Datasheet

Analog-to-Digital Converter (ADC)
Technical Data MC68HC908AB32 — Rev. 1.1
234 Analog-to-Digital Converter (ADC) Freescale Semiconductor
14.7.1 ADC Analog Power Pin (V
DDAREF
)
The ADC analog portion uses V
DDAREF
as its power pin. Connect the
V
DDAREF
pin to the same voltage potential as V
DD
. External filtering may
be necessary to ensure clean V
DDAREF
for good results.
NOTE: For maximum noise immunity, route V
DDAREF
carefully and place
bypass capacitors as close as possible to the package.
14.7.2 ADC Analog Ground Pin (A
VSS
/V
REFL
)
The ADC analog portion uses A
VSS
/V
REFL
as its ground pin. Connect the
A
VSS
/V
REFL
pin to the same voltage potential as V
SS
.
NOTE: Route A
VSS
/V
REFL
cleanly to avoid any offset errors.
14.7.3 ADC Voltage Reference High Pin (V
REFH
)
V
REFH
is the reference voltage for the ADC.
14.7.4 ADC Voltage In (V
ADIN
)
V
ADIN
is the input voltage signal from one of the eight ADC channels to
the ADC module.
14.8 I/O Registers
These I/O registers control and monitor ADC operation:
• ADC status and control register (ADSCR)
• ADC data register (ADR)
• ADC clock register (ADCLK)