The MAX722 and MAX723 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 a negative auxiliary output that is adjustable for LCDs. Each device accepts two input voltages. Power can come from a main battery (two or three alkaline or NiCAD), or an unregulated DC source such as an AC-DC wall adapter.
The MAX722/MAX723 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 also 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 MAX722 and MAX723 differ only in the lower fixed output voltage of the main regulator, with a 3.3V output for the MAX722 and a 3.0V output for the MAX723.
For flash memory or PCMCIA applications that require a +12V output voltage, refer to the MAX717–721 data sheet.
Key Features
Applications/Uses
Low 0.9V to 5.5V Battery Input Range
Unregulated 7V to 20V DC Input Range
Dual Regulated Outputs
Main Output: 3.3V/5V
Auxiliary Output: 0V to -100V
87% Efficiency at 200mA
Efficient PRAM Keep-Alive: 80% at 1mA
8W/in³ Power Density
60µA Quiescent Current
20µA Shutdown Mode with VREF Alive
500kHz Maximum Switching Frequency
±1.5% VREF Tolerance (Over Temp.)
Detect Output Power Failures
16-Pin Narrow SO Packages
Bar-Code Scanners
LCD Contrast Control
Medical Instrumentation
Palmtop Computers
Portable Data Communicators
Portable Data-Collection Equipment
Key Specifications:
Switch-Mode DC-DC Power Supplies
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