Multi-output power management ICs in infotainment systems: Page 7 of 8

October 30, 2013 //By Steve Knoth, Jeff Marvin, Linear Technology Corporation
Multi-output power management ICs in infotainment systems
With automotive infotainment systems being increasingly incorporating highly integrated and very powerful microprocessors and FPGAs, power management for these infotainment systems is growing more complex. A solution that helps to keep the designs simple is multi-output power management chips.
zero defects in the automotive assembly process. Further, the IC has very low standby current consumption, typically 12uA, which is desired in “always on” automotive navigation, security and safety systems which must maintain continuous power to real time clock circuits for temporal awareness, even when the engine is not running.

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

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