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HMC6832 output drive level

The HMC6832 data sheet states that its differential output voltage swing is 721mVpp typ when used in 3V3 LVPECL mode. To check: presumably, this is the swing of each output in the differential pair, so that the full differential output swing is 1.4Vpp into 100Ohms, right? Is that correct? In other words, is the output voltage swing of the HMC6832 similar to other ICs like the ADCLK948?

  • Hi,

    721mVpp output voltage is differential, not for a single branch. The measurement setup is shown in Figure-40 and the differential output result (difference of two branches) is shown in Figure-5.

    Regards,

    Kazim

  • kpeker,

    Thanks for clarifying that.

    I'm surprised, because that's 6dB lower than most PECL drivers, which typically give ~800mV single-ended.

  • Hi Tom,

    If I may weigh in here, I think I see where there is confusion. Looking at Table 2 in the HMC6832 datasheet with the Rterm=150 ohms, we see the following:

    721 mVpp with Voh=2.51 V and Vol=1.79 V. 

    The Vpp measurement is indeed made with a differential probe, but with the driver static.

    While toggling, you will see the output driver alternate between +721 and -721 mV.

    Therefore, you'll have Vpp=1.42V as measured with a differential probe while the driver is toggling, and is as expected for an LVPECL driver.

    -Paul Kern

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