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

Aug 1, 2010 12:00 PM
Sam Davis, Editor-in-Chief, PET

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.

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