CN111405749A - Analog-digital mixed PCB ground plane structure based on high-speed AD and design method - Google Patents

Abstract

The invention discloses an analog-digital mixed PCB ground plane structure based on high-speed AD and a design method thereof. The invention adopts a brand-new ground plane design form, namely an incomplete division form is adopted for an analog ground and a digital ground, and a proper amount of common-ground copper sheet with a proper width is reserved in the middle above the high-speed AD chip, so that the external radiation of high-speed digital signals as small as possible can be realized, and meanwhile, the analog circuit has enough anti-jamming capability on the digital circuit, and the invention has simple design and realization and is easy to develop.

Description

Analog-digital mixed PCB ground plane structure based on high-speed AD and design method

Technical Field

The invention belongs to the field of PCB boards, and particularly relates to an analog-digital hybrid PCB ground plane structure based on high-speed AD and a design method.

Background

With the development of the technology in the electronic industry, the application and the requirement of high-speed AD acquisition are higher and higher, and generally, a board card with the requirement of high-speed AD acquisition includes a high-speed digital circuit. In the current technical background, there are two kinds of processing of analog ground and digital ground, one is that the analog ground and the digital ground are completely divided, and the analog power ground and the digital power ground at the far end are commonly grounded, which has the advantages that the analog circuit is better resistant to the interference of the digital circuit, but has the disadvantages that the high-speed digital signal of the AD flows back too far, which causes larger radiation of the digital signal and increases crosstalk; one is to do not distinguish analog ground and digital ground, do not carry on any division in PCB upper ground level, its advantage is AD high-speed digital signal can be reflowed nearby, high-speed digital signal radiates to the outside the minimum, but the disadvantage is, the analog circuit resists the digital circuit to interfere poorly, there are more digital interference signals in the signal after sampling, can't realize the good performance of high-speed AD.

Disclosure of Invention

The invention provides an analog-digital mixed PCB ground plane structure based on high-speed AD and a design method thereof, which can ensure that an analog circuit has enough anti-interference capability on a digital circuit while realizing the external radiation of high-speed digital signals as small as possible, are simple and easy to implement and are suitable for single-path or multi-path high-speed AD design.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

a high-speed AD (analog-digital) based analog-digital hybrid PCB ground plane structure comprises an analog ground and a digital ground which are incompletely divided on a PCB ground plane, wherein the incomplete division line leaves a common ground space of the analog ground and the digital ground.

Further, the common ground space is located above and in the middle of the high-speed AD chip.

Furthermore, the common ground space is a space which is reserved from a dividing line along two sides of the AD front-end circuit to the middle when the pins of the AD chip are arranged at the highest row and is not intersected.

Furthermore, the size of the common ground space is 2-3 bonding pads.

In another aspect of the present invention, a method for designing an analog-digital hybrid PCB ground plane structure based on high-speed AD is further provided, including: a common ground space of an analog ground and a digital ground is arranged above and in the middle of the high-speed AD chip.

Further, the common ground space is formed in a manner including:

s1, starting from the edge of the board card, dividing upwards along two sides of each AD front-end circuit;

s2, when the pins of the AD chip are segmented to the uppermost row, the pins are segmented towards the middle, the segmentation lines are not intersected, and a common ground space is reserved;

and S3, after copper is paved on the ground plane, the common ground space is used as a common ground point of the analog ground and the digital ground.

Furthermore, the size of the common ground space is 2-3 bonding pads.

Compared with the prior art, the invention has the following beneficial effects:

the invention adopts a brand-new ground plane design form, namely an incomplete division form is adopted for an analog ground and a digital ground, and a proper amount of common ground copper sheet with a proper width is reserved at the middle part above the high-speed AD chip, so that the external radiation of high-speed digital signals can be realized as small as possible, and meanwhile, the analog circuit can be ensured to have enough anti-jamming capability on the digital circuit.

Drawings

Fig. 1 is a schematic structural view of the present invention.

Wherein:

1. a PCB board card; 2. an AD chip; 3. an AD front-end circuit; 4. a common ground space;

5. a digital circuit area.

Detailed Description

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art through specific situations.

The invention aims to design a ground segmentation form, adopts an incomplete segmentation method, and realizes that the design of a ground plane is no longer a factor for restricting the realization of a high-speed AD good index.

As shown in fig. 1, the method provided by the present invention is applicable to single-channel high-speed AD or multi-channel high-speed AD, and the specific division form is that, starting from the edge of the PCB board 1, the division is performed upward along both sides of each channel of the AD front-end circuit 3, when the AD chip 2 is reached, the division line continues upward right below the pin of the AD chip 2, when the pin of the AD chip 2 is at the uppermost row, the division line is divided toward the middle, the division line is not intersected, a common ground space 4 of about two to three pads is left, and the periphery of the division line is a digital circuit area 5; after the copper is laid on the ground plane, the common ground space 4 is used as a common ground point of the analog ground and the digital ground.

The size of the common ground space 4 is about two to three pads, so that the common ground space can bear the normal consumption current of an AD chip, the common ground space has sufficient current capacity for power supply direct current backflow, the common ground space has lower impedance for high-speed digital signal backflow, the division form of the analog ground and the digital ground can realize the external radiation of the high-speed digital signal as small as possible, and meanwhile, the analog circuit can have sufficient anti-jamming capability for the digital circuit.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (7)

1. An analog-digital hybrid PCB ground plane structure based on high-speed AD is characterized by comprising an analog ground and a digital ground which are incompletely divided on a PCB ground plane, wherein the incomplete division line leaves a common ground space of the analog ground and the digital ground.

2. The high-speed AD-based analog-to-digital hybrid PCB ground plane structure of claim 1, wherein the common ground space is located at the upper middle part of the high-speed AD chip.

3. The high-speed AD-based analog-digital hybrid PCB ground plane structure of claim 1, wherein the common ground space is a space left by dividing the common ground space from a dividing line along two sides of an AD front-end circuit to the uppermost row of pins of an AD chip to the middle without intersecting.

4. A high speed AD based analog-to-digital hybrid PCB ground plane structure according to any of the claims 1 to 3, characterized in that the common ground space size is 2-3 pads.

5. A design method of an analog-digital mixed PCB ground plane structure based on high-speed AD is characterized by comprising the following steps: a common ground space of an analog ground and a digital ground is arranged above and in the middle of the high-speed AD chip.

6. The design method of the high-speed AD-based analog-digital hybrid PCB ground plane structure according to claim 5, wherein the common ground space forming method comprises:

s1, starting from the edge of the board card, dividing upwards along two sides of each AD front-end circuit;

s2, when the pins of the AD chip are segmented to the uppermost row, the pins are segmented towards the middle, the segmentation lines are not intersected, and a common ground space is reserved;

and S3, after copper is paved on the ground plane, the common ground space is used as a common ground point of the analog ground and the digital ground.

7. The design method of the high-speed AD-based analog-digital hybrid PCB ground plane structure is characterized in that the common ground space is 2-3 pads.

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