Regulator burst mode consumes only 75uA of quiescent current

August 14, 2007 - Beijing - Linear Technology Corporation introduces the LT3680, a 3.5A, 36V step-down switching power supply that operates in Burst Mode to maintain The quiescent current is less than 75uA. Operating over a VIN range of 3.6V to 36V, the LT3680 is ideal for load dump and cold cranking in automotive applications. Its 4.6A internal switch provides up to 3.5A of continuous output current at voltages as low as 0.79V. The LT3680's burst mode operation features ultra-low quiescent current, making it ideal for applications such as automotive or telecom systems that require always-on operation and optimal battery operating time. The switching frequency from 250kHz to 2.4MHz is user-programmable, enabling designers to optimize efficiency while avoiding critical noise-sensitive frequency bands. Its 3mm x 3mm DFN-10 package (or thermally enhanced MSOP-10E) and high switching frequency allow the use of small external inductors and capacitors to create a compact and thermally efficient solution.

The LT3680 features a high frequency 4.6A, 95mΩ switch that integrates the necessary boost diodes, oscillators, control and logic circuitry in a single chip. Low ripple Burst Mode operation maintains high efficiency at low output current while maintaining output ripple below 15mVPK-PK. The LT3680 uses a special design approach to achieve high efficiency over a wide input voltage range, and the device's current mode topology enables fast transient response and excellent loop stability. Other features include external synchronization (from 250kHz to 2MHz), power good flag and soft start function.

Available in 1,000-piece quantities, each LT3680EDD and LT3680EMSE starts at $4.15 and $4.25, respectively. The LT3680IDD and LT3680IMSE are tested and guaranteed to operate at operating junction temperatures from -40°C to 125°C, and are priced at $4.98 and $5.10 each in 1,000-piece quantities. All versions are available from stock.

Photo caption: 36V, 3.5A buck converter consumes only 75uA of quiescent current

Performance Summary: LT3680

Wide input range: 3.6V to 36V

?Maximum output current is 3.5A

Low ripple (<15mVP-P) burst mode operation: IQ=75uA from 12VIN to 3.3VOUT

Adjustable switching frequency: 200kHz to 2.4MHz

Low shutdown current: IQ < 1uA

? Integrated boost diode

Syncable from 250kHz to 2MHz

? Power good mark

? Saturated switch design: 95mΩ on-resistance

?0.790V feedback reference voltage

? Output voltage: 0.79V to 30V

?Overheating protection

? Soft start function

? Small 10-pin thermally enhanced MSOP and (3mm x 3mm) DFN package



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