MAXIM MAX718CSE+

The MAX717-MAX721 CMOS power-supply ICs create dual, regulated DC outputs for small, battery-operated microprocessor systems. Each device generates a main output (3V or 5V, selectable) and an auxiliary output for flash memory or PCMClA (5V or 12V, selectable). Each device accepts up to three input voltages. Power can come from a main battery (two or three alkaline or NiCad cells), a lithium backup battery, or an unregulated DC source such as an AC-DC wall adapter. The MAX717-MAX721 provide three improvements over prior-art devices. Physical size is reduced - the high switching frequencies (up to 0.5MHz) made possible by MOSFET power transistors allow for tiny (<5mm diameter) surface mount magnetics. Efficiency is improved to 87% (10% better than with low-voltage regulators made in bipolar technology). And supply current is reduced to 60μA by CMOS construction and a unique constant-off-time pulse frequency modulation (PFM) control scheme. The MAX717-MAX721 differ only in shutdown and status functions and in the choice of a 3.0V or 3.3V main output.

• Low 0.9V to 5.5V Battery Operating Range
• Unregulated 7V to 20V DC Input Range
• Dual Regulated Outputs Main Output: 3.3V/5V Auxiliary Output: 5V/12V
• Efficiency at 200mA
• Efficiency PRAM Keep - Alive: 80% at 1mA
• 8W/in³ Power Density
• 60μA Quiescent Current
• ≥0μA Shutdown Mode with VREF Alive (MAX720/MAX721 only)
• 500kHz Maximum Switching Frequency
• ±1.5% VREF Tolerance Over Temp
• Detect Output Power Failures
• Detect Presence of AC Power
• 16 - Pin Narrow SO Packages

• Palmtop Computers
• Flash - Memory/PCMCIA Power Supplies
• Portable Data - Collection Equipment
• Medical Instrumentation
• Portable Data Communicators