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LMH7220: Changing the threshold

na na78
Guru 16770 points

Part Number: LMH7220

Hi

We are using LMH7220 because we need comparator with LVDS output.

We are about to change threshold of comparator dynamically by external DAC.

If there is any concern on changing threshold in our case, could you please point it out?

BestRegards

  • 0
    TI__Expert 3350 points
    Hello,

    Check the DC output resistance and the AC output impedance of the DAC. The DC resistance with respect to the input bias current of the LMH7220 should be low to achieve accurate reference levels. Also, the AC output impedance of the DAC should be low enough to avoid coupling of fast output transients through parasitic layout capacitance to the input, resulting in oscillation. A bypass cap at the comparator input can lower the AC output impedance of the DAC at the expense of increasing DAC’s settling time, but in many also causes oscillation at the output stage amplifier of the DAC due to excessive capacitance. In that case, a resistor with proper value in series with the output of the DAC before the bypass cap would prevent potential oscillation.

    Regards,