A DSP Powered Solid State Audio System
`Jason Kridrter. Mark Nadeskt‘. Pedro Gelaberr
`
`Texas Instruments Incorporated
`12203 Southwest Freeway
`Stafford. TX 774??
`
`ABSTRACT
`
`flash
`New audio compression algoritlttrts and rtort—vo1atiie
`rnerrtory technology have enabled the creation of portable solid-
`state persona] audio players. This paper presents a low-power
`portable
`audio system based on the Texas
`Instt1.l1't1ents
`TMS32I'.lC5000 DSP family. This system is designed to play
`music and other audio media stored on flash memory cards that
`can hold over an hour of CD quality music. The flash card
`provides higher audio quality than a casst-Ate tape. yet is smaller
`and more durable than a CD. The music or audio material
`downloaded to the flash is obtained from |icerr% distributors,
`either through the internet or through kiosks setup in retail
`outlets. All the audio decoding and watermarking required by
`this system is handled by the '[‘MS3‘20C5OD0 DSP. System
`performance characteristics are also presented.
`
`1.
`
`INTRODUCTION
`
`Cassette tape. Compact Disc, Mininiscm. and the associated
`personal. hand held audio players have captivated consumers
`with the ability to carry their music everywhere. However. these
`systems have several limitations that fail to address consumer‘:
`needs.
`First, consumers experience disappointment with the
`short battery life. Second, the sensitivity to physical vibration
`and I'I'ltDl.l01'I limits the use of these players in demanding mobile
`environments. such as jogging or cycling.
`'l'l1ird. ¢ottsurrter$'
`desire for comfort requires very small portable players. Fourth.
`consumers desire high fidelity audio and durable media storage.
`To addmss these limitations. this paper describes a low-power
`DSP impIen'tenta1:ion based on solid state media.
`This
`implerltetttation utilizes new distribution and compression
`technologies to provide high fidelity. long battery life. and shock
`resistant portable audio.
`
`2. SOLID STATE AUDIO
`
`2.1 Description
`
`A solid state audio player uses either volatile or non-volatile
`integrated circuit memory devices. instead of magnetic or optical
`media. This media provides a long shelf life and high resistance
`to vibration and motion [1]. The player is small,
`light and
`durable. Audio is output
`through a stereo headphone jack
`provided on the player. A flash card and a docking bay, or
`similar interface, provides the ability to exchange music between
`your personal computer and the solid state player. Distribution
`
`traditional media retail stores.
`or‘ the audio data can occttr at
`other retail outlets without
`traditional media warehousing. or
`irrternct-based
`retailers. This
`distribution
`concept
`allows
`consurrters to download audio media at a variety of locations
`without necessarily requiring the ownership of a computer with
`internet access or other expensive liardware. The data purchased
`at these distribution centers can be protected from piracy with
`digital waten'na.rl(s.
`This
`technique
`embeds
`inaudible
`identification infomtation that cart be recovered even from
`analog copies of the original source [2I. Outside of these
`features.
`the player provides the farnilisr human interface and
`furtctionality that is traditionally offered in a tape or CD player.
`'l"he features of a solid state audio player can also be integrated
`onto other systems. including personal data assistants. palm top
`computers. and wireless phones. By utilizing a proyarrunable
`DSP. additional
`features.
`such as
`recording. digital
`radio
`reception and wireless communication, can be added to the
`player. Other possible features are the use of acoustic noise
`cancellation to reduce background noise. speech recognition for
`voice eontmands and speech compression for ntentofdictation
`recording.
`
`22 System Overview
`
`Amplifier
`
`
`
`Figure 1: Solid State Audio ‘Block Diagram.
`
`Figure 1 illustrates one solution for the solid state audio system.
`This system utilizes a Texas Instruments TMS3'2OC5r000 family
`digital signal processor [DSP] as its processing engine and a
`flash card for media storage.
`In the system. the DSP responds to
`
`O-?BO3—504‘l-3i99 $10.00 til 1999 IEEE
`
`2283
`
`Samsung Exhibit 1034
`
`Samsung v. Affinity
`IPR2014-01181
`
`Page 00001
`
`Samsung Exhibit 1034
`Samsung v. Affinity
`IPR2014-01181
`Page 00001
`
`

`
`events from human input devices and updates a display to
`provide visual feedback to the user. When the user plays an
`audio track, the DSP accesses the compressed audio samples on
`the flash card. decompresses the samples in its internal memory.
