Finally, the LTC3676 supports simple and effective power sequencing which can be handled through serial communications or via pin strapping where power supply output voltages are tied to enable pins in the desired turn-on sequence. Internally each enable is delayed micro seconds to further time stagger the startup sequence. This feature is supported with precision low voltage enable thresholds so the sequencing is possible even with output voltages as low as 0.43V. Each supply voltage output is also soft-started to limit inrush current and produce clean voltage transitions. See Figure 2.
The LTC3676 also includes easily programmable power-down sequence control. The IC includes two registers for initializing a power down sequence configuration which will be followed at the next turn-off event or overpower fault condition. Each regulator (DC-DC and LDO) can be pre-set to any one of four time slots for shutdown. Each regulator output includes an internal pull-down resistor that is engaged when disabled to guarantee the controlled discharges as shown in Figure 3 and a low starting point for the next turn-on sequence
Figure 2. The LTC3676 Startup Sequence
Figure 3. The LTC3676 Power-Down Sequence
Conclusion
Modern automobiles have advanced significantly from those of yesteryear. Simple AM/FM radios have given way to modern technological advancements such as satellite radio, touch screens, navigation systems, Bluetooth, HDTV, integrated cell phones, media players, and video game systems. Further, by replacing discrete power IC components or traditional large overly-integrated PMICs (i.e. with audio, codecs, etc.), a system designer can use a new generation of compact Power Management Solutions ICs that integrate key power management functions for a new level of performance with