LT3686AIDD#PBF

LT3686AIDD#PBF is a chip designed by Linear Technologies, which is a synchronous, step-up DC/DC converter with output voltage scalability and adjustable frequency. The chip can operate from a 4V to 40V input voltage range, and it is capable of providing a continuous output current of 3A at a Vout range from 4.5V to 32V. The architecture utilizes two N-channel Power MOSFETs, and features input current measurement, output overload and over temperature protection.

To meet the needs of various applications, the LT3686AIDD#PBF provides up to eight pre-programmed frequency settings, the highest of which is 1MHz, giving designers the ability to optimize the efficiency and performance of the converter at any given output load. The part also features an Ultralow IQ no load operating mode, which reduces the quiescent current to 12µA, making it ideal for battery-powered applications.

The LT3686AIDD#PBF combines high efficiency and wide input voltage range with small, surface mount packages, allowing it to be used in a variety of applications including point-of-load converters, DC/DC inputs to high current regulators, transceivers, converters for automotive systems and higher power handheld applications.

Working Principle

The LT3686AIDD#PBF converters work by controlling the switching of two N-channel MOSFETs (used in its topology) to transfer power from the input source to the output. When the input voltage is applied, the controller switches the lower MOSFET ON, allowing current to flow through the input capacitors and inductor and to the output load. This initiates the energy transfer process. When the load current is high enough, the controller then turns off the lower MOSFET and simultaneously turns on the upper MOSFET, transferring energy stored in the inductor to the load.

The LT3686AIDD#PBF also implements a hysteretic control scheme, which adjusts the switching frequency automatically to help maintain a stable output voltage. The hysteretic control scheme works by ensuring that the input voltage is above the switching threshold when the lower MOSFET is turned on and below the switch-off threshold when it is turned off. This prevents excessively high or low input voltage from being applied to the load, allowing for a higher duty cycle, and a more efficient regulation loop.

In addition, the LT3686AIDD#PBF has several other features to optimize efficiency and design flexibility. An adjustable slope compensation feature minimizes the output voltage ripple at low load current, while an adjustable frequency range helps designers reduce the size of the output inductor and capacitors to reduce the overall area required on the PCB. The part also has an adjustable soft start feature, which reduces inrush current and prevents power surges during system startup, as well as thermal protection to prevent over-temperature conditions.