PGA411-Q1: Output waveform is abnormal

Kevin Xiong

Part Number: PGA411-Q1

Hi,

The input waveform of PGA411 is normal, but te output waveform is abnormal which has glitch. The glitch is periodical. Please refer to the figures. The upside of figure 1 is input and the lowside of figure 1 is output OCOS. The figure2 is OSIN and OCOS output.

My question is:

Why is the output waveform of OSIN and OCOS abnormal? How to resolve this issue?

Thanks.

Kevin Xiong

over 6 years ago

0 Clancy Soehren over 6 years ago

TI__Mastermind 23810 points

Kevin,

This is the AFE automatic offset calibration routine running and it is perfectly normal behavior. The procedure is described in the datasheet, and you can see when it is running by looking at those glitches.

What is happening is that every 400us while the routine is running, the AFE amplifier inputs are shorted in order to compensate for amplifier offset. This is timed to happen around the zero crossing. Since we only short at the zero crossing, no information is lost and the angle output should not be affected.

0 Kevin Xiong over 6 years ago in reply to Clancy Soehren

Expert 2340 points

Hi,

Could I disable the AFE offset calibration fuction?

Thanks.

Kevin Xiong

0 Clancy Soehren over 6 years ago in reply to Kevin Xiong

TI__Mastermind 23810 points

Kevin,

You cannot disable the AFE offset calibration. The glitches you see in the waveform are normal behavior and will not impact the angle output from the PGA411.

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PGA411-Q1: Output waveform is abnormal