MCP4641-103ESLASHML datasheet(70/92 Pages) MICROCHIP

70 / 92 page

MCP454X/456X/464X/466X

DS22107A-page 70

8.5

Design Considerations

In the design of a system with the MCP4XXX devices,

the following considerations should be taken into

account:

• Power Supply Considerations

• Layout Considerations

8.5.1

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 8-7 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 8-7:

Typical Microcontroller

Connections.

8.5.2

LAYOUT CONSIDERATIONS

Inductively-coupled AC transients and digital switching

noise can degrade the input and output signal integrity,

potentially masking the MCP4XXX’s performance.

Careful board layout minimizes these effects and

increases the Signal-to-Noise Ratio (SNR). Multi-layer

boards 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 environ-

ments may require shielding of critical signals.

If low noise is desired, breadboards and wire-wrapped

boards are not recommended.

8.5.3

RESISTOR TEMPCO

Characterization curves of the resistor temperature

coefficient

(Tempco)

are

shown

Figure 2-10,

Figure 2-21, Figure 2-32, and Figure 2-43.

These curves show that the resistor network is

designed to correct for the change in resistance as

temperature increases. This technique reduces the

end to end change is RAB resistance.

8.5.4

HIGH VOLTAGE TOLERANT PINS

High Voltage support (VIHH) on the Serial Interface pins

supports

user

configuration

the

Non-Volatile

EEPROM, Write Protect, and WiperLock feature.

VDD

VSS

0.1 µF

SCL

SDA

Note:

In many applications, the High Voltage will

only be present at the manufacturing

stage so as to “lock” the Non-Volatile

wiper value (after calibration) and the con-

tents of the EEPROM. This ensures that

the since High Voltage is not present

under normal operating conditions, that

these values can not be modified.

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