Datasheet

Analog-to-Digital Converter (ADC)
I/O Signals
MC68HC908LJ24/LK24 — Rev. 2.1 Data Sheet
Freescale Semiconductor Analog-to-Digital Converter (ADC) 341
16.7.1 ADC Voltage In (V
ADIN
)
V
ADIN
is the input voltage signal from one of the ten channels to the ADC
module.
16.7.2 ADC Analog Power Pin (V
DDA
)
The ADC analog portion uses V
DDA
as its power pin. Connect the V
DDA
pin to the same voltage potential as V
DD
. External filtering may be
necessary to ensure clean V
DDA
for good results.
NOTE: Route V
DDA
carefully for maximum noise immunity and place bypass
capacitors as close as possible to the package.
16.7.3 ADC Analog Ground Pin (V
SSA
)
The ADC analog portion uses V
SSA
as its ground pin. Connect the V
SSA
pin to the same voltage potential as V
SS
.
NOTE: On the 64-pin and 80-pin MC68HC908LJ24, V
SSA
is internally bonded
to V
SS
.
16.7.4 ADC Voltage Reference High Pin (V
REFH
)
V
REFH
is the power supply for setting the reference voltage V
REFH
.
Connect the V
REFH
pin to the same voltage potential as V
DDA
. There will
be a finite current associated with V
REFH
(see 24.12 5V ADC Electrical
Characteristics).
NOTE: Route V
REFH
carefully for maximum noise immunity and place bypass
capacitors as close as possible to the package.
16.7.5 ADC Voltage Reference Low Pin (V
REFL
)
V
REFL
is the lower reference supply for the ADC. Connect the V
REFL
pin
to the same voltage potential as V
SSA
. There will be a finite current
associated with V
REFL
(see 24.12 5V ADC Electrical Characteristics).