-circuit conditions and handles transient overloads better than controllers using hiccup-mode short-circuit protection.

Output voltage margining shifts output voltage by ±4% from the nominal value to simplify system test.Outputs also can be powered up and down in selectable equences to meet core and logic supply-rail requirements.The MAX1955/MAX1956 are available in a 28-lead thin QFN package with exposed pad.