Configurable applications processor tackles multiple mobile environments - Embedded.com

Configurable applications processor tackles multiple mobile environments

This “Product How-To” article focuses how to use a certain product in an embedded system and is written by a company representative.

Today's technologies and ever-greater consumer expectation levels result in high-end mobile handsets that contain an arsenal of computing power. To minimize development risk, time-to-market demands, and cost pressures, handset designers are driven to employ proven platforms for the major elements of their designs.

As a result, semiconductor vendors offer application processor platforms that include ICs, software stacks, reference designs, and design tools to produce complete but proprietary ecosystems. These different environments require intelligent power management for as many as thirty or more individual power domains, posing product designers a complex set of requirements that ideally require a uniform solution.

Space and complexity constraints render discrete power-management devices obsolete for today's high-end mobiles. In their place, dedicated power-management ICs — or PMICs — are available that use a system-level approach to supporting the various mobile environments. Besides the obvious advantages of saving board space, reducing the bill-of-materials and manufacturing costs, such devices may also integrate other circuit functions that simplify the design. Examples include audio CODECs, backlight LED drivers, and interfaces for memory cards and touchscreens.

In addition, PMICs often include a multimode battery charger that autonomously provides charger detection, charge control, and safety supervision for the battery pack. The result is a PMIC that significantly improves space efficiency and battery life, but that really only suits a particular vendor's mobile environment. For instance, Dialog Semiconductor's DA9035 specifically targets Marvell's W-CDMA platforms.

Flexibility adds value

While target-specific PMICs achieve vast performance improvements over their discrete-component predecessors, product designers would ideally prefer a single PMIC that they can tailor to suit a multitude of applications—and without incurring any significant compromises that would make this more flexible approach unattractive.

In this way, designers could re-use the same underlying PMIC architecture in a number of products, amortizing development costs and extending product lifetimes. Moreover, if the mobile platform is available in a variety of versions with different peripherals that suit various applications, being able to reconfigure the PMIC may enable the same basic design to reach a greater customer base at the lowest possible incremental development cost.

By means of example this video illustrates this by adding a camera module to an existing design. Click on picture to view.

Because each mobile platform defines resources such as the host processor, RF system, peripherals, hardware accelerators, multimedia coprocessors, and memory—all of which require power management support—designing a suitably flexible PMIC is quite a challenge. Most often, the power supplies for the processor core come from the dc/dc converters within the PMIC, and its low drop-out regulators (LDOs) then deliver clean and tightly-regulated system supplies.

As a result, every major platform change invokes the need for a change in power requirements—typically requiring new power supplies and a method to control power sequencing, ideally without adding overhead to the host processor.

Clearly, any configurable PMIC must offer sufficient hardware resources to maximise its applications potential but without making the silicon prohibitively expensive. The device must also be easy for product designers to apply, which implies the need for software and a programming interface that's easy to use and affordable. Ideally, it should also be possible to apply the PMIC to a given mobile reference platform without requiring any change of system software.

It's also highly desirable for the PMIC to be able to adapt to the multiple operating modes that high-end mobiles employ, at the same time ensuring robust power-up and power-down sequencing for the processor, co-processors, and peripherals. Ideally, the PMIC should detect and initiate power/wake-up and then relinquish power-management control to the host processor as the handset transitions between its operating modes.

Dialog Semiconductor's DA9052 is the first fully configurable, programmable-platform PMIC to become available. Its 7 x 7mm package provides up to 14 individual power supplies that comprise four dc/dc buck converters—providing 0.5 to 3.6V at up to 1A—and 10 programmable LDOs. Sixteen general-purpose I/Os are available to support system wake-up and peripheral control. The chip interfaces directly with a lithium-ion or lithium-polymer battery pack and features precise current/voltage charging powered from self negotiating USB or dc wall plug supply.

To cater for the most popular peripherals and user interfaces, the chip also integrates a white LED driver circuit that suits display backlighting, an ADC for system measurements, and a touchscreen controller. Two serial control interfaces enable communications with all common processor families—see figure 1:

Fig 1: The DA9052 integrates 4 dc/dc converters, 10 LDOS, and system monitoring and control functions.

To see a bigger version of this graphic click here.

A device with this complement of resources can become quite challenging to configure. Accordingly, an evaluation board is available to simplify development, complete with an onboard USB-to-I2C bridge that enables connection to a PC. Supporting all major ARM-based processor families, the graphical user interface within the Windows-compatible Power Commander configuration and programming utility presents a view of the PMIC's resources that permits easy and logically-organised access to configure the hardware.

On start-up, the software displays a configuration panel that allows you to select a predefined template for the target processor family from a pull-down menu, make modifications, and store the result as a new project—see figure 2:

Fig 2: The Power Commander Configuration Panel.

To see a bigger version of this graphic click here.

Clicking on the button of each LDO regulator opens its configuration panel, allowing you to assign it a name, select whether it will be enabled immediately or under power sequence control, and define its start-up voltage and any timing details.

Configuring the buck converters works in the same way. Additionally, you can set internal current limits and modify the converters' switching behaviour. For instance, it's possible to select constant frequency PWM operation when the wireless peripherals are active, but otherwise use comparatively noisy pulse skipping mode switching that offers greater efficiency, especially at light loads.Similarly, you can name each GPIO, configure it as an input or output, and define any applicable conditions. Clicking on the Power Sequence button then reveals a drag-&-drop timing screen, where you can define power-up and power-down sequences. This window mimics a processor's timing diagram specification—see figure 3:

Fig 3: An intuitive drag-&-drop interface configures power sequencing.

To see a bigger version of this graphic click here.

To minimise production costs, the final PMIC is produced as a one-time-programmable (OTP) device. The configuration process is thus responsible for generating the conditions that will be permanently programmed into the production PMIC to create a configuration that's precisely tailored to the target processor and its peripherals.Traditionally, developing a new platform-specific PMIC from the ground up typically takes 3 to 9 months. If the new PMIC is a modification of a previous design that simply requires a change to a metal layer on the chip, this time might come down to about 1 to 2 months. In either case, there will be appreciable NRE (non-recurring-engineering) costs that require recovery.

The DA9052 and its Power Commander utility dramatically changes this scenario, allowing product designers to configure and program a PMIC in less than an hour. Better yet, this design methodology dispenses with NRE costs as there is no charge for programming new batches of PMICs. Furthermore, and aside from the obvious benefits of minimising development costs and time-to-market, the flexibility that the DA9052 offers hugely reduces development risk and provides a uniform environment for future-proofing designs.

Mark Jacob is marketing Director for power management and audio atDialog Semiconductor (Kirchheim/Teck-Nabern, Germany) and has previously held positions in design management and strategic marketing since graduating in 1988 ” www.dialog-semiconductor.com.

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