Triple output, buck/buck/boost synchronous DC-DC for automotive start/stop systems

Analog Devices has released the Power by Linear LTC7815. The device is a high frequency (up to 2.25MHz) triple output (buck, buck, boost), the synchronous DC-DC controller which maintains all output voltages in regulation during automotive cold crank conditions. A 12V automotive battery can drop to less than 4V during engine restart or cold crank, causing reset of infotainment systems and other electronics that operate from 5V and higher. The high-efficiency synchronous boost converter supplies the two step-down converters, avoiding output voltage dropout when the car battery voltage drops, a useful feature in automotive start/stop systems that shut off the engine at idle to save fuel. Alternatively, the buck controllers can be powered from the input for a general-purpose triple output controller. The device runs from an input voltage of 4.5V to 38V during start-up and keeps operation down to 2.5V after start-up. The synchronous boost converter can provide output voltages up to 60V and can work with the synchronous switch fully ON at 100% duty cycle to pass through the input voltage when it is high to reduce noise and maximise efficiency. The two step-down converters can produce output voltages from 0.8V to 24V with the entire system delivering efficiency as high as 95%. Its low 45ns minimum on-time allows high step-down conversions while switching at 2MHz, avoiding critical noise-sensitive frequency bands such as AM radio and allows for smaller external components.