April 2, 2014 – Linear Technology Korea (CEO Hong Sa-kwak) announced the release of a 400mA, 40V step-down switching regulator (product name: LT3667) that provides dual LDO outputs in a 3mm x 5mm QFN or MSOP-16E package.

The LT3667 provides triple outputs in an ultra-compact solution suitable for automotive and industrial applications. With 60V transient input protection, it offers a VIN range of 4.3V to 40V, making it ideal for load dump and cold crank conditions in automotive applications. An internal 600mA integrated switch provides up to 400mA output current, which is distributed to the integrated load on the primary output and two LDOs. The primary switching channel is adjustable to output voltages as low as 1.2V, and each LDO can provide output voltages as low as 0.8V. For example, a typical application features a switch providing 5V 200mA, along with one LDO providing 2.5V 100mA and a secondary LDO providing 1.8V 100mA.

The LT3667 requires only 50µA of standby current, with all three channels regulated, making it ideal for always-on automotive applications. The LT3667's switching frequency is user-programmable in the range of 250kHz to 2.2MHz, allowing designers to optimize efficiency while avoiding noise-sensitive critical frequency bands. Each integrated LDO features a current limit function that is precisely programmable up to 200mA and additionally provides high reliability standards. Even if the LDO is powered by an independent input, powering the LDO from the primary switching output ensures high efficiency and low noise. The combination of a 3mm x 5mm QFN-24 package (or the thermally enhanced MSOP-16E) and a high switching frequency allows for smaller external capacitors and inductors, providing a compact and thermally efficient footprint.

The LT3667 integrates a high-efficiency 600mA switch, essential oscillator, control, logic circuitry, and LDO onto a single die. Special design techniques achieve high efficiency over a wide input voltage range, while the current-mode topology enables fast transient response and excellent loop stability. Other features include a power indicator, synchronization function, reverse battery protection, current and thermal limiting functions, and programmable undervoltage lockout.

The LT3667EUDD is available in a 3mm x 5mm 24-pin QFN package, and the LT3667EMSE is available in a thermally enhanced 16-pin MSOP package. The LT3667IUDD and LT3667IMSE have been tested and guaranteed to operate at junction temperatures from -40°C to 125°C, while the high-temperature version, the LT3667HUDD, has been tested and guaranteed to operate at junction temperatures from -40°C to 150°C. All versions of the LT3667 are available immediately.

Photo Caption: 40V, 400mA (IOUT), Triple Output DC/DC Converter