16µA I, 1.2A PWM Step-Down DC-DC Converters

The MAX1556/MAX1556A/MAX1557 are low-operating-current (16µA), fixed-frequency step-down regulators. High efficiency, low-quiescent operating current, low dropout, and minimal (27µA) quiescent current in dropout make these converters ideal for powering portable devices from 1-cell Li-ion or 3-cell alkaline/NiMH batteries. The MAX1556 delivers up to 1.2A; has pin-selectable 1.8V, 2.5V, and 3.3V outputs; and is also adjustable. The MAX1557 delivers up to 600mA; has pin-selectable 1V, 1.3V, and 1.5V outputs; and is also adjustable.

The MAX1556/MAX1556A/MAX1557 contain a low-on-resistance internal MOSFET switch and synchronous rectifier to maximize efficiency and dropout performance while minimizing external component count. A proprietary topology offers the benefits of a high fixed-frequency operation while still providing excellent efficiency at both light and full loads. A 1MHz PWM switching frequency keeps components small. Both devices also feature an adjustable soft-start to minimize battery transient loading.

The MAX1556/MAX1556A/MAX1557 are available in a tiny 10-pin TDFN (3mm x 3mm) package.

Applications

* Cell Phones/Smartphones * Digital Cameras and Camcorders * Handheld Instruments * PDAs and Palmtop Computers * Portable MP3 and DVD Players

* Up to 97% Efficiency

* 95% Efficiency at 1mA Load Current

* Low 16µA Quiescent Current

* 1MHz PWM Switching

* Tiny 3.3µH Inductor

* Selectable 3.3V, 2.5V, 1.8V, 1.5V, 1.3V, 1.2V, 1.0V, and Adjustable Output

* 1.2A Guaranteed Output Current (MAX1556/MAX1556A)

* Voltage Positioning Optimizes Load-Transient Response

* Low 27µA Quiescent Current in Dropout

* Low 0.1µA Shutdown Current

* No External Schottky Diode Required

* Analog Soft-Start with Zero Overshoot Current

* Small, 10-Pin, 3mm x 3mm TDFN Package