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TPD12S016 and EVM kit questions

Eric Hanisch
Intellectual 375 points
Other Parts Discussed in Thread: TPD12S016

We are looking to pass the HDMI compliance testing and we have questions/issues on the DDC/CEC capacitance testing from section 7-13 while using the TPD12S016 EVM dev kit.  We have are using a custom SOC that has the HDMI A side interface to the TPD12S016.  How do we tie the LS_OE and CT_HPD pins since our SOC doesnt have any GPIO that would control these? 

It appears LS_OE would get tied to the A side Hotplug detect line do we just tie the CT_HPD line high to fully enable the part at all times? 

If this is the case on the TPD12S016 EVM kit I assume to test this we supply +5V to the 5V supply pin and VCCA would be the A side voltage which our SOC supplies which is +3.3V.  We then leave the LS_OE On and CT_HPD On on the eval board.  But if we do this with both a 5V and 3.3V power supply on and take a measurement with a HIOKI 3522-50 the DDC lines read about 2.6nF which fails the section 7-13 spec of >50pF.  If you set the CT_HPD to Off then the measurement is around 20pF which would pass the test.

The overall question would be if our custom SOC having only the A side HPD pin can we really control and set the TPD12S016 into a mode where it would pass the section 7-13 DDC/CEC capactiance test both powered on and off? 

  • 0
    TI__Genius 12190 points

    Hi Eric,

    Yes, LS_OE would get tied to the A side Hotplug detect line and you can tie the CT_HPD line high to fully enable the part at all times. Importantly, the 7-13 Compliance spec is tested with the HPD signal tied to ground. This should set LS_OE low as well, in which case it will pass the 7-13 test. Here is a typical result performed here in the lab:

    DUT ON; LS_OE = L  CT_HPD = H; VBAT = 5.0V; VCCA = 1.8V

    7.13

    SDA_B

    SCL_B

    CEC_B

    C2: with testboard (pF)

    31

    31

    33

    C1: testboard (pF)

    21

    21

    21

    CDUT: less testboard (pF)

    10

    10

    12

    Pass/Fail

    Pass

    Pass

    Pass

    Voltage test

    5.0V

    5.0V

    45mV

    DUT ON; LS_OE = L  CT_HPD = L; VBAT = 5.0V; VCCA = 1.8V

    7.13

    SDA_B

    SCL_B

    CEC_B

    C2: with testboard (pF)

    40

    40

    33

    C1: testboard (pF)

    21

    21

    21

    CDUT: less testboard (pF)

    19

    19

    12

    Pass/Fail

    Pass

    Pass

    Pass

    Voltage test

    50mV

    50mV

    50mV

     

    DUT OFF; LS_OE = L  CT_HPD = L; VBAT = 0.0V; VCCA = 0.0V

    7.13

    SDA_B

    SCL_B

    CEC_B

    C2: with testboard (pF)

    41

    40

    34

    C1: testboard (pF)

    21

    21

    21

    CDUT: less testboard (pF)

    20

    19

    13

    Pass/Fail

    Pass

    Pass

    Pass

    Voltage test

    0V

    0V

    0V

     Regards,

  • 0 in reply to Guy Yater
    Intellectual 375 points

    I have a bench DC power supply set to 3.3V and connected to the EVM kit VCCA and another set at 5V connected the 5V supply input.  I removed the LS_OE jumper and used a wire short to connect pin 4 to 5 of the IC which should then connect the LS_OE pin to the A_HPD.  I left the CT_HPD jumper connected to On.  When I connect the HDMI TPA test fixture and ground the HOT_PLUG pin I see the CEC line measure in the 25pF range.  But when I measure the DDC lines they still measure in the nF range.  The only way I can get the DDC lines to read in the pF range is if I power off all the bench supplies or move the CT_HPD jumper to Off. 

    Does this sound correct or what am I missing?  I do only have the TPD12016 EVM connected to the HDMI compliance test fixture I dont have an actual HDMI device running through the EVM dev kit.  I am only trying to test with the top standard HDMI connector as well. 

  • 0 in reply to Eric Hanisch
    TI__Genius 12190 points

    Your setup is correct. With the HIOKI 3522-50, are you looking at Cp (parallel) or Cs (series)? Cp is the correct one to measure.

  • 0 in reply to Guy Yater
    Intellectual 375 points
    Ah yes I only have the HIOKI 3522-50 setup to display the Cs measurement. When I display the Cp measurement I see all the DDC and CEC lines read around 25pF. The HDMI Compliance Test Specification I have doesnt really state which measurement to use I guess which would have been nice. Cp makes more sence though thinking about it.

    Also one thing that was incorrect in my last post was I stated I only get the DDC lines into the pF range when I power off all the bench supplies. Actually I can get the DDC lines to measure in the pF range if I move the CT_HPD jumper to off or power off only the 3.3V VCCA DC supply to the EVM. This was of course only looking at the Cs measurement though.
  • 0 in reply to Eric Hanisch
    TI__Genius 12190 points

    Eric,

    Good, I should have remembered the Cs vs. Cp sooner. Just ignore Cs. Too bad the Compliance test doesn't make that very clear. Is there anything else we can help you with?

    Best Regards,

  • 0 in reply to Guy Yater
    Intellectual 375 points
    Guy,

    Thanks and it has been awhile since we tested our products with the old TI device and I wasnt involved as much in that testing I dont know if we looked at Cs or Cp on the old device even though I know it would still fail I would like to revist that test quick.

    Yes I wish the compliance test stated Cs or Cp better even though thinking about it Cp makes the most sense I think.

    I think we are good to go now though and will be using the new device. Thanks for the help.

    Eric
  • 0 in reply to Eric Hanisch
    Intellectual 375 points

    Guy,

    I guess we are a little confused now it sounded like the only have to pass the HDMI capactiance test was to use this new TPD12S016 part but if Cp is the correct measurement to use it appears that the old TPD12S521DBTR does pass the Cp measurement on the DDC lines only.  On our DDC lines i read around 33pF with power on and 22pF with no power.  This isnt taking into account the 14pF of the test jig so around 19pF and 8pF.  The CEC line wouldnt pass with power on since the reading is about 610pF but powered off it would pass at around 20pF.  Apparently our device testing wouldnt need to worry about the CEC line so if that is the case it appears we could stick with the old TPD12S521DBTR device for now. 

    I think during our original TPD12S521DBTR we were using only the Cs readings which of course fail both the old and new device. 

    Bottom line is if we truly dont need to pass the CEC line test for our specific piece of equipment I think we could stick with the older devices.

    Eric