TWI756143B - Load capacitance calculation system and load capacitance calculation method for crystal oscillator - Google Patents

Abstract

A load capacitance calculation system for a crystal oscillator includes a database, an operating interface, a processing module, a designated crystal capacitance search module, a chip pin capacitance search module, and a circuit board wiring capacitance search module. The load capacitance calculation method for the crystal oscillator in first is provided the operating interface for a user to input a crystal part number, a chip part number, a circuit board material type and a wiring length, and then the designated crystal capacitance search module and the chip pin capacitance search module, and the circuit board wiring capacitance search module find a crystal capacitance value, a chip pin capacitance value and a circuit board wiring capacitance value from the database; finally, calculate an external load capacitance value with the crystal capacitance value and the chip pin capacitance value and the circuit board wiring capacitance value.

Description

Load capacitance calculation system and load capacitance calculation method of crystal oscillator

The present invention relates to a computing system and a computing method, in particular to a load capacitance computing system and a load capacitance computing method of a crystal oscillator.

Generally speaking, in electronic circuits, crystal oscillators are usually used to synchronize operations, or as a reference for frequency. Among them, most common crystal oscillators are based on crystals such as quartz, and the natural frequency of crystal oscillators often depends on the size and cutting method of the crystal.

As mentioned above, the selection of crystal applications usually needs to consider the resonance frequency, load capacitance, excitation power, temperature characteristics and long-term stability. Among these factors, the load capacitance can directly affect the stability of the crystal oscillator. The general calculation formula of load capacitance is: Ce=2*CL-(Ci+Cs); among them, Ce is the external load capacitance value (External Load Capacitor Value), and CL is the specified crystal capacitive load (Specified Crystal Capacitive Load). ), Ci is the IC pin Capacitance, and Cs is the wiring capacitance on the PCB, including the capacitance of the crystal pad (PCB Trace Capacitance (include crystal pad capacitance)).

In the prior art, when the user wants to calculate the load content required by the crystal oscillator, it is usually necessary to search for the information provided by the manufacturer according to the crystal part number and the chip part number, so as to obtain the capacitive load value of the crystal and the IC value. The capacitance value of the pin, and then according to the design scheme corresponding to the material of the circuit board and the wiring length to find out the capacitance value of the PCB board wiring, and finally the capacitive load value of the crystal, the capacitance value of the IC pin and the PCB board wiring. Substitute the capacitance value into the above calculation formula of the external load capacitance value to obtain the load capacitance required by the crystal oscillator. However, most of the existing capacitance parameter search methods rely on manual search, which is very inconvenient, and the found parameters also need to be The calculation is performed manually, so that the user needs to spend more time and effort to know the load content required by the crystal oscillator.

In view of the prior art, when the user wants to know the load capacitance required by the crystal oscillator, he usually uses the crystal part number, chip part number, circuit board material type and wiring length to search and compare the data. Therefore, the main purpose of the present invention is to provide a load capacitance calculation system and a load capacitance calculation method of a crystal oscillator, which can Quickly know the load capacitance required for a crystal oscillator.

In order to solve the problems of the prior art, the necessary technical means adopted by the present invention is to provide a load capacitance calculation system of a crystal oscillator, which includes a database, an operation interface, a processing module, a specified crystal capacitance search module, a A chip pin capacitance search module and a circuit board wiring capacitance search module.

The database stores a specified crystal capacitance load comparison table, a chip pin capacitance comparison table, and a circuit board wiring capacitance comparison table.

The operation interface is for the user to input a crystal part number, a chip part number, a circuit board material type and a wiring length.

The processing module is electrically connected to the operation interface for sending a specified crystal capacitance search signal according to the crystal part number, a chip pin capacitance search signal according to the chip part number, and a circuit board material model and wiring length. A circuit board wiring capacitance search signal is sent out.

The specified crystal capacitance search module is electrically connected to the processing module and the database, and is used to search out a crystal capacitance value corresponding to the crystal part number from the specified crystal capacitance load comparison table according to the specified crystal capacitance search signal, and to find the crystal capacitance value corresponding to the crystal part number. The capacitance value is sent to the processing module.

