MMC2107 Datasheet, PDF (493/618 Pages) –

Freescale Semiconductor, Inc.
Queued Analog-to-Digital Converter (QADC)
Pin Connection Considerations
NOTE: This star-point scheme still requires adequate grounding for digital and
analog subsystems in addition to the star-point ground.
ANALOG POWER SUPPLY
DIGITAL POWER SUPPLY
+5 V
AGND
+5 V
PGND
+5 V
V_SS
QADC
V_DD
PCB
Figure 18-50. Star-Ground at the Point of Power Supply Origin
Other suggestions for PCB layout in which the QADC is employed
include:
• Analog ground must be low impedance to all analog ground points
in the circuit.
• Bypass capacitors should be as close to the power pins as
possible.
• The analog ground should be isolated from the digital ground. This
can be done by cutting a separate ground plane for the analog
ground.
• Non-minimum traces should be utilized for connecting bypass
capacitors and filters to their corresponding ground/power points.
• Minimum distance for trace runs when possible.
MMC2107 – Rev. 2.0
MOTOROLA
Queued Analog-to-Digital Converter (QADC)
For More Information On This Product,
Go to: www.freescale.com
Technical Data
493