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Power-management chip for latest embedded processors

 

Wolfson Microelectronics has introduced a new series of configurable power-management devices, the first being the WM8320 for use in portable multimedia and other handheld, batterypowered products. At an earlier stage in the development of its product line, Wolfson combined its audio-codec technology with power management in chips such as its WM8350; however, a company spokesman said that now, industry demand is for those functions to be on separate ICs. The audio codecs can benefit from a shift to a smaller geometry process, whereas the power devices on the chip do not—for that reason alone a discrete solution is preferable. However, Wolfson adds, even though the on-chip isolation of audio and power circuitry is good, feedback from customers who are designing space-constrained circuit boards indicates that they prefer to keep the power and audio circuitry apart physically to reduce circuit interactions, and therefore require the less integrated solution.

The 8320 chip has many of the same functions as the recently launched 831X family, but it is intended purely as a versatile companion chip for an embedded processor and so lacks the battery-charging and -management functions of that family. Specifi c target designs include any that use ARM-core-based processors, for products such as netbooks, mobile Internet devices, smartphones, handsets and digital photo frames. The chip has has two of Wolfson’s Buckwise synchronous dc/dc converters rated at 1.2A each, that offer high levels of transient performance to maintain voltage rails as product features switch on and off, as well as two conventional 1A buck regulators. There are 10 LDO (low-drop-out) linear voltage regulators, and you can parallel the two 1A regulators to generate a combined 1.6A output to support large memory banks or to increase effi ciency by pre-regulating any of the 10 LDOs. You confi gure the device by setting bits in a one-time-programmable non-volatile memory—after customers’ product development is complete, Wolfson anticipates that it will deliver most devices pre-programmed at final test. In development, you can set the device to powerup and confi gure from an external EEPROM to circumvent the limitations of OTP memory —in effect, it has a tiny BIOS to control its start-up.

The Buckwise regulators employ valley-mode control to set their output-voltage level and can thus continue regulation down to low output voltages of 0.6V. High switching frequencies allow you to use chip rather than wire-wound inductors; a typical output filter might use 0.5 µH and 10 µF.

The WM8320 comes in a 7x7mm BGA package and costs $3.72 (10,000).

A longer version of this article appears at www.edn-europe.com/article.asp?articleid=3482.

Wolfson Microelectronics, www.wolfsonmicro.com.