`verifies the digital
`ivaterrnark. and passes tl1e uncompressed
`audio samples to a DEA. The analog signal is then fed through
`the amplifier to drive stereo headphones.
`
`2.3 System Components
`
`The following subsections describe the hardware and sonware
`components of the solid state audio system.
`
`2.3.] Algorilluns
`There are several audio compression algorithms that reduce the
`amount of data nwessary to store the algorithms.
`If no
`compression
`techniques
`are
`utilized.
`enormous
`storage
`capabilities will be required. For example. CD3 contain I6-bit
`data samples at a 44.1 kHz rate. To store one minute of a CI)
`stereo signal would require about 10 Mbytes. Using perceptual
`coding techniques. music can be compressed to between 0.3 and
`1.0 Mbytes per minute with almost no discernible difference in
`the signal quality. These compression techniques reduce the
`storage requirements up to an order of magnitude. Typical audio
`compression standards that provide ('.'[)-quality audio at high
`compression factors are: Dolby Digital“ {AC-31'“) [3]. MPEG-
`1 Audio Layer 3 (MP3) [4]. MPEG-2 Advanced Audio Coding
`(AAC} [5], Adaptive Transform Coding (ATRAC)
`[I5] and
`Precision Adaptive Subband Coding (PASC) [7]. Utilizing a
`programmable
`solution.
`these
`algorithms
`can
`be
`easily
`prograrnmed into the DSP and switched at will. As future
`algorithms are developed. they can be downloaded to the solid
`state audio system as a system software upgrade.
`
`the music industry from piracy, vvatennarking
`To protect
`algorithms embed identification. such as the copyright owner.
`distributor
`and consumer equipment,
`in the data stream.
`Whenever
`the digital
`stream is copied.
`the identification
`information is also copied. thus providing a trace to the original
`source and allowing the use of copy protection schemes. The
`industry has not yet
`standardized any one watennarking
`algorithm. nor are there any copy protection methods that are
`widely standardized in consumer equipment. A programmable
`engine solves this problem by being able to switch between, or
`upgrade to. multiple watermarking algorithms.
`
`2.3.2 C5000 Family DSP
`
`The Texas Instruments C5000 family of programmable. catalog
`DSPs are well suited for this system The C5000 family offers a
`variety of peripherals and memory combinations for dificrent
`system needs. For the solid state audio system. using the
`'I'lvlS320\"CS49 eliminates the need for external memory due to
`its large on-chip memory [32K in 16-bit RAM and 16K in: 16-bit
`ROM} £3]. For instance. a complete 6-channel implementation
`of a Dolby Digital” decoder requires less titan t6l( words of
`program memory and around 16K words of data rnern-cry. The
`program can be burned into ROM and the remaining 16K words
`
`can be utilized for additional proprietary Features or other audio
`decoders.
`with fast
`external catalcn SRAM consuming
`approximately 6G0mW.
`the overall system power
`is greatly
`reduced by eliminating the need for external memory.
`Even though the TMSBZOVCS49 is a 16-bit architecture. its large
`performance [100 MIPS) allows the use o 'double precision (32-
`bit) arithmetic for audio algorithms. For example. a 20-bit
`impletttentatiorl
`(Class A) of
`a Dolby Digitalm decoder
`consumes less than 30 MIPS.
`This leaves over 20 MIPS
`available to perfonn other tasks. such as the human interface and
`system control. Most importantly. the 'I'MS320VCS49 consumes
`only 0.45 mAr'MlPS (1.125 rnW!MIPS at 2.5 V). making it an
`extremely attractive processor for battery operated systems.
`Recent advances in VLSI process technology have provided
`increasing
`computational
`performance
`and
`lower
`power
`consurnption in digital signal processors. These changes have
`led to the use of DSPs in power critical applications. Table 1
`shows a dramatic decrease in power in the last couple of years.
`This table shows that by 1999. power consumption will be half of
`what
`it was in 1997 for a device that now has 50% more
`performance.
`
`Table 1: '['MS320C5000: Power Efficient Performance.
