MCP4021 datasheet(47/64 Pages) MICROCHIP

47 / 64 page

DS21945E-page 47

MCP4021/2/3/4

7.0

DESIGN CONSIDERATIONS

In the design of a system with the MCP402X devices,

the following considerations should be taken into

account:

• The Power Supply

• The Layout

7.1

Power Supply Considerations

The typical application will require a bypass capacitor

in order to filter high-frequency noise, which can be

induced onto the power supply's traces. The bypass

capacitor helps to minimize the effect of these noise

sources on signal integrity. Figure 7-1 illustrates an

appropriate bypass strategy.

In this example, the recommended bypass capacitor

value is 0.1 µF. This capacitor should be placed as

close (within 4 mm) to the device power pin (VDD) as

possible.

The power source supplying these devices should be

as clean as possible. If the application circuit has

separate digital and analog power supplies, VDD and

VSS should reside on the analog plane.

FIGURE 7-1:

Typical Microcontroller

Connections.

7.2

Layout Considerations

Inductively-coupled AC transients and digital switching

noise can degrade the input and output signal integrity,

potentially masking the MCP402X’s performance.

Careful board layout will minimize these effects and

increase the Signal-to-Noise Ratio (SNR). Bench

testing has shown that a multi-layer board utilizing a

low-inductance ground plane, isolated inputs, isolated

outputs and proper decoupling are critical to achieving

the performance that the silicon is capable of providing.

Particularly harsh environments may require shielding

of critical signals.

If low noise is desired, breadboards and wire-wrapped

boards are not recommended.

VDD

VSS

0.1 µF

U/D

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