Power Electronics

ICs Manage Power For XScale Processors

Semiconductor vendors are crafting highly integrated power management ICs to handle the power requirements of Intel’s XScale processor family. These devices combine numerous switching and LDO regulators as well as battery management features. The various regulators are programmable over a high-speed serial bus, enabling the power management chips to support dynamic voltage management for reduced power consumption in the processor. These chips are designed to operate from a single-cell Li-Ion or Li-polymer battery.

National Semiconductor’s flexible power management unit, the LP3970 FlexPMU, features 12 integrated “power domains” for reduced board space and increased efficiency. The FlexPMU dramatically reduces board space and significantly lowers overall cost in handheld devices. Each FlexPMU supports real-time, software-controlled dynamic voltage management.

Offered in a 48-pin 7-mm ࡍ 7-mm × 0.8-mm LLP package, the LP3970 FlexPMU combines an efficient set of programmable power supplies and a flexible back-up battery management system. The LP3970 FlexPMU is fully compatible with Intel’s XScale product family and other processors designed for mobile use.

The LP3970 provides 11 low-noise LDO regulators, two dc-dc magnetic buck regulators, a back-up battery charger and four GPO's. A high-speed serial interface is included to program individual regulator output voltages as well on/off control. Other features include automatic switching to back-up battery, a precision internal reference, and protection against thermal and current overloads.

Available now, the LP3970 is priced at $4.50 in 1,000-unit quantities. For more information including a datasheet, see www.national.com/pf/LP/LP3970.html. .

Another device is Linear Technology’s LTC3445, an xScale microprocessor power supply in a 4-mm × 4-mm QFN. It contains a high-efficiency monolithic synchronous current-mode buck regulator, two LDO regulators, a PowerPath controller and an I2C interface in a single QFN package. The synchronous buck regulator can deliver up to 600 mA of output with efficiencies up to 93%. The user can select either a constant (1.5 MHz) or a spread spectrum switching frequency. The spread-spectrum option allows for a lower-noise regulated output as well as low noise at the input. For processor core voltages, the onboard I2C interface controls a 6-bit programmable dynamically adjustable output voltage range of 0.85 V to 1.55 V and a slew rate control.

The LTC3445 also contains two LDO voltage regulators to power additional xScale voltages such as VSRAM and VPLL. Both LDO output voltages are programmable with external resistors and can deliver up to 50 mA of output current.

The LTC3445 contains control circuitry (PowerPath) for automatic battery backup (typically a coin cell battery) when the main battery is disabled. Automatic Burst Mode operation reduces light-load supply current to only 360 µA and drops to 27 µA in shutdown.

Available from stock, the LTC3445 is priced starting at $2.45 each for 1000-piece quantities. For more details on this device including a datasheet, visit www.linear.com/pc/productDetail.do?navId=H0,C1,C1003,C1042,C1032,C1064,P8250 .

In addition to these parts, other vendors are currently developing power management ICs for the XScale processors. One company, Maxim Integrated Products, will build on its existing offerings of power management ICs for the XScale processors.

Last year, Maxim introduced the MAX1586/1587 power management ICs. (For a description of these parts, see www.maxim-ic.com/quick_view2.cfm/qv_pk/4140.) Now, the company is developing another power management IC aimed at the next processor in the XScale family. Expected to be released in the middle of this year, this new power manager will be comparable to the MAX1586/1587 but feature enhanced performance and smaller size.

Another vendor, Texas Instruments (www.ti.com), is also developing a power management IC targeting the XScale processors. The new chip is expected to be introduced later this year.

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