`
`"°"°’“““”“°
`MIPS
`
`33 V
`
`0.25 pm (L998)
`0. l8pm__(fi99}
`
`66
`100
`100
`
`For a more complex system. we TMS32DC54l0 offers twice as
`much
`on-chip RAM and
`lower
`power
`consumption
`(0.5’l't':mWlMIP)
`than the TMS320VC549 [91, This allows a
`TMS320C54l0 powered system to tackle more algorithms and
`provide additional battery life.
`In the coming years. this trend
`will continue. providing greater on-chip memory integration and
`even lower power consumption.
`
`2.3.3 Amplifier
`The DSP outputs decompressed digital audio samples that are
`then convened into an analog signal by a DAC before being
`amplified.
`There are several classes of amplifier circuit
`technology topologies available for
`this
`system.
`Class-A
`amplifiers are based on a single gain transistor circuit. These
`class-A amplifiers produce good signal quality but have the
`major drawback of large power consumption. Class—B amplifiers
`introduced two complementary transistors at the gain stage. By
`shutting off both transistors when no signal is present. class-B
`amplifiers offered improved power consumption. However,
`shutting off both transistors introduced significant distortion into
`the signal at
`the zero crossover point.
`thus making these
`amplifiers unacceptable for quality audio applications. Class-AB
`amplifiers improve the signal quality of a class-B design by
`biasing the output transistors so that a little quiescent current
`flows during the
`aero crossover.
`This
`increases power
`consumption from a class-B design. but offers lower power
`consumption than a class-A circuit [10]. A good example is the
`
`2284
`
`(cid:51)(cid:68)(cid:74)(cid:72)(cid:3)(cid:19)(cid:19)(cid:19)(cid:19)(cid:21)
`
`

`
`Texas Instruments 'l'PA3t}2 300mW stereo audio amplifier. ideal
`for headphone applications [I 1].
`
`In the near fixture. class-AB amplifiers will be replaced in
`portable applications by class—D amplifiers because of improved
`power consumption efficiency offered by this circuit topology.
`
`1.2 _
`
`1.0 '
`
`0.3
`
`0.5
`
`0.4 "
`
`Power-Watts
`
`Class-D
`
`Class-AB
`
`Figure 2: Class-D Amplifier Efficiency.
`
`(PWM)
`pulse-width modulation
`use
`amplifiers
`Class-I)
`The
`techniques to produce the amplified analog output.
`amplifier outputs high frequency square-waves of varying width
`that, when properly filtered. provide quality audio at the output
`of the speaker. Pull-up and pull-down transistors are used in
`completely on and completely off states. Because it bias current
`is not required to produce the appropriate transistor states. the
`class-D amplifiers have increased power efficiency. As shown in
`Figure 2, a class-D amplifier dissipates roughly one-fourth the
`power of a class-AB amplifier [12]. This allows the class-D
`amplifier to generate nearly three times the effective battery life
`as a class—AB amplifier [13].
`The TPADOSIJ-02 from Texas lnstniments is a fully integrated
`class-D amplifier well
`suited for portable systems.
`The
`TPAOGSIJOZ, with an 30 load, provides up to a 2W RMS output
`power per channel with an 30% etfciency rating [14].
`Soon
`these class-D amplifiers will be designed for extremely low
`power portable applications.
`
`Future audio amplifiers will integrate the PWM. eliminating the
`need for the stereo DAC and the FWM generation in the class~D
`amplifier. The DSP can generate the PWM. leaving only pu1l—up
`and pu|l—dowu transistors. the I-l~bridge.
`in the amplifier. This
`integration will reduce system power consumption and cost.
`
`2.3.4 Storage Medium
`Non-volatile flash memory technology offers portability and
`ruggedness not available in disc based media. With the
`popularity of digital still cameras. two standards have emerged in
`the
`last
`few years: Compact!‘-'lash'W and
`Smartlllledia.
`CompactFtash"'" cards are available in capacities from 4MB to
`64MB. CornpaetFlash'm includes an ATA controller interface as
`well as the flash memory. This embedded controller allows for
`industry-standard compatibility with many systems. Srriartllrledia
`
`utilizes flash memory. but has no controller functions and is
`based on a single flash chip solution. This reduces its cost, but
`limits the capacity of the card. SmartMcd.ia cards are available in
`capacities of 2MB to BMB. CornpactFlashT“ is a better choice
`for solid a state audio system due to its large capacity.
