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MT352 COFDM Demodulator
Data Sheet Features
* * * * * * * * * * * * * * * * * Nordig II and ETSI 300 744 compliant Superior Single Frequency Network performance Unique active Impulse-Noise filtering Single SAW operation Automatic co-channel and adjacent-channel interference suppression Clock generation from single low-cost 20.48 MHz crystal or external 4 or 27 MHz clock IF sampling at 4.57, 36.17 or 43.5 MHz from a single crystal frequency Channel bandwidth of 6, 7 & 8 MHz Blind acquisition capability (including 2 K / 8 K mode detect) Automatic spectral inversion detection Fast auto-scan and acquisition technology Very low software overhead Dual AGC control option Access to channel SNR, pre- and post-Viterbi bit error rates Compact 64 pin LQFP Less than 0.22 W power consumption Standby and sleep options
February 2005
Ordering Information MT352/CG/GP1N 64 Pin LQFP Trays MT352/CG/GP1Q 64 Pin LQFP Tape & Reel MT352/CG/GP2Q 64 Pin LQFP* Tape & Reel MT352/CG/GP2N 64 Pin LQFP* Trays * Pb Free Matte Tin 0o C to +70oC
Zarlink evaluation kits include application board, TNIM and supporting software based on industry standard operating systems. Device drivers are also available enabling rapid product development and reduction in time to market.
Description
MT352 is a superior third generation Coded Orthogonal Frequency Division Multiplex (COFDM) television demodulator that is both Nordig II and DVB (as defined in ETS 300 744 specification) compliant. It can be used in either 2 K or 8 K modes with 6, 7 or 8 MHz channels and is capable of addressing all modes of transmission. The device includes a high performance 10-bit A/D converter capable of accepting direct IF at 36.17 or 43.75 MHz. Sampling rates required for both these frequencies in 6,7 or 8 MHz OFDM channels can be generated from a single 20.48 MHz crystal. Alternatively, there is provision to replace this crystal with a 4 or 27 MHz external clock input.
Applications
* * * * * Set-top boxes Integrated digital televisions Personal video recorders Terrestrial PC reception Mobile and portable applications
RF in
ADC
IF to Baseband conversion & Interpolator
FFT
Pilot & Channel Processor
Symbol & Bit De-interleaver & Demapper
FEC MPEG TS
AGC Impulse Suppression Secondary 2-wire bus Symbol, Carrier & Timing Recovery
Tuner control
Control engine
Primary 2-wire bus
Figure 1 - Block Diagram
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Zarlink Semiconductor Inc. Zarlink, ZL and the Zarlink Semiconductor logo are trademarks of Zarlink Semiconductor Inc. Copyright 2003-2005, Zarlink Semiconductor Inc. All Rights Reserved.
MT352
Data Sheet
Unique algorithms that actively filter out impulse noise, without affecting normal performance, have been implemented. This reduces the interference effect from vehicles and electrical appliances, which is known to have significant detrimental effect on the quality of digital TV reception. Programming is simplified utilizing a high level command driven interface. A sophisticated engine controls all acquisition and tracking operations as well as controlling the tuner via a 2-wire bus. Any frequency range can be automatically scanned for digital TV channels. This mechanism ensures minimal interaction, maximum flexibility, fastest acquisition and the fastest auto scan capability of any chip in the market. Blind acquisition mode enables automatic detection of all OFDM signal parameters, including mode, guard and spectral inversion. The frequency capture range is sufficient to compensate for the combined offset introduced by the tuner and broadcaster. The device is packaged in a 64 pin LQFP and consumes less than 220 mW of power.
