Features

• Programmable Charge Current Up to 950mA
• Complete Linear Charger and Dual DC/DC Regulator
• Dual Fixed Outputs:
   1.8V at 800mA
   1.575V at 400mA
• No MOSFET, Sense Resistor or Blocking Diode Required
• Thermal Regulation Maximizes Charge Rate Without Risk of Overheating*
• Charges Directly from a USB Port
• Programmable Charge Current Termination
• Preset 4.2V Charge Voltage with ±1% Accuracy
• Charge Current Monitor Output for Gas Gauging
• Automatic Recharge
• Charge Status Output
• “Power Present” Output
• Soft-Start Limits Inrush Current
• Low Quiescent Current Buck Converter (40μA)
• Current Mode Operation, Constant Frequency (2.25MHz)
• Low Profi le (5mm × 3mm × 0.75mm) DFN Package

Typical Application

Description

The LTC3552-1 is a complete constant-current/constantvoltage linear charger and dual fi xed output DC/DC converter for single cell lithium-ion batteries. Its DFN package and low external component count make the LTC3552-1 ideally suited for portable applications. Furthermore, the LTC3552-1 is designed to work within USB power specifi cations.

No external sense resistor or external blocking diode are required due to the internal MOSFET architecture. The charge voltage is fixed at 4.2V and the charge current is programmed with a resistor. The charge cycle terminates when the charge current drops below the programmed termination threshold after the final float voltage is reached. When the input supply (wall adapter or USB supply) is removed, the LTC3552-1 enters a low current state dropping the battery drain current to less than 2μA. Thermal regulation maximizes charge rate without risk of overheating.

The synchronous step-down switching regulators generate fi xed output voltages of 1.8V and 1.575V. The switching frequency is set at 2.25MHz, allowing the use of small surface mount inductors and capacitors.