The chip pin capacitance search module is electrically connected to the processing module and the database, and is used to find a chip pin capacitance value corresponding to the chip part number from the chip pin capacitance comparison table according to the chip pin capacitance search signal , and transmit the chip pin capacitance value to the processing module.

The circuit board wiring capacitance search module is electrically connected to the processing module and the database, and is used to find a circuit corresponding to the circuit board material type and wiring length from the circuit board wiring capacitance comparison table according to the circuit board wiring capacitance search signal board routing capacitance value and transmit the board routing capacitance value to the processing module.

The processing module further calculates an external load capacitance value according to the crystal capacitance value, the chip pin capacitance value and the circuit board wiring capacitance value.

In an auxiliary technical means derived from the above-mentioned necessary technical means, the processing module further includes a calculation unit. The calculation unit has a built-in load capacitance calculation formula. The calculation unit calculates the crystal capacitance value, the chip pin capacitance value and the circuit board wiring. The capacitance value is substituted into the load capacitance calculation formula to calculate the external load capacitance value. Preferably, the load capacitance calculation formula is Ce=2*CL-(Ci+Cs), where Ce is the external load capacitance, CL is the crystal capacitance, Ci is the chip pin capacitance, and Cs is the circuit board wiring capacitance.

In an auxiliary technical means derived from the above-mentioned necessary technical means, the specified crystal capacitance search module inputs the crystal part number into a specified crystal capacitance search function, so as to search out the crystal capacitance value from the specified crystal capacitance load comparison table.

In an auxiliary technical means derived from the above-mentioned necessary technical means, the chip lead capacitance search module inputs the chip part number into a chip lead capacitance search function, so as to find the chip lead from the chip lead capacitance comparison table capacitance value.

In an auxiliary technical means derived from the above necessary technical means, the circuit board wiring capacitance search module inputs the circuit board material type and wiring length into a circuit board wiring capacitance search function, so as to search from the circuit board wiring capacitance comparison table output the board routing capacitance value.

In order to solve the problems of the prior art, another necessary technical means adopted by the present invention is to provide a method for calculating the load capacitance of a crystal oscillator, which includes the following steps (A) to (C).

Step (A) is to provide an operation interface for the user to input a crystal part number, a chip part number, a circuit board material type and a wiring length. Step (B) is to find out a crystal capacitance value from a specified crystal capacitance load comparison table according to the crystal part number, find out a chip pin capacitance value from a chip pin capacitance comparison table according to the chip part number, and according to the circuit board The material type and wiring length are used to find a circuit board wiring capacitance value from a circuit board wiring capacitance comparison table.

Finally, step (C) is to calculate an external load capacitance value according to the crystal capacitance value, the chip pin capacitance value and the circuit board wiring capacitance value.

In an auxiliary technical means derived from the above necessary technical means, step (B) is to use a specified crystal capacitance search module to input the crystal capacitance value into a specified crystal capacitance search function, so as to obtain the specified crystal capacitance load from the specified crystal capacitance load comparison table. Find out the crystal capacitance value.

In an auxiliary technical means derived from the above-mentioned necessary technical means, step (B) is to use a chip lead capacitance search module to input the chip lead capacitance value into a chip lead capacitance search function, so as to obtain the chip lead capacitance value from the chip lead capacitance value. Find the chip pin capacitance value in the comparison table.

In an auxiliary technical means derived from the above-mentioned necessary technical means, step (B) is to use a circuit board wiring capacitance search module to input the circuit board material type and wiring length into a circuit board wiring capacitance search function, so as to obtain from the circuit board Find the wiring capacitance value of the circuit board in the wiring capacitance comparison table.

