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LMG1025-Q1: IN+ / IN- voltage level

Part Number: LMG1025-Q1
Other Parts Discussed in Thread: TIDA-01573, LMG1020, SN65LVDS4, DS90LV028A

Hi Team,

The datasheet of the LMG1025-Q1 specifies a VIH High Threshold voltage of 1.7V (min) and 2.6V (max). Does this mean that any voltage between 1.7V and 2.6V will be interpreted as a "High" input, or does this parameter specify part-to-part variation in the VIH?

Another related question is about what happens when the VIH applied to the IN+/- pins is higher than 2.6V? My customer is using an LVDS driver with a 2.4V min and 3.1V Typ output voltgae. Could this damage the inputs of the LMG1025-Q1?

Thanks and Regards,

Mihir

  • Hi Mihir,

    Thanks for reaching out on e2e for LMG1025-Q1.

    1025 needs a 3v swing to switch properly. The min/max input threshold variation helps with the input hysteresis and specifies how much the input threshold on each part can vary across part and temperature.

    The 1025 inputs can withstand voltage as high as VDD or 5.25v found in the recommended operating conditions table of the LMG1025-Q1 datasheet. Since 1025 inputs IN+ and IN- needs a 3v input swing to reach the on/off thresholds the LVDS or input buffer needs to be able to switch from 0v to 3v.

    Let me know if this helps answer your questions, or you have any other questions.

    Thanks,

  • Hi Jeff,

    So what LVDS to CMOS Receiver would you recommend for use with the 1025? Even the http://www.ti.com/product/DS90LV028AQ-Q1 that is mentioned in the TIDA-01573 design guide has a 2.6V (Min), 3.1V (typ) output voltage.

    Thanks and Regards,

    Mihir

  • Thanks for the follow up Mihir,

    IN+ and IN- are not differential inputs. In order to use a LVDS on either IN+ or IN- (not both) it needs to be single ended output. I recommend SN65LVDS4 for a LVDS capable of 3.3V output with similar speeds to achieve 1ns pulses. SN65LVDS4 output min is 3V as well which stands up to the lmg1020 and lmg1025-q1 input spec. However, DS90LV028A should be able to work as well for most applications since the min 2.7V value is across corner temperature and also the minimum output voltage depends on the current sourcing capability with respect to the load.

    Thanks,