PGA280

Matthew Odinotski

Prodigy 120 points

Other Parts Discussed in Thread: PGA280, PGA281, TINA-TI

I have a board with a PGA280. The Analog supply is connected to +/-12V, VSop = 5V, DVdd = 3.3V.

I'm currently using the power on Reset values for all the settings (1/8V, 1:1, etc).

InN1 is connected to GND

InP1 is connected to a signal source (100hz, -5V to 5V sinewave)

Vocm = 2.048V

What I don't understand is why the outputs: Vop = (100hz sinewave from 2.1v to 2.775V) and Von = (inverted sineware from 2v to 1.32V).

Shouldn't these signals be centered around Vocm (or 2.048V)? and the sinewave crossing over the Vocm level?

What am I missing here?

thanks in advance for your help

Matthew

over 9 years ago

0 Collin Wells over 9 years ago

TI__Guru 62085 points

Hello Matthew,

Would you please post a scope shot of the input and output waveforms for us to take a look at?

Also, are any of the error indicators displaying an error?

0 Ian Williams over 9 years ago in reply to Collin Wells

TI__Mastermind 27715 points

Hello Matthew,

Based on your description, you should be seeing an output voltage centered around your Vocm input of 2.048V. However, without a circuit schematic or input/output waveforms available I cannot confirm this.

One step I recommend is downloading the TINA-TI reference simulation circuit for the PGA281 from the following link: http://www.ti.com/lit/tsc/sbom817

The PGA281 contains the same analog core as the PGA280 and can be used for debugging analog behavior. Modify this reference circuit in TINA-TI (our free SPICE simulator) using your circuit configuration and see if you can duplicate the issue.

Best regards,

Ian Williams
Linear Applications Engineer
Precision Analog - Op Amps

0 Matthew Odinotski over 9 years ago in reply to Collin Wells

Prodigy 120 points

Hi Collin,

No error indicators. After struggling with this for a few days, I just decided to replace the chip on the board, and everything started working. Maybe I stressed out the chip while testing the front end of the pga.

Thanks for your help

Matthew

0 Matthew Odinotski over 9 years ago in reply to Ian Williams

Prodigy 120 points

Hi Ian,

I had the chip replaced this afternoon, and it seems to have resolved the issue. I was working on the front end circuit, and maybe I stressed out the pga. I'll let you know if it happens again.

thanks for the suggestions

Matthew

0 Ian Williams over 9 years ago in reply to Matthew Odinotski

TI__Mastermind 27715 points

Hi Matthew,

Thank you for the update. Please let us know if you experience any more unexpected behavior while evaluating the PGA280.

Best regards,

Ian Williams

Amplifiers

Amplifiers forum

PGA280