TLC272: Voltage abnormal

Jingguo Wang

Part Number: TLC272
Other Parts Discussed in Thread: OPA2374

Hi team,

My customer use TLC272 for voltage follower in the follow SCH, they found the output voltage waveform is very different from V+ input waveform.

And when Vin=5V, the P-P value of waveform is about 4.2V.（blue: pin5 voltage; purple:pin7 voltage; green: pin7 voltage after filter ）

when Vin =8V, the P-P value of waveform is about 2.5V.

when Vin =0, the P-P value of waveform is about 0. seems normal.

So could you help to analysis the possible reason for this phenomenon? and is it normal phenomenon? because it doesn't leads to clear issue. But the waveform is abnormal.

over 1 year ago

0 Ashley Kang over 1 year ago

TI__Genius 16410 points

Hi Jingguo,

Could you provide a schematic? What is the supply voltage and is channel 1 also being used? If so, is it also showing issues?

Regards,
Ashley

0 Jingguo Wang over 1 year ago in reply to Ashley Kang

TI__Intellectual 2780 points

Sorry, the picture couldn't upload, I will sent it to you via email

0 Jingguo Wang over 1 year ago in reply to Jingguo Wang

TI__Intellectual 2780 points

I let customer use DC power source to supply V+, the issue shows the same.

0 Ashley Kang over 1 year ago in reply to Jingguo Wang

TI__Genius 16410 points

Hi Jingguo,

Attaching schematic here for reference:

Could you clarify what the capacitor and resistor values are?

Regards,
Ashley

0 Jingguo Wang over 1 year ago in reply to Ashley Kang

TI__Intellectual 2780 points

Hi Ashley, which capacitor and resistor do you need to clarify, I will get the information for you tomorrow, and could you give some possible reason for this phenomenon in advance?

0 Ashley Kang over 1 year ago in reply to Jingguo Wang

TI__Genius 16410 points

Hi Jingguo,

Could you get all of the capacitors and resistors you are showing in the schematic? That would be helpful for debugging. Also where is Vin being applied in this circuit? I see +12V near Q1 so would like to understand where Vin signal is inputted. Is this 12V applied when Vin is applied?

At this time, we need more information to better understand the customer application to understand the phenomenon.

Regards,
Ashley

0 Jingguo Wang over 1 year ago in reply to Ashley Kang

TI__Intellectual 2780 points

I have sent the full SCH to you , which may help you understand the voltage input, Could you give the recommend value of C101 C111 C106 and C107?

0 Jingguo Wang over 1 year ago in reply to Jingguo Wang

TI__Intellectual 2780 points

By the way, TL082IDR, TL074IDR, OPA2374 and TLC272IP, could you help to give a comparison table of these four devices? Customer want to know the key difference of that. The SCH is their application scenarios for a voltage follower, which one is most suitable choice?

0 Ashley Kang over 1 year ago in reply to Jingguo Wang

TI__Genius 16410 points

Hi Jingguo,

Copying schematic here for reference:

Capacitive loads are dependent on the customer application needs and what is in their signal chain. It is difficult for me to recommend a value for their capacitive loads as this can impact their overall design. What would be helpful for us is for the customer to explain what their current design is and we can recommend modifications to improve the design.

I noticed the recommended devices are different ranges of channel counts and packages. Does this mean the customer is open to different package options? It appears in the schematic that they are using a PDIP TLC272 and we have newer devices that we can recommend as alternative choices if that is what they are looking for.

Regards,
Ashley

0 Ashley Kang over 1 year ago in reply to Ashley Kang

TI__Genius 16410 points

Hi Jingguo,

Are there additional comments or questions from the customer on this thread? In the meantime, I will mark my last response as "TI Thinks Resolved" but please let us know if there are further questions.

Thank you!
Regards,
Ashley

Amplifiers

Amplifiers forum

TLC272: Voltage abnormal