Datasheet

19.6 Application information
This section contains information for using the ADC module in applications. The ADC
has been designed to be integrated into a microcontroller for use in embedded control
applications requiring an A/D converter.
19.6.1 External pins and routing
The following sections discuss the external pins associated with the ADC module and
how they are used for best results.
19.6.1.1 Analog supply pins
The ADC module has analog power and ground supplies (V
DDA
and V
SSA
) available as
separate pins on some devices. V
SSA
is shared on the same pin as the MCU digital V
SS
on
some devices. On other devices, V
SSA
and V
DDA
are shared with the MCU digital supply
pins. In these cases, there are separate pads for the analog supplies bonded to the same
pin as the corresponding digital supply so that some degree of isolation between the
supplies is maintained.
When available on a separate pin, both V
DDA
and V
SSA
must be connected to the same
voltage potential as their corresponding MCU digital supply (V
DD
and V
SS
) and must be
routed carefully for maximum noise immunity and bypass capacitors placed as near as
possible to the package.
If separate power supplies are used for analog and digital power, the ground connection
between these supplies must be at the V
SSA
pin. This should be the only ground
connection between these supplies if possible. The V
SSA
pin makes a good single point
ground location.
19.6.1.2 Analog reference pins
In addition to the analog supplies, the ADC module has connections for two reference
voltage inputs. The high reference is V
REFH
, which may be shared on the same pin as
V
DDA
on some devices. The low reference is V
REFL
, which may be shared on the same
pin as V
SSA
on some devices.
Application information
MC9S08PA60 Reference Manual, Rev. 1, 9/2012
550 Freescale Semiconductor, Inc.