Multi-output power management ICs in infotainment systems: Page 2 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.
levels demanded by automotive OEMs. Starting with the wide operating temperature range, power management ICs are challenged on two fronts. First, power conversion - even when highly efficient - must dissipate some level of power as heat. When several DC-DCs and LDO regulators are packed into a single device, the combined power dissipation can be significant, easily approaching two Watts or more. Typical PMIC packages such as the 6mm x 6mm 40 pin, exposed pad QFN have a thermal resistance of 33°C/W resulting in a junction temperature rise in excess of 60°C. When this is combined with the additional challenge of a wide ambient operating temperature range, the maximum junction temperature of the PMIC can often exceed 125°C. Even in body electronics, not under the hood, the ambient temperature inside a sealed plastic electronic control module can reach 95°C. Due to these temperature challenges many PMICs rated for 85°C, or even 125°C, are not sufficient for sustained high temperature operation.

Another key to operating an integrated power management device in a high ambient temperature environment is for the device to self-monitor its own die temperature and report when its junction temperature is getting too high so that the system controller can make an intelligent decision on whether to reduce power to the load(s). Operating system software can do this by turning off less critical functions or by turning down the performance in processors and other high power functions such as displays and network communications.

The environment within a current vehicle’s dashboard is crowded with electronics. Adding to this crowding are radios from Bluetooth to cell phone based network connectivity. Therefore, it is imperative that any additional entries to this thermally constrained environment not contribute excessive heat or EMI. There are strict Electromagnetic Compatibility (EMC) requirements which cover radiated and conducted emissions, radiated and conducted immunity or susceptibility, and Electrostatic Discharge (ESD). Being able to conform to these requirements affects the

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