New 2MHz Step-Down DC/DC Converters from Linear Need Only 2.7µA of Quiescent Current

Their internal high 75mOhm switches deliver efficiencies as high as 90%. The LT3975’s and LT3976’s Burst Mode® operation offers ultralow quiescent current, a feature that is also well suited for automotive and industrial systems applications that demand always-on operation and optimum battery life. The devices’ unique design maintains a minimum dropout voltage of only 500mV when the input voltage drops below the programmed output voltage, a functional necessity in applications subject to automotive cold-crank conditions. Switching frequency is user-programmable from 200kHz to 2MHz, and synchronizable from 250kHz to 2MHz, enabling the designer to optimize efficiency while avoiding critical noise-sensitive frequency bands. The combination of their 16-lead thermally enhanced MSOP package and high switching frequency keeps external inductors and capacitors small, providing a compact, thermally efficient footprint.

The LT3975 and LT3976 use a high efficiency 75mOhm switch, with the boost diode, 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 15mVPK-PK. Special design techniques and a new high voltage process deliver high efficiency over a wide input voltage range, and their current-mode topology enables fast transient response and excellent loop stability. Other features include a power good flag, soft-start capability and thermal protection.

The LT3975EMSE and the LT3976EMSE are packaged in a thermally enhanced MSOP-16, priced starting at $3.10 and $3.75 each, respectively for 1,000-piece quantities. The LT3975IMSE and LT3976IMSE are tested and guaranteed to operate from a -40°C to 125°C operating junction temperature and are priced at $3.41 and $4.13 each, respectively in 1,000-piece quantities. The LT3975HMSE and LT3976HMSE are tested and guaranteed to operate from a -40°C to 150°C operating junction temperature and are priced at $3.66 and $4.38 each, respectively in 1,000-piece quantities All versions are available from stock.

Summary of Features: LT3975 & LT3976
• Ultralow Quiescent Current: 2.7µA IQ at 12VIN to 3.3VOUT (LT3975) & 3.3µA IQ (LT3976)
• Low Ripple Burst Mode® Operation
< 15mVP-P
• Wide Input Range: Operation from 4.3V to 42V (LT3975) & 4.3 to 40V (LT3976)
• 2.5A Maximum Output Current (LT3975)
• 5A Maximum Output Current (LT3976)
• Excellent Start-Up & Dropout Performance
• Adjustable Switching Frequency: 200kHz to 2MHz
• Synchronizable Between 250kHz to 2MHz
• Accurate Programmable Undervoltage Lockout
• Low Shutdown Current: IQ = 700nA
• Power Good Flag
• Soft-Start Capability
• Thermal Shutdown Protection
• Current Limit Foldback with SS Override
• Saturating Switch Design: 75mOhm on Resistance
• Small, Thermally Enhanced 16-Pin MSOP Packages