Datasheet

MCP453X/455X/463X/465X
DS22096B-page 66  2008-2013 Microchip Technology Inc.
8.6 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
8.6.1 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 8-8 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 (V
DD
) 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, V
DD
and
V
SS
should reside on the analog plane.
FIGURE 8-8: Typical Microcontroller
Connections.
8.6.2 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.
8.6.3 RESISTOR TEMPCO
Characterization curves of the resistor temperature
coefficient (Tempco) are shown in Figure 2-12,
Figure 2-25, Figure 2-38, and Figure 2-51.
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 in R
AB
resistance.
8.6.4 HIGH VOLTAGE TOLERANT PINS
High Voltage support (V
IHH
) on the Serial Interface pins
is for compatibility with the nonvolatile devices.
V
DD
V
DD
V
SS
V
SS
MCP453X/455X/
463X/465X
0.1 µF
PIC
®
Microcontroller
0.1 µF
SCL
SDA
W
B
A