OMAP4460 Datasheet, PDF (432/444 Pages) Texas Instruments – Multimedia Device

OMAP4460
SWPS046A – JANUARY 2012
Public Version
www.ti.com
NOTE
The CSI21 and CSI22 MIPI CSI-2 application timings are described in Section 5.5.1.1,
Camera Serial Interface (CSI2) (especially, the timing conditions are specified in the “Timing
Conditions” tables of this section).
First, the following PCB guidelines for CSI2 working up to 1.0 Gbps are presented based on the three-step
design and validation methodology described in Section A.4.2, Three-step Design and Validation
Methodology for OMAP Boards.
For the design of the PCB differential lines on the OMAP board, the PCB designers need to keep in mind
the requirements of Step 1 and Step 2: the characteristic impedance must be 50 Ω, the total length must
be smaller than 100 mm, and the length mismatch requirements must be satisfied.
Then, after the PCB design is finished, the S-parameters of the PCB differential lines will be extracted with
a 3D Maxwell Equation Solver such as high-frequency structure simulator (HFSS) or equivalent, and
compared to the frequency-domain specification as outlined in Step 3 of design methodology. If the PCB
lines satisfy the frequency-domain spec, the design is done. Otherwise, the design needs to be improved.
A.4.3.1.1 Step 1: General Guidelines
The general guidelines for the PCB differential lines of CSI2 are given as:
• Single-ended Z₀ = 50 Ω
• Total conductor length on OMAP board < 100 mm.
In the step, the general rule of thumb for the space S = 2 * W is not designated (see Figure A-24). It is
because although the S = 2 * W rule is a good rule of thumb, it is not always the best solution. The
electrical performance will be checked with the frequency-domain specification in Step 3. Even though the
designers does not follow the S = 2 * W rule, the differential lines are ok if the lines satisfy the
frequency-domain specification in Step 3.
A.4.3.1.2 Step 2: Length Mismatch Guidelines
A.4.3.1.2.1 Step 2: Length Mismatch Guidelines—CSI21 and CSI22 MIPI CSI-2 @ 1.0 Gbps
The guidelines of the length mismatch for CSI-2 are presented in Table A-8. The intralane length
mismatch must be less than 0.5 mm, and the interlane length mismatch must be less than 1.5 mm.
Table A-8. Length Mismatch Guidelines for CSI-2 @ 1.0 Gbps
PARAMETER
Operating speed
UI (bit time)
Intralane skew (UI / 300)
Length between N and P traces
Interlane skew (UI / 100)
Length between pairs
TYPICAL VALUE
1000
1000
3
0.5
10
1.5
UNIT
Mbps
ps
ps
mm
ps
mm
A.4.3.1.2.2 Step 2: Length Mismatch Guidelines—CSI21 and CSI22 MIPI CSI-2 @ 824 Mbps
The guidelines of the length mismatch for CSI-2 are presented in Table A-9.
Table A-9. Length Mismatch Guidelines for CSI-2 @ 824 Mbps
PARAMETER
Operating speed
TYPICAL VALUE
824
UNIT
Mbps
432 OMAP4460 Processor Multimedia Device PCB Guideline
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