MT352 CG YYWW*W *
Pin 1 Corner
Figure 2 - Package Outline
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MT352
Pin Description
Pin Description Table Pin No MPEG pins 47 48 49-53, 56-58 61 62 63 11 6 Control pins 4 5 23 24 10 12, 15-18 44 35 36 42 41 43 9 27 26 Analog inputs 30 31 Supply pins VIN VIN positive input negative input I I CLK1 DATA1 XTI XTO SLEEP SADD(4:0) SMTEST CLK2/GPP0 DATA2/GPP1 AGC1 AGC2/GPP2 GPP(3) RESET OSCMODE PLLTEST Device power down Serial address set Scan mode enable Serial clock tuner Serial data tuner Primary AGC Secondary AGC General purpose I/O Device reset Crystal oscillator mode PLL analogue test Serial clock Serial data Low phase noise oscillator I I/O I O I I I I/O I/O O I/O I/O I I O CMOS CMOS Open drain CMOS CMOS Open drain 5 5 MOSTRT MOVAL MDO(0:7) MOCLK BKERR MICLK STATUS IRQ MPEG packet start MPEG data valid MPEG data bus MPEG clock out Block error MPEG clock in Status output Interrupt output O O O O O I O O Open drain CMOS CMOS Tristate Name Description I/O Type
Data Sheet
V
mA
3*3 3*3 3*3 3*3 3*3 3*3 3*3 5
1 1 1 1 1
1 6
6
3*3 3*3 3*3 5 5 5 5 5 5 3*3 6 6 6 6 6
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Zarlink Semiconductor Inc.
MT352
Pin Description Table (continued) Pin No 21 22 7, 19, 37, 39, 59, 64 2, 13, 45, 54, 1, 3, 8, 14, 20, 25, 38, 40, 46, 55, 60 28 29, 32 33 34 Name PLLVDD PLLGND CVDD VDD GND AVDD AGND DVDD DGND ADC digital supply Core logic power I/O ring power Core and I/O ground ADC analog supply Description PLL supply I/O S S S S S S S S S Type V 1*8 0 1*8 3*3 0 1*8 0 1*8 0
Data Sheet
mA
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Zarlink Semiconductor Inc.
MT352 Table of Contents
Data Sheet
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Pin Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.0 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1.1 Analogue-to-Digital Converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1.2 Automatic Gain Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1.3 IF to Baseband Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1.4 Adjacent Channel Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.5 Interpolation and Clock Synchronisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.6 Carrier Frequency Synchronisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.7 Symbol Timing Synchronisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.8 Fast Fourier Transform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.9 Common Phase Error Correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.10 Channel Equalisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.11 Impulse Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.12 Transmission Parameter Signalling (TPS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 1.13 De-Mapper. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 1.14 Symbol and Bit De-Interleaving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 1.15 Viterbi Decoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 1.16 MPEG Frame Aligner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 1.17 De-interleaver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 1.18 Reed-Solomon Decoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 1.19 De-scrambler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 1.20 MPEG Transport Interface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2.0 Software control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3.0 Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3.1 2-Wire Bus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 3.2 Host . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 3.2.1 Tuner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 3.2.2 Examples of 2-Wire Bus Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.2.3 Primary 2-Wire Bus Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.3 MPEG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3.3.1 Data Output Header Format. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3.3.2 MPEG data output signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 3.3.3 MPEG Output Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 3.3.3.1 MOCLKINV = 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.3.3.2 MOCLKINV = 0. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 4.0 Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 4.1 Recommended Operating Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 4.2 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 4.3 DC Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 4.4 Crystal Specification and External Clocking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 5.0 Application Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
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MT352 List of Figures
Data Sheet
Figure 1 - Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Figure 2 - Package Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Figure 3 - OFDM Demodulator Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Figure 4 - FEC Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Figure 5 - Primary Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Figure 6 - Primary 2-Wire Bus Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Figure 7 - DVB Transport Packet Header Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Figure 8 - MPEG Output Data Waveforms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Figure 9 - MPEG Timing - MOCLKINV = 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Figure 10 - MPEG Timing - MOCLKINV = 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Figure 11 - Crystal Oscillator Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Figure 12 - Typical Application Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
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MT352 List of Tables
Data Sheet
Table 1 - Programmable Address Details for 2-Wire Bus in TNIM Evaluation Application. . . . . . . . . . . . . . . . . . . 13 Table 2 - Timing of 2-Wire Bus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Table 3 - MOCLKINV = 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Table 4 - MDOSWAP = 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Table 5 - MDOSWAP = 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
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MT352
1.0 Functional Description
Data Sheet
A functional block diagram of the MT352 OFDM demodulator is shown in Figure 3. This accepts an IF analogue signal and delivers a stream of demodulated soft decision data to the on-chip Viterbi decoder. Clock, timing and frequency synchronization operations are all digital and there are no analogue control loops except the AGC. The frequency capture range is large enough for all practical applications. This demodulator has novel algorithms to combat impulse noise as well as co-channel and adjacent channel interference. If the modulation is hierarchical, the OFDM outputs both high and low priority data streams. Only one of these streams is FEC-decoded, but the FEC can be switched from one stream to another with minimal interruption to the transport stream.
