Datasheet

Analog-to-Digital Converter (ADC)
MC68HC908LJ12 — Rev. 2.1 Technical Data
Freescale Semiconductor Analog-to-Digital Converter (ADC) 309
15.7.1 ADC Voltage In (V
ADIN
)
V
ADIN
is the input voltage signal from one of the nine channels to the
ADC module.
15.7.2 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.
15.7.3 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 Section 23. Electrical
Specifications).
NOTE: Route V
REFH
carefully for maximum noise immunity and place bypass
capacitors as close as possible to the package.
15.7.4 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 Section 23. Electrical Specifications).