DVD player solution based on MT1389 single chip

0 Introduction
Since the launch of MTK's third-generation single-chip MT1389, it has been recognized by the industry for its high cost-effectiveness and has been widely used in domestic mainstream machines and some imported machines. Therefore, it is necessary to analyze the principle of the DVD system composed of the MT1389 single chip. The author has conducted a relatively comprehensive test on the DVD machine circuit composed of the MT1389 single chip, and combined with many years of practical experience and teaching results, the main working principle of this system has been analyzed for reference by colleagues and enthusiasts.

1 Basic composition of a single-chip DVD player composed of MT1389
1.1 Block diagram of a single-chip DVD system
1.2 Description of the composition of a single-chip DVD system
In Figure 1, MT1389 completes the functions of preamplification, digital servo control, system control, audio and video decoding, video encoding, video digital-to-analog conversion, and has built-in Ac-3 and DTS decoders, so it is also called a single-chip DVD system. The pin functions of MT1389 are shown in Figure 2.

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This chip can form a DVD system together with a driver IC, SDRAM memory, Flash-Rom memory, audio DAC digital/analog conversion circuit, etc. It integrates an analog signal front-end processor, a digital servo processor that can perform disc servo control, an AV decoder that can decode video signals in formats such as MPEGl/MPEG2/MPEG4/JPEG, and process audio signals in formats such as DVD-Audio/Dolby Digital (AC-3)/D-TS/MP3, and a built-in 32-bit CPU (RISC) for system control. It also contains 6 12-bit, 108-MHz digital video converters, which can provide image quality currently only available on high-priced models.
The system clock of this chip is completed by an external 27-MHz quartz crystal oscillator and internal circuits, and other system clocks can be obtained by PLL phase-locked loop frequency division. The power supply for the I/O interface part, analog and digital circuits is 3.3 V±0.15 V, and the internal CPU uses 1.8 V.
The system working storage area is an external SDRAM used as the system working storage area of ​​16Mbit~64Mbit (for AV decoding). The external FLASH-ROM memory can be selected from 8 Mbit to 64 Mbit.

2 Composition and working principle of the main circuit
2.1 Composition of the laser head reading control circuit
The laser head assembly of this machine adopts the HD60/62 dual-wavelength laser head produced by Japan Sanyo Company, which is connected to the mainboard by a 24-core flexible cable (see Figure 3). The specific description is as follows:

⑴, ⑵ focusing coil drive input terminal; ⑶, ⑷ tracking coil drive input terminal; ⑸, ⑹, ⑼, ⑽ CD/DVD photoelectric detection signal output terminal; ⑺ CD/DVD photoelectric detection signal selection output control input terminal; ⑻ CD/DVD radio frequency signal output terminal; ⑹, ⑽ three-beam tracking signal output terminal; ⒀ reference voltage input terminal; ⑿, 〔24〕 ground terminal; 〔14〕, 〔21〕 laser head component power supply (5 V) input terminal; 〔16〕, 〔22〕 empty pin; 〔17〕 CD laser diode power adjustment potentiometer selection signal input terminal; 〔18〕 DVD laser diode power adjustment potentiometer selection signal input terminal; 〔19〕 CD laser diode power input terminal; ⒇ laser power monitoring signal output terminal; 〔23〕 DVD laser diode power input terminal.
In Figure 3, A~D, E, F are photosensitive tubes for reading CD/VCD signals; a~d are photosensitive tubes for reading DVD signals. The ⑩ pin of the 24-pin socket of the laser head assembly is the working voltage of the photosensitive detector, the ⑩ pin is the reference voltage terminal, and the ⑦ pin is the CD/DVDRF signal output control terminal.
The focusing error signals of CD and DVD are respectively added to the ⑶~⑹ pins and ⑻~〔11〕 pins of the MTl389 from the ⑼, ⑽, ⑸, and ⑹ pins of the 24-pin connector of the laser head assembly. The tracking error signal of CD is connected to the 〔18〕 and 〔19〕 pins of MTl389D through the 〔11〕 and 〔15〕 pins of the 24-pin connector. The tracking error signal of DVD is still obtained by photosensitive tubes A, B, C, and D. The RF signal of CD is synthesized into an RF signal by the A~D photosensitive tubes in the laser head assembly and connected to the ⑹ pin of the MTl389 through the flexible cable and the ⑻ pin of the 24-pin connector. DVD is an RF signal, which is synthesized into RF signal by photosensitive tubes a~d in the laser head assembly, and added to the ⑻ pin of the 24-pin connector through the flexible cable and connected to the ⑹ pin of MTl389 through C141. As for whether the output of CONl⑻ pin is CD or DVDRF signal, it is determined by the level of IOA signal added to the ⑺ pin of the 24-pin connector.
2.2 Laser diode power control circuit
2.2.1 Circuit structure It
is mainly composed of the internal circuit of 1389〔22〕,〔23〕 pins and components such as Q1 and Q2, and the working voltage is +3.3 V/5 V, as shown in Figure 4.

