THS6222: Need CVBS (composite video) driver

Hello Victor,

I can help find a line driver / video amp to help here.  With THS6222 the bandwidth is high enough for CVBS and standard definition video.  However, Full HD (1080p) would require a higher bandwidth part.

We also design the THS6222 for differential line driving.  Video signals are typically single-ended per channel, meaning only one signal conductor.  For THS6222 best operation is when driving a differential signal; using the part for single-ended line driving could cause performance issues.  Our newer THS6232 line driver is optimized for differential line driving, but also can operate the two internal amplifiers independently if the common mode input/output voltages are set correctly.

I would recommend looking at the THS6232 if you are interested in a differential line driver but do not need the bandwidth.  THS6222 is an option if you know you will use the device to drive a differential output.  If you are using a transformer on the output, you may be able to use THS6222.  You would need to provide a differential input to the line driver to enable best performance, as driving the THS6222 single-endedly (only one input signal) limits the performance (output swing, distortion).

While our THS7xxx video amps are more legacy devices, we do have op-amps which have the differential gain and differential phase specifications relevant for analog video: OPA354 and OPA356.

I can provide better recommendations as you share more about your circuit.

Best,

Alec

Hello Alec,

Thank you for the prompt response.

I thinking about using THS6222 (or 6232) as diferential driver for output transformer (Coilcraft PWB1010LC).
(https://www.coilcraft.com/en-us/products/transformers/wideband-rf-transformers/smt/pwb/pwb1010/)

My goal is transmitting CVBS (NTSC) with CAT6 (6A) twisted pair (100 Ohm) at least 100 meters. 200 meters OK also
My source signal is single-ended. And I need your advice what is the best way to convert single-ended to to diff. for THS6222 diff. inputs.
What OpAmp can best fit? Single supply is highly preferred.

Also I need also "solution" (with tranformer input and SE output) for remote side. Probably not only OpAmp/line receiver, but also video restorer\equalizer....

-- Best Regards,

Victor

P.S.
I think I can drive THS6222 (THS6232) directly from single-ended source according SLOA072.
Simply connecting D2IN+ with capacitor to ground.

Hello Victor,

Thank you for the additional details!  This sounds like a cool project, I am glad to help.  Your resource (SLOA072) is a good one, I think we can start with this approach.  While you can use the THS6222 or THS6232 single-endedly, there are a few compromises on signal-to-noise ratio and output swing.  These may be tolerable depending on how the CVBS signal attenuates over the distance.

From what I read it appears the system will need to communicate analog video over a distance, likely between a source instrument/sensor in one room and an observation screen/console in another.  If we are needing the output current to be higher but do not need a high voltage supply, the OPA2675 would also be a good device to examine here.  The OPA2675 has high output current drive and good distortion performance.

For analog video, we may observe the differential gain & phase to be insufficient when using these devices.  We do have dual op-amps of the OPA354 and OPA356 if video fidelity proves to be an issue here.  The OPAx354 or OPAx356 (single or dual op-amp) would also work for the receive path to do differential signal to single-ended signal.  

Even though they are older parts, the THS7316/THS7372/THS7376 are devices which have DC restore and AC sync-tip circuits, along with internal filters and fixed gain options.  These may be appealing on the receive path before you drive a display.

I will spend some time this week looking into our best recommendation for this project.  Overall I think you and I have a good initial approach.  We do have a work holiday on Wednesday, so I may not respond until closer to the end of the week.

All of the amplifiers I discussed above should work in single-supply.

Best,

Alec

Hi Alec,

Thanks for the long reply.

Let's celebrate the New Year first! 

Happy New Year! Wishing you all the best in 2025!

-- Best Regards,

Victor

Hello Victor,

Happy New Year!  I will follow-up in 2025 .

Best,

Alec

Hello Alec,

Bellow a table that I composed browsing and searching TI for video related amplifiers/line drivers
Most interest chips highlighted green. Could you help me with manage cable capacitance, please.
See OD (output drive) in table, please. What part is best for 100 m. CAT5/6 cable with ~6 nF capacitance? OPA2674/2677?
What chip you would like to use for such design requirment?

I`m not limited with parts from the table. Let me know if other IC`s available.

-- Best Regards,
Victor

Hello Victor,

I will review your requirements and help provide good recommendations.

You will have an update from me this week.

Thank you for sharing the details you have provided so far.

Best,

Alec

Hello Alec
Is cable equalisation critical for my design?

See Xavier Ramus "A Numerical Solution to an Analog Problem" for example, please.

https://www.ti.com/lit/an/sboa124/sboa124.pdf

Where is right place for such circuit. At transmitter or receiver end?
There are also interesting chips from Renesas for receiver.

