MCP3204 datasheet(18/20 Pages) MICROCHIP

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MCP3204/3208

DS21298B-page 18

Preliminary

6.5

Utilizing the Digital and Analog

Ground Pins

The MCP3204/3208 devices provide both digital and

analog ground connections to provide another means

of noise reduction. As shown in Figure 6-5, the analog

and digital circuitry is separated internal to the device.

This reduces noise from the digital portion of the device

being coupled into the analog portion of the device. The

two grounds are connected internally through the sub-

strate which has a resistance of 5 -10

Ω.

If no ground plane is utilized, then both grounds must

be connected to V

SS on the board. If a ground plane is

available, both digital and analog ground pins should

be connected to the analog ground plane. If both an

analog and a digital ground plane are available, both

the digital and the analog ground pins should be con-

nected to the analog ground plane. Following these

steps will reduce the amount of digital noise from the

rest of the board being coupled into the A/D Converter.

FIGURE 6-5:

Separation of

Analog

and

Digital

Ground Pins.

Digital Side

-SPI Interface

-Shift Register

-Control Logic

Analog Side

-Sample Cap

-Capacitor Array

-Comparator

Substrate

5 - 10

Ω

Analog

Ground Pin

Digital

Ground Pin

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