July 19, 2012 – Linear Technology Korea (CEO Hong Sa-kwak) announced the development of the LT3975, a 42V step-down switching regulator that provides 2.5A continuous output current and quiescent current consumption of only 2.7µA. The LT3976 product also operates from 40V input, provides a maximum output current of 5A, and has quiescent current consumption of only 3.3µA. Both products have an input voltage range of 4.2V to nominal 40V, making them ideal for automotive and industrial applications. The 75mΩ internal switch provides approximately 90% high efficiency.

The Burst Mode® operation of the LT3975 and LT3976 provides very low quiescent current, making them well-suited for automotive and industrial system applications requiring always-on operation and optimized battery life. With this unique design approach, these products maintain a minimum dropout voltage of 500mV when the output voltage drops below the programmed input voltage. This is an essential feature for applications susceptible to automotive cold-crank conditions. The switching frequency is user-programmable in the range of 200kHz to 2MHz and can be synchronized from 250kHz to 2MHz. Therefore, designers can optimize efficiency while avoiding frequency bands sensitive to noise. Additionally, by utilizing the 16-pin MSOP package with enhanced thermal performance and high switching frequency, ultra-small external inductors and capacitors can be used, enabling a compact and thermally efficient footprint.

The LT3975 and LT3976 use a high-efficiency 75mΩ switch and integrate a boost diode, oscillator, control, and logic circuits on a single die. The low ripple Burst Mode operation maintains high efficiency at low output currents while keeping output ripple below 15mVPK-PK. These products achieve high efficiency across a wide input voltage range through unique design techniques and new high-voltage process implementation, and the current-mode topology realizes fast transient response and excellent loop stability. Other features include a power good flag, soft start function, and thermal protection function.

The LT3975EMSE and LT3976EMSE are offered in an MSOP-16 package with enhanced thermal performance, with prices starting at $3.10 and $3.75 per unit respectively, based on 1,000-unit quantities. The LT3975IMSE and LT3976IMSE are tested and guaranteed to operate over a temperature range of -40°C to 125°C. Prices are $3.41 and $4.13 per unit respectively, based on 1,000-unit quantities. The LT3975HMSE and LT3976HMSE are also tested and guaranteed to operate over a temperature range of -40°C to 150°C, with prices of $3.66 and $4.38 per unit respectively, based on 1,000-unit quantities. All versions are available for purchase now. For more information, refer to www.linear.com/product/LT3975 and www.linear.com/product/LT3976.


Photo caption: 42V, 2.5A/5A (IOUT), 2MHz step-down DC/DC converter with quiescent current consumption of 2.7µA

Product Features: LT3975 & LT3976

• Ultra-low quiescent current: 2.7μA IQ (LT3975) and 3.3μA IQ (LT3976) at 12VIN to 3.3VOUT
• Low ripple Burst Mode® operation below 15mVP-P
• Wide input range: operates from 4.3V to 42V (LT3975) & 4.3V to 40V (LT3976)
• 2.5A maximum output current (LT3975)
• 5A maximum output current (LT3976)
• Excellent startup and dropout performance
• Adjustable switching frequency: 200kHz to 2MHz
• Synchronizable from 250kHz to 2MHz
• Programmable precision low voltage lockout
• Low shutdown current: IQ = 700nA
• Power good flag
• Soft start function
• Thermal shutdown protection function
• Current limit foldback with SS override function
• Saturating switch design: 75mΩ on-resistance
• Compact 16-pin MSOP package with enhanced thermal performance