36V input dual step down regulator
1 min read
The LT3688 from Linear Technology is a dual 800mA, 36V input step down switching regulator with dual power on reset and a watchdog timer. According to Linear, the device's 3.8 to 36V input voltage range makes it ideal for load dump and cold crank conditions commonly found in automotive applications. Its dual 1.2A internal switches are optimised to deliver up to 800mA of continuous output current from each channel at output voltages as low as 0.8V.
The device has a Burst Mode to provide quiescent current of only 115µA, making it well suited for applications such as automotive or telecom systems which demand always on operation and optimum battery life. Switching frequency is user programmable from 350 to 2.2MHz to optimise efficiency while avoiding critical noise sensitive frequency bands. The LT3688's 4 x 4mm QFN-24 (or thermally enhanced TSSOP–24) package and high switching frequency keep external inductors and capacitors small to provide a compact, thermally efficient footprint.
According to linear, the integrated microprocessor supervisor functions support high reliability applications such as automotive electronic control units. Each power on reset timer and the watchdog timer timeout periods are independently programmable using external capacitors. Tight accuracy specifications and glitch immunity have been utilised to ensure reliable reset operation of a system without false triggering. Linear claims the open collector RST will pull down if output voltage drops 10% below the programmed value. The watchdog timer monitors for watchdog falling edges grouped too close together or too far apart.
