Power Electronics

Mobile Systems Poised to Take Advantage of Power-Pinching ICs and Architectures

Longer battery life provided by new ICs and innovative power management will drive design of mobile systems, including smartphones, tablets and other portable, hand-held products.

Find a downloadable version of this story in pdf format at the end of the story.

The new mobile generation is ready for a great leap forward based on Intel’s new Atom Z6xx microprocessor system and Freescale’s two-IC chipset that supports it.

These new ICs along with system power management designs will provide:

• Small size
• Low weight
• Low power requirements
• Long battery life
• Small overall system footprint
• Battery recharge capability
• Minimum operating temperature
• Reasonable cost for the specific application

One reason for recent improvements is that semiconductor processing now allows smaller feature sizes and more transistors and functions per IC. This means that it is possible for an IC to provide circuits to support microprocessor functions. Because of the power levels involved it is usually necessary to use a separate IC for the battery-based power supply.

Lower Power Processing

To enhance the growth of mobile computing, Intel Corporation unveiled its newest Atom™ processor-based platform. This technology package provides significantly lower power consumption and targets a broad range of computing devices, such as high-end smartphones, tablets and other mobile handheld products. As noted by Intel, “As a result of our efforts, the Atom processor is pushing the boundaries of higher performance at significantly lower power to show what’s possible as handheld devices become small, powerful mobile computers.”

The platform includes the Intel® Atom™ processor Z6xx Series Family and Platform Controller Hub MP20. This platform has been repartitioned to include the Intel Atom processor Z6xx, which combines the 45nm Intel Atom processor core with 3-D graphics, video encode and decode, as well as memory and display controllers into a single SoC design. It also includes the MP20 Platform Controller Hub, which supports a range of system-level functions and I/O blocks.

50% Less Power Use In Standby

Compared with the previous Atom platform, the Z6xx offers:

• Power reduction: 50x in standby, 0.5x in operation
• Performance: 2x graphics processing speed
• Footprint: 2x reduction in p.c. board area
Completing the mobile system design are Freescale’s support chips. They are part of Intel’s reference design and are supported with drivers and software from Intel and third party developers. Freescale supplies an efficient, highly integrated two-IC chipset for mobile device applications, as shown in Fig. 1. One IC is a buck-boost dc-dc regulator that provides 3.3V from a single cell Li-ion battery. The second, a power management IC provides:

• Battery charging and monitoring
• Audio processing/amplifiers
• LCD backlight and interface functions

By separating the 3.3V supply, you can easily adapt the system for 2/3 cell solutions by r eplacing the buck/boost with a buck regulator, which enables re-use levels between products. Also, separation of a high current 3.3V supply provides optimal thermal performance between devices within the system.

The SCCS900842/R2 power supply IC (Fig. 2) contains a fully integrated, four-switch, synchronous buck-boost dc-dc converter and a low noise, LDO. The IC operates from a single-cell Li-ion battery and steps up or down an input voltage that can range from 3.0 to 4.4V and provides a 3.3V fixed output. Also, it provides two pins to monitor the status of the IC; a digital status signal and an analog output voltage proportional to the average output current. The IC is housed in a 3x3 mm, PB-free, wafer level chip scale package (WLCSP) with a 0.4mm pitch.

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Key 900842 Features

• Uses internal power MOSFETs
• 1.625 MHz PWM switching frequency
• Seamless transition between buck and boost modes
• Uses internal compensation
• Low-power operating mode

Freescale’s buck-boost topology provides higher efficiency than two-stage configurations that boosts the battery voltage to 5V and then steps it down to 3.3V. Typically, Freescale’s buck-boost circuit is over 90% efficient, which extends battery life.

The SC900841JVK/R2 is a high-efficiency, power management IC (PMIC) that can provide all the operating voltages for ultra-mobile platforms using its 29 voltage rails. It has nine switching power supplies running at frequencies from 1.0 to 4.0 MHz, 17 LDOs and three 3.3V power switches. It incorporates a switching mode Li-ion battery charger. The power supply chip is fully configurable and controllable through its SPI and mini SPI interfaces.

Key Features

• Single chip provides complete system power management, battery charging and audio support
• Fully programmable dc-dc switching and LDO regulators, and load switches
• LCD backlight using LED drivers
• SPI interface (12.5 MHz/25 MHz operation)
• Real time clock (RTC)
• 8 Interrupt capable GPIOs and 8 GPOs
• 22-channel ADC
• 4 GPOs for controlling platform switches
• I/O interrupt and reset controller

Audio features provided by the chip include a 16-bit voice CODEC with a signal-to-noise ratio exceeding 85 dB, and a 24-bit audio DAC with a signal-to-noise ratio exceeding 100 dB and a thermal harmonic distortion of better than 0.1%. The chip also incorporates analog/digital microphone support, a Class A line-out amplifier, Class AB earpiece amplifier, Class AB headset amplifier, a 500 mW class-D loudspeaker amplifier, and headset detection. There’s also a 22-channel, 10-bit ADC able to implement touch screen, battery vitals, and voltage monitoring functions.

The power management IC and power supply IC work together with the Atom Z6xx to cut power consumption and increase battery life. When specific system functions are not being used, the microprocessor disables power going to that function. Then, the chip reapplies power to the function when it is activated. The chip’s intelligent charger incorporates a switching CV/CC charger and performs charge status monitoring.

In virtually all applications, some functions are not powered up simultaneously, so power and thermal and power effects are not an issue. If, for some reason too many functions are powered at the same time, an over-temperature sensor in the PMIC chip causes the entire system to be disabled.

Download the story in pdf format here.

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