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THS7360: Gain issue

Shu-Cheng LIN
Guru 11785 points
Part Number: THS7360
Other Parts Discussed in Thread: THS7368

Hi Sirs,

Sorry to bother you.

We have use THS7360.

1. Could you help check the schematic is OK ?

2. Our SF Channel VGA IN RGB is 700mV, But  after passing SF Channel output will be 3v. It's will make the LCD panel lighting too strong.

As i know the VGA spec is 1.4v when no link display, after connect display the impedance is 75 ohm/75 ohm = 0.7v.

So have any setting on 7360 and we missing?

However, we have try to in parallel 33ohm with 75 ohm, looks the level will OK, but we don't sure any risk on this?

Need you suggest for us. 

Many thanks!!

  • 0
    Guru 11785 points

    Hi Sirs,
    Soft remind, any update on this case??

    Thanks!!

  • 0
    TI__Genius 15975 points

    Hi Shu,

    1. The schematic looks OK.

    2. The THS7360 has 4.5V/V gain on the SF channels. As a result, if the input is 700mVpp on the THS7360, then the output will be around 3.15Vpp (0.7 times 4.5V/V). I think what you need here is a gain of 2V/V on the SF channels.

    You can solve this issue by increasing the output series resistors R98, R94 and R93 to 262.5ohms, so that the voltage going into LCD panel is 0.7V. The voltage at the LCD panel is mainly the voltage division of the resistors at the THS7360 output, mainly 3.15x(75/(262.5+75)) which equals 0.7V.

    The better way of solving this is by replacing the THS7360 with THS7368, which is a 6-dB (2V/V) drop in pin-to-pin replacement of the THS7360.

    Best Regards,

    Rohit