The rate at which disk drives are shrinking in physical size while soaring in capacity means that all other storage technologies that hope to usurp the throne of the premier magnetic storage medium are going to have their work cut out to keep up, and big investment is still going into creating ever better drives – and the electronics that they require. The first all-CMOS mass storage chip set for 2.5 and smaller hard disk drive developers is claimed by AT&T Co’s AT&T Microelectronics in Berkeley Heights, New Jersey. The parts on offer are the Reach2 read-channel device and two servo-channel devices, the Search1 multiprocessor and Spin1 servo data converter. The company reckons that the new parts reduce chip count in drive units by up to five components and eliminate application-specific glue logic and many discretes normally used so that all that is needed to complete a drive are preamplifier, memory, and servo-motor drive circuitry. When fully operational, the 0.9-micron chips are claimed to dissipate less than 1W. The read channel device integrates the analogue read channel, frequency synthesiser, and servo demodulator circuitry for multi-zone, constant-density writing and reading in a single chip package.
Closer packing densities
It is claimed to be the first read-channel architecture to use dedicated data and servo paths, including separate optimised filters to help eliminate noise and enable a much closer packing density on the disk than current read channels allow. The device is programmable and supports data rates from 6.67Mbps to 30Mbps. The Search1 integrates all the circuitry needed for the position and spindle-servo systems and is claimed to be the first triple processor device for mass storage, integrating fast general purpose processor, signal processor and servo timing processor on one chip. The processors operate asynchronously, which is claimed to mean that the chip makes possible higher accuracy, leading to potentially better packing density on disk and a lower data-error rate. Independent clock control and power-down circuitry provides over 800 unique power-down modes for building battery-saving features into laptop drives. The device is also AT&T’s first standard product fully characterised at 3V – there’s also a 5V version. Spin1 is a low-power signal processing servo data converter that interfaces to either an 8 or 16-bit microcontroller. It increases accuracy from 8 bits to the 10 bits now needed for accurate placement of data and servo paths on the disk and also contains power-down circuitry. The company is also offering a comprehensive development kit that supports direct RS-232 hook-up to a hard-drive system with the necessary software package and assemblers to develop drive software. A second-party microcontroller emulator is also available. The development kit is $2,500. The 1,000-up price is $25 for the Reach2, sampling now with production in the third quarter; $20 for Search1, in production now, and $10 for Spin1, sampling now with volume in the third quarter.
