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.
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