Method for adjusting DDR working frequency through television demodulation SOC

Abstract

The invention relates to a method for adjusting DDR (Double Data Rate SDRAM) working frequency through a television demodulation SOC (System On Chip). When television signals are demodulated, interference caused by DDR action is transmitted to a channel demodulation module to reduce performance of the channel modulation module. The DDR working frequency chip adjusting method disclosed by the invention adopts a clock selector, a control state machine and two DDR clock sources, wherein the control state machine generates optimal selection signals according to a central frequency point F of a frequency band to be demodulated and a safe frequency point distance W; the control state machine controls the clock selector to select one of the two DDR clock sources as a signal output of DDR clocks. According to the method, a clock source selecting function to DDR is added in the television demodulation SOC chip, so that interference signals caused by DDR can be removed from a specific frequency band when a television program transmitted within the specific frequency band is demodulated, so as to reduce input noise of the channel demodulation module and improve properties of the channel demodulation module.

Description

technical field [0001] The invention belongs to the technical field of integrated circuits, and relates to a method for adjusting a DDR operating frequency by a television demodulation SOC chip. Background technique [0002] DDR SDRAM (Double Speed ​​Synchronous Dynamic Random Access Memory, referred to as DDR) is an important peripheral of the SOC (System On Chip, System On Chip) chip. The DDR interface has a high operating frequency and a large operating current, which will cause high conduction interference and radiation interference on the chip and circuit system. If the frequency band of the interference caused by DDR is not within the frequency band of the input signal of the sensitive circuit of the SOC, usually this interference will not affect the performance of the SOC. [0003] The TV demodulation SOC chip refers to the SOC that includes the TV transmission channel demodulation module. Commonly used TV channel demodulation modules include cable TV transmission s...

AI Technical Summary

Problems solved by technology

Since the video output clock must meet the video output standard, the frequency of the external crystal oscillator input clock must be kept constant and cannot be adjusted according to the method described in patent CN201320003017.3

The interference generated by the DDR clock in the TV demodulation SOC chip is an important interference faced by the channel demodulation module

The DDR clock is independent of the clock of the channel demodulation module, and it is impossible to reduce the interference generated by the DDR clock by adjusting the clock of the channel demodulation module according to the method described in patent CN201320003017.3

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