USB clock generation circuit

A clock generation circuit and circuit technology, applied in the direction of electrical digital data processing, instruments, etc., can solve the problems of slow start of crystal oscillator, limited product flexibility, expensive price, etc., and achieve the effect of ensuring application requirements

CN111597133AActive Publication Date: 2020-08-28成都盛芯微科技有限公司
4 Cites 0 Cited by

Patent Information

Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Publication Date
2020-08-28

Smart Images

  • Figure 1
    Figure 1
  • Figure 2
    Figure 2
  • Figure 3
    Figure 3
Patent Text Reader

Abstract

The invention discloses a USB clock generation circuit, which comprises a crystal oscillator circuit module and an RC oscillator module for providing a clock signal for the USB module, and is characterized in that the RC oscillator module is connected to the crystal oscillator circuit module and receives a reference clock provided by the crystal oscillator circuit module; the RC oscillator modulecomprises an RCO sub-circuit, a synchronous pulse generation sub-circuit, a counter sub-circuit, a switch control sub-circuit and a clock synthesis sub-circuit; the RCO sub-circuit outputs a first control signal; the synchronous pulse generation sub-circuit is connected to the crystal oscillation circuit module and outputs a second control signal; the counter sub-circuit is connected with the RCOsub-circuit and the synchronous pulse generation sub-circuit and outputs a third control signal; and the clock synthesis sub-circuit outputs a clock signal required by the USB module after operation.According to the technical scheme, the reference clock is provided through the crystal oscillator circuit module, and the synchronous pulse generation sub-circuit is added to enable the reference clock to synchronize the RCO sub-circuit, and the application requirement of the full-speed USB clock is met.
Need to check novelty before this filing date? Find Prior Art

Description

technical field

[0001] The invention relates to the technical field of integrated circuits, in particular to a USB clock generating circuit. Background technique

[0002] At present, in SOC (System-on-a-Chip, system on chip), there are usually two types of methods for providing clocks for digital circuits:

[0003] 1. Use a crystal oscillator to generate a reference clock, and then multiply the frequency by the internal PLL (Phase Locked Loop) to generate the required clock frequency, such as figure 1 shown. The advantage of this method is: high frequency accuracy; the disadvantage is: the start-up of the crystal oscillator is slow, usually more than 1ms, resulting in a long wait for the start-up of the digital circuit.

[0004] 2. The RC oscillator is used, and after calibration, a more accurate clock is provided to the digital circuit, such as figure 2 shown. The method has the advantages of fast start-up, simple circuit and low cost. The disadvantage is: the frequen...

Examples

Embodiment Construction

[0031] It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

[0032] The present invention will be further described below in conjunction with the accompanying drawings.

[0033] An embodiment of the present invention provides a USB clock generating circuit for generating a low-cost full-speed USB clock. The USB clock can be used not only for a USB module, but also for scenarios such as an MCU.

[0034] Such as image 3 , Figure 4As shown, the USB clock generation circuit includes a crystal oscillator circuit module, and the circuit also includes an RC oscillator module that provides a clock signal for the USB module, and the RC oscillator module is connected to the crystal oscillator circuit module and receives the crystal oscillator circuit module The reference clock CK_XO provided; the RC oscillator module includes an RCO subcircuit, a synchronous pulse generation subcircu...