Figure 3 - OFDM Demodulator Diagram The FEC module shown in Figure 4 consists of a concatenated convolutional (Viterbi) and Reed-Solomon decoder separated by a depth-12 convolutional de-interleaver. The Viterbi decoder operates on 5-bit soft decisions to provide the best performance over a wide range of channel conditions. The trace-back depth of 128 ensures minimum loss of performance due to inevitable survivor truncation, especially at high code rates. Both the Viterbi and Reed-Solomon decoders are equipped with bit-error monitors. The former provides the bit error rate (BER) at the OFDM output. The latter is the more useful measure as it gives the Viterbi output BER. The error collecting intervals of these are programmable over a very wide range.
Figure 4 - FEC Block Diagram The FSM controller shown in Figure 3 above controls both the demodulator and the FEC. It also drives the 2-wire bus to the tuner. The controller facilitates the automated search of all parameters or any sub-set of parameters of the received signal. It can also be used to scan any defined frequency range searching for OFDM channels. This
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MT352
Data Sheet
mechanism provides the fast channel scan and acquisition performance, whilst requiring minimal software overhead in the host driver. The algorithms and architectures used in the MT352 have been heavily optimized to minimize hardware and chip area. This is proven by its 220 mW (typical) power consumption, which is the lowest of any OFDM device in the market today.
1.1
Analogue-to-Digital Converter
The MT352 has a high performance 10-bit analogue-to-digital converter (ADC) which can sample a 6, 7 or 8 MHz bandwidth OFDM signal, with its spectrum centred at: * * * * * 4.57 MHz near-zero IF 36.17 MHz IF 43.75 MHz IF Crystal oscillator with a 20.48 MHz crystal 4 MHz or 27 MHz clock input
The ADC can be clocked using:
An on-chip programmable phase locked loop (PLL) is used to generate the ADC sampling clock. The crystal frequency of 20.48 MHz is used for 36.17 MHz IF sampling and 19.6267 MHz is used for 43.75 MHz IF sampling. Note that this 19.6267 MHz sampling clock can be generated from the 20.48 MHz crystal by appropriately programming the PLL. Hence the same 20.48 MHz crystal can support 6, 7 and 8 MHz OFDM as well as 36.17 and 43.75 MHz IF.
1.2
Automatic Gain Control
An AGC module compares the absolute value of the digitized signal with a programmable reference. The error signal is filtered and is used to control the gain of the amplifier. A sigma-delta modulated output is provided, which has to be RC low-pass filtered to obtain the voltage to control the amplifier. Upper and lower limits can be set to the AGC control voltage using registers. The programmable AGC reference has been optimized. A large value for the reference leads to excessive ADC clipping and a small value results in excessive quantization noise. Hence the optimum value has been determined assuming the input signal amplitude to be Gaussian distributed. The latter is justified by applying the central limit theorem in statistics to the OFDM signal, which consists of a large number of randomly modulated carriers. This reference or target value may have to be lowered slightly for some applications. Slope control bits have been provided for the AGCs and these have to be set correctly depending on the Gain-versus-Voltage slope of the gain control amplifiers. The bandwidth of the AGC is set to a large value for quick acquisition then reduced to a small value for tracking. The AGC is free running during OFDM channel changes and locks to the new channel while the tuner lock is being established. This is one of the features of MT352 used to minimize acquisition time. A robust AGC lock mechanism is provided and the other parts of the MT352 begin to acquire only after the AGC has locked. Two AGC control outputs are available, one to drive an RF amplifier and the other to control an IF amplifier. The parameters for both loops are programmable. In the default mode, only the IF AGC loop is activated.
