General Description
The SY20518 is a 2.6V to 5.5V input voltage range, high
efficiency, fixed frequency Buck-Boost converter that can
provide up to 2A of continuous current to a load that
requires a voltage below equal or above the input voltage.
The converter can provide power for system powered by
either a two-cell or three-cell alkaline, Ni-Cd or Ni-MH
batteries, or a single cell Li-Ion or Li-polymer battery.
The SY20518 is based on a fixed frequency, pulse-widthmodulation (PWM) controller using synchronous
rectification to obtain maximum efficiency. The output
voltage and compensation circuit can be programmed
using an external RC network.
The part automatically transitions to PFM mode under light
load conditions, to maintain high efficiency across the
entire load range.
During shutdown, the load is disconnected from the
battery and the part only consumes 0.1µA of current (typ.).
The device is available in a 2 mm ×3 mm QFN package.

Features
 2.6V to 5.5V Input Voltage Range
 2A Continuous Output Current Capability
 Adjustable Output Voltage between 2.6V and 3.8V
Independent of the Input Voltage
 1 MHz (typ.) Fixed Frequency Operation
 Four low RDSON Internal Power Switches
 Seamless Buck-Boost Transition
 Output Disconnect During Shutdown
 Power Good Indicator
 Built In Thermal Shut Down Protection, Hard
Short Protection

Applications
 Handheld Instruments
 MP3/MP4 Players
 Digital Cameras/Camcorders
 Personal Medical Products
 High Power LED’s
 Two-cell and three-cell alkaline, Ni-Cd or Ni-MH or
single cell Li battery powered products