Linear Technology’s 55V, 1.2A Step-Down DC/DC Converter

ELECTRONICS:  Linear Technology Corp.’s LT3991 is a 1.2A, 55V step-down switching regulator with an integrated boost diode. Its Burst Mode® operation keeps quiescent current under 2.8 µA in no load standby conditions. The LT3991’s 4.3 to 55V input voltage range makes it ideal for automotive and industrial applications. Its internal 1.7A switch can deliver up to 1.2A of continuous output current to voltages as low as 1.19V. The LT3991’s Burst Mode operation offers ultralow quiescent current, making it well suited for applications such as automotive or industrial systems that demand always-on operation and optimum battery life. Switching frequency is user programmable from 200 kHz to 2MHz, enabling the designer to optimize efficiency while avoiding critical noise-sensitive frequency bands. The combination of its 10-lead 3 mm x 3 mm DFN or thermally enhanced MSOP packages and high switching frequency keep external inductors and capacitors small, providing a compact, thermally efficient footprint.

The LT3991 utilizes a high efficiency 1.7A, 440 mOhm switch, with the necessary 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 15 mVPK-PK. Special design techniques and a new high voltage process enable high efficiency over a wide input voltage range, and the LT3991’s current mode topology enables fast transient response and excellent loop stability. Other features include a power good flag, soft-start capability, external clock synchronization and internal compensation.

The LT3991EDD is packaged in a 3 mm x 3 mm DFN-10, and the LT3991EMSE is packaged in a thermally enhanced MSOP-10, priced starting at $2.95 each for 1,000 piece quantities. The LT3991IDD and LT3991IMSE are tested and guaranteed to operate from a -40 to 125C operating junction temperature and are priced at $3.28 each in 1,000 piece quantities.

- Edited by Liz Taurasi