`
`The CompactFlash""“ Association has defined 5V and 3.3V
`cards, but there are also allowances for lower voltage cards. With
`the availability of flash at 1.8V. the CornpactFlashT“ Association
`could easily incorporate a LSV CompactFlash""" card in its
`standard in the near future.
`
`2.3.5 Manual Input Device and Display
`
`The C5000 family of DSP devices provides a general purpose
`U0 bus for communicating with peripherals. including external
`interrupts to eliminate polling loops. To get an estimate of the
`power consumed by a display. we examined the Densitron
`LM40l2—'I'N ldxl character ‘LCD display. This LCD display is
`85mm x 36mm X l2.8mrn in volume and consumes lmA with a
`single 5V supply [15]. This LCD display has the primary
`advantage of using an LED haelolight and. therefore, does not
`require a voltage inverter. The back-light requires 30rru\ when
`lit.
`
`2.3.6 Batteries
`
`Two “AA" batteries provide the desired volume. weight. and
`current capacity for our player. Duracel|® “AA“ alkaline
`batteries provide 2,8S{JmA-hours of capacity [16]. At a current
`loading of 50m.A. Rayovac Reusable Alkaline” “
`" batteries
`provide approxirrtatiely l.700111A—hours of capacity and nickel-
`cedmium
`rechargeable batteries provide approitimately
`800n1.A-hours of capacity [17].
`
`2.4 System Performance
`
`This solid state audio player improves on current portable players
`by offering longer battery life, ruggedness. large data capacity.
`and small size.
`
`2.4.1 Battery Life
`some
`To compute the typical battery life of the system.
`An
`assumptions about
`the flash operation must be made.
`uncompressed 481:]-Iz.
`I6—bit data stream is equivalent to a data
`rate of 1.526 Mbitsis. For CD-quality audio. an MPEG-2 AAC
`compressed data strearn requires only I28ltbitsr's. The MPEG-2
`AAC algorithm requires a new frame of less than 688 bytes every
`43rns [4]. Assuming the flash sleeps for 40:115. consuming
`200pA. and is running for 3ms, consuming 45rn.A. the average
`current would be 3.3mA (or llmw}.
`
`All of the steady~state device U0 is driven by the transfer of the
`audio data stream.
`It is possible to estirnaoe that each sample will
`require an average of less than 50 pin toggles.
`If each pin has a
`capacitance of -10pF and the sample rate is 48kHz. the device 00
`power is approximately a single niilliwatt with 3.3V lJ'Os
`
`2285
`
`(cid:51)(cid:68)(cid:74)(cid:72)(cid:3)(cid:19)(cid:19)(cid:19)(cid:19)(cid:22)
`
`

`
`(cid:51)(cid:68)(cid:74)(cid:72)(cid:3)(cid:19)(cid:19)(cid:19)(cid:19)(cid:23)
`
`and cassette tape players. First, this syrrcm provides two to four
`times the battery life of current players
`Second. the media is
`durable and rugged
`Thir-3. high st-miconductor
`integration
`results in a small. lightweight player. Fl‘-'lI1h, the player provides
`large. high fidelity storage capacity that can be upgraded as flash
`technology improves. Finally. the pro -,rarnmable nature of the
`C54Jt allows for future compatibility with emerging standards
`and implernentations of additional featu. :5.
`
`4. REFERENCES
`
`[4]
`
`[5]
`
`[B]
`
`[9]
`
`SanDislt CompactFlash"'" webpage:
`DS df
`htt
`:.-itwww
`disk c
`dow loa CF
`[2] Cox J.. Killian J.. Leighton T.. and Sharnoon T.. “Secure
`Spread Spectrum Watermarking for Multimedia." Technical
`Report 95-I0. ©NEJ: Research institute.
`[3] ATSC T3.-'S‘l‘~{J‘|.6. "Digital Audio Compression (AC—3),“
`ATSC. July 1994.
`ISOIIEC I 1172-3 "International Standard: Coding of
`Moving Pictures and Associated Audio for Digital Storage
`media at up to about l.SMbitts.“ 1993.
`ISO.-‘IEC 13818-7 “MPEG-2 Advanced Audio
`Co-ding.AAC.” ISOHIEC. Apr I997.
