SAA5531 Philips Semiconductors, SAA5531 Datasheet - Page 92

• Manufacturer Part Number: SAA5531
• Description: Enhanced TV microcontrollers with On-Screen Display OSD
• Manufacturer: Philips Semiconductors

Philips Semiconductors
25 EMC GUIDELINES
Optimization of circuit return paths and minimisation of
common mode emission will be assisted by using a double
sided printed-circuit board (PCB) with low inductance
ground plane.
On a single sided PCB local ground plane under the
whole IC should be present as shown in Fig.41. This
should be connected by the widest possible connection
back to the PCB ground connection, and bulk electrolytic
decoupling capacitor. It should preferably not connect to
other grounds on the way and no wire links should be
present in this connect. The use of wire links increases
ground bounce by introducing inductance into the ground.
The supply pins can be decoupled at the pin to the ground
plane under the IC. This is easily accomplished using
surface mount capacitors, which are more effective than
leaded components at high frequency.
2000 Feb 23
handbook, full pagewidth
Enhanced TV microcontrollers with
On-Screen Display (OSD)
under-IC GND plane
GND connection
note: no wire links
other
GND
connections
Fig.41 Power supply connections for EMC.
GND
3.3 V
electrolytic decoupling capacitor (2 F)
V SSC
92
Using a device socket will unfortunately add to the area
and inductance of the external bypass loop.
A ferrite bead or inductor with resistive characteristics at
high frequencies may be utilised in the supply line close to
the decoupling capacitor to provide a high-impedance.
To prevent pollution by conduction onto the signal lines
(which may then radiate) signals connected to the V
supply via a pull-up resistor should not be connected to the
IC side of this ferrite component.
OSCGND should be connected only to the crystal load
capacitors and not the local or circuit GND.
Physical connection distances to associated active
devices should be short.
Output traces should be routed with close proximity to
mutually coupled ground return paths.
V SSA
ferrite beads
SM decoupling capacitors (10 to 100 nF)
IC
under-IC GND plane
Preliminary specification
MBK979
SAA55xx
DD