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LMH6586: LMH6586 PCB File and Clamp Voltage

Part Number: LMH6586

We are using LMH6586 in our design. Could you please share the PCB Board File for reference. 

In datasheet, they are recomending to use 300mV Clamp voltage for optimum use. what is the advantage of it. 

If I clamp it by 300mV, does output has the same offset?

  • Hello Manikandan,

    We do not have PCB board files for this device. You can find some design recommendations in the Applications Information section starting on page 18.
    You can also use this application note as reference : High Speed Layout Guidelines (Rev. A) (ti.com)  

    One of the benefits of the clamp is to reduce the power consumption.
    Can you explain your question If I clamp it by 300mV, does output has the same offset? 
    The clamp just clips the voltages. There is a little explanation in the section labeled "AC COUPLING" in the datasheet.

    Thanks,
    Rami

  • As per my understanding,

    Sync Base Tip is  -0.3mV

    Vmax is  0.7mV

    If I ac Coupled my input, the sync base tip seen at -300mV gets clamped to 300mV and Vmax to 1.3V, due to DC restore.If I choose gain=2, they my sync base tip will be at 0.6mV and Vmax to 2.6V

    To remove the DC Bias from the output, is it okay to add 220uF to set the cutoff frequency around 9.5Hz. So, my Stanag Signals won't get distorted. (50Hz signal- 25fps) .Only source terminated.

    If it is both source and load terminated, it will experience little distortion. Am I right?

    What approach do you recommend to remove the DC Bias?

  • Hey Manikandan,

    I don't see why that wouldn't work. I'm not familiar with stanag signal standards though. I see that they're pretty low frequency. Was there a particular specification you were worried about violating?
    Yes if you terminate both ends of a signal you would see distortion. If I'm understanding what you're envisioning properly, you would effectively create a divider here and cut your signal in half. 



    Thanks,
    Rami

  • LMH6586 output will have dc offset, which i can't give it to my receiver . So, i have to use AC coupling to remove dc Bias.  If i use normal 100nF, Cut off frequency will be quite high (High Pass Filter) and my pulse signal will looks like differentiated output. So, i have to choose capacitor greater than 100uF. My worry is about is there will be any stability issue due to this?

  • Hey Manikandan,

    100uF may be a bit too large. I think this would cause too high of a settling time and really affect your responsivity. I'm not very confident here that you'll be able to set a cutoff frequency so low while also maintaining the 50Hz signal. 
    How are you using the LMH6585? Are you utilizing it as a crosspoint switch? I mainly ask to see if there is another device we could possibly try to move you to

    Thanks,
    Rami

  • Yes, I am using LMH6586 as a crosspoint Switch. It selects 22 signals out of 108 inputs. We are using 4 IC's for this configuration.

    I chose 220uF after seeing the impedance chart of the capacitor. And as per simulation, RC filter sets the cutoff frequency less with less attenuation compared to other capacitor.

    Is there any Ibis model to try this simulation out?

  • Unfortunately, there isn't an IBIS model for this. This is a bit of an older device, so I don't anticipate a model being created anytime soon. The 200uF is quite a bit off from what the datasheet recommends so I would be hesitant to using it this way. If you do decide to move forward, I know it's not ideal, but I recommend testing it in on your own board first. It doesn't look like we have breakout boards for this package, but I did find some online if you look up "Treedix 6pcs TQFP". 

    Thanks,
    Rami