CN213426567U

CN213426567U - PCB board crystal oscillator wiring structure

Info

Publication number: CN213426567U
Application number: CN202022872610.4U
Authority: CN
Inventors: 舒进权
Original assignee: Shanghai Visteon Automotive Electronic Systems Co ltd
Current assignee: Shanghai Visteon Automotive Electronic Systems Co ltd
Priority date: 2020-12-02
Filing date: 2020-12-02
Publication date: 2021-06-11
Anticipated expiration: 2030-12-02

Abstract

The utility model relates to a PCB crystal oscillator wiring structure, wherein the PCB comprises a plurality of signal layers which are arranged in a mutually stacked way and are used for transmitting signals, and a crystal oscillator module is arranged on one outer signal layer; the crystal oscillator module comprises a crystal oscillator, a first capacitor and a second capacitor; the second pin of the crystal oscillator is connected with the first capacitor, and the first pin of the crystal oscillator is connected with the second capacitor; the other ends of the first capacitor and the second capacitor are connected and are connected to the reference ground of the adjacent signal layer through a single-point grounding via hole. Compared with the prior scheme, the prior layout is more compact, and the interference shielding capability of the crystal oscillator module is stronger. Thereby improving the stability of the upper system.

Description

PCB board crystal oscillator wiring structure

Technical Field

The utility model relates to an automobile intelligent control technical field especially relates to a PCB board brilliant wiring structure that shakes.

Background

At present, in the design of printed circuit boards in the automotive field, the clock signal is high in speed and sensitive and easy to interfere, but the signal is extremely important to the stability of the whole system. The following principles are thus applied to the layout and routing of the passive crystal oscillator circuit on the printed circuit board:

1. the layout of the crystal oscillator module is as close to the chip end as possible, and the crystal oscillator and the chip need to be on the same plane, so as to reduce the wiring length, thereby reducing the possibility of interference and interference.

2. For the crystal oscillator module, copper is required to be paved around the module, so that the whole module is isolated from the outside, and the purpose of shielding the outside interference is achieved.

3. The line width of the signal line impedance 50 Ω is tightly controlled for the passive crystal oscillator signal and adjacent layers must be referenced to ground to ensure the integrity of the signal over the entire path and its return path (reference plane) for the signal.

This presents more crosstalk problems as the trend of today's printed circuit boards is moving towards high density and small area. As shown in fig. 1, in the conventional design, the ground of the matching capacitors C1 and C2 of the passive crystal oscillator Y1 and the ground of the protection crystal oscillator module are interconnected, so that other signals near the ground of the protection may couple interference to the ground of the protection, thereby indirectly affecting the ground of the matching capacitors of the crystal oscillator, which may result in the quality degradation of the signals output by the crystal oscillator, seriously affecting the stability of the whole system, resulting in a long development period and a cost problem of redeveloping the printed circuit board.

To the defect that prior art exists, provide the utility model discloses.

SUMMERY OF THE UTILITY MODEL

The embodiment of the utility model provides a purpose is to prior art structural shortcoming, provides a PCB board crystal oscillator wiring structure, and this design separates the protection ground of crystal oscillator module itself and the inside matching electric capacity's of crystal oscillator module differentiation to solve the problem that the ground is disturbed. Furthermore, this solution makes the whole body more compact, so that the interconnection of the clocks can be made shorter, which means better signal integrity and less possibility of interference.

In order to achieve the above object, an embodiment of the present invention provides a PCB board crystal oscillator wiring structure, which is realized through the following technical scheme:

a PCB crystal oscillator wiring structure is disclosed, wherein the PCB comprises a plurality of signal layers which are mutually stacked and used for transmitting signals, and a crystal oscillator module is arranged on one outer signal layer; the crystal oscillator module comprises a crystal oscillator, a first capacitor and a second capacitor; the second pin of the crystal oscillator is connected with the first capacitor, and the first pin of the crystal oscillator is connected with the second capacitor; the method is characterized in that: the other ends of the first capacitor and the second capacitor are connected and are connected to the reference ground of the adjacent signal layer through a single-point grounding via hole.

