Sanyo LA7693X series super chip principle analysis - Power Circuit - Circuit Diagram

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Sanyo LA7693X series super chip actually integrates the original single-chip TV small signal processor LA76820 and microprocessor LC85F4538 into the same chip. It is widely used in Sanyo CK14/CK21D/CK25D (PuPing TV series), CK15F/CK21F/ CK25F/CK29F (flat flat TV series) and other popular color motor hearts. The Sanyo LA super chip introduced in China mainly includes LA76930E and LA76932E. Their internal circuit structure and pin sequence are the same. The main difference is the difference between the CPU part ROM memory and the user RAM memory. The LA76930 external crystal frequency is 32kHz for 21-inch color motor type; the LA76932 external crystal frequency is 32.768kHz for 26/29/34-inch large-screen color TV.

The super chip LA76932 consists of three parts: TV signal processor, microcontroller and on-screen OSD. The typical application circuit is shown in the figure.

I. TV signal processing section * fast. AGC controlled high gain IF amplifier (three-stage gain up to 65dB).

* Video demodulation is accomplished using a PLL phase-locked loop synchronous detector that does not require adjustment.

* PLL phase-locked loop audio IF demodulation to eliminate the inherent buzzer interference caused by internal carrier reception and improve sound quality.

* Built-in video and audio AV/TV switch selection switch.

* Built-in chrominance signal trap, bandpass filter, skin tone correction circuit.

* Built-in brightness delay line, aperture correction circuit, nuclear noise reduction circuit and black level extension circuit, the image quality is significantly improved.

* PAL/NTSC color signal demodulation with single crystal, SECAM color difference interface, and debugless SECAM decoder chip (LA7642), can complete PAL/NTSC/SECAM three color system decoding.

* Built-in 1H baseband delay circuit.

* Built-in automatic dynamic balance AKB system, not only can automatically complete the white balance adjustment, but also always maintain the white balance correctness.

* The field scanning circuit adopts dual automatic frequency adjustment and 50/60Hz automatic recognition. The size of the field picture remains constant when there is no signal.

2. Microprocessor Control Section* Built-in 3 oscillators: RC oscillator for system clock: VCO voltage controlled oscillator for system clock and OSD clock. The external crystal oscillator is used for time base timing, system clock, and PLL phase-locked loop control reference clock with a frequency of 32.768kHz.

* CPU execution instruction cycle time is 0.848μs, bus cycle time is 0.424μs; programming ROM capacity is 32kB, CGROM capacity is 16kB, RAM capacity is 512B, on-screen display (OSD) RAM is 352×9 bits.

* Built-in 5-channel 8-bit DAC, 3-channel 7-bit PWM output, two 16-bit timer/counters, one 14-bit timebase timer, one 8-bit synchronous serial interface and I2C bus compatible interface; with ROM correction Function, 15 interrupt sources and 9 card quantization interrupt systems, fully integrated system clock generator and display clock generator, crystal clock adopts PLL control mode.

3. OSD display characteristic screen display: 36×16 dot matrix (set by software), display range 36 dots×8 lines, control range 8 dots×8 lines, maximum display characters 252, each divided into 16×7 dot matrix and 8× 9 dot matrix two parts, display 16 colors, 16 background colors, character edge / shadow color 16 kinds, with smooth, underline and italic characters and other display effects, can display 臼, Chinese and English.