THS4561: Large value feedback resistors and channel mismatch

sfsdfsdf asdasdsad

Part Number: THS4561

Hello,

I'm using THS4561 in energy measurement application. I have quite high impedance resistor divided connected to mains (1.6M ohm and 6k) and then circuit as per attached picture.

I have 3 circuits like this and the problem is there is about 0.5% mismatch between them. I could see that in THS4561 datasheet resistors are relatively low value while these are quite high value. I wonder if such mismatch could be caused by using 178k resistors instead of, say, 10k?

Regards,

Jacek.

over 2 years ago

0 Michael Steffes over 2 years ago

Guru 48395 points

You are probably oscillating, R58 and R59 should not be zero ohms, more like 50ohm.

0 Alec Saebeler over 2 years ago in reply to Michael Steffes

TI__Mastermind 23049 points

Hello Jacek,

I would agree with Michael, you should check for stability in your circuit. Is there a reference design or prior revision you are using for guidance on your design? I am also not sure why you selected R58 & R59 to be zero Ohms. I can look at your circuit and help advise you on a stability analysis, but if you have not done it before, it may be easier to refer to prior amplifier threads on stability and TI's Precision Labs videos on amplifier stability.

Let me know if you would like me to share those resources explicitly here on this thread.

Best,

Alec

0 sfsdfsdf asdasdsad over 2 years ago

Prodigy 10 points

Yes it was oscillating. We fixed it by changing R58 and R59 to 50 ohms.

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THS4561: Large value feedback resistors and channel mismatch