Union Semiconductor UM3501

UM3501 is a high-efficiency pulse-width-modulated (PWM) step-down DC-DC converter, capable of delivering 600mA output current over a wide input voltage range from 2.5V to 5.5V. The target application of UM3501 is for portable electronic devices that are powered from 1-cell Li-ion battery or from other power sources within the range such as cellular phones, PDAs and handy-terminals. Internal synchronous rectifier with low RDS(ON) dramatically reduces conduction loss at PWM mode. No external Schottky diode is required in practical application. The UM3501 automatically turns off the synchronous rectifier while the inductor current is low and enters discontinuous PWM mode. This can increase efficiency at light load condition.

UM3501 enter shutdown mode and consumes less than 0.1uA when EN pin is pulled low. The operation frequency is set to 1.2MHz. This along with small SOT23-5 package and DFN6L 2.0×2.0 package provides small PCB area application. Other features include lower internal reference voltage with 2% accuracy, over temperature protection, and over current protection.

UM3501 is a monolithic switching mode step-down DC-DC converter. It utilizes internal MOSFETs to achieve high efficiency and can generate very low output voltage by using internal reference at 0.6V. It operates at a fixed switching frequency, and uses the slope compensated current mode architecture. This step-down DC-DC converter supplies 600mA output current at VIN = 3.6V with input voltage range from 2.5V to 5.5V.

• High Efficiency: Up to 90%
• 1.2MHz Constant Switching Frequency
• 600mA Output Current
• Integrated Main Switch and Synchronous Rectifier. No Schottky Diode Required
• 2.5V to 5.5V Input Voltage Range
• Low Quiescent Current: 50μA
• Thermal Fault Protection
• <1μA Shutdown Current
• Lead Free SOT23-5 Package and DFN6L 2.0×2.0 Package

• Cellular and Smart Phones
• Microprocessors and DSP Core Supplies
• Wireless and DSL Modems
• PDAs, GPS MP3 Player Portable Instruments