MegaQ: An Automatic Composite Video Equalizer
ISL59601, ISL59602, ISL59603, ISL59604, ISL59605

https://www.renesas.com/ja/document/dst/isl59601-isl59602-isl59603-isl59604-isl59605-datasheet?srsltid=AfmBOorBADiBm9WmSm7zPX5jFHP1we68po2NfmpHregP5kFBjsKbqVla

But, unfortunately with "Last Time Buy" status.
Any similar parts from TI available?

-- Best Regards,

Victor

Hello Victor,

I am asking around about cable equalization and best practices.  In general I see customers using THS6222 and other line drivers on the TX side, with either an FDA or no RX circuitry.

I have not seen recent use of dedicated line receiver parts; we can help recommend an FDA/op-amp/video buffer on the receive path if needed to drive a load or boost the signal for video quality.

I should have time to recommend some best parts today and tomorrow.  I will also check on any TI parts which are competitive against the ISL devices.

We do see most of the key design choices on the transmit side of the circuit, whether for line driving or video.

Best,

Alec

Hello Alec,

Thank you for the answer.

I think we need fo choose from chips with Diff. Gain, Diff. Phase specified in datasheet.

I think such chips was really designed ande tested for Video applications.

My chioce (for today`s evening) are OPA2674, OPA2677

But will waiting for your recommendations.

--
Best Regards,

Victor

Hello

Thank you.
What abour reciever side?

Alec Saebeler said:

I have not seen recent use of dedicated line receiver parts; we can help recommend an FDA/op-amp/video buffer on the receive path if needed to drive a load or boost the signal for video quality.

I should have time to recommend some best parts today and tomorrow.  I will also check on any TI parts which are competitive against the ISL devices.

-- Regards,

Victor

Hello Victor,

I will follow-up with a good receiver recommendation.

Can you confirm the signal chain/path at (and after) the receiver?  Does the receiver need to drive a display or some other load?

Best,

Alec

Hello

Receiver will drive two load.

- Onboard CVBD-HDMI converter

- Remote (2-5 meters) Display/TV/Recorder

-- Regards,

Victor

Hello Victor,

Thank you!  Is the onboard converter matched/terminated to 75 Ohms or 50 Ohms?  

If you have a part number or block diagram of the system, it may help me out.  I am admittedly a visual learner .

Best,

Alec

Hello

ADV7850 planned for CVBS to HDMI. ADV7850 can be not matched on-board because very short trace. I will decide later.

Alec Saebeler said:

I will follow-up with a good receiver recommendation.

I would like to notice you that I need CVBS 100-Ohm twisted pair line receiver with input transformer at current moment.

You no need any diagram for answering this question.

-- Best Regards,

Victor

Hello Victor,

Would you consider the OPA693 as a receiver?  I would also say the OPA354 could do well here if you do not want to use the OPA693.

I can also help you design with the OPA2674/77 as receivers; there are ways to use a differential output and convert to single-ended.  This may be extra effort but it would give you a simpler BOM.

I suggest the OPA693 as my first recommendation, namely due to the output current drive and high bandwidth (for stability of capacitive driving).

Are you needing a transformer recommendation, or support for designing a receive amp circuit post-transformer?  

If I need clarification or you have other ideas, please share.  

Best,

Alec

Hello Alec,

Thank you for the answer.

On picture below my line driver (OPA2674) schematic "as is" at current moment.

The same isolation transformer will be used on receiver`s input side.
But I would like to use something with "cable equalisation" on receiver input
if this really have matter. Then (after "diff. receiver-equalizer" ) I can use OPA693 as buffer for driving two load - onboard ADV7850 and
cable for external video equipment (TV, Video-recorder, etc.)

-- Regards,

Victor

Hello Victor,

I have a better understanding of what you need.  Let me draw up a recommendation for cable equalization prior to an OPA693 (or similar) stage.

Thank you for sharing the transformer, this helps me out also.

Best,

Alec

Hello Alec,

Any news?

Can you provide link for real support? I can`t wait next 30 days.

-- Best Regards,

Victor

Hello Victor,

I will have an update with cable equalization circuitry to you tomorrow.  Thank you for your patience.

Best,

Alec

Hello Victor,

This is the document I am using as a guide.  You are welcome to consider the VCA822 if you find it aligns with your needs.  The document is for cable equalization for Cat5e.

https://www.ti.com/lit/an/sboa125/sboa125.pdf

Best,

Alec

Thank you... Is that all that you can provide after 20 (twenty!) days of waiting?
Please, don`t answer any my questions in the future. You will save my time and your time also.