JPH10190167A - Circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit board which does not malfunction due to noise without mixing of noise from a digital signal processing part into an analog signal processing part. SOLUTION: In a surface layer 29, a digital signal process section 27 and an analogue signal process section 25 are unmixedly arranged, and also in a reverse layer 30, they are arranged so that an analogue signal process section 26 is not disposed at a lower location of the digital signal process section 27, and a digital signal process section 28 is not located at a lower location of the analogue signal process section 25. Further, in an inner layer, all regions corresponding to the upper and lower location relationship of the analogue signal process sections 25, 26 are grounded in GND layers 23, 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit board, and more particularly, to a circuit board for processing digital signals and analog signals on the same board.

[0002]

2. Description of the Related Art Conventionally, in a device in which components are mounted on a multilayer printed circuit board, circuit components are mounted on a front surface layer and a back surface layer, and a plurality of inner layer copper foil portions are provided inside the printed circuit board. There are known technical means in which the two layers are respectively assigned to a solid GND plane and a power supply plane.

Further, in an electric circuit in which an analog signal processing section and a digital signal processing section are mixed, the analog signal processing section and the digital signal processing section are designed to prevent noise from the digital signal processing section from entering the analog signal processing section. In general, a technique of separating and disposing them on a substrate is widely used.

Further, in order to reduce noise mixing or radiation, technical means such as filling a blank portion where no pattern exists on the component mounting surface (front and back surfaces) of the substrate with a GND surface is generally known. is there.

FIG. 4 is a diagram showing an example in which components (surface mount components) are mounted on both sides of a four-layer printed circuit board.

In this conventional four-layer printed circuit board 101, a pattern surface is provided on a front surface layer 102 and a back surface layer 105, and circuit components 106 and 107 are mounted thereon. The inner copper foil portions 103 and 104 are provided inside the printed circuit board.
Are arranged. Of these, the inner layer copper foil portion 103 is connected to GND.
As the surface, the inner copper foil portion 104 is used as a power supply surface.

[0007]

However, in a small digital voice recording device, especially in a portable device,
The audio (analog) signal processing unit and digital signal processing unit must be mounted together in a limited space, but the printed circuit board used is small and thin, so in the case of a multilayer printed circuit board, The distance between each layer is reduced. Therefore, in addition to noise mixing from adjacent patterns in the same layer, noise mixing from patterns in vertically adjacent layers cannot be ignored.

Generally, in a printed circuit board in which an analog signal processing section and a digital signal processing section are mixed,
There have been many reports of adverse effects caused by noise entering the power supply line due to the operation of the digital signal processing unit.

As described above, when a circuit for handling a digital signal is provided near a power supply line, particularly, a power supply line of an analog signal processing unit, various noises generated from the circuit via the power supply line are generated. There is a problem that the signal is mixed into the analog signal processing unit.

In particular, conventionally, in a multilayer printed circuit board in which a solid power supply surface is disposed as one of the inner layers of the multilayer printed circuit board, noise is transmitted to an analog signal processing unit vertically adjacent through the power supply surface. This causes inconvenience that the analog circuit malfunctions.

The present invention has been made in view of the above problems, and has as its object to provide a circuit board in which noise from a digital signal processing unit does not enter an analog signal processing unit.

[0012]

In order to achieve the above object, a first circuit board of the present invention is a multi-layer circuit board for processing digital signals and analog signals on the same board. Circuit components are arranged so that the digital signal processing area for processing digital signals and the analog signal processing area for processing analog signals are not mixed. The analog signal processing area is arranged so as not to be located in the corresponding area, and the digital signal processing area is arranged so as not to be located in the area corresponding to the vertical positional relationship with the analog signal processing area. At least in the other two layers , All areas corresponding to the vertical position relationship with the analog signal processing area are grounded.

[0013] To achieve the above object, a second aspect of the present invention is provided.
Is a multi-layer circuit board that processes digital signals and analog signals on the same board, and includes, on a first exterior surface, a digital signal processing area for processing digital signals and an analog signal processing area for processing analog signals. Circuit components are arranged so as not to coexist, and the second exterior surface on the back side of the first exterior surface also has an area corresponding to the digital signal processing area of the first exterior surface in the vertical positional relationship. So that the analog signal processing area is not located at
Further, the digital signal processing area is arranged so as not to be located in a region corresponding to the analog signal processing area on the first exterior surface in the vertical position, and in the two inner layers adjacent to the exterior surface, An area in which the analog signal processing area on the exterior surface and the vertical positional relationship correspond to each other is grounded.

[0014] To achieve the above object, a third aspect of the present invention is provided.
In the second circuit board, in the second circuit board, in one inner layer, all areas corresponding to the digital signal processing area on the first exterior surface in the vertical positional relationship correspond to ground, and in the other inner layers, all the areas are connected to the power supply. A potential.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing a partial configuration of a multilayer printed circuit board according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a main configuration of a digital voice recording / reproducing apparatus to which the multilayer printed circuit board shown in FIG. 1 is applied.

