LTC1909-8 - Wide Operating Range, No RSENSE Step-Down DC/DC Controller with SMBus Programming

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 VIN and VOUT.

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.

Features

SMBus/I²C™ Programmable Output Voltage: 1.3V to 3.5V
No Sense Resistor Required
2% to 90% Duty Cycle at 200kHz
tON(MIN)
True Current Mode Control
Stable with Ceramic COUT
Power Good Output Voltage Monitor and 50µs Timer
Wide VIN 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