1.3
IF to Baseband Conversion
Sampling a 36.17 MHz IF signal at 20.48 MHz results in a spectrally inverted OFDM signal centred at 4.79 MHz. Sampling a 43.75 MHz IF signal at 19.6267 MHz gives a non-inverted signal at 4.5 MHz. The first step of the demodulation process is to convert this signal to a complex (in-phase and quadrature) signal in baseband. A correction for spectral inversion is implemented during this conversion process. Note also that the MT352 has control mechanisms to search automatically for an unknown spectral inversion status.
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1.4 Adjacent Channel Filtering
Data Sheet
Adjacent channels, in particular the Nicam digital sound signal associated with analogue channels, are filtered prior to the FFT.
1.5
Interpolation and Clock Synchronisation
MT352 uses digital timing recovery and this eliminates the need for an external VCXO. The ADC samples the signal at a fixed rate, for example, 20.48 MHz. Conversion of the 20.48 MHz signal to the OFDM sample rate is achieved using the time-varying interpolator. The OFDM sample rate is 64/7 MHz for 8 MHz and this is scaled by factors 6/8 and 7/8 for 6 and 7 MHz channel bandwidths. The nominal ratio of the ADC to OFDM sample rate is programmed in a MT352 register (defaults are for 20.48 MHz sampling and 8 MHz OFDM). The clock recovery phase locked loop in the MT352 compensates for inaccuracies in this ratio due to uncertainties of the frequency of the sampling clock.
1.6
Carrier Frequency Synchronisation
There can be frequency offsets in the signal at the input to OFDM, partly due to tuner step size and partly due to broadcast frequency shifts, typically 1/6 MHz. These are tracked out digitally, without the need for an analogue frequency control (AFC) loop. The default frequency capture range has been set to 285 kHz in the 2 K mode and 142 kHz in the 8 K mode. However, these values can be doubled, if necessary, by programming an on-chip register. It is recommended that this larger capture range be used for channel scan in order to find channels with broadcast frequency shifts, without having to adjust the tuner. After the OFDM module has locked, the frequency offset can be read from an on-chip register.
1.7
Symbol Timing Synchronisation
This module computes the optimum sample position to trigger the FFT in order to eliminate or minimize intersymbol interference in the presence of multi-path distortion. Furthermore, this trigger point is continuously updated to dynamically adapt to time-variations in the transmission channel.
1.8
Fast Fourier Transform
The FFT module uses the trigger information from the timing synchronization module to set the start point for an FFT. It then uses either a 2 K or 8K FFT to transform the data from the time domain to the frequency domain. An extremely hardware-efficient and highly accurate algorithm has been used for this purpose.
1.9
Common Phase Error Correction
This module subtracts the common phase offset from all the carriers of the OFDM signal to minimize the effect of the tuner phase noise on system performance.
1.10
Channel Equalisation
This consists of two parts. The first part involves estimating the channel frequency response from pilot information. Efficient algorithms have been used to track time-varying channels with a minimum of hardware. The second part involves applying a correction to the data carriers based on the estimated frequency response of the channel. This module also generates dynamic channel state information (CSI) for every carrier in every symbol.
1.11
Impulse Filtering
MT352 contains several mechanisms to reduce the impact of impulse noise on system performance.
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1.12 Transmission Parameter Signalling (TPS)
Data Sheet
An OFDM frame consists of 68 symbols and a superframe is made up of four such frames. There is a set of TPS carriers in every symbol and all these carry one bit of TPS. These bits, when combined, include information about the transmission mode, guard ratio, constellation, hierarchy and code rate, as defined in ETS 300 744. In addition, the first eight bits of the cell identifier are contained in even frames and the second eight bits of the cell identifier are in odd frames. The TPS module extracts all the TPS data, and presents these to the host processor in a structured manner.
