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Switching regulator offers 55V transient protection

Posted: 17 May 2011 ?? ?Print Version ?Bookmark and Share

Keywords:switching regulator? step-down regulator? automotive applications?

Linear Technology Corp. has announced the LT3645, a 500mA (IOUT), 36V step-down switching regulator and integrated LDO packaged in a 3mm x 3mm QFN-16 package (or thermally enhanced MSOP-12E). The LT3645 operates from a VIN range of 3.6V to 36V with transient protection to 55V, making it able for load dump and cold-crank conditions found in automotive applications.

The device's internal 0.75A internal switch can deliver up to 500mA of continuous output current to 0.8V. The LT3645 uses a constant switching frequency of 750kHz to minimize noise while optimizing efficiency.

Powering the LDO from the primary switching output is said to offer 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 750mA, 450mVCESAT switch, with oscillator, control, logic circuitry and LDO integrated into a single die. It is said that the special design techniques enable a wide input voltage range while its current mode topology allows fast transient response and excellent loop stability.

A current-limited DA pin provides 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 310mV dropout voltage. The LT3645 also provides a power good flag, soft-start and thermal shutdown.

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