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Hi Lonnie, Are you talking about the layout trace length control of TMDS signal? Regards, Sean |
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Dear Sean No, I worried about failed eye pattern at signal integrity. So, I recommended buffer IC as like equalizer. Could you provide real pattern length and Synaptics specification? Best regards Lonnie Kim |
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Dear Lonnie, Yesterday we have discussed with Synaptics on the issue of the long trace length of HDMI. According to Synaptics RD, the only problem is that when the box uses a long HDMI cable (for example, longer than 10M), it may cause a bad signal at far-end side, but a short HDMI cable should be no problem (for example, 1.5~2M) Currently, Synaptics RD is checking this issue internally and will give us their advice before noon tomorrow. Will let you know if there is any update tomorrow. Thanks, Regards, Sean |
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Dear Sean I received below information about HDMI and USB pattern requirement from Synaptics Korea. Please check with your PCB routing then feedback to me. we have Max length requirement for HDMI and USB. For DDR, Customer should copy our reference layout. HDMI.Routing 14 Target impedance 100 ohms differential 15 Minimum gap between differential pair and other signals 17.5 mils 16 Trace length from SoC to ESD component 2.50 inches maximum 17 Trace length from ESD component to HDMI connector 0.25 inches maximum 18 Trace Length Match within diff. pair (p to n) : ±40mil 19 Trace Length Match between diff. pairs : ±100mil 21 Traces breaking in and out of ESD and connector must be symmetrical. 22 Void reference plane below large pads of the ESD and CM choke, as recommended by the component manufacturer USB Routing 30 Target impedance 90 ohms differential 31 Minimum gap between differential pair 10 mils 32 Trace Length From SoC to CM choke : 6 inches maximum 33 Trace Length From CM choke to connector : 1 inches maximum 34 Trace Length Match within diff. pair (p to n) To within ±40 mil 35 Preferably no via from the SoC to the USB connector. The number of vias for the two signals must be the same. 36 Do not route USB traces under crystals, oscillators, clock synthesizers, magnetic devices or ICs that use or duplicate clocks. Best regards Lonnie Kim |
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Hi Lonnie, Thanks for your information. Actually, we have worked with Synaptics China team to review the layout a few weeks ago and definitely we will follow Synaptics's layout rule and requirement for the DDR, HDMI and USB. These suggestion you provided are the same as comment provided by Synaptics China ,and also are the common layout rule based on our experience. Regards, Sean |
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Dear Sean Okay. Good. What is your next step? Best regards Lonnie Kim |
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Dear Sean You can check pattern routing length using layout program. Please update ASAP. Best regards Lonnie Kim |
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Synaptics layout comment for HDMI trace.png (78,266 bytes) |
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Hi Lonnie, Please refer attached for the layout comment from Synaptics. Please note that there is no requirement for the trace length from SoC to ESD components. Thanks. ============================================================================ 16 Trace length from SoC to ESD component 2.50 inches maximum ============================================================================ |
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Hi Lonnie, Have checked with Synaptics China team and send information of TI redirver IC "tmds181" to Synaptics review but haven't got response yet. Will ask Synaptics to feedback on this asap and keep you posted once there's any update from Synaptics. Thanks. Regards, Sean |
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Hi Lonnie, We have discussed with Synaptics China team yesterday and they think that the TI tmds181 is OK as HDMI redriver used with Synaptics VS550. Regards, Sean |
- yk.jung ( (ALTech) Younkwang Jung ) developer
