LMH6642: Supply of strain gauge full bridges

Jan Bock

Part Number: LMH6642
Other Parts Discussed in Thread: INA317, INA188, INA333, PGA281, PGA280, PGA204

Hi,

My customer tries to improve his design of an amplifier card. His main interest is to improve the supply of strain gauge full bridges:

The current system looks like follows:

Strain gauge impedance = 350 Ω
5V Sensor bridge supply
12 LMH6642 (SOT-23) + voltage ref from a microcontroller (likely with an internal DAC ) = means he can supply 4 bridges with one LMH (4*350 Ω / 5 V = 57 mA)

I already talked with an other FAE about this and we gathered the following points for improvement:

lower amount of OP if a OPAMP is used that can drive more current
The bandwidth of the LMH6642 is from our view not needed
The customer also want to reduce the size so do we have a OPAMP can driving higher currents
The supply must be bipolar
low 1/F noise is needed
low current and voltage noise is needed

So do we have some advise for the customer to improve his application. Which device would fit best for the application.

Thanks for looking into this

Jan

over 3 years ago

0 Hasan Babiker31 over 3 years ago

TI__Genius 15555 points

Hello Jan,

Can you clarify what bandwidth is needed here? and the gain that is being used?

Best,

Hasan Babiker

0 Erik Brehl over 3 years ago in reply to Hasan Babiker31

Prodigy 10 points

Hello Hasan,

the bandwidth is about 1kHz. The gain for the supply is 1 (picture).

POW_IN is 9V.

Best Regards,

Erik

0 Hasan Babiker31 over 3 years ago in reply to Erik Brehl

TI__Genius 15555 points

Hello Erik,

I've moved your thread to the precision team so they can better help recommend a device. For now can you clarify on the following points:

In your latest post you mention a supply of 9V but earlier you mention a 5V supply.
Also what is the output current you are trying to achieve here?

Best,

Hasan Babiker

0 Raymond Zhang1 over 3 years ago

TI__Guru 53751 points

Hi Jan,

I think that Instrumentation Amplifier (IA) will meet your requirements, such as INA333 or INA317 or INA188 part. Enclosed are the links that it may help you to select your IAs.

BTW, you can use bipolar for INA333 or INA317 family, except the overall supply rail can not exceed 7V (e.g. +/- 3.3V or asymmetrical supply rails ).

https://www.ti.com/lit/ug/tidub00/tidub00.pdf?ts=1614632082022&ref_url=https%253A%252F%252Fwww.ti.com%252Ftool%252FTIPD170%253FkeyMatch%253DSTRAIN%2BGAUGE%2BINSTRUMENTATION%2526tisearch%253DSearch-EN-everything

https://e2e.ti.com/support/amplifiers/f/14/t/818894

https://www.ti.com/amplifier-circuit/instrumentation/products.html?pqs=paqs&familyid=500#p480=1&p358min=1.8;4.5&p358max=5.5;5.5

We also have programmable instrumentation amplifier (PGA), such as PGA204, PGA280 and PGA281, but I do not believe that these are you are looking for.

If you need further assistant, please let us know. We are able to simulate your strain gauge configuration after you have selected IA that will meet your requirements.

Best,

Raymond

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LMH6642: Supply of strain gauge full bridges