36V, with 55V Transient Protection, 500mA(IOUT), Step-Down DC/DC Converter with Integrated LDO

Its internal 0.75A internal switch can deliver up to 500mA of continuous output current to 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 primary switcher channel, the integrated LDO can be used for an additional low noise output of up to 200mA of continuous current at voltages as low as 0.8V. Powering the LDO from the primary switching output offers both high efficiency and low noise for applications such as microprocessor core voltages. The LT3645 provides a compact, thermally efficient dual output solution, with its 3mm x 3mm QFN-16 package (or thermally enhanced MSOP-12E) and high switching frequency, which keeps external capacitors and inductor small.

The LT3645’s main switcher utilizes a high efficiency 750mA, 450mVCESAT switch, with the necessary oscillator, control, logic circuitry and LDO 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. A current-limited DA pin offers an additional level of protection to improve overall reliability. The linear regulator operates from the VCC2 pin at voltages ranging from 1.2V to 16V with only a 310mV dropout voltage. Other features of the LT3645 include a power good flag, soft-start and thermal shutdown.