TMS320F28335: usage of ADC driver amplifier OPA325 vs TLV6001

beesetty rajesh

Part Number: TMS320F28335
Other Parts Discussed in Thread: OPA325, TLV6001

Dear Experts,

I am working on a customized TMS320F28335 board. There are some final things that I want to get clarified. There is a section of circuit that conditions +/-4V signal to 0-3V that is connected to the analog pins of micrcontroller. I have a doubt in this regard. There are two TI links that you can find on this page. The first one uses TLV600X that converts differnetial to single ended and the same output can be connected directly to the ADC pin. On the other hand, OPA325 is a recommended IC to use as a ADC driver.

Would you recommend to use a single TLV600X that functions as a conditioner as well as a ADC driver, or use another OPA325 or TLV600X to use a buffer?

Or else can I use the single TLV600 circuit(scaling and shifting) and an RC circuit at the output.

TI's differential to single ended recommendation link OPA325 link

Regards,

Rajesh BN.

7 months ago

0 Benjamin Collier 7 months ago

TI__Mastermind 21841 points

Hi,

Please allow me to get back to you about this tomorrow.

Best Regards,

Ben Collier

0 Benjamin Collier 7 months ago in reply to Benjamin Collier

TI__Mastermind 21841 points

Hi Rajesh,

I would think that it is ok to use a single TLV600X as conditioner and an ADC driver. I would like to ask another coworker to confirm, but they will be out of office until Monday, if you are able to wait.

Best Regards,

Ben Collier

0 beesetty rajesh 7 months ago in reply to Benjamin Collier

Expert 1055 points

That means a single TLV6001 without even an RC at the output. But I think RC circuits is always recommended at any input to remove the noise pick up, or before a high switching circuit like ADC.

Would you say that TLV6001 can inherently caters these issues?

0 Benjamin Collier 7 months ago in reply to beesetty rajesh

TI__Mastermind 21841 points

Hi,

I think that the RC circuit will still be needed, but I think you can accomplish your goal with a single amplifier. Again, please allow me to consult a coworker on Monday.

Also, I think that you find this app note helpful: https://www.ti.com/lit/SPRACT6

Best Regards,

Ben Collier

0 Benjamin Collier 7 months ago in reply to Benjamin Collier

TI__Mastermind 21841 points

Hi,

I think my conclusions from last week are correct, TLV6001 with proper passive components should be able to convert your large input voltage to something that is acceptable for ADC input.

Some considerations:

TVL6001 has a relatively high input offset voltage, and it has a relatively low bandwidth.

The input offset voltage will affect your DC accuracy, and the bandwidth will affect the settling time of your samples. You could read more about that in the app note that I already linked and this one: https://www.ti.com/lit/pdf/spracw9

These drawbacks may be acceptable depending on your application, or you could use the OPA325 in its place to help with these issues.

Best Regards,

Ben Collier

0 beesetty rajesh 7 months ago in reply to Benjamin Collier

Expert 1055 points

In that Case, I'll use a quad OPA325 IC. So, Out of four ICs,

one IC to convert differential to single ended,

2nd IC to provide 1.5V offset.

3rd OPAMP will be used as a voltage follower circuit for safety related circuitry- Over voltage/current etc.

So, one opamp is left unused in the quad IC.

Coming back to my fundamental doubt, can I give the 1st opamp's Output to the microcontroller followed by a RC circuit? Or shall I have to use the left opamp as a voltage follower followed by a RC circuit?

The thing bothering me is, cascading op-amps induces noise.

What would you suggest?

Regards,

rajesh BN.

+1 Benjamin Collier 7 months ago in reply to beesetty rajesh

TI__Mastermind 21841 points

Hi,

Please take a look at this application note: https://www.ti.com/lit/SPRACT6

It is common to use a single amplifier with an RC circuit on its output.

Best Regards,

Ben Collier

C2000™︎ microcontrollers

C2000 microcontrollers forum

TMS320F28335: usage of ADC driver amplifier OPA325 vs TLV6001