MCP3302 datasheet(21/40 Pages) MICROCHIP

21 / 40 page

 2002 Microchip Technology Inc.

DS21697B-page 21

MCP3302/04

6.7

Utilizing the Digital and Analog

Ground Pins

The MCP3302/04 devices provide both digital and ana-

log ground connections to provide another means of

noise reduction. As shown in Figure 6-11, the analog

and digital circuitry are 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 VSS 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, as shown in

Figure 6-11. Following these steps will reduce the

amount of digital noise from the rest of the board being

coupled into the A/D Converter.

FIGURE 6-11:

Separation of Analog and

Digital Ground Pins.

MCP3302/04

Analog Ground Plane

DGND

AGND

VDD

0.1 µF

Substrate

5 - 10

Ω

Digital Side

-SPI Interface

-Shift Register

-Control Logic

Analog Side

-Sample Cap

-Capacitor Array

-Comparator

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