The via hole is a through hole, and the diameter of the through hole is not less than 0.30 mm.

The diameter of the through hole is 0.30mm-0.50 mm.

The diameter of the through hole is 0.35 mm.

The PCB further comprises a controller, wherein the controller comprises a clock input pin and a clock output pin, the clock input pin is respectively connected with the second pin of the crystal oscillator and the first capacitor through a resistor, and the clock output pin is respectively connected with the first pin of the crystal oscillator and the second capacitor and used for driving the crystal oscillator to form a clock signal.

And a protection ground for protecting the crystal oscillator module is also arranged on the signal layer provided with the crystal oscillator module.

Compared with the prior art, the beneficial effects of the utility model are that: the whole crystal oscillator module is connected with the system ground in a single-point ground mode, so that the crystal oscillator module is protected to have a cleaner ground, and a more stable clock is provided for the system. Compared with the prior scheme, the prior layout is more compact, and the interference shielding capability of the crystal oscillator module is stronger. Thereby improving the stability of the upper system.

Drawings

The above features and advantages of the present invention will become more apparent and readily appreciated from the following description of the exemplary embodiments thereof taken in conjunction with the accompanying drawings.

FIG. 1 is a prior art PCB crystal oscillator module design;

fig. 2 is a schematic structural diagram of a signal layer of a PCB board with a crystal oscillator module according to an embodiment of the present invention;

fig. 3 is a schematic circuit diagram of a crystal oscillator module according to an embodiment of the present invention.

Detailed Description

The invention will be described in further detail below with reference to the accompanying drawings so as to facilitate understanding by those skilled in the art:

reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are exemplary and intended to be used for explaining the present invention, and should not be construed as limiting the present invention.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "horizontal", "top", "bottom", "inner", "outer", "circumferential", and the like, indicate orientations and positional relationships based on the orientations and positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the device or element so referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the present invention.

In the present application, unless expressly stated or limited otherwise, the first feature may be directly on or directly under the second feature or indirectly via intermediate members. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

As shown in fig. 3, which is a schematic diagram of the crystal oscillator module, the clock input pin and the clock output pin of the controller (vehicle-mounted MCU), the resistor R1, the crystal oscillator Y1, the first capacitor C1, and the second capacitor C2 are arranged from left to right in sequence. The clock input pin is respectively connected with a second pin of a crystal oscillator Y1 and a first capacitor C1 through a resistor R1; the clock output pin is respectively connected with the first pin and the second capacitor of the crystal oscillator Y1 through C2, and is used for driving the crystal oscillator Y1 to form a clock signal. The second pin of the crystal oscillator Y1 is connected with the first capacitor C1, and the first pin of the crystal oscillator Y1 is connected with the second capacitor C2. The other ends of the first capacitor C1 and the second capacitor C2 are connected to ground.

Referring to fig. 2, fig. 2 is an interconnection form on a printed circuit board, and unlike the prior art, a first capacitor C1 and a second capacitor C2 are connected to a reference ground of an adjacent signal layer through a single-point ground via.

For high speed clock signals, the parasitic inductance of vias in Printed Circuit Boards (PCBs) is more important than the parasitic capacitance. As clock rates increase, their signals become more and more sensitive to inductance. The through holes are all through holes.

There is an approximation of the magnitude of the inductance for a via as follows: l-5.08 h [ In (4h/d) +1]

Where L is the via inductance, unit nH

h is the via length, in

d-via diameter, in

For the same product, the length of the through hole is fixed, so that the larger through hole can obtain smaller inductance, and the influence on the clock is smaller. However, the large through holes mean that a larger layout and routing space is required, and the cost is also required to be larger. It is therefore necessary to select a suitably sized through hole, with a diameter (inner diameter) of 0.30mm to 0.5mm being a relatively preferred embodiment.

The diameter (inner diameter) of the through hole selected in the embodiment is 0.35mm, and the outer diameter is 0.65 mm.

