SAA55XX Datasheet, PDF (77/84 Pages) NXP Semiconductors – TV microcontrollers with Closed Captioning (CC) and On-Screen Display (OSD)

Philips Semiconductors
TV microcontrollers with Closed Captioning (CC)
and On-Screen Display (OSD)
Preliminary specification
SAA55xx
24 ELECTROMAGNETIC COMPATIBILITY (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 a local ground plane under the
whole Integrated Circuit (IC) should be present as shown
in Fig.32. 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.
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_DD 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 ground.
Physical connection distances to associated active
devices should be short.
Output traces should be routed with close proximity to
mutually coupled ground return paths.
handbook, full pagewidth
other
GND
connections
under-IC GND plane
GND connection
note: no wire links
GND +3.3 V
electrolytic decoupling capacitor (2 µF)
ferrite beads
SM decoupling capacitors (10 to 100 nF)
under-IC GND plane
VSSC
VSSA
IC
MBK979
2000 Feb 23
Fig.32 Power supply connections for EMC.
77