saa569x NXP Semiconductors, saa569x Datasheet - Page 108

• Manufacturer Part Number: saa569x
• Description: Enhanced Tv Microcontrollers With On-screen Display Osd
• Manufacturer: NXP Semiconductors

Philips Semiconductors
31 EMC GUIDELINES
Optimization of circuit return paths and minimization of
common mode emission will be assisted by using a double
sided printed-circuit board with low inductance ground
plane.
On a single sided printed-circuit board, a local ground
plane under the whole IC should be present, as shown in
Fig.50. 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 connection. 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.
2002 May 06
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.50 Power supply connections for EMC.
GND
3.3 V
electrolytic decoupling capacitor (2 F)
V SSC
108
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.
Pin 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
mutually coupled ground return paths.
V SSA
ferrite beads
SM decoupling capacitors (10 to 100 nF)
SAA567x; SAA569x
IC
under-IC GND plane
Objective specification
MBK979
DD