As shown in the figure, the audio recording / reproducing apparatus includes a microphone 1 for converting audio into an electric signal, and an audio output from the microphone 1 is amplified by a microphone amplifier 2 connected thereto. ing. The output of the micro-amplifier 2 is input to an A / D converter 4 via a low-pass filter 3. The analog audio signal amplified by the microphone amplifier 2 is subjected to anti-aliasing noise by the low-pass filter 3. An unnecessary frequency band for preventing the occurrence of the above is cut off and input to the A / D converter 4.

The A / D converter 4 converts an audio signal, which is an analog signal, into a digital signal and then inputs the digital signal to a digital signal processing unit 5. The digital signal processing unit 5 converts (encodes) the audio signal converted into the digital signal into data of a predetermined format.
And a process of converting (decoding) the encoded data into a digital signal again. It is assumed that the digital signal processing unit 5 is configured by a DSP.

The digital signal decoded by the digital signal processing unit 5 is input to a D / A converter 6. The audio signal converted to an analog signal by the D / A converter 6 is amplified through a low-pass filter 7 that cuts an unnecessary frequency band to reduce quantization noise, and amplifies the audio signal. Is input to a power amplifier 8 that drives Further, the audio signal amplified by the power amplifier 8 is converted into sound and emitted by a speaker 9 which emits sound.

On the other hand, an I / O data buffer 10 for temporarily storing coded data is connected to the digital signal processing 5, and data from the I / O data 10 is used for the operation of each unit. Is input to the main control unit 11 for controlling

The main control unit 11 is constituted by a CPU called a one-chip microcomputer, controls the whole apparatus, is connected to the I / O data buffer 10, and is connected via an I / O interface 12. Recording unit 1
6 is connected. The recording unit 16 includes a recording / reading unit 13, a recording medium 1 including a semiconductor memory, and the like.
4, the control unit 15 and the write / read unit 1
Numeral 3 exchanges data with the main controller 11 via the I / O interface 12. The control unit 15 is connected to the main control unit 11 and controls writing and reading of data on the recording medium 14 via the writing / reading unit 13 under the control of the main control unit 11. ing. It is assumed that the storage medium 14 is a removable memory card.

Further, the main control section 11 has an operation input section 17 for instructing an operation mode of the audio recording / reproducing apparatus,
A display unit 18 for displaying an operation mode, a recording time, and the like is connected. Note that the display unit 18 is assumed to be an LCD (liquid crystal display element).

Of the constituent elements described above, the microphone amplifier 2, low-pass filter 3, A / D converter 4, D / A converter 6, low-pass filter 7, and power amplifier 8 are parts for handling analog signals. These are designed to be mounted in the analog signal processing area on the printed circuit board shown in FIG. On the other hand, the digital signal processing unit (DSP)
5, I / O data buffer 10, main control unit 11, display unit 18, I / O interface 12, operation input unit 17
Are parts for handling digital signals, which are mounted in a digital signal processing area on the printed circuit board.

The microphone 1, the speaker 9
Is mounted on an exterior part (not shown) of the audio recording and reproducing apparatus, and is connected to the printed circuit board shown in FIG. 1 by lead wires.

FIG. 1 is a sectional view showing a state where components are mounted on a printed circuit board according to the first embodiment of the present invention as described above.

As shown in the figure, the printed circuit board 21 of the present embodiment has a four-layer structure, and has a surface layer 29 (first layer).
Each layer of the back layer 30 (fourth layer) is provided with wiring in a normal pattern. In the first and fourth layers, analog signal processing areas 25 and 26 are located on the left side in the figure.
Are provided, and digital signal processing areas 27 and 28 are provided on the right side.
Are arranged. That is, the microphone amplifier 2, the low-pass filter 3, the A / D converter 4, the D / A converter 6,
Elements for handling analog signals, such as the low-pass filter 7 and the power amplifier 8, are disposed in the analog signal processing areas 25 and 26, while the digital signal processing units (DSP) 5 and I
/ O data buffer 10, main control unit 11, display unit 18,
Elements for handling digital signals, such as the I / O interface 12 and the operation input unit 17, are digital signal processing areas 27 and 2.
8.

Since the A / D converter 4 and the D / A converter 6 handle both analog signals and digital signals, these elements serve as boundaries between the area of the analog signal processing area and the area of the digital signal processing area. It is designed so that the wiring pattern of the digital signal is not routed to the area of the analog signal processing area.

