电池或墙上适配器供电系统，为逻辑电路及LCD供电概述

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.关键特性

• 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

  应用/使用 条码扫描仪 LCD对比度调节 医疗仪表 掌上电脑 便携式数据通信 便携式数据收集设备