micro HDMI for Jetson TX1 and NXP signal-conditioning IC IP4788CZ32 (IP4786CZ32 )

Hi All,

Do you have any experience with micro HDMI?
Jetson TX1 HDMI signals -> NXP signal-conditioning IC IP4786CZ32 -> micro HDMI connector (HDMI type D from WE PN: 685 119 248 123).

If so, please send any suggestions.

NXP http://www.nxp.com/products/discretes-and-logic/esd-protection-tvs-filtering-and-signal-conditioning/application-specific-esd-and-esd-emi-solutions/hdmi-and-memory-card-signal-conditioning/dvi-and-hdmi-interface-esd-and-overcurrent-protection-ddc-cec-buffering-hot-plug-detect-and-backdrive-protection:IP4786CZ32
WE http://katalog.we-online.de/en/em/COM_MICRO_SMT_HORIZONTAL/685119248123?m=n&sp=http%3A%2F%2Fwww.we-online.com%2Fweb%2Fen%2Fwuerth_elektronik%2Fsearchpage.php%3Fsearch%3D685%2B119%2B248%2B123&_ga=1.162793848.598782523.1467883532


What’s the problem you met? Following the instruction of IP4786CZ32 pins will be OK. Just pay attention to the pin assignment of micro connector.

I have a 2 questions:
– 1st – AC or DC HDMI signal coupling
according the “JetsonTX1_OEM_Product_DesignGuide.pdf” section 6.3.1 HDMI / Figure 19: HDMI Connection Example / Table 42. HDMI Interface Signal Routing Requirements
you require the AC coupling (100nF serial caps on TXC+/- TXD0+/-,1+/-,2+/-),
but the specification for IP4788CZ32 / IP4786CZ32 doesn’t have that serial caps

  • so the question is, use AC coupling or DC coupling?
    (IP4788CZ32 is recommended by NXP for new design)

– 2nd – level shifter for HDMI_CEC and HDMI_HPD (DP1_HPD)
according the “JetsonTX1_OEM_Product_DesignGuide.pdf” Table 40. Jetson TX1 HDMI / DP Pin Descriptions

  • HDMI_CEC (Open Drain, 1.8V)
  • DP1_HPD (CMOS – 1.8V)
    according the Nvidia Reference Design “P2597_B02_OrCAD_schematics.pdf”
  • HDMI_CEC page 14 “HDMI connector” is 3V3 from Jetson TX1 side
  • HDMI_HPD page 14 “HDMI connector” is 1V8 from Jetson TX1 side
  • so the question is, use 1V8 / 3V3 for both
    or copy your ref. design and use:
  • HDMI_CEC 3V3 - so in this case use a direct connection to the IP4788CZ32 pin 29
    (VCC_SYS = 3V3 pin 27 / VCC = 5V0 pin 11 )
    and for
  • HDMI_HPD 1V8 /3V3 level shifter


Hi MrZet,

  1. I did not find internal AC cap based on IP4788CZ32 datasheet, so these AC cap are needed.

  2. On TX1 chip, HDMI_CEC and DP1_HPD are both 1.8V pins. HDMI_CEC is connected to connector thru a gating circuitry, that is for outside HDMI device’s voltage level and so the level shifter for HDMI_HPD. VCC_SYS is 3.3V, so just copying ref. design is OK .

Hi Trumany,

Thanks for your valuable comments.

I hereby confirm the correct operation of my TX1 CARRIER board with micro HDMI (type D) in configuration:
TX1 <=> AC CAP <=> IP4788CZ32 <=> micro HDMI.


When using something like IP4788CZ32
are the ferrite beads (LB1 ~ LB8) and the 499 Ohm resistors (R562…R586) connecting to Q505 needed?

What are the purpose of these components on the development board?

Also how should HDMI_CEC be connected to IP4788CZ32?

Those beads and resistors are must, please just follow it strictly.

I can see a CEC pin in data sheet of IP4788CZ32 which i think can be connected to HDMI_CEC of TX1, or you can touch NXP to confirm.

For my Jetson TX1 carrier board I use the following solution:

  • serial AC CAP for D0+/- D1+/- D2+/- CK+/- (TX1 <=> IP4788CZ32)
  • in case of IP4788CZ32 VCC(sys)=3V3
    – the level shifter for “CEC” and “HPD” and inverter for “HPD” signal.
  • in case of IP4788CZ32 VCC(sys)=1V8
    – the “CEC” connected directly to TX1 (no level shifter) and inverter for “HPD” signal.

Additional according to the IP4788CZ32 specification - beads and resistors are not required.

— solution already tested and working properly —


Why do you need an inverter on the Hot plug signal?

Is there some discussion about this in any of the documentation?

Mr Zet and Geoffreywall, I am interested in using this NXP chip as well. Could one of you weigh in on the purpose of the Inverter on the Hot plug that was asked about in the last post? I didnt see anything about an inverter in the documentation either.