As mentioned above, the load capacitance calculation system and load capacitance calculation method of the crystal oscillator provided by the present invention mainly provide an operation interface for the user to input the crystal part number, chip part number, circuit board material type and wiring length, and then Use the specified crystal capacitor search module to find the crystal capacitance value from the specified crystal capacitor load comparison table according to the crystal part number, and use the chip pin capacitance search module to find the chip lead from the chip pin capacitance comparison table according to the chip part number. The pin capacitance value, and the circuit board wiring capacitance search module is used to find the circuit board wiring capacitance value from the circuit board wiring capacitance comparison table according to the circuit board material type and wiring length. The pin capacitance value and the circuit board wiring capacitance value are respectively substituted into the load capacitance calculation formula, and the external load capacitance value can be quickly and conveniently calculated for the user's reference.

The specific embodiments adopted by the present invention will be further described by the following embodiments and drawings.

Please refer to the first figure, the first figure is a system block diagram of the load capacitance calculation system of the crystal oscillator provided by the preferred embodiment of the present invention. As shown in the first figure, a load capacitance calculation system 100 for a crystal oscillator includes a database 1, an operation interface 2, a processing module 3, a specified crystal capacitance search module 4, and a chip pin capacitance search module Group 5 and a circuit board wiring capacitance search module 6 .

The database 1 stores a specified crystal capacitance load comparison table 11 , a chip pin capacitance comparison table 12 , and a circuit board wiring capacitance comparison table 13 . Wherein, the database 1 may be stored in a smart phone, a computer host, a tablet computer or a remote server, for example.

In this embodiment, an example of the specified crystal capacitance load comparison table 11 is as follows: Crystal part number Crystal capacitance value (pf) 7W25000034 15 7W25000061 15 SSP025000FFCH-S 15 7W25000025 15 6N33000129 15 7W50000024 15

In this embodiment, an example of the chip pin capacitance comparison table 12 is as follows: Wafer part number Chip capacitance (pf) 88E1514-A0-NNP2C000 5 USX2065-JZH-TR 2

In this embodiment, an example of the circuit board wiring capacitance comparison table 13 is as follows: Circuit board material model Wiring Length (mil) Board Layout Capacitance Value (pf) NPG-170D/RTF(H1) 500 1.75 NPG-170D/RTF(H1) 600 2.1 NPG-170D/RTF(H1) 700 2.45 NPG-170D/RTF(H1) 800 2.8 NPG-170D/RTF(H1) 900 3.15 NPG-170D/RTF(H1) 1000 3.5 NPG-170D/RTF(H1) 1100 3.85 NPG-170D/RTF(H1) 1200 4.2

The operation interface 2 is for the user to input a crystal part number, a chip part number, a circuit board material type and a wiring length. In this embodiment, the above-mentioned crystal part number, chip part number and circuit board material number are the serial numbers provided by the manufacturer, but are not limited to this. In other embodiments, they can also be user-defined serial numbers. There may be more than two numbers on the same item. In addition, the operation interface 2 is displayed by, for example, a smart phone, a tablet computer or a computer host, and the displayed screen actually has a plurality of inputs corresponding to the crystal part number, chip part number, circuit board material type and wiring length. A grid is used for the user to input the crystal part number, wafer part number, circuit board material type and wiring length.

The processing module 3 is electrically connected to the operation interface 2 for sending a specified crystal capacitance search signal (not shown in the figure) according to the crystal part number, and a chip pin capacitance search signal (not shown in the figure) according to the chip part number shown), and send a circuit board wiring capacitance search signal (not shown) according to the type of circuit board material and wiring length. In practice, the processing module 3 is, for example, a computing module in a smart phone, a tablet computer, or a computer host.

The specified crystal capacitance search module 4 is electrically connected to the processing module 3 and the specified crystal capacitance load comparison table 11 of the database 1, and is used to find out a correspondence from the specified crystal capacitance load comparison table 11 according to the specified crystal capacitance search signal The crystal capacitance value of the crystal part number is sent to the processing module 3 .

In this embodiment, the specified crystal capacitance search module 4 inputs the crystal material number into a specified crystal capacitance search function, so as to search out the crystal capacitance value from the specified crystal capacitance load comparison table 11; wherein, the specified crystal capacitance search function For example, corresponding to the search function established in the specified crystal capacitance load comparison table 11, the corresponding crystal capacitance value can be found from the specified crystal capacitance load comparison table 11 according to the input crystal part number.

