cx25870 Conexant Systems, Inc., cx25870 Datasheet - Page 139

• Manufacturer Part Number: cx25870
• Description: Video Encoder With Adaptive Flicker Filtering And Hdtv Output
• Manufacturer: Conexant Systems, Inc.

CX25870/871
Flicker-Free Video Encoder with Ultrascale Technology
3.4.1 Device Decoupling
3.4.2 Power Supply Decoupling
3.4.3 COMP Decoupling
3.4.4 VREF Decoupling
3.4.5 VBIAS Decoupling
100381B
3.4 Decoupling
For optimum performance, all capacitors should be located as close as possible to
the device, and the shortest possible leads (consistent with reliable operation)
should be used to reduce the lead inductance. Chip capacitors are recommended
for minimum lead inductance. Radial lead ceramic capacitors can be substituted
for chip capacitors and are better than axial lead capacitors for self-resonance.
Values are chosen to have self-resonance above the pixel clock.
The best power supply performance is obtained with a 0.1
decoupling each group of VAA pins and each group of VDD pins to GND. The
capacitors should be placed as close as possible to the device VAA/VDD pins and
GND pins and connected with short, wide traces.
ripple; the 0.1
Inclusion of a 0.01
pins and GND/VSS pins will improve power supply decoupling at intermediate
frequencies as well.
verified to prevent latchup. A linear regulator is recommended to filter the analog
power supply if the power supply noise is greater than or equal to 200 mV. This is
especially important when a switching power supply is used, or low voltage
interface is implemented, and the switching frequency is close to the raster scan
frequency. About 5 percent of the power supply hum and ripple noise less than
1 MHz will couple onto the analog outputs.
The COMP pin must be decoupled to the closest VAA pin, typically with a 0.1
ceramic capacitor. Low-frequency supply noise will require a larger value. The
COMP capacitor must be as close as possible to the COMP and VAA pins. A
surface-mount ceramic chip capacitor is preferred for minimal lead inductance.
Lead inductance degrades the noise rejection of the circuit. Short, wide traces will
also reduce lead inductance.
A 1.0
A 0.1
The 47
When a linear regulator is used, the proper power-up sequence must be
!
!
F ceramic capacitor should be used to decouple this input to GND.
F ceramic capacitor should be used to decouple this output to GND.
!
F capacitor shown in
!
F capacitors are for high-frequency power supply noise rejection.
!
Conexant
F and a 1.0
!
F capacitor between the group of VAA/VDD
Figure 3-2
is for low-frequency power supply
3.0 PC Board Considerations
!
F ceramic capacitor
3.4 Decoupling
!
3-9
F