THS6002: OP-AMP Unused pins

Sandeep Puttaswamy

Part Number: THS6002
Other Parts Discussed in Thread: TLV3502

Hi,

For our project we are using THS6002 has a Receiver Amplifier. THS6002 is a Dual Differential line Drivers & Receivers.

In our application we are using only Receiver Op-amps, Driver Op-amps are unused.

For the unused Op-amps we have connected a Zero Ohm Resistor to ground. Please find the below screen shot for reference.

Kindly let me know if the unused Op-amps connected like in the above screen shot makes sense. If the connections are not proper kindly suggest the recommended connection.

Thank you.

Kind Regards,

Sandeep

over 4 years ago

+1 kai klaas69 over 4 years ago

Guru 140200 points

Hi Sandeep,

I would connect the +inputs of unused OPAmps to signal ground and run the unused amplifiers as noninverting amplifiers with a gain of 2 by mounting 1k resistors in the feedback loop, as shown in figure 1 or 59 of datasheet.

As the THS6002 is a current feedback OPAmp and needs a resistor between the -input and output, wiring the unused OPAmps as simple voltage followers would not work.

Leave the outputs of unused THS6002 unconnected, apart from the feedback resistors, or course.

Kai

+1 Sima Jalaleddine over 4 years ago

TI__Mastermind 28875 points

Hello Sandeep,

Since these are current feedback amplifiers, I also would suggest following Kai's advice. This is a e2e thread explaining the reasoning for this suggestion.

Thank you,

Sima

+1 Sandeep Puttaswamy over 4 years ago in reply to kai klaas69

Prodigy 60 points

Hi Kai,

Thank you soo much for your valuable suggestion.

I will follow your suggestion for unused Op-amp.

Thanks & Regards,

Sandeep

0 Sandeep Puttaswamy over 4 years ago in reply to Sima Jalaleddine

Prodigy 60 points

Hello Sima ,

Thanks for suggestion and providing some good documents for understanding the things better.

Thanks & Regards,

Sandeep

0 Sandeep Puttaswamy over 4 years ago in reply to Sandeep Puttaswamy

Prodigy 60 points

Hello Kai,

With respect to OP-AMP's unused pins, we need one more suggestion. We are using an Equalizer AD8145 in our project. The unused OP-AMP's are connected like in the below screen shot.

Kindly review the circuit and please let us know your valuable suggestion.

Thank you.

Kind Regards,

Sandeep

+1 kai klaas69 over 4 years ago in reply to Sandeep Puttaswamy

Guru 140200 points

Hi Sandeep,

as the AD8145 is a chip from AD, you would need to ask AD.

Kai

+1 Sandeep Puttaswamy over 4 years ago in reply to kai klaas69

Prodigy 60 points

Hello Kai,

I Apologies for posting AD chip query.

One more suggestion is needed on Comparator chip. We have used TLV3502 as a Comparator in our project. The unused OP-AMP is connected as in the below screen shot.

Kindly review the circuit and please let us know your valuable suggestion.

Thank you.

Kind Regards,

Sandeep

+1 kai klaas69 over 4 years ago in reply to Sandeep Puttaswamy

Guru 140200 points

Hi Sandeep,

you could connect one input to the lower supply voltage of TLV3502 and the other input to the higher supply voltage of TLV3502.

Kai

+1 Sima Jalaleddine over 4 years ago in reply to Sandeep Puttaswamy

TI__Mastermind 28875 points

Hello Sandeep,

Kai's suggestion is also correct, but for this comparator family, inputs to ground is acceptable as well.

From comparator's group: https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/422729/tlv3502-unused-inputs-and-output

Thank you,

Sima

0 Sandeep Puttaswamy over 4 years ago in reply to kai klaas69

Prodigy 60 points

Hello Kai,

Thanks for your valuable suggestion.

Kind Regards,

Sandeep

0 Sandeep Puttaswamy over 4 years ago in reply to Sima Jalaleddine

Prodigy 60 points

Hello Sima,

Thanks for your valuable inputs and also for the link.

Kind Regards,

Sandeep

0 kai klaas69 over 4 years ago in reply to Sandeep Puttaswamy

Guru 140200 points

Hi Sandeep,

the recommendation with the two grounded input terminals given by the phenomenal Art Kay has to do with the fact that the TLV3502 provides a built-in hysteresis of 6mV, I guess. With a comparator not showing this internal hysteresis, grounding both input terminals would probably not be a good idea.

Kai

0 Sima Jalaleddine over 4 years ago in reply to kai klaas69

TI__Mastermind 28875 points

Hello Kai,

I believe this is correct. Grounding the inputs won't cause any damage to the device, but can cause chatter. For this family of devices, this shouldn't have this problem due to the 6mV internal hysteresis. For most careful/best configuration would be what you mentioned which is to connect the inputs to the power rails or two different not low impedance voltages. I am moving this thread to the comparator team for confirmation.

Thank you,

Sima

0 Chuck Sins over 4 years ago in reply to Sima Jalaleddine

TI__Mastermind 25990 points

All good points made by everyone on this post. Shorting the two inputs should not create any chatter on the output due to the internal hysteresis of the comparators. One slight modification to the proposal would be to short the two pins together and then connect this junction to ground either directly or through a small resistor. Just in case there is an excessive amount of noise, shorting the pins directly together will prevent any differential voltage being detected across the inputs.

Chuck

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THS6002: OP-AMP Unused pins