The chip pin capacitance search module 5 is electrically connected to the processing module 3 and the chip pin capacitance comparison table 12 of the database 1, and is used for searching out the chip pin capacitance comparison table 12 according to the chip pin capacitance search signal. A chip pin capacitance value corresponding to the chip part number, and the chip pin capacitance value is sent to the processing module 3 .

In this embodiment, the chip lead capacitance search module 5 inputs the chip part number into a chip lead capacitance search function, so as to find the chip lead capacitance value from the chip lead capacitance comparison table 12; The pin capacitance lookup function is, for example, a lookup function corresponding to the lookup function established in the chip pin capacitance comparison table 12, and the corresponding chip pin capacitance can be found from the chip pin capacitance comparison table 12 according to the input chip part number. value.

The circuit board wiring capacitance search module 6 is electrically connected to the processing module 3 and the circuit board wiring capacitance comparison table 13 of the database 1, and is used to search out the circuit board wiring capacitance comparison table 13 according to the circuit board wiring capacitance search signal. A board wiring capacitance value corresponding to the board material type and wiring length.

In this embodiment, the circuit board wiring capacitance search module 6 inputs the circuit board material type and wiring length into a circuit board wiring capacitance search function, so as to find the circuit board wiring capacitance value from the circuit board wiring capacitance comparison table 13 ; Wherein, the circuit board wiring capacitance lookup function is, for example, a lookup function corresponding to the lookup function established by the circuit board wiring capacitance comparison table 13, and can be found from the circuit board wiring capacitance comparison table 13 according to the inputted circuit board material model and wiring length from the circuit board wiring capacitance comparison table 13 Corresponding circuit board wiring capacitance value.

As mentioned above, the processing module 3 further includes a calculation unit 31 in this embodiment, and the calculation unit 31 has a built-in load capacitance calculation formula Ce=2*CL−(Ci+Cs); wherein, the calculation unit 31 will Specify the crystal capacitance value returned by the crystal capacitance search module 4 into CL, and the chip pin capacitance value returned by the chip pin capacitance search module 5 into Ci, and the circuit board wiring capacitance search module 6. The returned circuit board wiring capacitance value is substituted into Cs; thereby, the Ce calculated by the calculation unit 31 using the above-mentioned load capacitance calculation formula is an external load capacitance value. For example, when the crystal part number, chip part number, circuit board material type and wiring length entered by the user in the operation interface 2 are 7W25000061, USX2065-JZH-TR, NPG-170D/RTF(H1) and 800 respectively , the specified crystal capacitance search module 4, chip pin capacitance search module 5 and circuit board wiring capacitance search module 6 will find 15pf, 2pf and 2.8pf respectively, and the calculation unit 31 calculates the external load capacitance value Ce= 2*15–(2+2.8), that is, the external load capacitance value is 25.2pf.

In addition, the search function used by the above-mentioned specified crystal capacitance search module 4, chip pin capacitance search module 5 and circuit board wiring capacitance search module 6 may be, for example, the VLOOKUP function in EXCEL.

Please continue to refer to the second figure, which is a flow chart showing the steps of the load capacitance calculation system of the crystal oscillator provided by the preferred embodiment of the present invention. As shown in the first and second figures, based on the above-mentioned load capacitance calculation system 100 for a crystal oscillator, a load capacitance calculation method for a crystal oscillator in this embodiment includes the following steps S101 to S103 .

First, step S101 is to provide an operation interface 2 for the user to input a crystal part number, a chip part number, a circuit board material type and a wiring length.

Step S102 is to find out a crystal capacitance value from a specified crystal capacitance load comparison table 11 according to the crystal part number, find out a chip pin capacitance value from a chip pin capacitance comparison table 12 according to the chip part number, and according to the circuit board The material type and wiring length can be found from a circuit board wiring capacitance comparison table 13 to find a circuit board wiring capacitance value.

