March 11, 2013 //By Nathan Hanagami, Steve Knoth and Marty Merchant
Submitted by eetimes on Mon, 03/11/2013 - 00:00
voltage down to about ~5V during cold crank, or from high voltage spikes. The automotive electronics not only need to survive these harsh voltage changes, but also need to continue operating. The LTC3375 has a push-button controller and external pass-FET regulator that can be used to enable an external high voltage buck, which in turn supplies the LTC3375 with a safe regulated voltage. See
Figure 5 for details of the IC’s regulated output voltage performance during a high voltage transient. The external pass-FET regulator can also be used to keep alive a microprocessor during cold-cranking operation if the external buck regulator drops out of regulation. The external enable pins allow the buck regulators to be enabled externally, with I
2C, or a combination of both. The programmable interrupt (IRQ) and reset (RST) pins allow the micro to be alerted when an input voltage is below the under-voltage lockout (UVLO) threshold or an output voltage is out of regulation. See
Figure 6 for details.
Figure 5: LTC3375 high voltage transient performance Click on image to enlarge 
Figure 6: LTC3375 driven by a high voltage upstream buck converter
Click on image to enlarge
Conclusion
Technological advances in automotive infotainment, such as satellite radio, touch screens, navigation systems, Bluetooth and HDTV, have enhanced the driving experience in modern-day automobiles. Further, by replacing discrete power IC components or traditional large overly-integrated PMICs with a single multi-output octal buck IC; a system designer can integrate key power management functions for a new level of performance with smaller and simpler solutions. The LTC3375 is an example of this new generation of multi-output converter IC. It is a digitally programmable high efficiency multi-output power supply IC containing eight synchronous buck converters (IOUT up to 1A each) all powered from independent 2.25V to 5.5V input supplies, with low output voltage capability. Since up to 15 different output current configurations are possible, this flexibility allows a system designer
