Features

• 1.6V to 5.5V Input Voltage Range
• Internal Soft-Start
• Selectable 1.7MHz or 2.6MHz Constant Frequency Operation
• Internal Oscillator can be Synchronizable to an External Clock, 1MHz to 3MHz Range
• High Efficiency: Up to 95%
• Very Low Quiescent Current: Only 65µA During Burst Mode® Operation
• 600mA Output Current (V_IN = 1.8V, V_OUT = 1.2V)
• 750mA Peak Inductor Current
• No Schottky Diode Required
• Low Dropout Operation: 100% Duty Cycle
• 0.613V Reference Voltage
• Stable with Ceramic Capacitors
• Shutdown Mode Draws <1µA Supply Current
• Current Mode Operation for Excellent Line and Load Transient Response
• Overtemperature Protection
• Available in a Low Profile (0.75mm) 8-Lead
  (3mm × 3mm) DFN Package

Typical Application

Description

The LTC3409 is a high efficiency, monolithic synchronous buck regulator using a constant frequency, current mode architecture. The output voltage is adjusted via an external resistor divider.

Fixed switching frequencies of 1.7MHz and 2.6MHz are supported. Alternatively, an internal PLL will synchronize to an external clock in the frequency range of 1MHz to 3MHz. This range of switching frequencies allows the use of small surface mount inductors and capacitors, including ceramics.

Supply current during Burst Mode operation is only 65µA dropping to <1µA in shutdown. The 1.6V to 5.5V input voltage range makes the LTC3409 ideally suited for single cell Li-Ion, Li-Metal and 2-cell alkaline, NiCd or NiMH battery-powered applications. 100% duty cycle capability provides low dropout operation, extending battery life in portable systems. Burst Mode operation can be user enabled, increasing efficiency at light loads, further extending battery life.

The internal synchronous switch increases efficiency and eliminates the need for an external Schottky diode. Internal soft-start offers controlled output voltage rise time at start-up without the need for external components.

Protected by U.S. Patents, including 5481178, 6580258, 6304066, 6127815, 6498466, 6611131.