DRA722_17 Datasheet, PDF (374/408 Pages) Texas Instruments – Infotainment Applications Processor

DRA722, DRA724, DRA725, DRA726
SPRS956B – MARCH 2016 – REVISED JANUARY 2017
www.ti.com
Table 8-27. MIPI D-PHY Interface Signals in the Device (continued)
SIGNAL NAME
csi2_0_dx1
csi2_0_dx2
csi2_0_dx3
csi2_0_dx4
csi2_1_dx0
csi2_1_dx1
csi2_1_dx2
BOTTOM BALL
AF1
AF2
AH4
AH3
AG5
AG6
AH7
SIGNAL NAME
csi2_0_dy1
csi2_0_dy2
csi2_0_dy3
csi2_0_dy4
csi2_1_dy0
csi2_1_dy1
csi2_1_dy2
BOTTOM BALL
AE2
AF3
AG4
AG3
AH5
AH6
AG7
8.5.7.1 CSI2_0 and CSI2_1 MIPI CSI-2 (1.5 Gbps)
8.5.7.1.1 General Guidelines
The general guidelines for the PCB differential lines are:
• Differential trace impedance Z₀ = 100 Ω (minimum = 85 Ω, maximum = 115 Ω)
• Total conductor length from the Device package pins to the peripheral device package pins is 25 to 30
cm with common FR4 PCB and flex materials.
NOTE
Longer interconnect length can be supported at the expense of detailed simulations of the
complete link including driver and receiver models.
The general rule of thumb for the space S = 2 × W is not designated (see Figure 8-19, Guard Illustration).
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. Even though the designer
does not follow the S = 2 × W rule, the differential lines are ok if the lines satisfy the frequency-domain
specification.
Because the MIPI signals are used for low-power, single-ended signaling in addition to their high-speed
differential implementation, the pairs must be loosely coupled.
8.5.7.1.2 Length Mismatch Guidelines
8.5.7.1.2.1 CSI2_0 and CSI2_1 MIPI CSI-2 (1.5 Gbps)
The guidelines of the length mismatch for CSI-2 are presented in Table 8-28.
Table 8-28. Length Mismatch Guidelines for CSI-2 (1.5 Gbps)
PARAMETER
Operating speed
UI (bit time)
Intralane skew
Interlane skew (UI / 50)
(1) sdc12, scd21, scd12, sdc21, scd11, sdc11, scd22, and sdc22
TYPICAL VALUE
UNIT
1500
Mbps
667
ps
Have to satisfy mode-conversion S parameters⁽¹⁾
13.34
ps
8.5.7.1.3 Frequency-domain Specification Guidelines
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 the high-frequency structure simulator (HFSS) or equivalent, and
compared to the frequency-domain specification as defined in the section 7 of the MIPI Alliance
Specification for D-PHY Version v1-01-00_r0-03.
If the PCB lines satisfy the frequency-domain specification, the design is finished. Otherwise, the design
needs to be improved.
374 Applications, Implementation, and Layout
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