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Low-pass filter for sampling at small duty ratio

A technology of low-pass filter and duty cycle, applied in the direction of frequency selection two-terminal pair network, multi-terminal pair network, etc., can solve the problem of increasing chip cost, increasing filter voltage error, and increasing sensitivity of leakage current in resistors and other issues to achieve the effect of saving chip cost and reducing capacitor area

Pending Publication Date: 2021-10-08
SOUTHCHIP SEMICON TECH SHANGHAI CO LTD
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In semiconductor chips, the density of capacitors is generally low. In order to achieve a large capacitance value, it needs to occupy a large chip area and increase the cost of the chip.
On the other hand, although the resistance density is high, the resistance value cannot be increased blindly, because an excessively large resistance will increase the sensitivity to the leakage current in the resistance and increase the voltage error of the filter

Method used

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  • Low-pass filter for sampling at small duty ratio
  • Low-pass filter for sampling at small duty ratio
  • Low-pass filter for sampling at small duty ratio

Examples

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Embodiment Construction

[0014] The present invention will be described in detail below in conjunction with the accompanying drawings.

[0015] figure 2 It is a low-pass filter block diagram of switched capacitor sampling. It can be seen that by adding a sampling switch in front of the ordinary RC filter, the switching frequency is Fsw and the duty cycle is D.

[0016] image 3 Compare the output waveforms of a normal low-pass filter and a switched-capacitor low-pass filter. Among them, VIN is the input waveform, a square wave with a frequency of 1KHZ, VOUT1 is the output waveform of the ordinary low-pass filter, and VOUT2 is the output waveform of the switched capacitor low-pass filter. The capacitor value used by the switched capacitor low-pass filter is 1 / 10 of the capacitor value of the ordinary low-pass filter.

[0017] It can be seen that the waveforms of the two are very close, and the time constant of the main envelope is exactly the same. In fact, almost the same filtering effect can be ...

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Abstract

The invention belongs to the technical field of analog circuits, and particularly relates to a low-pass filter for small-duty-ratio sampling. The filter comprises a capacitor and a resistor, and further comprises a sampling switch; the starting end of the sampling switch is connected with an input end, the other end of the sampling switch is grounded after passing through the resistor and the capacitor in sequence, and the connecting point of the resistor and the capacitor is an output end; and the duty ratio of the sampling switch is less than 1. The invention has the beneficial effects that the capacitance area can be greatly reduced, and the chip cost is saved.

Description

technical field [0001] The invention belongs to the technical field of analog circuits, and in particular relates to a sampling low-pass filter with a small duty cycle. Background technique [0002] figure 1 It is an RC filter composed of ordinary resistors and capacitors, and its cut-off frequency is determined by the reciprocal of the product of resistors and capacitors [0003] [0004] In order to achieve a very low cutoff frequency, a large RC constant is required. In semiconductor chips, the density of capacitors is generally low. In order to realize a larger capacitance value, it needs to occupy a large chip area and increase the cost of the chip. On the other hand, although the resistance density is high, the resistance value cannot be increased blindly, because an excessively large resistance will increase the sensitivity to the leakage current in the resistance and increase the voltage error of the filter. Contents of the invention [0005] Aiming at the ab...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H03H11/04
CPCH03H11/04
Inventor 陈俊宇
Owner SOUTHCHIP SEMICON TECH SHANGHAI CO LTD
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