UM3429S

UM3429S 600mA, 500KHz, Synchronous Step-Up DC-DC Converter UM3429S SOT23-6 General Description 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 low shutdown current lower than 1μA, inrush current limit. Applications Features z z z z z z z z z z z z Digital Cameras LCD Bias Supplies Handheld Instruments Wireless Handsets GPS Receivers All one cell 、tow cell alkaline NiCD、NiMH or Li-ion battery Powered products z z z z z 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 Typical Application Circuit Efficiency vs. Output Current 100 95 VOUT=3.3V 90 Efficiency (%) 85 80 75 70 65 VIN=1.2V VIN=1.5V VIN=2.4V VIN=3.0V 60 55 50 1 10 100 1000 Output Current (mA) ________________________________________________________________________ http://www.union-ic.com Rev.04 Aug.2019 1/12 UM3429S Pin Configurations Top View M: Month Code UM3429S SOT23-6 Pin Description Pin Number Symbol 1 SW 2 GND 3 FB 4 ____________ 5 VOUT 6 VIN SHDN Description Switch Pin. Connect external inductance to VIN. Keep these PCB trace lengths as short and wide as possible. Ground. Provide a short direct PCB path between GND and the negative electrode of COUT and CIN. Feedback Input Pin. Connect to the center point of the external resistor divider and set the output voltage by: R1 VOUT =0.6V 1+ R2 Logic Controlled Shutdown Input. Low logic active. In shutdown mode, all functions are disabled drawing