A 400mA, 40V step-down switching regulator has been released by Linear Technology Corporation with dual LDO outputs. This latest device is packaged in a 3mm by 5mm QFN or MSOP-16E and offers a highly compact, triple output solution for automotive and industrial applications.
The LT3667 operates from a VIN range of 4.3V to 40V with transient protection to 60V, making it ideal for load-dump and cold-crank conditions found in automotive applications. Its internal 600mA internal switch delivers up to 400mA, which is distributed to the combined loads of the primary output and both of the LDOs.
The primary switching channel delivers outputs as low as 1.2V, whereas each LDO can deliver outputs as low as 0.8V. For example, a common application will have the switcher delivering 200mA at 5V, with one LDO delivering 100mA at 2.5V and the second delivering 100mA at 1.8V.
This device requires only 50µA of quiescent current when all three channels are in regulation, making it ideal for always-on automotive applications.
The switching frequency is user programmable from 250kHz to 2.2MHz, enabling optimised efficiency while avoiding critical noise-sensitive frequency bands. Each integrated LDO has an accurate programmable current limit up to 200mA, offering an additional level of reliability. Although the LDOs can be powered by independent inputs, powering them from the primary switching output ensures both high efficiency and low noise.
The main switcher utilises a high efficiency 600mA switch with the necessary oscillator, control, logic circuitry and LDOs integrated into a single die.
Special design techniques enable high efficiency over a wide input voltage range while its current-mode topology enables fast transient response and excellent loop stability.
Other features include power indicators, synchronisation capability, reverse-battery protection, current and thermal limiting and programmable undervoltage lockout.
