Dual DC−DC Regulator for Electronic Organizer

The MC33680 is a dual DC−DC regulator designed for electronic organizer applications. Both regulators apply Pulse−Frequency−Modulation (PFM). The main step−up regulator output can be externally adjusted from 2.7V to 5V. An internal synchronous rectifier is used to ensure high efficiency (achieve 87). The auxiliary regulator with a built−in power transistor can be configured to produce a wide range of positive voltage (can be used for LCD contrast voltage). This voltage can be adjusted from +5V to +25V by an external potentiometer.

FEATURES:

• Low Input Voltage, 1V up

• Low Quiescent Current in Standby Mode: 35μA typical

• PFM and Synchronous Rectification to ensure high efficiency

(87 @60mA Load)

• Adjustable Main Output: +2.7V to +5V

nominal 3.3V @ 100mA max, with 1.8V input

• Auxiliary Output Voltage: +5V to +25V

+5V @ 25mA max, with 1.8V input

+25V @ 15mA max, with 1.8V input

• Current Limit Protection

• Power−Good Signal with Programmable Delay

• Battery Low Detection

• Lithium Battery or Supercap Back−up

• 32−Pin LQFP Package

APPLICATIONS:

• Digital Organizer and Dictionary

• Dual Output Power Supply (For MPU, Logic, Memory, LCD)

• Handheld Battery Powered Device (1−2 AA/AAA cell)