`{6} Tsutsui. I(.. et. al.. "ATRAC: Adaptive Transform Coding
`for MiniDisc,"AES. San Francisco. October l992.
`[T] Pohlmann. K. C.. "The PASC Algorithm. Part 1." Mint
`Magazine, vol 16. no 3. March 1992.
`'TMS32OC54x. TMS320LC54x. '1“MS320V"C54.at Fixed-
`Point Digital Signal Processors," Literature #SPRS039B.
`Texas Instruments, February 1998.
`"l'MS3ZZOLJC5-410 Fixed-Point Digital Signal Processor."
`Texas instrurnents. March 1993.
`I10] Sodra A. and Smith K. Microelectronic Circuits. Saunders
`College Publsihing. Philadelphia. 199'].
`[I 1] "'1"PA302. TPASDZV 300-mw Stereo Audio Power
`Amplifier." Literature #SLOSl74A. Texas Instruments.
`March 1997.
`(121 Texas Instruments Mixed Signal and Analog Products‘
`“Cla.ss—D Amplifier Efficiency" web page:
`htm
`' www.t’
`I! c
`[13] Texas Instruments‘ "Semiconductors in the News" web
`page: http'.g[www.ti.g91;g_scJ51oestnewstl998.-’9§O69a.htm
`[14] '°'I'PAOtl5D(}2 Class-D Stereo Audio Power Amplifier.“
`Literature #3105227. Texas Instruments. August 1998.
`[15] "l Line X 16 Characters DCD Module." Literature #510138.
`Densitrort Corporation. CA.
`[16] Duraoell® webpage: http:r'lwww.tlt1raceli.corn
`[17] Rayovac webpage: http'lgwww.ra_y_o trac.c Int‘ e
`[18] "Portable CD Player SI.-S290 SL-S295 Operating
`Instructions." Panasonic. Japan, 1990.
`
`_ le 2: Powe Consurntionf the do s st.
`‘t im
`i SanDisk SDCFB—48—lDl Com
`bit-.1!-_VJ..
`
`i Texas Instruments TPAISZ Stereo Amlifier
`Z Densitron LM4012-TN l6xl LCD Disla |
`i
`I Device U0
`lt'rlW
`I
`- Vol .; Reulators 80% efficienc
`
`II T
`
`able 2 shows the power consumption for the individual
`components in the solid state audio system. For at 3‘! system.
`two “AA" batteries would be needed. For the l38mW system
`shown here.
`this would offer about 39 operating hours. For
`comparison. a typical CD player consumes 600m‘W and operates
`for approximately 9 hours on 2 “AA" batteries [I8].
`
`2.4.2 Storage Duration
`With CompactFlash cards supporting 64MB capacity, storage is
`currently available in siaeable quantities. Using the previously
`mentioned algorithms to compress the audio signal. these cards
`could store between 64 to 123 minutes of CD quality music. As
`flash technology progresses.
`the storage capacity will double.
`offering greater storage capacity than CDs and cassette tapes.
`
`2.4.3 Ruggedn
`The solid state audio system described here does not use any
`moving parts. allowing the system to be much more robust and
`reliable than those relying on moving media. This system does
`not have any magnetic heads. optical components. or motors that
`require care and maintenance. For solid state devices.
`typical
`reliability numbers are:
`3* Mean Time Between Failures
`1,000,000 hours.
`is Vibration resistance to ISG pealt~to—peak and
`> Shock resistance of 200013 (maximum).
`
`(MTBF) greater
`
`than
`
`2.4.4 Size and Weight
`
`The availability of compact packages. such as the microstar ball
`grid arrays (j1'BGA) and surface mount technology. allows for a
`very dense system. For example. the '['MS320VC549 is available
`in a 144-pin Microstar ball grid array package. with a volume of
`only
`12mm long.
`12mm Wide
`and
`1.4mm tall. The
`CompactFlash“‘ cards measure 36.4mm long. 42.8mm wide
`and 194mm tall with a weight of ll.4g. Due to the lack of any
`motors and mechanical components. the system is extremely
`light. with most of the weight due to the batteries.
`
`3. CONCLUSION
`
`This system proves the feasibility of using aTMS32OC50D0 135?
`as the processing engine of a solid state audio system.
`It also
`demonstrates several advantages over "AA" battery powered CD