Datasheet

Pinout and Signal Descriptions
Technical Data MC68HC912D60A — Rev. 3.1
42 Pinout and Signal Descriptions Freescale Semiconductor
3.4 Power Supply Pins
MC68HC912D60A power and ground pins are described below and
summarized in Table 3-1.
All power supply pins must be connected to appropriate supplies.
On no account must any pins be left floating.
3.4.1 Internal Power (V
DD
) and Ground (V
SS
)
Power is supplied to the MCU through V
DD
and V
SS
. Because fast signal
transitions place high, short-duration current demands on the power
supply, use bypass capacitors with high-frequency characteristics and
place them as close to the MCU as possible. Bypass requirements
depend on how heavily the MCU pins are loaded.
3.4.2 External Power (V
DDX
) and Ground (V
SSX
)
External power and ground for I/O drivers. Because fast signal
transitions place high, short-duration current demands on the power
supply, use bypass capacitors with high-frequency characteristics and
place them as close to the MCU as possible. Bypass requirements
depend on how heavily the MCU pins are loaded.
3.4.3 V
DDA
, V
SSA
Provides operating voltage and ground for the analog-to-digital
converter. This allows the supply voltage to the ATD to be bypassed
independently. Connecting V
DDA
to V
DD
if the ATD modules are not
used will not result in an increase of power consumption.
3.4.4 Analog to Digital Reference Voltages (V
RH
, V
RL
)
V
RH0
, V
RL0
: reference voltage high and low for ATD converter 0.
V
RH1
, V
RL1
: reference voltage high and low for ATD converter 1.
If the ATD modules are not used, leaving V
RH
connected to V
DD
will not
result in an increase of power consumption.