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ch7318 replacement with sn75dp139

steven kim
Prodigy 20 points
Other Parts Discussed in Thread: SN75DP139

I want to replace the ch7318 to sn75dp139.

When I have replace the ch7138 with sn75dp139(48pin)  (same footprint and pin assignment in my pcb except some control pin)  -> data signal pin & power pin = same (3.3vcc) /

but i it does not work , can anyone point my mistake ? i dont know why

some control pin 

- ch7318  pin 3(TRIM) : output current increasing +/-10% <--> sn75dp139(SRC):edge rate control

- ch7318 pin 4(HPDEN): HPD inverting/non-inverting selection <--> sn75dp139(I2C_EN) : HDMI/DVI selection\

- ch7318 pin 6(Analog-rext) : 1.2k ohm  <--> sn75dp139 : 4.02kohm

- ch7318 pin 34(CCT1) : pre-emphasis control with CCT2  <--> sn75dp139(HPDINV) : HPD inverting /non-inverting selection

- ch7318 pin 35(CCT2) : pre-emphasis control with CCT1  <--> sn75dp139(OVS) :DDC Source level offset  selection

before replace( ch7318) : pin3 ,4 : 10kohm pull down./ pin 6 : analog_rext(1.2k/1% ohm) / pin 34,35 : 10kohm pull down

after replace(sn75dp139) : pin3 : 10kohm pull down.  / pin4 : 10kohm pull up / pin 6 : 4.02k/1% ohm)/pin 34,35 : 10kohm pull down

  • 0
    TI__Mastermind 23815 points
    Hi Steve,

    Your configuration looks right,
    could you check if HPD_SRC is following the value of HPD_SNK?
    on DDC source side you need 2k pullups to 3.3V, on DDC sink side you need 2k pullups to 5V, do you have this values?

    Regards
  • 0 in reply to Moises Garcia
    Prodigy 20 points

    Hi, quote

    - HDP_SRC = HDP_SNK = High (when HDMI cable insert)

    - DDC source side 2k pullup to 3.3V, DDC sink side 4k(change to 2k) pullup to 5V,

    Q: how can i  up the level of  signal / clock output .  when i compare the output level of signal/clock  with the level of CH7318.

    the output level of SN75DP139 is too low (3-4 times smaller than CH7318).

    steven kim

    regards.

  • 0 in reply to steven kim
    TI__Mastermind 23815 points

    Hi Steven,

    Be sure there is communication in DDC, if DP++ source can't read display's EDID it won't send video.

    If you have clock output, do you have video output too? do you have input video?

    FOr this device you can change VOS by changin Rvasdj, refer to DS figure 19.

    Regards