INA333: PSpice model issue

ArTzy

Mastermind 20350 points

Part Number: INA333
Other Parts Discussed in Thread: LM7705

Hello Team,

See attached simulation. This simulation tells that the gain isn’t stable throughout the voltage range, it may be due to Common Mode Input to Supply voltage issue.

Can you please confirm this.

Regards,
Archie A.

https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/14/INA333-Current-Sense_5F00_Gain_5F00_Test.asc

over 3 years ago

+1 Raymond Zhang1 over 3 years ago

TI__Guru* 77501 points

Hi Archie,

ArTzy said:
This simulation tells that the gain isn’t stable throughout the voltage range, it may be due to Common Mode Input to Supply voltage issue.

There are no issues with the PSpice model. The simulation did not optimize the Vcm and Vref for the output voltage range in INA333 IA, so the simulation is operating outside of the linear region under certain conditions. I am unable to assist you LTSpice simulator due to the license agreements.

INA333 E2E 08152023.TSC

This is what the simulation is configured in LTSpice, which the output voltage range is limited.

If you want to maximize the INA333's output voltage swing, you need set the Vcm near mid supply rail or 2.5Vdc and change the Vref from GND to approx. 1.25V or so. The Vout's transfer function is: Vout = Gain*Vdiff + Vref.

If you have other questions, please let me know.

Best,

Raymond

0 Abdul Choudhury over 3 years ago

Prodigy 30 points

I am using the values but still seeing the gain varying widely across the range.

Can this be setup to give an attenuation of 1.0667, input voltage range 0.2V to 4.8V (V Source) outputting 0.1875V to 4.5V.

0 Raymond Zhang1 over 3 years ago in reply to Abdul Choudhury

TI__Guru* 77501 points

Hi Abdul,

Abdul Choudhury said:
Can this be setup to give an attenuation of 1.0667, input voltage range 0.2V to 4.8V (V Source) outputting 0.1875V to 4.5V.

If I play around the calculation, here is what I am able to get. I am not sure what does attenuation 1.0667 mean (do you mean Gain = 10.667 V/V?)

The Vout_min is able to swing down to 0.3V and the Vout_max can swing up to 5.2V on a single supply of 5.5Vdc.

If you want to swing below 0.3V, you may need use LM7705, a -0.232Vdc switched capacitor voltage inverter (charge pump converter) or slightly negative supply rail.

I think that you want to get this output configuration. Please let me know. You would need a fairly constant Vcm mode voltage and differential input signal is going to swing above and below the Vcm mode, which is approx. 2.4Vdc for the setup.