Based on the above, in this embodiment, step S102 is to use the specified crystal capacitance search module 4 to input the crystal material number into a specified crystal capacitance search function, so as to search from the specified crystal capacitance load comparison table 11 according to the crystal material number. The crystal capacitance value is obtained, and the chip pin capacitance search module 5 is used to input the chip part number into a chip pin capacitance search function, so as to find out the chip pin capacitance value from the chip pin capacitance comparison table 12 according to the chip part number In addition, step S102 also utilizes circuit board wiring capacitance search module 6 to input circuit board material model and wiring length into a circuit board wiring capacitance search function, so as to obtain a comparison table 13 from circuit board wiring capacitance according to circuit board material model and wiring length Find out the board routing capacitance value in .

Finally, step S103 is to calculate an external load capacitance value according to the crystal capacitance value, the chip pin capacitance value and the circuit board wiring capacitance value.

To sum up, in the prior art, if the user wants to know when the load capacitance required by the crystal oscillator is, it is often necessary to use the crystal part number, chip part number, circuit board material type and wiring length as the basis to manually It is very time-consuming and labor-intensive to search for data and compare the relevant capacitance parameters, and then further calculate the required capacitance value. Compared with this, the load capacitance calculation system of the crystal oscillator provided by the present invention and the load The capacitance calculation method mainly provides an operation interface for the user to input the crystal part number, chip part number, circuit board material model and wiring length, and then use the specified crystal capacitor to find the module from the specified crystal capacitance load comparison table according to the crystal part number. Find out the crystal capacitance value, and use the chip pin capacitance search module to find out the chip pin capacitance value from the chip pin capacitance comparison table according to the chip part number, and use the circuit board wiring capacitance to find the module according to the circuit board material type and type. The wiring length is used to find the wiring capacitance value of the circuit board from the wiring capacitance comparison table of the circuit board. Finally, the calculation unit of the processing module further substitutes the capacitance value of the crystal, the capacitance value of the chip pin and the wiring capacitance value of the circuit board into the calculation formula of the load capacitance. Quickly and conveniently calculate the external load capacitance value for user reference.

Through the detailed description of the preferred embodiments above, it is hoped that the features and spirit of the present invention can be described more clearly, and the scope of the present invention is not limited by the preferred embodiments disclosed above. On the contrary, the intention is to cover various modifications and equivalent arrangements within the scope of the claimed scope of the present invention.

100: Load capacitance calculation system of crystal oscillator 1: Database 11: Specified crystal capacitance load comparison table 12: Chip pin capacitance comparison table 13: Circuit board wiring capacitance comparison table 2: Operation interface 3: Processing modules 31: Computing unit 4: Specify the crystal capacitor to find the module 5: Chip pin capacitance search module 6: Circuit board wiring capacitor search module

The first figure is a system block diagram showing the load capacitance calculation system of the crystal oscillator provided by the preferred embodiment of the present invention; and The second figure is a flow chart showing the steps of the load capacitance calculation system of the crystal oscillator provided by the preferred embodiment of the present invention.

100: Load capacitance calculation system of crystal oscillator

1: Database

11: Specified crystal capacitance load comparison table

12: Chip pin capacitance comparison table

13: Circuit board wiring capacitance comparison table

2: Operation interface

3: Processing modules

31: Computing unit

4: Specify the crystal capacitor to find the module

5: Chip pin capacitance search module

6: Circuit board wiring capacitor search module

Claims (10)

