42V, 750mA Step-Down Regulator with 2.5μA Quiescent Current and Integrated Diodes

The LT3973 is an adjustable frequency monolithic buck switching regulator that accepts a wide input voltage range up to 42V, and consumes only 2.5μA of quiescent current. A high efficiency switch is included on the die along with the catch diode, boost diode, and the necessary oscillator, control and logic circuitry. Low ripple Burst Mode operation maintains high efficiency at low output currents while keeping the output ripple below 10mV in a typical application. A minimum dropout voltage of 530mV is maintained when the input voltage drops below the programmed output voltage, such as during automotive cold crank. Current mode topology is used for fast transient response and good loop stability. A catch diode current limit provides protection against shorted outputs and overvoltage conditions, with thermal shutdown providing additional fault protection. An accurate programmable undervoltage lockout feature is available, producing a low shutdown current of 0.75μA. A power good flag signals when VOUT reaches 90% of the programmed output voltage. The LT3973 is available in small, thermally enhanced 10-lead MSOP and 3mm × 3mm DFN packages.

Applications

* Automotive Battery Regulation

* Power for Portable Products

* Industrial Supplies

* Gate Drive Bias

* Ultralow Quiescent Current

2.5μA IQ at 12VIN to 3.3VOUT

* Low Ripple Burst Mode® Operation

Output Ripple < 10mVP-P

* Wide Input Voltage Range: 4.2V to 42V Operating

* Adjustable Switching Frequency: 200kHz to 2.2MHz

* Integrated Boost and Catch Diodes

* 750mA Output Current

* Excellent Start-Up and Dropout Performance

* Fixed Output Voltages: 3.3V, 5V

* 1.9μA IQ at 12VIN

* Accurate Programmable Undervoltage Lockout

* Low Shutdown Current: IQ = 0.75μA

* Internal Catch Diode Current Limit

* Power Good Flag

* Thermal Shutdown

* Small, Thermally Enhanced 10-Lead MSOP and (3mm × 3mm) DFN Packages