Features

• SMBus/I²C™ Programmable Output Voltage: 1.3V to 3.5V
• No Sense Resistor Required
• 2% to 90% Duty Cycle at 200kHz
• t_ON(MIN) </= 100ns
• True Current Mode Control
• Stable with Ceramic C_OUT
• Power Good Output Voltage Monitor and 50µs Timer
• Wide V_IN Range: 4V to 36V (Abs Max)
• Precision Resistor Divider and Reference Provide ±1.35% Output Voltage Accuracy Over Temperature
• Adjustable Switching Frequency and Current Limit
• Forced Continuous Control Pin
• Programmable Soft-Start
• Output Overvoltage Protection
• Optional Short-Circuit Shutdown Timer
• Available in a 28-Lead SSOP Package

Typical Application

Description

The LTC1909-8 is a synchronous step-down switching regulator controller with a digitally programmable output voltage. The output voltage is selected from one of two 5-bit settings programmed into internal registers via a 2-wire SMBus/I²C interface. The interface features safeguards against invalid output voltages and allows the microprocessor to turn the regulator on and off. Valley current control delivers very low duty cycles without requiring a sense resistor. Operating frequency is selected by an external resistor and is compensated for variations in V_IN and V_OUT.

Discontinuous mode operation provides high efficiency operation at light loads. A forced continuous control pin reduces noise and RF interference and can assist secondary winding regulation by disabling discontinuous mode operation when the main output is lightly loaded.

Fault protection is provided by internal foldback current limiting, an output overvoltage comparator and optional short-circuit shutdown timer.

The LTC1909-8 is available in the 28-lead SSOP package.