2.2.2 Working Principle (Self-test Process When No CD Is Installed)
The LD01 control signal outputted from the 1389〔23〕pin is added to the base of Q1, and the signal LD02 outputted from its〔22〕pin is added to the base of Q2. When the machine is turned on (without a CD), if LD01 is low level and LD02 is high level, the base of Q1 is low level at this time. Since its emitter is high level, Q1 is turned on, and the +3.3 V voltage is added to the emitter of Q1 through R1, and a voltage of about 2.2 V is generated on the collector. This voltage is added to the〔19〕pin of the 24-pin connector through L1, and is added to the CD laser diode of the laser head assembly through the 24-pin flexible cable, causing it to emit light. Since there is no disc on the movement tray, LD01 quickly becomes high level, while LD02 becomes low level, making the base of Q2 low level. After it is turned on, there is a voltage of about 2.2 V on the collector, which is added to the 〔23〕 pin of the 24-pin connector through L2 and then connected to the DVD laser diode through a flexible flat cable to make it work. After repeating this process, LD01 and LD02 are both high level, and the CD and DVD laser diodes do not emit light. The movement self-test ends, and the machine is in the state of waiting for the disc to be loaded. [page]

2.3 Laser head power adjustment potentiometer selection circuit (CD/DVD mode selection circuit)
2.3.1 Circuit composition It is
mainly composed of the internal circuit of pin 1389〔93〕 and components such as Q1, Q2, Q3, etc. The working voltage is +5 V, as shown in Figure 5.

2.3.2 Working Principle
When the signal IOA of the 1389〔93〕pin is low, it is added to the base of Q1 through R1, making its collector high, and added to the gate of Q3 through R3, making it saturated and conducting. Since the drain of Q3 is grounded, its source is also equivalent to grounding, which will make one end of the VR-DVD (DVD laser diode power potentiometer) on the laser head assembly grounded, and the photosensitive diode PD in the laser head is also connected to its other end. At this time, the monitoring signal taken out from the ⒇ pin of the 24-pin socket of the laser head assembly reflects the working condition of the DVD laser diode. This signal is input through the ⒇ and 〔21〕pins of 1389, and is processed by the internal APC circuit to control the level of LD02, thereby achieving the purpose of controlling the light intensity of the laser diode. In addition, when IOA is low, it is also added to the ⑺ pin of the 24-pin connector, so that the laser head assembly outputs the composite signal of photosensitive tubes a~d, that is, the DVDRF signal, which is output from the ⑻ pin of the 24-pin connector.
It can be seen that in DVD state, IOA signal is low level. When IOA is high level, Q1 collector is low level, Q3 is cut off; high level is added to Q2 gate through R2, making it saturated and turned on, ⒄ pin of 24-pin connector is grounded, VR-CD on laser head is selected, and the monitoring signal on CONl⒇ pin reflects the working condition of CD laser diode. This signal is also added to ⒇ and 〔21〕 pins of 1389D, so that the level of LD01 is controlled, so as to achieve the purpose of controlling CD laser tube. In addition, this high level signal selects the composite signal of A~D photosensitive tube, that is, CDRF signal, which is also output from ⑻ pin of 24-pin connector. It can be seen that in CD state, 10A is high level.
2.4 System control circuit
After the system is powered on, the reset signal is input from 1389 (105) pin to reset the system CPU. The CPU reads the operating software in the Flash-Rom and stores the read data in the random dynamic memory SDRAM. The 1389 internal reduced instruction set processor (RISC) initializes the CPU I/O interface and the input and output interfaces of each unit. When the system works normally, the optical disc signal read by the laser head assembly is input from the 1389 pin (6). After being processed by the internal RF signal amplifier and servo signal processor, the video data signal is sent to the video decoder for decoding, and then the analog video signal is output through the digital video signal converter; the digital audio signal output by the audio digital signal processor is output from the audio output unit from the (164) to (166) pins to the audio DAC. The spindle, feed, tracking and focus signals in the servo signal are output from the pins (37), (38), (41) and (42) respectively to control the servo signal driver.

3 Conclusion
Through the test of typical models, the signal flow and working principle of the main circuit of the whole machine are analyzed more comprehensively, practically and accurately. The single-chip DVD player has a compact structure, small size, low power consumption, relatively complete functions, and rich audio and video output interfaces. The DVD system based on the single-chip MTl389 is not only the mainstream of desktop DVD players, but also can be easily composed of portable DVD players, car DVD players, TV/DVD combination players, etc.