1.13
De-Mapper
This module generates soft decisions for demodulated bits using the channel-equalized in-phase and quadrature components of the data carriers as well as per-carrier channel state information (CSI). The de-mapping algorithm depends on the constellation (QPSK, 16QAM or 64QAM) and the hierarchy = 0, 1, 2 or 3). Soft decisions for both low- and high-priority data streams are generated.
1.14
Symbol and Bit De-Interleaving
The OFDM transmitter interleaves the bits within each carrier and also the carriers within each symbol. The deinterleaver modules consist largely of memory to invert these interleaving functions and present the soft decisions to the FEC in the original order.
1.15
Viterbi Decoder
The Viterbi decoder accepts the 5-bit soft decision data from the OFDM demodulator and outputs a decoded bitstream. The decoder does the de-puncturing of the input data for all code rates other than 1/2. It then evaluates the branch metrics and passes these to a 64-state path-metric updating unit, which in turn outputs a 64-bit word to the survivor memory. The Viterbi decoded bits are obtained by tracing back the survivor paths in this memory. A traceback depth of 128 is used to minimize any loss in performance, especially at high code rates. The decoder re-encodes the decoded bits and compares these with received data (delayed) to compute bit errors at its input, on the assumption that the Viterbi output BER is significantly lower than its input BER.
1.16
MPEG Frame Aligner
The Viterbi decoded bit stream is aligned into 204-byte frames. A robust synchronization algorithm is used to ensure correct lock and to prevent loss of lock due to noise impulses.
1.17
De-interleaver
Errors at the Viterbi output occur in bursts and the function of the de-interleaver is to spread these errors over a number of 204-byte frames to give the Reed-Solomon decoder a better chance of correcting these. The deinterleaver is a memory unit which implements the inverse of the convolutional interleaving function introduced by the transmitter.
1.18
Reed-Solomon Decoder
Every 188-byte transport packet is encoded by the transmitter into a 204-byte frame, using a truncated version of a systematic (255,239) Reed-Solomon code. The corresponding (204,188) Reed-Solomon decoder is capable of correcting up to eight byte errors in a 204-byte frame. It may also detect frames with more than eight byte errors. In addition to efficiently performing this decoding function, the Reed-Solomon decoder in MT352 keeps a count of the number of bit errors corrected over a programmable period and the number of uncorrectable blocks. This information can be used to compute the post-Viterbi BER.
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1.19 De-scrambler
Data Sheet
The de-scrambler de-randomizes the Reed-Solomon decoded data by generating the exclusive-OR of this with a pseudo-random bit sequence (PRBS). This outputs 188-byte MPEG transports packets. The TEI bit of the packet header is set to indicate uncorrectable packets.
1.20
MPEG Transport Interface
MPEG data can be output in parallel or serial mode. The output clock frequency is automatically chosen to present the MPEG data as uniformly spaced as possible to the transport processor. This frequency depends on the guard ratio, constellation, hierarchy and code rate. There is also an option for the data to be extracted from the MT352 with a clock provided by the user.
2.0
Software control
Acquisition of an OFDM channel and frequency scan for OFDM channels are controlled by an on-chip state machine, which minimizes the software requirement in the host processor. To acquire a channel, the host programs the channel frequency in the MT352. The on-chip state machine then writes the frequency information to the tuner, awaits tuner lock and acquires the OFDM channel to generate the transport stream. The controller can be made to automatically search for every parameter in the OFDM signal, including spectral inversion status. Furthermore, this controller will re-acquire the channel in the event of an interruption to the incoming signal. To scan a frequency range, the host programs the start and end frequencies for the search as well as the step size, which defaults to 8 MHz. The MT352 then automatically scans the frequency range by appropriately programming the tuner and searching for OFDM signals. Once a channel has been located, the host is interrupted to read the channel information from the MT352. Then MT352 continues the search. By default, only the channels which can generate a reliable transport stream are reported, but there is also provision for locating very weak channels. The frequency capture range of MT352 can be maximized to capture channels with frequency offsets without reprogramming the tuner, in both 2 K and 8 K modes. The above approach to channel acquisition and scan has resulted in very fast acquisition and scan times whilst minimizing software overhead in the host processor. Furthermore, all this functionality has very efficiently been mapped into hardware to result in a device consuming less than 220 mW of power.