On the other hand, the printed circuit board 21 is provided with two layers (a second layer and a third layer) as inner conductive portions, and one of the inner conductive portions is a solid GND layer 24. I have. Further, another inner layer conductive portion has a solid GND layer 23 in an area adjacent to the analog signal processing area 25,
The area adjacent to the digital signal processing area 27 is the solid power supply layer 22.

The analog signal processing areas 25 and 2
The power supply to 6 is performed by the wiring pattern of the front surface layer 29 or the back surface layer 30.

As described above, the printed circuit board of the present embodiment has a structure in which an analog signal processing area for processing analog signals and a digital signal processing area for processing digital signals must be provided on the same substrate. After the analog signal processing area and the digital signal processing area are separated from each other, in the analog signal processing area, at least the contact area of the inner layer adjacent to the component mounting surface (front and back surfaces) is a solid GND layer. This prevents the noise from being mixed into the analog signal processing area from the power supply surface of the inner layer containing much noise, and the GND surface is provided immediately below the component mounting surface in the analog signal processing area, thereby allowing the same substrate to be used. Electromagnetic noise from the above digital signal processing area and unsolicited external noise are prevented,
Recording and reproduction with less noise can be performed.

Next, a second embodiment of the present invention will be described.

FIG. 3 is a sectional view showing a state where components are mounted on the printed circuit board according to the second embodiment. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

The printed circuit board according to the second embodiment has a six-layer structure as shown in the figure, and similarly to the above-described first embodiment, analog signal processing areas 25 and 26 and digital signal processing areas 27 and 26. 28 are separately provided in separate areas.

The printed circuit board 31 according to the second embodiment comprises:
A power supply layer 22 and a GND layer 23 disposed inside;
Wiring layers 32 and 33 are further disposed between the ND layer 24 and the ND layer 24.

In this embodiment, in addition to the effects of the first embodiment, a shielding effect on the wiring of the wiring layers 32 and 33 inside the analog signal processing area can be expected.

[Appendix] According to the embodiment of the present invention described in detail above, the following configuration can be obtained. That is, (1) first conversion means for converting an analog audio signal into a digital signal, recording means for recording audio data digitized by the first conversion means, and digital data recorded by the recording means. Reading means for reading a signal;
A second converting means for converting the digital signal read by the reading means into an analog audio signal, wherein the above means are mounted on the same printed circuit board.
The area that handles the analog audio signal and the area that handles the digital signal are arranged so as to be different from each other, and at least the area that handles the analog audio signal has at least two inner layer portions adjacent to the area. A circuit board, which is grounded.

[0038]

As described above, according to the first and second aspects of the present invention, it is possible to provide a circuit board in which noise from the digital signal processing unit does not enter the analog signal processing unit and does not malfunction due to noise.

According to the third aspect of the present invention, a circuit board free from malfunction due to noise can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a partial configuration of a multilayer printed circuit board according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a main configuration of a digital audio recording / reproducing apparatus to which the multilayer printed board shown in FIG. 1 is applied.

FIG. 3 is a sectional view showing a partial configuration of a multilayer printed circuit board according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view showing an example in which surface mount components are mounted on both sides of a conventional four-layer printed circuit board.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 ... Printed circuit board 22 ... Power supply layer 23 ... GND layer 24 ... GND layer 25 ... Analog signal processing area 26 ... Analog signal processing area 27 ... Digital signal processing area 28 ... Digital signal processing area 29 ... Front layer 30 ... Back layer

Claims (3)

[Claims] 1. A multi-layer circuit board for processing digital and analog signals on the same substrate, wherein a digital signal processing area for processing digital signals and an analog signal processing area for processing analog signals coexist on the same layer. The circuit components are arranged so that the analog signal processing area is not located in a region corresponding to the vertical position relationship with the digital signal processing area in other layers. The digital signal processing area is arranged so as not to be located in the area corresponding to the vertical positional relationship, and in at least the other two layers, the area corresponding to the analog signal processing area and the vertical positional relation is entirely grounded. Circuit board. 2. A multi-layer circuit board for processing digital signals and analog signals on the same substrate, wherein a first signal processing surface has a digital signal processing area for processing digital signals and an analog signal processing area for processing analog signals. Circuit components are arranged so as not to be mixed, and also in the second exterior surface on the back side of the first exterior surface, an area corresponding to the digital signal processing area of the first exterior surface in the up-down positional relationship Wherein the analog signal processing area is not located in the area, and the digital signal processing area is not located in a region corresponding to the analog signal processing area of the first exterior surface in the vertical position. In the two inner layers adjacent to the first exterior surface, all the regions corresponding to the analog signal processing area of the first exterior surface and the vertical positional relationship correspond to ground, Board. 3. In one inner layer, all areas corresponding to the digital signal processing area of the first exterior surface and the vertical positional relationship correspond to ground, and in the other inner layers, all the areas are set to the potential of the power supply. The circuit board according to claim 2.