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THS7353 - Recommended range for AC coupling capacitor in AC bias mode

Kawai
Guru 19775 points
Other Parts Discussed in Thread: THS7353

Hi Team,

Our customer will use THS7353 in AC bias mode. I have similar post for AC coupling cap, however, could you advise us the recommended range for the input AC coupling cap ?

e2e.ti.com/.../393379

In the datasheet there is an description example for 1.0uF and 4.7uF. How about using the value over 4.7uF ? How large do you think you could use for the input AC coupling cap ?

Best Regards,
Kawai

  • 0
    TI__Genius 15975 points

    Hello Takushi-san,

    As mentioned in the THS7353 datasheet for the AC-bias mode and also from the equation provided in the e2e post, for a 21kohms input and using either the 1uF cap or 4.7uF sets the high pass corner frequency at 7.6Hz or 1.6Hz respectively.

    Video applications with sync signals typically require this high pass corner frequency to be close to 4.0 Hz for lower droop or tilt in the sync signal, so using 4.7uF ac coupling capacitor is usually sufficient (this being the case for THS7353 only as it presents an input resistance of 21kohms in AC bias mode). You could use as high a value over 4.7uF, but it would only shift the 1.6Hz to a lower value close to DC or 0Hz which is more than sufficient and not generally necessary.

    Best Regards,

    Rohit