MC68HC908LJ12 Datasheet, PDF (39/413 Pages) Freescale Semiconductor, Inc – 8-bit microcontroller units

General Description
1.6 Pin Functions
Description of pin functions are provided here.
1.6.1 Power Supply Pins (V_DD and V_SS)
V_DD and V_SS are the power supply and ground pins. The MCU operates
from a single power supply.
Fast signal transitions on MCU pins place high, short-duration current
demands on the power supply. To prevent noise problems, take special
care to provide power supply bypassing at the MCU as Figure 1-4
shows. Place the C1 bypass capacitor as close to the MCU as possible.
Use a high-frequency-response ceramic capacitor for C1. C2 is an
optional bulk current bypass capacitor for use in applications that require
the port pins to source high current levels. V_SS must be grounded for
proper MCU operation.
1.6.2 Analog Power Supply Pin (V_DDA)
V_DDA is the voltage supply for the analog parts of the MCU. Connect the
V_DDA pin to the same voltage potential as V_DD. For maximum noise
immunity, route V_DDA via a separate trace and place bypass capacitors
as close as possible to the package (see Figure 1-4).
MCU
V_DD
0.1 µF
C1(a)
V_SS
0.1 µF
C1(b)
V_DDA
+
C2(a)
+
C2(b)
V_DD
NOTE: Component values shown
represent typical applications.
V_DD
Figure 1-4. Power Supply Bypassing
Technical Data
40
General Description
MC68HC908LJ12 — Rev. 2.1
Freescale Semiconductor