Dual supply and Ref voltage

Hi jingum2 

Thank you for contacting us and sharing your questions with the team.

To give the correct recommendation, I would like to confirm these data as I understand them in your schematic diagram.

• Target applications is Current Sensing through 1Kohm Rsense (R4)
• Supply values: +Vs =5V and -Vs = -3.3V
• Vref= 1.03125V using a -3.3V to a res divider (R3//R2), and to buffer (OP1177).
• Intended input voltage range  = 0 to 2V
• Rg = 320, Gain is approximately = 32

Basing the results from the Instrumentation Amplifier Diamond Plot Tool, the conditions above will work. If you want to try other combinations and conditions, I recommend using the diamond plot tool: https://tools.analog.com/en/diamond/#difL=0&difR=0.00005&difSl=0&gain=32&l=0&pr=AD8421&r=2&sl=0&tab=1&ty=1&vn=-3.3&vp=5&vr=1.031

Here are some reference materials for your guidance:

https://www.analog.com/en/education/education-library/videos/4605020056001.html

https://www.analog.com/en/app-notes/an-1401.html

Please contact the team if you have additional questions.

Regards,

Hi, Arsol

First of all, thank you for your assistance.

I want to input -1V to AD8421 Vref in order to convert the input range of 0V to 2V voltage to an output range of -1V to 1V.

I have modified the existing circuit diagram as shown below.

Q1. Is there any issue applying -1V to Vref?

Q2. What additional measures can be taken to minimize noise in the AD8421 output?

Thank you.

Hi, Arsol

First of all, thank you for your assistance.

I want to input -1V to AD8421 Vref in order to convert the input range of 0V to 2V voltage to an output range of -1V to 1V.

I have modified the existing circuit diagram as shown below.

Q1. Is there any issue applying -1V to Vref?

Q2. What additional measures can be taken to minimize noise in the AD8421 output?

Thank you.

Hi jingum2, 

In your 1st question; there will be no issue as long as your Vref value is within the recommended range (min = -Vs to max = +Vs) and if you intended to use the -1V.

I don't know what kind of noise you are referring into the output. For us to give the proper suggestions, Can you please expound further the details of this noise?

Regards,

Please let us know if you can provide these details being requested on your end. For the team to understand your inquiry further and be able recommend the suitable answers.