- SS-HQ1 Application Notes -
Ver.1.0.0 January 7, 2005
20
3.6. Noise Countermeasures
3.6.1. Introduction
Important Information for Mounting
We recommend a board design of four layers or more to reduce as much noise as possible at the stage of
board design.
Ensure that ground connections are done properly. In addition to employing a multilayer board design, use a
ground plane or other means to minimize ground impedance. Employ sufficient noise countermeasures with
respect to signal separation, such as using a ground layer.
The CXD3172AR uses a mixed power supply consisting of digital (VDD and VSS) and analog (AVD and AVS)
power supplies. Regarding the digital and analog pattern configuration of multilayer boards, it makes no
difference in the effect on noise whether the power supply (for VDD and AVD) is separate or together. However,
better noise resistance has been verified on evaluation boards with pattern configurations featuring a common
ground (VSS and AVS) instead of separate grounds.
Unused input pins should be pulled up or down as necessary. For details on pin processing, refer to the Empty
Pin processing shown in "3.2.1 Processing of Empty Pins in Each Mode".
Care should be taken in the component layout and wiring because the CXD3172AR includes several analog
cells (for A/D, D/A, EVR, and other functions). In particular, do not arrange the oscillator for the encode clock
(connected to ESCI, ESCO, and ECK - pins 86, 87, and 88, respectively) or the pattern route near the pins or
pattern used for the analog cell. This may cause noise, so position the oscillator as close as possible to the
ESCI, ESCO, and ECK pins.
For systems spanning multiple camera boards, we recommend arranging the three chips (CCD, CXA2096N,
and CXD3172AR) on the same board if possible.
Disadvantages of Multiple Boards
If the CCD and CXD3172AR are on separate boards, connectors and the like increase the H1, H2, and RG
loads, which pose a risk that the conditions for driving the CCD may not be met. This may also increase
CXD3172AR power consumption. For separate boards, set the parameters to adjust drivability, delay, and duty
to match the drive clock waveform conditions of your CCD. For details on the parameter settings for adjusting
drivability, delay, and duty, sees 11.3, "Adjustment of TG Phase."
Special care is needed if the CCD and CXA2096N are on separate boards because this lengthens the CCD
output signal line, making it more susceptible to noise from nearby circuits.
Arranging the CXA2096N and CXD3172AR on separate boards also increases loads of PBLK, CLPOB, XSHP,
XSHD, XRS, and CLPDM. This poses a risk that the conditions for driving the CXA2096N may not be met.