600mA, 1MHz, Synchronous Step-Up DC-DC Converter
UM3429S SOT23-6
UM3429DA DFN8 2.0×2.0
General Description
The UM3429 is synchronous rectified, fixed frequency, step-up DC/DC converter series
delivering high efficiency in low profile SOT23-6 and DFN8 2.0×2.0 packages. It features true
output load disconnection and adjustable output. With an internal NMOS switch, PMOS
synchronous rectifier and high switching frequency of 1MHz, the UM3429 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
1MHz high frequency lead to the fewest number of external parts needed thereby saving BOM
cost and PCB area. At light load, UM3429 enters automatically 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
Digital Cameras
Up to 92% Efficiency
Output Load Disconnection
LCD Bias Supplies
Handheld Instruments
Wireless Handsets
GPS Receivers
Internal Synchronous Rectifier
Low Voltage Start-Up: 0.85V
Input Current Limit
Pulse Skipping Mode Operation with
Typical IQ as 40μA
Shutdown Current Lower than 1µA
1MHz Switching Frequency for Low
Profile Inductor/Capacitor
Input Voltage: 0.5V to 5.0V
Output Voltage: 2.5V to 5.5V
Anti-Ringing Control to Reduce EMI
Typical Application Circuit
Efficiency vs. Output Current
Efficiencyvs. Load Current
100
95
90
85
80
75
70
65
60
55
50
VOUT=3.3V
4.7µH
VOUT
3.3V
250mA
SW
VIN
VOUT
+
4.7µF
2-CELL
AA
1M
UM3429
10µF
SHDN
FB
OFF ON
220k
GND
VIN=1.2V
V
IN=1.2V
IN=1.5V
VIN=1.5V
V
VIN=2.4V
VIN=2.4V
VIN=3.0V
VIN=3.0V
1
10
100
1000
OutputCurrent(mA)
________________________________________________________________________
http://www.union-ic.com Rev.02 Mar.2016 1/12