current follower op amp recommendation for TMS570LS20216 ADC input

Duke Lee

Other Parts Discussed in Thread: TMS570LS20216, OPA4336, OPA2320

Hello,

My project is using TMS570LS20216.

My question is op-amp selection for ADC input.

Actual input range is 0 to +5V and I'm using precision resistor (2K ohm + 3K ohm) to divide input to make 0 to 3V out (REF5030 as reference 3V)

1st try on directly connected condition makes dropped read out value.(4070 for 5V input)

2nd try using OPA4336 as simple current follower makes worse result (more dropped value, max read out not exceed 2500).

3rd try using OPA2320 makes a better result, 3V input that divided from 5V read out is 4088 (4095 desired on 12bit reading).

I can use +5.2V supply only. by this reason, I need to use single supply R2R OP AMP.

What OP AMP can be the best selection?

Thank you.

over 9 years ago

0 Anthony F. Seely over 9 years ago

TI__Guru 68940 points

Duke,

Have you tried using the tools from WEBENCH design center? Especially on the Amplifiers page?

The equivalent circuit of the TMS570LS20216 can be found in the datasheet and you can use this to model the load of the MCU on the amplifier.

0 Anthony F. Seely over 9 years ago in reply to Anthony F. Seely

TI__Guru 68940 points

Hi Duke,

Did you get the answer you needed?

0 Duke Lee over 9 years ago in reply to Anthony F. Seely

Prodigy 60 points

Once I got reply, but the answer was not good enough, That time I'd like to get recomendation to select an op-amp from TI.

Anyway, I found suitable one and solved.

Thanks

0 Anthony F. Seely over 9 years ago in reply to Duke Lee

TI__Guru 68940 points

Oh - what did you do to get the reply then? Post a question on one of the amplifier forums.
Would also be good to understand what the shortcoming of the recommendation was - in case someone else has the same issue they may find this post and save some time.

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current follower op amp recommendation for TMS570LS20216 ADC input