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LMG1020EVM-006: The problem of the shortening of pulse width from input signal(J3) to gate signal

WONHEE CHOI
Prodigy 10 points
Part Number: LMG1020EVM-006
Other Parts Discussed in Thread: LMG1020

Hello.

While I have tested the LMG1020-EVM board, I noticed that the width of input pulse signal(J3) shorten by 50ns at gate signal.

For instance, if I drive the pulse signal has 100KHz Freq.,100ns width at the input signal, I could get the 100KHz Freq., 50ns width pulse signal at gate(Vg).

What is the problem?

Best Regards

  • 0
    TI__Prodigy 645 points

    Hello Mr Choi,

    Since many bench-signal generators cannot produce good pulses at the 1-2 ns pulse width range, the board includes a circuit which shortens the input pulse. This way, a signal generator which can produce a 50ns pulse or shorter can drive this EVM. On the EVM schematic, AND gate U3 and the associated R-C filter on one input is responsible for this pulse-shortening. This can be seen on the scope captures in section 8. If this is objectionable,You can change the amount of pulse shorting by adjusting the RC, you could remove it completely by removing the C11 and shorting R9. This would remove the pulse-shortening but still use the AND gate to buffer the signal. Alternatively you can remove the AND gate completely and drive the LMG1020 directly from your signal generator by removing R10 and installing a jumper in the currently un-populated R3 location.

    Hope that helps,

    Nathan