INA326: Negative current issue with TINA & INA326

jean paul guarrera

Prodigy 40 points

Part Number: INA326
Other Parts Discussed in Thread: INA826

Dear,

I'm trying to simulate with TINA FIGURE 16. Programmable ±5mA Current Source. of INA326 datasheet

Recreating the file

INA326_jp.TSC

It simulates well +5mA to 0mA , but the curve is flattedned to 200uA from 2.5 to 5V ... MAybe an issue with the INA326 model ?

How can I simulate to obtain -5mA ?

thanks in advance

over 3 years ago

0 jean paul guarrera over 3 years ago

Prodigy 40 points

0 jean paul guarrera over 3 years ago

Prodigy 40 points

0 kai klaas69 over 3 years ago in reply to jean paul guarrera

Guru 140200 points

Hi Jean,

yes, I have the same problem with the simulation.

Kai

0 Tamara M Alani over 3 years ago in reply to jean paul guarrera

TI__Genius 10850 points

Hi Jean,

Thank you for your post, I can help you.

There's nothing wrong with the model, the circuit is incorrect. When VDAC is greater than 2.5V, the voltage seen at the inverting node of the INA is beyond the supplies. That is why you see it flattening as it rails. In order to get this to work, I have 2 options for you:

You may use the INA326 with +/-2.5V supplies, but you need to make the following changes to the circuit:
1. VCM = 1.25V
2. VDAC = 0V to 2.5V
3. Change the resistor on the output from 49.9-ohm to 25-ohm
4. You will get IOUT = -5mA to 5mA
If you don't want to limit VDAC, you may use the INA826 with +/-10V supplies (VDAC here is 0V to 5V).

Here are the TINA files for each option:

INA326 Programmable current source.TSC

INA826 programmable current source.TSC

0 Tamara M Alani over 3 years ago in reply to Tamara M Alani

TI__Genius 10850 points

One more thought!

If you want to stick with the INA326 and need VDAC to be 0V to 5V, then you can divide down the VDAC output to 0 to 2.5V with a simple resistive divider:

INA326 Programmable current source (2).TSC