42V, 750mA(IOUT), 2.2MHz Step-Down DC/DC Converter Needs Only 2.5µA Quiescent Current

The unique design of the LT3973 maintains a minimum dropout voltage of only 530mV when the output voltage drops below the programmed output voltage, ideal for applications subjected to scenarios such as automotive cold-crank. Switching frequency is user programmable from 200kHz to 2.2MHz, enabling the designer to optimize efficiency while avoiding critical noise-sensitive frequency bands. The combination of its 10-lead 3mm x 3mm DFN-10 (or thermally enhanced MSOP) package and high switching frequency keeps external inductors and capacitors small, providing a very compact, thermally efficient footprint.

The LT3973 utilizes a high efficiency 250mVCESAT switch, with the necessary boost and catch diodes, oscillator, control and logic circuitry integrated into a single die. Low ripple Burst Mode operation maintains high efficiency at low output currents while keeping output ripple below 10mVPK-PK. Special design techniques and a new high voltage process enable high efficiency over a wide input voltage range, and the LT3973’s current mode topology enables fast transient response and excellent loop stability. Other features include a power good flag, internal catch diode current limit and thermal protection.

The LT3973EDD is packaged in a 3mm x 3mm DFN-10, and the LT3973EMSE is in a thermally enhanced
MSOP-10, priced starting at $2.75 and $2.85 each, respectively for 1,000 piece quantities. The LT3973IDD and LT3973IMSE are tested and guaranteed to operate from a -40°C to 125°C operating junction temperature and are priced at $3.03 and $3.14 each, respectively in 1,000 piece quantities. The LT3973HDD and LT3973HMSE are tested and guaranteed to operate from a -40°C to 150°C operating junction temperature and are priced at $3.38 and $3.49 each, respectively in 1,000 piece quantities All versions are available from stock. For more information, visit www.linear.com/product/LT3973.

Summary of Features: LT3973

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 & Catch Diodes

750mA Output Current

Excellent Start-up & Dropout Performance

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 & (3mm x 3mm) DFN Packages

42V, 750mA(IOUT), 2.2MHz Step-Down DC/DC Converter with IQ= 2.5µA