3.0
Interfaces
Figure 5 - Primary Interfaces The MT352 interfaces to other parts of a terrestrial receiver system can be partitioned into three groups: the host controller, the tuner and the MPEG decoder. One other pin, the Status output, is multi-functional and can directly
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Data Sheet
drive a LED to show the status of a range of different internal lock flags. Alternatively, it can drive an audio transducer to give an audio frequency that is dependent upon the error rate of the received signal. This feature can be used for faster installation of a system where the aerial may need to be adjusted, as signal strength is not the best guide for the optimum aerial position for COFDM reception.
3.1 3.2
* *
2-Wire Bus Host
DATA1 (pin 5) serial data, the most significant bit is sent first. CLK1 (pin 4) serial clock.
The primary 2-wire bus serial interface uses pins:
The 2-wire bus address is determined by applying VDD or VSS to the SADD[4:0] pins. In the current TNIM evaluation application, the 2-wire bus address is 0001 111 R/ W with the pins connected as follows: ADDR[7] VSS ADDR[6] VSS ADDR[5] SADD[4] VSS ADDR[4] SADD[3] VDD ADDR[3] SADD[2] VDD ADDR[2] SADD[1] VDD ADDR[1] SADD[0] VDD
Not programmable
Table 1 - Programmable Address Details for 2-Wire Bus in TNIM Evaluation Application When the MT352 is powered up, the RESET pin 28 should be held low for at least 50ms after VDD has reached normal operation levels. As the RESET pin goes high, the logic levels on SADD[4:0] are latched as the 2-wire bus address. ADDR[0] is the R/ W bit. The circuit works as a slave transmitter with the lsb set high or as a slave receiver with the lsb set low. In receive mode, the first data byte is written to the RADD virtual register, which forms the register sub-address. The RADD register takes an 8-bit value that determines which of 256 possible register addresses is written to by the following byte. Not all addresses are valid and many are reserved registers that must not be changed from their default values. Multiple byte reads or writes will auto-increment the value in RADD, but care should be taken not to access the reserved registers accidentally. Following a valid chip address, the 2-wire bus STOP command resets the RADD register to 00. If the chip address is not recognized, the MT352 will ignore all activity until a valid chip address is received. The 2-wire bus START command does NOT reset the RADD register to 00. This allows a combined 2-wire bus message, to point to a particular read register with a write command, followed immediately with a read data command. If required, this could next be followed with a write command to continue from the latest address. RADD would not be sent in this case. Finally, a STOP command should be sent to free the bus. When the 2-wire bus is addressed (after a recognized STOP command) with the read bit set, the first byte read out is the contents of register 00.
3.2.1
Tuner
The MT352 has a General Purpose Port that can be configured to provide a secondary 2-wire bus. Master control mode is selected by a single register control bit. The allocation of the pins is: GPP0 pin 35 = CLK2, GPP1 pin 36 = DATA2.
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3.2.2 Examples of 2-Wire Bus Messages
KEY: S P A Italics Start Condition Stop condition Acknowledge MT352 output W R NA RADD Write (=0) Read (= 1) NOT Acknowledge Register Address
Data Sheet
Write operation - as a slave receiver: S DEVICE ADDRESS Read operation - MT352 as a slave transmitter: S DEVICE ADDRESS R A DATA (reg 0) A DATA (reg 1) A DATA (reg 2) NA P W A RADD (n) A DATA (reg n) A DATA (reg n+1) A P
Write/read operation with repeated start - MT352 as a slave transmitter: S DEVICE ADDRESS W A RADD (n) A S DEVICE ADDRESS R A DATA (reg n) A DATA (reg n+1) NA P
3.2.3
Primary 2-Wire Bus Timing
Figure 6 - Primary 2-Wire Bus Timing Where: S = Start Sr = Restart, i.e., start without stopping first. P = Stop.
