SgtSiff
Posts: 5
Joined: Tue Feb 05, 2019 8:12 pm

TPD12S016 HDMI ESD & CM3

Tue Feb 05, 2019 8:43 pm

Is anybody able to give feedback on the following schematic please?

I'm trying to design an open source CM3 prototyping board that has hand soldering friendly components, so I'm hoping to replace the BGA ESD5384 with a TSSOP TPD12S016:

Image

I have pulled LS_OE and CT_HPD high via 10K resistors, I believe this should disable any power saving and ensure the i2c lines are pulled up appropriately.

As far as I can tell, HDMI_HPD is active low, so I have used a mosfet inverter for this (in line with the original schematic). I figure it made more sense to put this in between the CM3 and the ESD IC.

My main concern is the CEC line, I'm not sure what to do with it and I'm not sure what the function of Q3 is in the original schematic:

Image

According to the datasheet, CEC is pulled up internally.

Datasheet for the aforementioned ESD IC:

http://www.ti.com/lit/ds/symlink/tpd12s016.pdf
http://www.ti.com/lit/an/slla324/slla324.pdf

Thanks!

aBUGSworstnightmare
Posts: 1365
Joined: Tue Jun 30, 2015 1:35 pm

Re: TPD12S016 HDMI ESD & CM3

Wed Feb 06, 2019 5:48 am

Data sheet of Q3 https://www.diodes.com/assets/Datasheets/AP2331.pdf

What do you need CEC for?

SgtSiff
Posts: 5
Joined: Tue Feb 05, 2019 8:12 pm

Re: TPD12S016 HDMI ESD & CM3

Wed Feb 06, 2019 3:06 pm

Q3 being the mosfet on the CEC line ;)

I don't need CEC but I want to maintain all functionality

evangruda
Posts: 4
Joined: Thu Feb 14, 2019 3:29 pm

Re: TPD12S016 HDMI ESD & CM3

Thu Feb 14, 2019 3:31 pm

Hi,
I am currently working on a school project and am wondering if you have tested this. I don't have access to an oven to solder the BGA but want HDMI access on the board I am designing. Thank you!

gsh
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 1418
Joined: Sat Sep 10, 2011 11:43 am

Re: TPD12S016 HDMI ESD & CM3

Fri Feb 15, 2019 9:12 am

Q3 was added to avoid pulling the CEC line low when the device is powered off. Otherwise any other devices connected to the CEC system will stop working when the Pi is powered off (lots of people chained the HDMI through an audio system into the TV, the audio system uses the audio return path from the TV, and takes volume up / down information from the TV through CEC, when you power off the Pi without that MOSFET the output drivers of the SoC will pull the pin low and stop the CEC from working)

Gordon
--
Gordon Hollingworth PhD
Raspberry Pi - Director of Software Engineering

Return to “Compute Module”