Linear Technology Introduces Integrated LDO Step-Down DC/DC Converter

Crystal oscillator

Photocoupler

Linear Technology Corporation (Linear Technology Corporation) Release LT3645, the device comprises a 500mA (IOUT), 36V step-down switching regulator and an integrated LDO, LT3645 using 3mm x 3mm QFN package or MSOP-12E. Operating over a VIN range of 3.6V to 36V, the LT3645 features 55V transient protection, making it ideal for load dump and cold crank conditions found in automotive applications. Its 0.75A internal switch delivers up to 500mA of continuous output current at voltages as low as 0.8V. The LT3645 uses a constant switching frequency of 750kHz to minimize noise while optimizing efficiency. In addition to the main switching channels, the integrated LDO can be used to provide additional low noise output, providing up to 200mA of continuous current at voltages as low as 0.8V. For applications such as microprocessor core voltages, powering the LDO with the main switch output provides high efficiency and low noise. With its 3mm x 3mm QFN-16 (or thermally enhanced MSOP-12E) package and high switching frequency, which allows the use of small external capacitors and inductors, the LT3645 offers a compact and thermally efficient dual output solution.

The LT3645's main switch is a high efficiency 750mA, 450mV CESAT switch that integrates the necessary oscillators, controls, logic and LDOs on a single chip. Thanks to a special design approach, the device achieves high efficiency over a wide input voltage range, while its current mode topology enables fast transient response and excellent loop stability. The current-limited DA pin provides additional protection to improve overall stability. The linear regulator operates from the VCC2 pin, which has a voltage range of 1.2V to 16V and a dropout voltage of only 310mV. Other features of the LT3645 include power good flag, soft start, and thermal shutdown.

The LT3645EUD is available in a 3mm x 3mm 16-lead QFN package and is priced at $2.25. The LT3645EMSE is available in a 12-lead thermally enhanced MSOP package and is priced at $2.35. The industrial grades LT3645IUD and LT3645IMSE are tested and guaranteed to operate over the -40°C to 125°C operating temperature range and are priced at $2.48 and $2.59, respectively. The LT3645HMSE has been tested and guaranteed to operate over the -40°C to 150°C operating temperature range and is priced at $2.84. All of the above are the price of each piece of the 1,000-piece purchase price, and all versions are available from stock. For more information, please visit