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Value Min. 0 200 200 1300 600 200 100 100 note 1 20 200 Max. 450
Data Sheet
Parameter CLK clock frequency (Primary) Bus free time between a STOP and START condition Hold time (repeated) START condition LOW period of CLK clock HIGH period of CLK clock Set-up time for a repeated START condition Data hold time (when input) Data set-up time Rise time of both CLK and DATA signal. Fall time of both CLK and DATA signals, (100 pF to ground) Set-up time for a STOP condition
Symbol fCLK tBUFF tHD;STA tLOW tHIGH tSU;STA tHD;DAT tSU;DAT tR tF tSU;STO Table 2 - Timing of 2-Wire Bus
Unit kHz ns ns ns ns ns ns ns ns ns ns
Note 1. The rise time depends on the external bus pull up resistor. Loading prevents full speed operation.
3.3 3.3.1
MPEG Data Output Header Format
Figure 7 - DVB Transport Packet Header Byte
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Data Sheet
After decoding the 188-byte MPEG packet, it is output on the MDO pins in 188 consecutive clock cycles. Additionally when the ENTEI bit in the CONFIG register (0x8A) is set high (default), the TEI bit of any uncorrectable packet will automatically be set to '1'. If ENTEI bit is low then TEI bit will not be changed (but note that if this bit is already 1, for example, due to a channel error which has not been corrected, it will remain high at output).
3.3.2
MPEG data output signals
The MPEGEN bit in the CONFIG register must be set low to enable the MPEG data. The maximum movement in the packet synchronization byte position is limited to 1 output clock period. MOCLK will be a continuously running clock once symbol lock has been achieved, and is derived from the symbol clock. In Figure 8, MOCLK is shown in with MOCLKINV = '1', the default state. All output data and signals (MDO[7:0], MOSTRT, MOVAL & BKERR) change on the negative edge of MOCLK (MOCLKINV = 1) to present stable data and signals on the positive edge of the clock. A complete packet is output on MDO[7:0] on 188 consecutive clocks and the MDO[7:0] pins will remain low during the inter-packet gaps. MOSTRT goes high for the first byte clock of a packet. MOVAL goes high on the first byte of a packet and remains high until the last byte has been clocked out. BKERR goes low on the first byte of a packet where uncorrectable bytes are detected and will remain low until the last byte has been clocked out.
Figure 8 - MPEG Output Data Waveforms
3.3.3
MPEG Output Timing
Maximum delay conditions: VDD = 3.0 V, CVDD = 1.62 V, Tamb = 70oC, Output load = 10 pF Minimum delay conditions: VDD = 3.6 V, CVDD = 1.98 V, Tamb = 0oC, Output load = 10 pF MOCLK frequency = 61.44 MHz.
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3.3.3.1 MOCLKINV = 1
Parameter Data output delay tD Setup Time tSU Hold Time tH Maximum Delay Conditions 7 ns 0.5 ns 8 ns Minimum Delay Conditions 0.3 ns 5 ns 8 ns Table 3 - MOCLKINV = 1
Data Sheet
The setup time is due to the delay on MOSTRT, MOVAL and BKERR. MDO[0] is faster since it uses a stronger output driver cell.
