LMH5401EVM: Step response under-damped, differential output amplitude discrepant

Yilun Xu

Part Number: LMH5401EVM
Other Parts Discussed in Thread: LMH5401

Hi there,

I was trying to test the LMH5401EVM output with the square wave input.

As shown in the figure below, the green and purple channels are the differential inputs (positive and negative).

The yellow and blue channels are the outputs. It seems that the step response is under-damped. And the differential positive and negative outputs are asymmetric.

The DC power input is +-1.7V.

My question is how to obtain the critically-damped response and the identical differential output amplitude?

Can we change some resistor and capacitor values to realize this? Any model can be used for simulation?

Thanks and best,

Yilun

over 1 year ago

0 Hruday Kumar Mudireddy over 1 year ago

TI__Expert 3320 points

Hi Yilun,

What is the gain you have set? Can you also share the schematic?

Thanks,

Hruday

0 Yilun Xu over 1 year ago in reply to Hruday Kumar Mudireddy

Prodigy 80 points

Hi Hruday,

I used the LMH5401EVM. I didn't make any modifications on the board. Therefore, the gain should be the default value of LMH5401EVM.

Thanks and best,

Yilun

0 Hruday Kumar Mudireddy over 1 year ago in reply to Yilun Xu

TI__Expert 3320 points

Hi Yilun,

Typically reducing the gain should improve the transient response. We have TINA model available for LMH5401. I am attaching the TINA reference design, you can play with the gains to get the desired response.

0647.LMH5401.tsc

Thanks & Regards,

Hruday

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LMH5401EVM: Step response under-damped, differential output amplitude discrepant