Union Semiconductor UM3429S

The UM3429S is synchronous rectified, fixed frequency, step-up DC/DC converter series delivering high efficiency in low profile SOT23-6 package. It features true output load disconnection and adjustable output. With an internal NMOS switch, PMOS synchronous rectifier and high switching frequency of 500KHz, the UM3429S is capable of supplying 3.3V output at 100mA from a single AA cell input or 250mA from a 2-cell AA input using low profile inductors and ceramic capacitors. Current mode PWM control with internal compensation as well as the synchronous rectifier and 500KHz high frequency lead to the fewest number of external parts needed, thereby saving BOM cost and PCB area. At light load, UM3429S automatically enters into pulse skipping mode to keep high efficiency. An internal resistor will be connected to VIN when the switch is idle that eliminates switch ringing and reduces EMI interference. The device also features inrush current limit.

• Up to 92% Efficiency
• Output Load Disconnection
• Internal Synchronous Rectifier
• Low Voltage Start-Up: 0.85V
• Input Current Limit
• Pulse Skipping Mode Operation with Typical IQ as 20μA
• Shutdown Current Lower than 1μA
• 500KHz Switching Frequency for Low Profile Inductor/Capacitor
• Input Voltage: 0.5V to 5.0V
• Output Voltage: 2.5V to 5V
• Anti-Ringing Control to Reduce EMI

• Digital Cameras
• LCD Bias Supplies
• Handheld Instruments
• Wireless Handsets
• GPS Receivers
• All one cell, two cell alkaline, NiCD, NiMH or Li-ion battery Powered products