Figure 9 - MPEG Timing - MOCLKINV = 1
3.3.3.2
MOCLKINV = 0
MDOSWAP = 0 Parameter Data output delay tD Setup Time tSU Hold Time tH Maximum Delay Conditions 8 ns 8 ns 1.5 ns Table 4 - MDOSWAP = 0 Minimum Delay Conditions 0.7 ns 15 ns 0.5 ns
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Data Sheet
The hold time is due to the fast output on MDO[0]. If MDOSWAP is set to 1 the data output is on MDO[7] which has a slower driver. This improves the hold time: MDOSWAP = 1 Parameter Data output delay tD Setup Time tSU Hold Time tH Maximum Delay Conditions 8 ns 8 ns 3 ns Table 5 - MDOSWAP = 1 Minimum Delay Conditions 0.7 ns 15 ns 1.2 ns
Figure 10 - MPEG Timing - MOCLKINV = 0
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4.0
4.1
Data Sheet
Electrical Characteristics
Recommended Operating Conditions
Recommended Operating Conditions Table
Parameter Power supply voltage: periphery core Power supply current: periphery 1 core Input clock frequency 2 CLK1 primary serial clock frequency Ambient operating temperature ADC Input Impedance @ 36 MHz Symbol VDD CVDD IDDP IDDC XTI fCLK 0 2 16*00 3*0 1*62 Min. Typ. 3*3 1*8 1 120 20*48 25*00 450 70 Max. 3*6 1*98 Units V V mA mA MHz kHz C k
1. Current from the 3*3 VV supply will be mainly dependent on the external loads. 2. The min/max frequencies given are those supported by the oscillator cell. Frequencies outside these limits are acceptable with an external clock signal.
4.2
Absolute maximum ratings
Absolute Maximum Ratings Table Parameter Power supply Voltage on input pins (5 V rated) Voltage on input pins (3.3 V rated) Voltage on output pins (5 V rated) Voltage on output pins (3.3 V rated) Storage temperature Operating ambient temperature Junction temperature Symbol VDD CVDD VI VI VO VO TSTG TOP TJ Min. -0.3 -0.3 -0.3 -0.3 -0.3 -0.3 -55 0 +3.6 +2.0 5.5 VDD + 0.3 5.5 VDD + 0.3 150 70 125 Max. V V V V V V C C C Unit
Note: Stresses exceeding these listed under absolute maximum ratings may induce failure. Exposure to absolute maximum ratings for extended periods may reduce reliability. Functionality at or above these conditions is not implied.
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4.3 DC Electrical Characteristics
Parameter Operating voltage core Supply current Supply current sleep mode Outputs IOH 2 mA 3.0 > VDD > 3.6 Output levels IOL 2 mA 3.0 > VDD > 3.6 IOL 6 mA 3.0 > VDD > 3.6 GPP(3:0), DATA1, AGC1, AGC2, IRQ MDO(7:0), MOVAL, MOSTRT, MOCLK, Output capacitance Not including track STATUS, BKERR GPP(3:0), DATA1, AGC1, AGC2 IRQ Output leakage (tri-state) Inputs Input levels 3.0 > VDD > 3.6 -0.5 Vin VDD+0.5 V Input levels 3.0 > VDD > 3.6 -0.5 Vin +5.5 V Input levels Input leakage Current Input capacitance Input capacitance 3.0 > VDD > 3.6 Capacitances do not include track All inputs SLEEP, SMTEST, MICLK, CLK1, OSCMODE SADD(4:0), DATA1, GPP(3:0) VIL MICLK, SADD(4:0), SLEEP, OSCMODE GPP(3:0), CLK1, DATA1, RESET VIH 2.0 3.6 VOL MDO(7:0), MOVAL, MOSTRT, MOCLK, STATUS, BKERR VOL VOH 2.4 1.62 > CVDD > 1.98 CVDD IDDCORE 1.62 1.8 120 200 periphery Conditions Pins Symbol VDD Min. 3.0 Typ. 3.3
Data Sheet
Max. 3.6
Unit V
1.98
V mA A
V
0.4
V
0.4
V
3.0
pF
pF
1
A
V
VIH
2.0
V
0.8 1 1.8 3.6
V A pF pF
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4.4 Crystal Specification and External Clocking
Parallel resonant fundamental frequency (preferred) Tolerance over operating temperature range Tolerance overall Typical load capacitance Drive level Equivalent series resistance
XTI XTO
Data Sheet
20.4800 MHz 25 ppm 50 ppm 27 pF 0.4 mW max. <50
OSCMODE
XT1
C1
C2
Figure 11 - Crystal Oscillator Circuit
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5.0 Application Circuit
Data Sheet
Figure 12 - Typical Application Circuit
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