1

The previous models of the Raspberry Pi used different circuits to connect its 5 V power rail to the HDMI connector, i.e. How much current can I draw from each model's HDMI socket?

Especially the latest Pi 3B+ uses a RT9741CGV High-side power switch.

The Pi 4's schematics does not show something equivalent, i.e. 5V_HDMI is only listed as being connected to the HDMI connectors without revealing the respective power circuit.

The Foundations blog shows the part of the PCB (picture):

enter image description here

What is the function of the ICs labelled "BV=92R" and "JGJ 851" with respect to the HDMI ports?

Ghanima
  • 15,855
  • 15
  • 61
  • 119
  • quite possibly D4 – jsotola Jun 25 '19 at 23:49
  • @Ghanima, I googled and found "BV=" belongs to a manufacturer but could not find the full top marking code "BV=92R", I guess it is specially manufactured only for Rpi, therefore this internal use code is not published. And I guess this 3 leg guy is for Rpi to supply 5V power source to HDMI monitor, through connector pin18. TI has an app report for this: HDMI 5V Source Requirement - Application Report, TI April 2013 ( http://www.ti.com/lit/an/snva412a/snva412a.pdf ) – tlfong01 Jul 01 '19 at 09:14
  • That chip is marked 6V not BV. The rest of the numbers vary and are probably a date code. – Alistair Buxton Dec 01 '20 at 09:02

2 Answers2

1

I have a broken RP 4 with this 6v=XXX SMD missing. Took me a while to work out what it does so shareing my findings.

It looks like a P-channel mosfet acting as a 0v drop diode. It powers the two JGJ chips from the board's 5v rail and the HDMI port's 5v pin. I think it's a MMBFJ174.

The JGJ chips are connected to the HDMI port's SDA,SCL,CEC and HPD pins so are something to do with EDID. Without this FET the board boots okay but there is no display. Shorting the pads for pins 1 and 3 gets the display working.

Tim P
  • 111
  • 1
0

The marking information "6V=" is RichTek RT9742, Please refer to https://www.richtek.com/Products/Power%20Switch/RT9742?sc_lang=en

user155122
  • 1