Multi-output power management ICs in infotainment systems: Page 6 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.
this 3ns edge rate control mode, but can also be individually set via I2C, to a faster 1ns rate, to improve efficiency, if limited edge rate and emissions control is not required.

In addition to switching time control, the LTC3676 offers some other EMI suppression tools. The frequency of the buck regulators can be changed from 2.25MHz to 1.12MHz. Also, to minimize the input ripple, which can end up radiating through the power input wiring, the buck regulators can be staggered between two different clock phases.

The LTC3676 is also capable of providing considerable power, in excess of 10W. This can result in substantial circulating currents and so it is imperative to provide an uninterrupted path for this current to circulate. In particular, slots in the ground plane, which force the large circulating currents to flow around them, create slot antennas. But other obstacles, such as changing layers, contribute some energy in the EMI signature and should be minimized. Ideally the top and bottom layers should be all, or mostly, ground plane, with the signal layers flowing internally. Since this is usually not practical, some thought needs to go into how the ground plane will be connected prior to commencing layout. For example, it is not a good idea to put the LTC3676 into a corner or tab on the PCB. This will make it very difficult to properly route the ground plane. However, it is a good idea to route the high circulating current areas of the LTC3676 first, to ensure the most optimum layout possible.

If EMI control is planned and executed with the concepts of source suppression and antenna elimination in mind, it is possible to create a full power system that is a good EMI neighbor without increasing product cost or weight.

More Key Features

The LTC3676 fully satisfies the automotive ESD requirements of 2kV HBM and 1000V CDM which is another key requirement for approaching

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