A load capacitance calculation system for a crystal oscillator, comprising: a database, which stores a specified crystal capacitance load comparison table, a chip pin capacitance comparison table, and a circuit board wiring capacitance comparison table; an operation interface for the user to input a crystal part number, a chip part number, a circuit board material type and a wiring length; A processing module, electrically connected to the operation interface, is used for sending a specified crystal capacitance search signal according to the crystal part number, and sending a chip pin capacitance search signal according to the chip part number, and according to the circuit The board material type and the wiring length send a circuit board wiring capacitance search signal; A specified crystal capacitance search module, which is electrically connected to the processing module and the database, and used to search out a corresponding crystal part number from the specified crystal capacitance load comparison table according to the specified crystal capacitance search signal. Crystal capacitance value, and transmit the crystal capacitance value to the processing module; A chip pin capacitance search module is electrically connected to the processing module and the database, and is used for searching out a corresponding chip material from the chip pin capacitance comparison table according to the chip pin capacitance search signal. and transmit the chip pin capacitance value to the processing module; and A circuit board wiring capacitance search module, which is electrically connected to the processing module and the database, and is used to search out a circuit board corresponding to the circuit board from the circuit board wiring capacitance comparison table according to the circuit board wiring capacitance search signal. Material type and the wiring capacitance value of the circuit board of the wiring length, and transmit the wiring capacitance value of the circuit board to the processing module; The processing module further calculates an external load capacitance value according to the crystal capacitance value, the chip lead capacitance value and the circuit board wiring capacitance value. The load capacitance calculation system for a crystal oscillator according to claim 1, wherein the processing module further comprises a calculation unit, the calculation unit has a built-in load capacitance calculation formula, and the calculation unit is the crystal capacitance value, the The chip pin capacitance value and the circuit board wiring capacitance value are substituted into the load capacitance calculation formula to calculate the external load capacitance value. The load capacitance calculation system for a crystal oscillator according to claim 2, wherein the load capacitance calculation formula is Ce=2*CL-(Ci+Cs), Ce is the external load capacitance value, and CL is the crystal capacitance value , Ci is the pin capacitance value of the chip, and Cs is the wiring capacitance value of the circuit board. The load capacitance calculation system for a crystal oscillator according to claim 1, wherein the specified crystal capacitance search module inputs the crystal part number into a specified crystal capacitance search function, so as to obtain the specified crystal capacitance load comparison table from the specified crystal capacitance search function. Find out the crystal capacitance value. The load capacitance calculation system for a crystal oscillator according to claim 1, wherein the chip pin capacitance search module inputs the chip part number into a chip pin capacitance search function, so as to compare the chip pin capacitance with the chip pin capacitance Find the chip pin capacitance value in the table. The load capacitance calculation system for a crystal oscillator according to claim 1, wherein the circuit board wiring capacitance search module inputs the circuit board material type and the wiring length into a circuit board wiring capacitance search function, so as to obtain information from the circuit board wiring capacitance search function. Find the wiring capacitance value of the circuit board in the circuit board wiring capacitance comparison table. A method for calculating a load capacitance of a crystal oscillator, comprising the following steps: (A) Provide an operation interface for the user to input a crystal part number, a chip part number, a circuit board material type and a wiring length; (B) Find out a crystal capacitance value from a specified crystal capacitance load comparison table according to the crystal part number, find out a chip pin capacitance value from a chip pin capacitance comparison table according to the chip part number, and according to the circuit The board material type and the wiring length are obtained from a circuit board wiring capacitance comparison table to find a circuit board wiring capacitance value; and (C) Calculate an external load capacitance value according to the crystal capacitance value, the chip lead capacitance value and the circuit board wiring capacitance value. The method for calculating the load capacitance of a crystal oscillator according to claim 7, wherein in step (B), a specified crystal capacitance search module is used to input the crystal part number into a specified crystal capacitance search function, so as to obtain the specified crystal capacitance from the specified crystal capacitance search function. Find the crystal capacitance value in the crystal capacitance load comparison table. The method for calculating the load capacitance of a crystal oscillator according to claim 7, wherein in step (B), a chip lead capacitance search module is used to input the chip part number into a chip lead capacitance search function, so as to automatically Find the chip pin capacitance value in the chip pin capacitance comparison table. The load capacitance calculation system for a crystal oscillator according to claim 7, wherein the step (B) is to use a circuit board wiring capacitance search module to input the circuit board material type and the wiring length into a circuit board wiring capacitance search module In the function, the wiring capacitance value of the circuit board is searched out from the wiring capacitance comparison table of the circuit board.

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