The embodiment of the present invention is evaluated by the following experiments:

two oscillation circuits of fig. 1 and 3 were fabricated using an AH03200009 passive crystal oscillator of type TXC. The parameter information of the crystal oscillator is shown in table 1:

table 1:

the following evaluation items were used:

and (4) measuring the resonance frequency of the quartz crystal by using a signal analyzer in a wireless non-contact mode at room temperature.

And (3) measuring the peak-peak value of the waveform voltage of the resonance signal by contacting a quartz crystal pin with a voltage probe of an oscilloscope at room temperature.

And (3) starting oscillation time, namely connecting one channel of an oscilloscope with a chip direct current power supply point and connecting the other channel with a quartz crystal pin under the room temperature condition. After starting up, the starting position of the direct current power supply is selected as the starting point, the position where the amplitude of the oscillation signal reaches 80% of the stable oscillation amplitude is selected as the end point, and the time difference of the starting point and the end point is the oscillation starting time. (reference standard IEC-60679-6)

And power consumption is the power consumed by the quartz crystal oscillator under the room temperature condition.

Negative resistance (| -R |). the maximum negative resistance provided by the quartz crystal oscillation circuit under the condition of room temperature. (reference standard IEC-60444 method B)

The frequency-temperature characteristic is the change characteristic of the resonance frequency of the quartz crystal under the condition of continuous change of the temperature of minus 40 ℃ to plus 85 ℃.

The room temperature condition refers to that the humidity is 50-70% in an open space at 25 ℃ (+/-3 ℃).

Frequency deviation is (resonance frequency-nominal frequency)/nominal frequency, and relative frequency deviation is frequency deviation-single own frequency deviation (FL).

In the above evaluation experiment, the following instruments were used:

s & A250B quartz crystal electrical characteristic measuring system

Electrical characteristics of the upper plate of the quartz crystal oscillator:

and (4) evaluation results:

the electrical characteristics (room temperature conditions) of the quartz crystal oscillator are shown in table 2:

table 2:

the electrical characteristics of the upper plate of the quartz crystal oscillator are shown in table 3:

table 3: initial state C12017-8 pF, C12016-8 pF

Can find out by above-mentioned aassessment project, the embodiment of the utility model provides an in the operating temperature range of whole crystal oscillator, its frequency deviation all is superior to prior art, possesses more stable clock frequency.

It should be noted that the above is a detailed description of the present invention, and it should not be considered that the present invention is limited to the specific embodiments, and those skilled in the art can make various modifications and variations on the above embodiments without departing from the scope of the present invention.

Claims

1. A PCB crystal oscillator wiring structure is disclosed, wherein the PCB comprises a plurality of signal layers which are mutually stacked and used for transmitting signals, and a crystal oscillator module is arranged on one outer signal layer; the crystal oscillator module comprises a crystal oscillator, a first capacitor and a second capacitor; the second pin of the crystal oscillator is connected with the first capacitor, and the first pin of the crystal oscillator is connected with the second capacitor; the method is characterized in that: the other ends of the first capacitor and the second capacitor are connected and are connected to the reference ground of the adjacent signal layer through a single-point grounding via hole.

2. The PCB board crystal oscillator wiring structure of claim 1, wherein: the via hole is a through hole, and the diameter of the through hole is not less than 0.30 mm.

3. The PCB board crystal oscillator wiring structure of claim 2, wherein: the diameter of the through hole is 0.30mm-0.50 mm.

4. The PCB board crystal oscillator wiring structure of claim 3, wherein: the diameter of the through hole is 0.35 mm.

5. The PCB board crystal oscillator wiring structure of claim 4, wherein: the PCB further comprises a controller, wherein the controller comprises a clock input pin and a clock output pin, the clock input pin is respectively connected with the second pin of the crystal oscillator and the first capacitor through a resistor, and the clock output pin is respectively connected with the first pin of the crystal oscillator and the second capacitor and used for driving the crystal oscillator to form a clock signal.

6. The PCB board crystal oscillator wiring structure of claim 5, wherein: and a protection ground for protecting the crystal oscillator module is also arranged on the signal layer provided with the crystal oscillator module.