[Arm-netbook] MK802 mini pc case removed

[Tsvetan Usunov, OLIMEX LTD]

HDMI lines need 3x Rclamp2405 TVS devices to protect A10 from ESD discharges which most TVs will induct in the HDMI cable, when you connect the cable to the board there may be small glitch voltage spikes with high amplitude which may destroy A10 video buffers, this is why they put the TVS on these lines, to take this ESD discharges, but as these devices should be with very low capacity or they will damp the signals which are with very high speed on HDMI  there are no many manufacturers to offer them and the price is high
the empty pads you see on the picture next to HDMI connector are for 3 TVS devices which are not populated
Tsvetan

  ----- Original Message ----- 
  From: 3dobjectifying 
  To: Linux on small ARM machines 
  Sent: Wednesday, May 30, 2012 10:54 AM
  Subject: Re: [Arm-netbook] MK802 mini pc case removed


  how do you mean HDMI protection?


  HDCP is still on.. it will not work on my none compatible HDMI monitor.


  Ed


  On Wed, May 30, 2012 at 10:16 AM, Tom Cubie <mr.hipboi at gmail.com> wrote:




    On Wed, May 30, 2012 at 3:30 AM, Henrik Nordström <henrik at henriknordstrom.net> wrote:

      tis 2012-05-29 klockan 22:09 +0300 skrev Tsvetan Usunov - OLIMEX Ltd:


      > SY8008 is low cost step down DCDC
      > what is interesting here is that they do not use AXP209 which means
      > that they either abuse A10 specs, either the power sequencing is not
      > so critical for A10


      I would not think the power sequencing is that critical as long as RESET
      is held at least until power is stable + 300us.


      > seeing that they spare the expensive TVS (one TVS cost as much as
      > SY8008 and there are 3 for the HDMI protection)  looks like this
      > vendor loves to gamble and do not care too much for the long term
      > reliability of this product


      Yes, not having protection on HDMI is gambling for sure.


    Aha, their engineer told me that they have the video jitter problem that they can not
    solve. Maybe it's related with this. 
      Regards
      Henrik




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